Tropical Storm Sergio

Tropical Depression Sergio 1200 Hours October 12 2018
Tropical Depression Sergio 1200 Hours October 12 2018

NWS National Hurricane Center Miami FL 900 AM MDT Fri Oct 12 2018

The center of Sergio  (see 11 videos below) crossed the central portion of the Baja California peninsula and is now moving over the Sea of Cortez. The convection has weakened and is displaced to the north of the still vigorous low-level circulation. Based on observations from the automatic stations of the Mexican Navy, the initial intensity is 35 kt. The effect of the high terrain and shear will result in additional weakening, and Sergio will likely become a tropical depression this afternoon and dissipate over northwestern Mexico later today or tonight.

Sergio is moving toward the northeast at 20 kt embedded within the mid-latitude westerlies. This track should continue until dissipation in about 12 hours over Northwestern Mexico.

The primary threat associated with Sergio and its remnants continues to be life-threatening flash flooding and mudslides within mountainous terrain in the Mexico states of Baja California Sur, Sonora, portions of the desert southwest and the U.S. Southern Plains through the weekend.

FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 27.5N 111.9W   35 KT  40 MPH - Tropical Storm (N Isla Tortuga. Mexico)
 12H  13/0000Z 29.5N 109.0W   25 KT  30 MPH - Tropical Depression (Los Pescados, Mexico)
 24H  13/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 900 AM MDT Fri Oct 12 2018

Tropical Storm Sergio –  The center of Sergio crossed the central portion of the Baja California peninsula and is now moving over the Sea of Cortez. The convection has weakened and is displaced to the north of the still vigorous low-level circulation. Based on observations from the automatic stations of the Mexican Navy, the initial intensity is 35 kt. The effect of the high terrain and shear will result in additional weakening, and Sergio will likely become a tropical depression this afternoon and dissipate over northwestern Mexico later today or tonight.

Sergio is moving toward the northeast at 20 kt embedded within the mid-latitude westerlies. This track should continue until dissipation in about 12 hours over Northwestern Mexico.

The primary threat associated with Sergio and its remnants continues to be life-threatening flash flooding and mudslides within mountainous terrain in the Mexico states of Baja California Sur, Sonora, portions of the desert southwest and the U.S. Southern Plains through the weekend.

FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 27.5N 111.9W   35 KT  40 MPH - Tropical Storm (ESE Isla Tortuga, Mexico)
 12H  13/0000Z 29.5N 109.0W   25 KT  30 MPH - Tropical Storm (Los Pescados, Mexico)
 24H  13/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM PDT Thu Oct 11 2018

Tropical Storm Sergio –   The cloud pattern of Sergio continues to show organization with a couple of cyclonically curved hooking bands, however the convection in these bands is weak to moderate. Dvorak estimates suggest that the initial intensity still is 55 kt. Sergio is about to move over cooler waters and the shear is forecast to increase significantly, so the expected weakening process should begin later today. Nevertheless, the cyclone should still be a tropical storm when it moves over the Baja California peninsula, but it should dissipate once it moves over the high terrain of the Mexican mainland over the state of Sonora.

Satellite fixes indicate that Sergio is moving toward the northeast about 17 kt. The storm is embedded within the deep-layer southwesterly flow associated with a broad mid-latitude trough located just off the U.S. west coast. This flow pattern will continue to steer Sergio toward the northeast with an increase in forward speed. Track models are in excellent agreement and unanimously bring Sergio over the central portion of the Baja California peninsula in about 24 hours and so does the official forecast.

The primary threat associated with Sergio and its remnants continues to be life-threatening flash flooding and mudslides within mountainous terrain in the Mexico states of Baja California Sur, Sonora, the U.S. Southern Plains, and the Ozarks through the weekend. For more information about this potential hazard, see products from the Weather Prediction Center and your local weather forecast office.

FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 22.2N 118.7W   55 KT  65 MPH - Tropical Storm (WSW Puerto San Carlos, Mexico)
 12H  12/0000Z 24.2N 116.2W   50 KT  60 MPH - Tropical Storm (WSW Puerto San Carlos, Mexico)
 24H  12/1200Z 27.0N 113.0W   40 KT  45 MPH - Tropical Storm (Casas Blancas,Mexico)
 36H  13/0000Z 29.5N 109.0W   25 KT  30 MPH - Tropical Storm (Los Pescados,Mexico)
 48H  13/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 PM PDT Wed Oct 10 2018

Tropical Storm Sergio –  This evening’s satellite presentation depicts a rather ragged and elongated banding eye-like feature with fragmented curved bands encircling the periphery of cyclone. The subjective intensity estimates from TAFB and SAB, however, still yield an initial intensity of 55 kt.

The UW-CIMSS shear analysis shows that the westerly shear has increased to 15-20 kt, and the Decay-SHIPS as well as the global models indicate that the shear magnitude will increase further to near 50 kt prior to landfall. This inhibiting upper wind pattern along with slightly cooler oceanic temperatures should influence some further weakening as it approaches the Baja California peninsula. Sergio is forecast to move inland over Baja California Sur on Friday and into the northwestern Mexico state of Sonora early Saturday as a depression. At the end of the forecast period, Sergio is expected to further degenerate into a post-tropical weak low over the southwestern United States. The intensity forecast is based on the NOAA-HCCA, and the GFS/ECMWF global models which show Sergio making landfall Friday as a tropical storm.

The initial motion is estimated to be northeastward, or 050/14 kt, and this general motion is forecast through the entire 72 hour period with a continued increase in forward speed. Sergio will be approaching the central Baja California peninsula Friday, although the tropical-storm-force winds are likely to arrive Thursday night. There is continued high confidence in the forecast track as the available large-scale and hurricane models are clustered tightly together through 72 hours. The NHC forecast lies in the middle of the guidance cluster and is close to the TVCN/HCCA consensus models.

The primary threat associated with Sergio and its remnants continues to be life-threatening flash flooding and mudslides within mountainous terrain in the Mexico states of Baja California Sur, Sonora, the U.S. Southern Plains, and the Ozarks through the weekend. For more information about this potential hazard, see products from the Weather Prediction Center and your local weather forecast office.

FORECAST POSITIONS AND MAX WINDS

INIT  11/0300Z 20.0N 121.5W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 12H  11/1200Z 21.8N 119.3W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 24H  12/0000Z 24.4N 116.4W   50 KT  60 MPH - Tropical Storm (WSW Puerto San Carlos, Mexico)
 36H  12/1200Z 27.2N 113.1W   45 KT  50 MPH - Tropical Storm (San Juan, BC Mexico)
 48H  13/0000Z 30.0N 109.1W   30 KT  35 MPH - Tropical Storm (Rancho el Coyote,, Mexico)
 72H  14/0000Z 34.4N  98.8W   20 KT  25 MPH - Tropical Storm (Hollister, OK)
 96H  15/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 AM PDT Wed Oct 10 2018

Tropical Storm Sergio –  This morning’s conventional satellite presentation reveals little change in Sergio’s cloud pattern. The majority of the deep convection resides in the north portion of the circulation with some new bursts developing in the south semicircle. Consequently, the initial intensity will be kept again at 60 kt, and is supported by the TAFB and SAB Dvorak intensity estimates.

Gradual spin down of the cyclone is still expected to commence soon as Sergio begins its trek over decreasing sea surface temperatures and into a region of increasing southwesterly vertical shear and a drier mid-level troposphere. Over the weekend, after quickly moving over the central Baja California peninsula, Sergio should weaken further over the state of Sonora in northwestern Mexico, degenerate into a remnant low early Sunday, and is forecast to dissipate over the Southern Plains of the United States, although this dissipation could occur sooner, as indicated in the European global models.

The initial motion is estimated to be east-northeastward, or 065/10 kt, within the mid-tropospheric southwesterly flow produced by a mid-latitude trough extending southwestward over the eastern Pacific from the southwestern United States. Sergio should continue to accelerate toward the east-northeast or northeast over the next few days, and approach Baja California Sur on early Friday. The NHC forecast is basically an update of the previous advisory and is close to the various multi-model consensus aids.

The primary threat associated with Sergio and its remnants will likely be life-threatening flash flooding and mudslides within mountainous terrain in the Mexico state of Sonora, the U.S. Southern Plains and the Ozarks through the weekend. For more information about this potential hazard, see products from the Weather Prediction Center and your local weather forecast office.Tropical Storm Sergio Distances 0200 Hours October 10 2018

FORECAST POSITIONS AND MAX WINDS

INIT  10/0900Z 17.5N 124.9W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 12H  10/1800Z 18.8N 122.9W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 24H  11/0600Z 20.6N 120.4W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 36H  11/1800Z 23.0N 117.7W   50 KT  60 MPH - Tropical Storm (WSW Puerto San Carlos, Mexico)
 48H  12/0600Z 25.4N 114.7W   50 KT  60 MPH - Tropical Storm (WSW San Juanico, Mexico)
 72H  13/0600Z 30.3N 107.3W   35 KT  40 MPH - Tropical Storm (La Nariz, Mexico)
 96H  14/0600Z 34.5N  97.8W   20 KT  25 MPH - Tropical Storm (Duncan, OK)
120H  15/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM PDT Tue Oct 09 2018

Hurricane Sergio appears to have resumed its slow weakening. Cloud tops on the western half of the hurricane have warmed, and Dvorak classifications from TAFB and SAB have decreased. However, recent AMSR-2 and SSMIS images indicate that the hurricane still has a large but well-defined inner-core in the low and mid-levels. The initial intensity is set at 70 kt, based on a blend of Final-T and CI numbers from TAFB and SAB, and the most recent UW-CIMSS SATCON estimate.

There has been almost no change to the intensity forecast and only very gradual weakening is forecast during the next 36 to 48 h. Beyond that time, Sergio will pass over colder SSTs, including the still-present cold wake of former Hurricane Rosa, and continued weakening is expected as the cyclone approaches the Baja California peninsula. Sergio is therefore still forecast to be a tropical storm when it reaches the west coast of the Baja California peninsula in a few days. Rapid weakening is likely after Sergio makes its final landfall in northwestern mainland Mexico late this week, and the cyclone will likely dissipate or become a remnant low shortly after moving inland.

Virtually no change has been made to the track forecast, which remains near the TVCN and HCCA consensus aids. All of the global and regional models show that Sergio will accelerate generally northeastward for the next 3 days, approaching the Baja California peninsula on Friday. There is still some disagreement among the models regarding the exact speed of Sergio through that time, but there is very little cross-track spread. Confidence in the track forecast is fairly high.

Hurricane Sergio Distances 0500 Hours October 9 2018
Hurricane Sergio Distances 0500 Hours October 9 2018

Moisture associated with the remnants of Sergio is expected to affect portions of northwestern Mexico, the southwestern United States, and the U.S. southern plains over the weekend and could potentially cause heavy rainfall in this region. For more information about this potential hazard, see products from the Weather Prediction Center and your local NWS forecast office.

FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 16.6N 127.4W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 12H  10/0000Z 17.1N 126.3W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 24H  10/1200Z 18.1N 124.4W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 36H  11/0000Z 19.7N 122.0W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 48H  11/1200Z 21.7N 119.3W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 72H  12/1200Z 26.2N 113.5W   50 KT  60 MPH - Tropical Storm (S Punta Abreojos, Mexico)
 96H  13/1200Z 31.0N 106.0W   25 KT  30 MPH - Tropical Depression (Rancho San Antonio, Mexico)

NWS National Hurricane Center Miami FL 200 AM PDT Mon Oct 08 2018

Hurricane Sergio  continues to have a large 60 nmi diameter eye with several mesovorticies within it. Although the cloud pattern is quite symmetric around the eye, the cloud tops are not very cold, likely due to some ocean upwelling beneath the hurricane. The Dvorak estimates are largely unchanged from earlier and still support an initial intensity of 80 kt.

Sergio is now drifting northwestward in weak steering currents. A shortwave trough is expected to approach Sergio from the north, and that feature, and a large trough over the southwestern United States should cause Sergio to turn northeastward tonight. This motion with an increase in forward speed is expected through the remainder of the week. The models are in good agreement overall, and the NHC track forecast lies near the middle of the guidance envelope. Based on this forecast, Sergio is expected to be very near the Baja California peninsula in about 4 days.

Sergio is expected to hold its strength or weaken only slightly during the next day or so while it remains in a favorable atmospheric environment. However, steady weakening is expected after that time due to increasing shear, drier air, and progressively cooler waters along the forecast track. Based on the intensity guidance and environmental conditions, Sergio is expected to be a tropical storm by the time it nears the Baja California peninsula. The cyclone should weaken quickly once it moves inland. The NHC intensity forecast is an update of the previous one and near the HCCA and IVCN guidance.

Recent ASCAT data was very helpful in analyzing the 34- and 50-kt wind radii.

FORECAST POSITIONS AND MAX WINDSHurricane Sergio Distances 0500 Hours October 8 2018

INIT  08/0900Z 15.2N 128.1W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 12H  08/1800Z 15.7N 128.3W   75 KT  85 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 24H  09/0600Z 16.4N 127.9W   75 KT  85 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 36H  09/1800Z 17.2N 126.6W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 48H  10/0600Z 18.2N 124.8W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 72H  11/0600Z 21.4N 120.0W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 96H  12/0600Z 26.5N 114.0W   45 KT  50 MPH - Tropical Storm (WSW Punta Abreojos, Mexico)
120H  13/0600Z 33.0N 106.5W   25 KT  30 MPH - Tropical Storm (White Sands Missile Range, NM)

NWS National Hurricane Center Miami FL 800 AM PDT Sun Oct 07 2018

Hurricane Sergio –  Somewhat quickly and unexpectedly, Sergio took on the appearance of an annular hurricane overnight. The eye of the hurricane expanded, nearly doubling in size (now 70 n mi across), and most of the banding features disappeared. However, IR imagery over the past hour or two indicates that the hurricane is still somewhat asymmetrical, suggesting that the hurricane may not have a classical annular structure, at least not yet. The initial intensity has been lowered to 90 kt, in agreement with the latest current intensity estimates from TAFB and SAB.

The hurricane continues to move due west with an initial forward speed of 7 kt. Sergio is still expected to slow down and turn first northward, and then northeastward over the next couple of days. By mid-week, a mid-level shortwave trough moving southward off coast of California should cause Sergio to accelerate northeastward toward the Baja California peninsula. The global models remain in fairly good agreement on the track of the cyclone through the middle of next week, and only small changes were made to the NHC track forecast to move it closer to the model consensus.

As long as Sergio can maintain its annular-like structure, only slow weakening is anticipated due to continued effects of ocean upwelling combined with the slow forward motion of the hurricane. By the end of the forecast period, Sergio will be moving over much cooler SSTs located west of the Baja California peninsula, and a faster weakening rate is forecast. Given the lower initial intensity of Sergio, the official intensity forecast is a little lower for the first two days of the forecast, but is very similar beyond that time.

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 14.5N 126.8W   90 KT 105 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 12H  08/0000Z 14.8N 127.6W   85 KT 100 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 24H  08/1200Z 15.2N 128.2W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 36H  09/0000Z 15.9N 128.1W   75 KT  85 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 48H  09/1200Z 16.7N 127.3W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 72H  10/1200Z 18.8N 123.8W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 96H  11/1200Z 22.0N 119.5W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
120H  12/1200Z 26.5N 114.0W   45 KT  50 MPH - Tropical Storm (WSW Punta Abreojos, Mexico)

NWS National Hurricane Center Miami FL 200 AM PDT Sun Oct 07 2018

Hurricane Sergio appears to have lost some strength during the past several hours. Deep convection has decreased in intensity, and the eye appears larger and more ragged in recent satellite images. The initial intensity is lowered a little to 100 kt, which is near the upper end of the satellite intensity estimates, and this could be a little generous.

The hurricane is still moving westward at about 7 kt, and a slow westward or west-northwestward motion is expected for the next 12 hours. The steering currents are expected to weaken later today, and Sergio will likely drift northwestward and northward tonight and Monday. After that time, a large trough over the southwestern United States is expected to cause Sergio to move toward the northeast with increasing forward speed. The track models are tightly clustered, and only small changes were made to the previous NHC forecast.

The predicted slow motion of the tropical cyclone during the next couple of days will likely cause ocean upwelling, which could result in continued slow weakening in the short term. In the longer range, the models show Sergio moving into an atmospheric environment of drier air and stronger shear and over waters cooler than 26 deg C, which should continue the weakening trend or even accelerate it. The NHC intensity forecast is largely an update of the previous one, and it is in best agreement with the IVCN and HCCA models.

FORECAST POSITIONS AND MAX WINDS

INIT  07/0900Z 14.6N 126.1W  100 KT 115 MPH - Category 3 (WSW Cabo San Lucas, Mexico)
 12H  07/1800Z 14.7N 127.0W   95 KT 110 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 24H  08/0600Z 15.0N 127.7W   90 KT 105 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 36H  08/1800Z 15.7N 127.8W   85 KT 100 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 48H  09/0600Z 16.5N 127.2W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 72H  10/0600Z 18.5N 124.3W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 96H  11/0600Z 22.0N 119.6W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
120H  12/0600Z 26.6N 114.2W   45 KT  50 MPH - Tropical Storm (WSW Punta Abreojos, Mexico)

NWS National Hurricane Center Miami FL 800 AM PDT Sat Oct 06 2018

Hurricane Sergio has remained nearly steady-state since last night and the clear eye is still surrounded by very cold cloud tops. The initial intensity remains 110 kt, based on a blend of subjective and objective Dvorak intensity estimates. The primary moderating factor for Sergio’s intensity over the next few days will likely be sea surface temperatures since GFS and ECMWF SHIPS diagnostics suggest that the environment will be otherwise favorable. Sergio is now moving west-southwestward at around 6 kt, likely just fast enough to outrun its own cold wake. Little change in Sergio’s intensity is expected for the next day or so while the hurricane is forecast to continue moving at around this same forward speed. By early next week, a slower motion will likely cause some weakening to occur, as Sergio becomes trapped over colder upwelled waters, with further weakening likely when Sergio reaches much cooler waters to the north. The ocean-coupled regional models show more weakening than currently indicated by the official forecast, while DSHP and LGEM show a stronger storm, probably in part because those models use a constant ocean field. Confidence in the intensity forecast is not very high, and it is likely that the faster Sergio moves, the stronger it will be.

The global models are in fairly good agreement on the general track of Sergio through the middle of next week, but they disagree on how quickly Sergio will move along that path. Sergio is still forecast to make a sharp u-turn toward the northeast over the next 3 days and then accelerate in that direction between 72 and 120 h. Most of the models are showing a slightly slower forward speed than earlier cycles. However there are still large differences in their representation of a shortwave trough off the coast of California that will cause Sergio’s acceleration, and the model spread remains high. The new official track forecast is similar to the previous advisory but generally shows a slower speed, especially after 48 h, in line with the latest track consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 14.7N 124.0W  110 KT 125 MPH - Category 3 (WSW Isla Socorro, Mexico)
 12H  07/0000Z 14.5N 125.0W  110 KT 125 MPH - Category 3 (WSW Isla Socorro, Mexico)
 24H  07/1200Z 14.5N 126.0W  105 KT 120 MPH - Category 3 (WSW Isla Socorro, Mexico)
 36H  08/0000Z 14.9N 126.8W  100 KT 115 MPH - Category 3 (WSW Isla Socorro, Mexico)
 48H  08/1200Z 15.5N 127.0W   90 KT 105 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 72H  09/1200Z 17.2N 125.6W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 96H  10/1200Z 19.5N 122.0W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
120H  11/1200Z 23.6N 117.0W   50 KT  60 MPH - Tropical Storm (WSW Puerto San Carlos, Mexico)

NWS National Hurricane Center Miami FL 200 PM PDT Fri Oct 05 2018

Hurricane Sergio – This afternoon’s satellite presentation shows that Sergio has become a little better organized. Eyewall cloud temperatures have once again cooled, and the ragged, cloud-filled eye has warmed during the past 6 hours. Accordingly, the subjective and objective T-numbers support increasing the initial intensity to 105 kt for this advisory.

As mentioned in this morning’s discussion, unforeseen short term inner-core structure changes could cause some intensity fluctuations. Since the environment is forecast to remain favorable during the next 24 hours or so, little change in strength is forecast, and again, the cyclone could become a little stronger than reflected in the forecast. Beyond this period, gradual weakening is expected through day 5 as Sergio moves toward decreasing sea-surface temperatures and into a more stable surrounding environment. The Decay-SHIPS and LGEM intensity guidance, as well as the large-scale models, show increasing southwesterly shear disrupting Sergio’s outflow pattern after 72 hours. The intensity forecast is similar to the previous package, and is just above the NOAA-HCCA and IVCN consensus models and below the statistical intensity aids.

Sergio’s motion is estimated to be west-southwestward, or 250/6 kt within the mid-level steering flow produced by a building high pressure system located north-northeast of the Hawaiian Islands. By early next week, a decrease in forward speed and a turn toward the northwest to north-northwest is forecast as the aforementioned mid-level high retrogrades in response to an amplifying trough over the southwestern United States and Baja California peninsula. Beyond day 3, increasing southwesterly mid-tropospheric flow should induce a northeastward accelerated motion through day 5. The NHC forecast is again adjusted south of the last advisory through 48 hours, and is close to the various multi-model consensus guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 15.7N 122.3W  105 KT 120 MPH - Category 3 (WSW Isla Socorro, Mexico)
 12H  06/0600Z 15.3N 123.1W  105 KT 120 MPH - Category 3 (WSW Isla Socorro, Mexico)
 24H  06/1800Z 14.9N 124.3W  100 KT 115 MPH - Category 3 (WSW Isla Socorro, Mexico)
 36H  07/0600Z 14.8N 125.4W  100 KT 115 MPH - Category 3 (WSW Cabo San Lucas, Mexico)
 48H  07/1800Z 15.1N 126.3W   90 KT 105 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 72H  08/1800Z 16.7N 126.5W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 96H  09/1800Z 18.9N 123.9W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
120H  10/1800Z 22.0N 119.3W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 800 AM PDT Fri Oct 05 2018

Hurricane Sergio – GOES-16 images and a 1054 UTC ATMS microwave overpass indicate that Sergio’s 25 n mi eye has become a bit ragged this morning, and has continued to cool. Despite the eye’s irregularity, the inner core convection is still intact and is producing very cold (-76C) cloud tops. Primarily due to the eye adjustment temperature, however, the subjective and objective satellite intensity estimates, as well as a recent SATCON analysis, have again decreased to 95-100 kt, and the initial intensity is subsequently lowered to 100 kt.

Although due to the possibility of unpredicted inner core structure changes in the short term which could cause Sergio to strengthen again, the current weakening trend is expected to continue through day 5 as Sergio moves toward decreasing oceanic temperatures and into a stabilizing surrounding atmosphere. The statistical intensity guidance as well as the large-scale models show increasing southwesterly shear entering the picture after 72 hours. This should also aid in the forecast weakening trend. The official forecast is just an update of the previous one and follows the NOAA-HCCA consensus and is just above the Florida State Superensemble.

Sergio is moving a little left of the previous 6-hr motion…now westward, or 280/7 kt. A gradual turn toward the west-southwest during the next 36 hours is expected as high pressure located north-northeast of the Hawaiian Islands builds to the north of Sergio. Over the weekend, a decrease in forward speed and a turn toward the northwest is forecast as the aforementioned mid-level high retrogrades in response to an amplifying trough over the southwestern United States and Baja California peninsula. Beyond the 72 hour period, increasing southwesterly mid-tropospheric flow should induce a northeastward accelerated motion through the remaining portion of the forecast. The NHC forecast is adjusted a little toward the south of the last advisory through 72 hours to agree more with the various consensus models, but is quite similar in motion and forward speed beyond that period.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 15.9N 121.8W  100 KT 115 MPH - Category 2 (WSW Isla Socorro, Mexico)
 12H  06/0000Z 15.8N 122.7W   95 KT 110 MPH - Category 2 (WSW Isla Socorro, Mexico)
 24H  06/1200Z 15.5N 123.8W   90 KT 105 MPH - Category 2 (WSW Isla Socorro, Mexico)
 36H  07/0000Z 15.2N 125.0W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  07/1200Z 15.3N 126.0W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 72H  08/1200Z 16.5N 126.8W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 96H  09/1200Z 18.5N 125.0W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)
120H  10/1200Z 21.5N 120.8W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 200 PM PDT Thu Oct 04 2018

Hurricane Sergio remains an impressive hurricane. Although the cloud pattern is still symmetric and well organized, the eye has become ragged and cloud filled at times. The current satellite intensity estimates range from 102 to 127 kt, and the initial intensity is set to 115 kt based on a blend of these data. The environmental conditions along Sergio’s future path are expected to gradually become less favorable during the next several days, with decreasing mid-level humidities, cooler SSTs, and a slight increase in wind shear. In response, all of the models show a gradual weakening trend through the period, and the NHC forecast does as well. This forecast lies near the intensity consensus aids and is largely an update of the previous one.

The hurricane is still moving to the northwest at 8 kt. A gradual turn to the left, or west, is expected during the next couple of days as a mid-level ridge builds to the north-northwest of Sergio. Late this weekend, a decrease in forward speed is expected as the ridge retreats in response to a large trough over the southwestern United States. This change in the steering pattern should cause the cyclone to turn northeastward by the end of the forecast period. The only notable change in the track forecast is a sharper northward and northeastward turn at days 4 and 5, to come in better agreement with the latest consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 15.5N 119.9W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 12H  05/0600Z 15.9N 120.8W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 24H  05/1800Z 16.1N 121.9W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 36H  06/0600Z 15.9N 123.2W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  06/1800Z 15.7N 124.5W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 72H  07/1800Z 15.7N 126.6W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 96H  08/1800Z 16.8N 127.4W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)
120H  09/1800Z 18.3N 126.2W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)

NWS National Hurricane Center Miami FL 800 AM PDT Thu Oct 04 2018

Hurricane Sergio remains a strong hurricane this morning, with subjective Dvorak estimates range from 5.5 (102 kt) to 6.5 (127 kt). While some slightly drier air has been ingested into the eyewall, cloud top temperatures have cooled recently and Sergio appears poised to once again close off this dry air channel. Based on these data, the initial intensity is held at 120 kt. The intensity forecast is mostly a continuation of the previous advisory, but is slightly lower after 24 hours to reflect a blend of HCCA and other consensus aids. Vertical wind shear from GFS/SHIPS is forecast to remain at or below approximately 10 kt through 48 hours before increasing to above 15 kt by Saturday. The primary limiter on Sergio’s intensity appears to be SSTs which will drop off gradually, especially by the end of the forecast.

Sergio is continuing to move northwestward around the mid-level ridge which extends into the Pacific off of Mexico. The initial motion is 320/8 kt. Objective track guidance is in fairly good agreement on a gradual turn toward the west tonight and Friday in response to a second ridge which builds in from the west. Guidance remains in decent agreement on Sergio then turning back northeastward by the end of the forecast period as this ridge lifts northward and a highly-amplified mid-level trough digs into western North America. The official track forecast is very similar to the previous advisory through day 4 with a small shift eastward thereafter to reflect a slightly earlier northeast turn in the guidance. This track philosophy is supported by essentially all of the ECMWF/GFS ensemble members as well.Hurricane Sergio Distances 0500 Hours October 4 2018

FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 15.0N 119.3W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 12H  05/0000Z 15.6N 120.2W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 24H  05/1200Z 16.0N 121.5W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 36H  06/0000Z 16.0N 122.8W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 48H  06/1200Z 15.7N 124.1W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 72H  07/1200Z 15.6N 126.6W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 96H  08/1200Z 16.3N 128.2W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
120H  09/1200Z 17.9N 127.6W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)

NWS National Hurricane Center Miami FL 200 AM PDT Thu Oct 04 2018

Hurricane Sergio intensity is estimated to have increased just a little more this morning, and it remains a powerful category 4 hurricane. Subjective Dvorak estimates are T6.5/127 kt from TAFB and T6.0/115 kt from SAB, and the initial intensity is raised to 120 kt, which is a blend of these numbers and very close to the latest objective ADT estimate. Sergio’s maximum winds are expected to change little over the next 12-24 hours, and the hurricane’s intensity could very well be modulated by difficult-to-forecast internal processes such as eyewall replacement cycles. After 48 hours, an increase in shear and gradually cooling sea surface temperatures should result in some weakening, especially when Sergio moves more slowly at the end of the forecast period and possibly upwells some cooler water from below. The updated NHC intensity forecast is nudged downward during the first 48 hours to follow the latest consensus aids, but no changes were made to the previous forecast beyond 48 hours.

The hurricane’s initial motion is northwestward, or 320/7 kt, with Sergio located along the southwestern periphery of a mid-level ridge extending westward from Mexico. This ridge is expected to build westward and connect to another mid-level ridge located near the central Pacific Ocean, forcing Sergio to turn westward, or even south of due west, between 36-72 hours. By days 4 and 5, a large trough near the west coast of the United States should have greater influence, causing Sergio to slow down and turn northward by the end of the forecast period. The track guidance is tightly clustered for much of the forecast period, although a notable southward shift among the guidance, especially from the ECMWF, required a bit of a southward shift in the official forecast as well.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0900Z 14.4N 118.8W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 12H  04/1800Z 15.1N 119.7W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 24H  05/0600Z 15.8N 121.0W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 36H  05/1800Z 16.0N 122.2W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 48H  06/0600Z 15.8N 123.5W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 72H  07/0600Z 15.5N 126.2W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 96H  08/0600Z 16.0N 128.5W   80 KT  90 MPH - Category 1 (ESE Hilo, Hawaii)
120H  09/0600Z 17.5N 128.5W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 PM PDT Wed Oct 03 2018

Hurricane Sergio satellite presentation continues to look impressive this afternoon. Several mesovortices can be identified rotating within the eye. However, the eye is somewhat obscured by upper-level clouds and the eyewall edge is not clearly defined. Based on a blend of subjective Dvorak estimates from TAFB and SAB, the advisory intensity estimate is held at 110 kt, which is the same as in the previous advisory. Sergio should remain in quite favorable atmospheric and oceanic conditions for the next day or two, and additional strengthening is expected through Thursday. By Friday, Sergio will be moving over slightly cooler sea-surface temperatures and through a drier mid-level air mass, which should initiate gradual weakening.

Sergio is currently heading toward the northwest, or 305/8 kt. By Friday and Saturday, the storm is forecast to slow and turn west-northwestward to westward while a mid-level ridge builds to the north and northwest of the hurricane. The official track forecast lies close to the equally weighted dynamical model consensus, TVCN.

It is of interest to note that a small disturbance currently located a few hundred n mi to the west-southwest of Sergio is expected to be drawn into the larger circulation of the hurricane overnight.Hurricane Sergio Distances 1100 Hours October 3 2018

FORECAST POSITIONS AND MAX WINDS

INIT  03/2100Z 13.3N 117.9W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 12H  04/0600Z 14.1N 118.8W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 24H  04/1800Z 15.2N 120.1W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 36H  05/0600Z 15.8N 121.2W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 48H  05/1800Z 16.1N 122.4W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  06/1800Z 15.8N 124.9W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 96H  07/1800Z 15.6N 127.5W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
120H  08/1800Z 16.4N 129.2W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 AM PDT Wed Oct 03 2018

Hurricane Sergio  – There has been little change to the overall organization of the hurricane overnight. Recent microwave data continue to show that the eyewall is open to the northwest and that there is some northeast to southwest displacement of the low- and mid-level centers due to northeasterly shear. A blend of the various objective and subjective satellite intensity estimates yields an initial intensity of 100 kt. The global models suggest that the shear currently affecting Sergio will decrease over the next 24 to 36 hours, which should allow for strengthening. The NHC intensity forecast calls for Sergio to reach peak intensity in about 36 hours, and it is near the upper-end of the intensity guidance. After that time, slightly cooler waters and the entrainment of drier mid-level air are forecast to cause gradual weakening, but Sergio is expected to remain a hurricane through the entire forecast period.

Sergio is moving west-northwestward or 300 degrees at 10 kt. The western portion of a mid-level ridge to the north of Sergio is expected to weaken during the next day or so, which should cause the hurricane to move northwestward at a slightly slower forward speed. By the weekend, another ridge is predicted to build to the northwest of Sergio, and this should force the hurricane to turn westward. The track guidance is in good agreement through 48 hours, but there is increasing cross-track spread thereafter. The updated NHC forecast is near the middle of the guidance envelope for the first two days, but lies between the more northern GFS solution and the consensus aids thereafter.Hurricane Sergio Distances 2300 Hours October 2 2018

FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 12.3N 116.7W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 12H  03/1800Z 13.0N 117.8W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 24H  04/0600Z 14.0N 119.0W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 36H  04/1800Z 15.0N 120.3W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 48H  05/0600Z 15.8N 121.5W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  06/0600Z 16.3N 124.0W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 96H  07/0600Z 16.3N 127.0W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
120H  08/0600Z 16.8N 130.0W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 PM PDT Tue Oct 02 2018

Hurricane Sergio has intensified significantly today. The eye of the hurricane has become better defined, and is embedded in very cold convective cloud tops. Outer banding features are also well defined. Upper-tropospheric outflow is strong over the western and southern portions of the circulation, and a little restricted to the northeast. The advisory intensity is set, probably conservatively, to 100 kt in agreement with a Dvorak estimate from SAB. Only modest northeasterly shear is expected to affect Sergio over the next few days. That, along with warm waters and a very moist middle troposphere, should be conducive for further strengthening. The official forecast is near the upper end of the intensity guidance model suite.

The system continues moving mostly westward, or 280/11 kt. There is little change to the track forecast reasoning from the previous couple of advisory packages. A mid-level ridge to the north of Sergio should weaken within the next 12 to 24 hours as a broad trough drops in from the northwest. These changes in the steering flow should cause the hurricane to turn toward the west-northwest by this evening or tonight, and to begin moving northwestward on Wednesday. The official track forecast is is very similar to the previous one and, again, follows the latest multi-model consensus.

Some slight enlargements to the wind radii were made over the eastern semicircle of Sergio based on scatterometer data.Hurricane Sergio Distances 0500 Hours October 2 2018

FORECAST POSITIONS AND MAX WINDS

INIT  02/2100Z 11.2N 115.1W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 12H  03/0600Z 12.0N 116.3W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 24H  03/1800Z 13.1N 117.8W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 36H  04/0600Z 14.2N 119.1W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 48H  04/1800Z 15.2N 120.5W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 72H  05/1800Z 16.3N 123.0W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 96H  06/1800Z 16.5N 126.0W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
120H  07/1800Z 16.5N 128.5W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)

NWS National Hurricane Center Miami FL 900 AM MDT Tue Oct 02 2018

Hurricane Sergio – The cloud pattern of Sergio continues to become better organized on satellite imagery. The hurricane has a very cold cloud-topped central dense overcast, with a developing eye, surrounded by curved banding features. The current intensity is set at 85 kt based on a blend of subjective and objective Dvorak estimates. Sergio is forecast to continue moving over warm waters, under moderate vertical shear and within a moist mid-level airmass for the next few days. Therefore, additional strengthening is likely, and Sergio will probably become a major hurricane in a day or so. The official intensity forecast is close to the latest model consensus, IVCN.

The hurricane has been moving westward at a slightly slower pace, and the motion estimate is 270/11 kt. A mid-level ridge to the north of the system will soon be eroding, due to a trough dropping in from the northwest. This change in steering currents should result in Sergio turning toward the west-northwest today followed by a northwestward motion in 2-3 days. In the latter part of the forecast period, the ridge builds back in, and this is likely to cause the tropical cyclone to turn back toward the west. The NHC track forecast is similar to the previous one and follows the dynamical model consensus, TVCN, fairly closely.

FORECAST POSITIONS AND MAX WINDS

INIT  02/1500Z 10.6N 114.0W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 12H  03/0000Z 11.2N 115.3W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 24H  03/1200Z 12.2N 116.9W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 36H  04/0000Z 13.3N 118.2W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 48H  04/1200Z 14.3N 119.6W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  05/1200Z 15.9N 122.1W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 96H  06/1200Z 16.5N 125.0W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
120H  07/1200Z 16.5N 128.0W   80 KT  90 MPH - Category 1 (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 300 AM MDT Tue Oct 02 2018

Hurricane Sergio – Geostationary satellite imagery indicates that Sergio continues to strengthen. The center is located within a fairly symmetric CDO with cloud tops of -70 to -80 degrees C. Earlier microwave data showed a well-defined eye and inner core, but a more recent AMSU overpass suggests that there has been some slight erosion of the eastern portion of the eye, possibly due to some intrusion of dry mid-level air. Dvorak intensity estimates ranged from 75 to 90 kt, and the initial intensity has been increased to a possibility conservative 75 kt for this advisory.

The intensity forecast remains somewhat uncertain. Although Sergio has developed an inner core and strengthened during the past 12 hour or so, the dynamical models suggest northeasterly shear will increase over the hurricane today. This is expected to temper the intensification somewhat over the next 12-24 hours, however, most of the guidance shows at least gradual strengthening during the next day or so. The NHC intensity forecast calls for a gradual increase in wind speed over the next 36-48 hours, and is close to the IVCN model consensus. After 72 h, cooler waters and the entrainment of drier air is expected to cause gradual weakening.Hurricane Sergio Distances 2300 Hours October 1 2018

Sergio is moving slightly south of due west or 265/12 kt. The hurricane is currently located to the south of a mid-level ridge, and Sergio should continue westward today. The global models show the western portion of the ridge weakening over the next several days, which should cause Sergio to turn west-northwestward, then northwestward on Wednesday. By late in the week, another ridge is predicted to build to the northwest of Sergio and the hurricane is forecast to turn back toward the west. The overall guidance envelope has changed little this cycle, and the new NHC track is similar to the previous advisory and close to the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  02/0900Z 10.7N 113.2W   75 KT  85 MPH - Category 1 (WSW Acapulco, Mexico)
 12H  02/1800Z 10.9N 114.7W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 24H  03/0600Z 11.7N 116.4W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 36H  03/1800Z 12.7N 117.8W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  04/0600Z 13.8N 119.0W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  05/0600Z 15.6N 121.7W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 96H  06/0600Z 16.5N 124.6W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
120H  07/0600Z 16.7N 127.5W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)

NWS National Hurricane Center Miami FL 300 PM MDT Mon Oct 01 2018

Tropical Storm Sergio  has not strengthened like the models and NHC have predicted up to this point. Although the storm continues to have a well-defined curved band over the south and east portions of the circulation, there are pronounced dry slots that have entrained into the inner core. Recent microwave images show a well-defined low-level eye, but the mid-level structure is less organized now as compared to several hours ago. The initial intensity is again held at 60 kt, in agreement with an average of the Dvorak classifications from TAFB and SAB.

The intensity forecast remains challenging. The wind shear around Sergio is expected to be low for the next several days, besides for a brief increase in the 24- to 48-hour time period. These conditions and warm SSTs beneath the cyclone during the next few days support strengthening. However, as mentioned above, the storm has been struggling with dry air entrainment and that could continue to plague the system. The latest models continue to show steady strengthening, and the NHC forecast does likewise. However, this forecast shows a slower rate of intensification in the short term. Beyond a few days, a combination of slightly lower SSTs and a decrease in moisture should cause a slow weakening trend. The NHC intensity forecast is in best agreement with the IVCN model. Tropical Storm Sergio Distances 1100 Hours October 1 2018

Sergio is moving just south of due west at 11 kt. A westward motion at about the same forward speed is expected during the next day or so while the storm remains on the south side of a mid-level ridge. A turn to the west-northwest is expected by late Tuesday followed by a northwestward motion on Wednesday as the western portion of the mid-level ridge erodes due to a large scale mid- to upper-level trough near the southwestern U.S. By the end of the forecast period, a ridge is expected to build to the north of Sergio, which should cause a turn back to the left. The models have shifted to the south and west this cycle, and the NHC track forecast has been adjusted in those directions.

FORECAST POSITIONS AND MAX WINDS

INIT  01/2100Z 11.3N 111.0W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  02/0600Z 11.3N 112.7W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  02/1800Z 11.6N 114.8W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 36H  03/0600Z 12.4N 116.5W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  03/1800Z 13.5N 118.0W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 72H  04/1800Z 15.4N 120.2W  100 KT 115 MPH - Category 3 (WSW Manzanillo, Mexico)
 96H  05/1800Z 17.0N 123.0W   95 KT 110 MPH - Category 2 (WSW Manzanillo, Mexico)
120H  06/1800Z 17.8N 126.0W   85 KT 100 MPH - Category 2 (WSW Manzanillo, Mexico)

NWS National Hurricane Center Miami FL 900 AM MDT Mon Oct 01 2018

Tropical Storm Sergio is almost a hurricane. Satellite images indicate that the central convection has been increasing in intensity during the past several hours, but there are still no indications of an eye in that data. Microwave imagery does show an eye feature, however. The outer bands are not particularly well organized, and there are some dry slots beyond the inner core. The initial intensity is held at 60 kt, following a blend of the latest Dvorak estimates.

As mentioned in the previous discussion, the models have been too bullish on Sergio strengthening during the past couple of days. This could be due to the aforementioned dry slots that were not well predicted by both the statistical and dynamical guidance. Looking ahead to the next several days, the environmental conditions are mixed. The wind shear and SSTs appear conducive for strengthening during the next couple of days, so steady intensification is predicted during that time period. However, as seen during the past day or two, dry air could slow the intensification rate. Beyond a couple of days, the models show a brief increase in shear and a steady decrease in mid-level moisture and SSTs. These conditions will likely end the opportunity for strengthening and cause a slow weakening trend. The NHC intensity forecast is about the same as the previous one, and it lies between the usually reliable HCCA and IVCN consensus models.

Sergio is moving westward at 10 kt steered by a mid-level ridge to its north and northeast. A continued westward motion is expected for another day followed by a turn to the west-northwest and then the northwest as the western side of the ridge weakens due to a large-scale trough near the southwestern United States. By the end of the forecast period, a ridge is expected to build to the north of Sergio, which should cause a turn back to the left. The models are in very good agreement overall, and little change has been made to the previous forecast track.

FORECAST POSITIONS AND MAX WINDS

INIT  01/1500Z 11.5N 109.5W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  02/0000Z 11.4N 111.2W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  02/1200Z 11.7N 113.4W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 36H  03/0000Z 12.4N 115.3W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  03/1200Z 13.3N 116.8W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  04/1200Z 15.3N 119.3W  100 KT 115 MPH - Category 3 (WSW Manzanillo, Mexico)
 96H  05/1200Z 17.0N 121.8W   95 KT 110 MPH - Category 2 (WSW Manzanillo, Mexico)
120H  06/1200Z 18.0N 124.3W   85 KT 100 MPH - Category 2 (WSW Manzanillo, Mexico)

NWS National Hurricane Center Miami FL 300 AM MDT Mon Oct 01 2018

Tropical Storm Sergio – Convective pattern in infrared satellite imagery has waxed and waned since the previous advisory. A previously large, solid curved band has become broken during the past couple of hours, but the comma head or CDO of the cloud band has increased in size while cloud tops have cooled to near -80C. Passive microwave imagery indicates that within the comma head feature an 18-20-nmi-wide closed eye has developed in the low-levels, while the mid- and upper-level eye remains open and ragged. Subjective intensity estimates remain T3.5/55 kt from TAFB and SAB. However, based on the well-defined, low-level eye, the intensity has been nudged upward to 60 kt for this advisory.

The initial motion is now 270/12 kt, based primarily on microwave satellite fix positions. Sergio is forecast to move generally westward for the next 36 hours or so, under the influence of a strong, deep-layer ridge located to the north of the cyclone. By 48 hours, a mid- to upper-level trough moving southeastward along and offshore of the western U.S. is expected to gradually erode the western part of the ridge, allowing Sergio turn west-northwestward on day 2 and move northwestward on days 3-5. The new NHC track forecast is similar to the previous advisory track, and lies near a blend of the consensus models TCVA, TVCE, and HCCA.Tropical Storm Sergio Distances 2300 Hours September 30 2018

Both the statistical and dynamical intensity models have been too bullish on Sergio strengthening during the past 36 hours. Although the environment is quite moist with near 80 percent mid-level humidity values, a pronounced dry intrusion eroding the inner-core convection remains. By the time the dry air mixes out, modest northerly vertical wind shear is expected to hinder development in the 24-48 hour period. By 72 hours and beyond, the shear is forecast to decrease below 10 kt, but Sergio will be moving over cooler waters at that time. Given the mixed environmental signals, the official intensity is on the conservative side and remains well below the stronger HCCA and FSSE models, and closer to the simple consensus model IVCN.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 11.5N 108.6W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  01/1800Z 11.4N 110.3W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  02/0600Z 11.5N 112.5W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 36H  02/1800Z 12.0N 114.5W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  03/0600Z 12.8N 116.1W  100 KT 115 MPH - Category 3 (WSW Manzanillo, Mexico)
 72H  04/0600Z 14.9N 118.8W  100 KT 115 MPH - Category 3 (WSW Manzanillo, Mexico)
 96H  05/0600Z 16.8N 121.2W   95 KT 110 MPH - Category 2 (WSW Manzanillo, Mexico)
120H  06/0600Z 17.9N 123.2W   90 KT 105 MPH - Category 2 (WSW Manzanillo, Mexico)

NWS National Hurricane Center Miami FL 300 PM MDT Sun Sep 30 2018

Tropical Storm Sergio – Satellite imagery over the past several hours as well as microwave and scatterometer data indicate that the center of Sergio is farther south than previously analyzed. The deep convection near the center has become ragged in appearance and elongated from east-west. However, microwave data continues to show a well-defined mid-level circulation, and satellite intensity estimates are unanimously supporting 55 kt, which will be the initial intensity for this advisory.

The initial motion estimate is now 260/11 kt, partially due to adjustment of the center farther south. Otherwise, there are no changes in the forecast track philosophy from the previous advisory. For the next couple of days, Sergio should move generally westward or just south of due west around the southern periphery of a large deep-layer subtropical ridge extending from Mexico westward across the eastern Pacific. By 48 hours, a mid- to upper-level trough moving southeastward along and offshore of the western U.S. will erode the western part of the ridge. This will allow the cyclone to turn west-northwestward to northwestward from 48- to 96-hours with a gradual decrease in forward speed. Very near the end of the forecast period, the trough should shift eastward and low- to mid-level ridging should build to the northwest of the cyclone. This pattern change should induce a more westward turn by 120 hours.

Despite the current ragged appearance of the cyclone, the environment of low-shear, high-moisture, and warm waters are expected to support a period of rapid intensification sometime within the next 36 hours or so. By 36 hours, northeasterly shear is expected to develop over the storm and increase to 25 kt by 48 hours. This should at least limit the rate of intensification if not weaken the cyclone slightly from 48- to 72-hours. After that time, global models indicate that the shear will lessen to under 10 kt for the remainder of the forecast period. There may be a window of time beginning after 72 hours where some additional strengthening could occur. By 96 hours, the system will then be moving over waters of 26-27 C very near a gradient of cooler SSTs just to the north. The current intensity forecast calls for a steadying of intensity after the shear abates, then a slow weakening trend commences by the end of the period due to cooler SSTs. Other than a slight delay in Sergio becoming a hurricane, the intensity forecast is essentially the same as the previous forecast and remains close to the dynamical model consensus. Based on this intensity forecast, Sergio is still forecast to become a major hurricane on Tuesday.

FORECAST POSITIONS AND MAX WINDS

INIT  30/2100Z 11.5N 106.3W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  01/0600Z 11.4N 108.1W   65 KT  75 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  01/1800Z 11.2N 110.4W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 36H  02/0600Z 11.4N 112.6W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  02/1800Z 11.9N 114.5W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  03/1800Z 13.8N 117.5W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 96H  04/1800Z 16.0N 120.0W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
120H  05/1800Z 17.3N 122.0W   90 KT 105 MPH - Category 2 (WSW Manzanillo, Mexico)

NWS National Hurricane Center Miami FL 1000 AM CDT Sun Sep 30 2018

Tropical Storm Sergio – Recent microwave data indicate that the inner core of Sergio continues to become better defined, with an eye-like feature evident. However, this eye feature is not yet apparent in geostationary satellite imagery. Deep convection with cloud top temperatures of -70 C are concentrated around the storm’s center as well as along a prominent banding feature on the south side. The average of available satellite intensity estimates support an intensity of 50 kt, which will be the initial intensity for this advisory.

The initial motion estimate is 270/11 kt. There continues to be no significant changes in the forecast track philosophy from the previous few forecasts. For the next couple of days, Sergio should move generally westward or just south of due west around the southern periphery of a large deep-layer subtropical ridge that extends from Mexico westward across the eastern Pacific. By 48 hours, a mid- to upper-level trough will move southeastward along and offshore the western U.S., which will erode the ridge from the west. This will allow the cyclone to turn west-northwestward then northwestward from 48- to 96-hours with a gradual decrease in forward speed. Thereafter, the trough should shift eastward and low- to mid-level ridging should build to the northwest of the cyclone. This pattern change should induce a more westward turn toward the end of the forecast period.

Sergio will remain in an environment of low-shear, high-moisture, and over warm waters for the next 24 hours or so, which should result in rapid intensification. This is in agreement with rapid intensification indices from the SHIPS model of 40 to 45 percent over the next 24 hours. By 36 hours, northeasterly shear is expected to develop over the storm environment and increase to 25 kt by 48 hours. This should at least limit the rate of intensification if not weaken the cyclone slightly from 48- to 72-hours. After that time, global models indicate that the shear will lessen to under 10 kt by 96 hours, but by that time the system will be moving over waters of 26-27 C very near a gradient of cooler SSTs just to the north. Based on this, the intensity remains steady from 72- to 96-hours and then shows slow weakening by the end of the period. The intensity forecast is a little higher that the previous advisory, and is close to the dynamical model consensus. Based on this intensity forecast, Sergio is forecast to become a major hurricane by Tuesday.

FORECAST POSITIONS AND MAX WINDS

INIT  30/1500Z 12.1N 105.4W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  01/0000Z 12.1N 107.0W   65 KT  75 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  01/1200Z 11.8N 109.2W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 36H  02/0000Z 11.7N 111.4W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  02/1200Z 12.0N 113.5W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  03/1200Z 13.6N 116.6W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 96H  04/1200Z 16.0N 119.0W  100 KT 115 MPH - Category 3 (WSW Manzanillo, Mexico)
120H  05/1200Z 17.5N 121.5W   90 KT 105 MPH - Category 2 (WSW Manzanillo, Mexico)

NWS National Hurricane Center Miami FL 400 AM CDT Sun Sep 30 2018

Tropical Storm Sergio –  Microwave and infrared satellite images, along with scatterometer wind data, indicate that Sergio has continued to become better organized, with strong convection now more concentrated near the center. However, scatterometer data showed that the inner-core wind field is still rather loose and not particularly well-defined quite yet. The initial intensity has been increased to 45 kt based on a Dvorak satellite intensity estimate of T3.0/45 kt from TAFB and SAB, which is supported by a 0536 UTC ASCAT pass that contained a few 45-kt vectors east of the center.

The initial motion estimate is 270/10 kt. There is no significant change to the previous forecast track or reasoning. For the next 48 hours or so, Sergio should move generally westward along the southern periphery of a large, deep-layer subtropical ridge that extends from Mexico westward across the eastern and central Pacific. By 72 hours, a broad mid- to upper-level trough is forecast to drop southward and southeastward over the southwestern U.S. and the northeastern Pacific, producing a break in the ridge which will allow Sergio to move toward the northwest at a slower forward speed through 120 hours. The new NHC track forecast is similar to but slightly south of the previous advisory track, and lies close to an average of the consensus models TVCE, HCCA, and FSSE.

Sergio is forecast to remain in a low-shear, warm-water, and high-moisture environment for the next 36 hours or so, during which time rapid intensification is expected. In the 48- to 72-hour period, the vertical shear is forecast by the GFS and ECMWF global models to increase from the northeast at around 25 kt, which should act to cap the strengthening process, and possibly even induce some weakening. By 96 and 120 hours, the shear is expected to decrease to 5 kt or less, which would favor re-strengthening. However, due to the uncertainty in how much Sergio’s inner-core wind field will be disrupted by the aforementioned strong shear, the intensity forecast is simply leveled off at 95 kt at 72 hours and beyond. The official intensity forecast is slightly higher than the previous advisory and closely follows the IVCN consensus model, which is lower than the more robust HCCA and FSSE models, which bring Sergio to near category 4 strength in 36-48 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z 12.0N 104.3W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  30/1800Z 12.0N 105.9W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 24H  01/0600Z 11.9N 108.2W   75 KT  85 MPH - Category 1 (WSW Acapulco, Mexico)
 36H  01/1800Z 11.6N 110.4W   90 KT 105 MPH - Category 1 (WSW Acapulco, Mexico)
 48H  02/0600Z 11.7N 112.4W  100 KT 115 MPH - Category 2 (WSW Acapulco, Mexico)
 72H  03/0600Z 13.0N 115.9W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 96H  04/0600Z 15.2N 118.6W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
120H  05/0600Z 17.1N 120.8W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)

NWS National Hurricane Center Miami FL 1030 AM CDT Sat Sep 29 2018

Tropical Storm Sergio – Satellite imagery indicates that convection associated with the low pressure area south-southwest of Acapulco has continued to become better organized, with the low-level center embedded under the convective overcast and near a developing complex of bands in the southeastern semicircle. Based on this and continuity from earlier scatterometer data, advisories are being initiated on Tropical Storm Sergio with 35 kt winds.

Sergio is expected to be in an environment of light vertical shear and high humidity, and over warm sea surface temperatures for the next 3 days or so, which should result in steady strengthening. Near the end of the forecast period, the storm may encounter increasing northeasterly shear which could limit intensification. The intensity forecast, which is near the intensity consensus, calls for steady strengthening through 96 h, with Sergio becoming a hurricane by 48 h.Tropical Storm Sergio Satellite 1000 Hours September 29 2018

The initial motion is a somewhat uncertain 285/11. Sergio should be steered generally westward for the next three days or so by the subtropical ridge over Mexico. After that time, the cyclone should approach a weakness in the ridge caused by a large mid- to upper-level trough over California, and this should lead to a turn toward the northwest. The track guidance is in good agreement with this scenario, and the forecast track lies near the HCCA corrected consensus model.

FORECAST POSITIONS AND MAX WINDS

INIT  29/1530Z 12.4N 102.1W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  30/0000Z 12.7N 103.5W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, Mexico)
 24H  30/1200Z 12.9N 105.3W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, Mexico)
 36H  01/0000Z 12.9N 107.3W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, Mexico)
 48H  01/1200Z 12.8N 109.3W   65 KT  75 MPH - Category 1 (WSW Acapulco, Mexico)
 72H  02/1200Z 13.0N 113.5W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 96H  03/1200Z 15.0N 117.0W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
120H  04/1200Z 16.5N 119.0W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)

NWS Central Pacific Hurricane Center Honolulu HI 800 AM HST Thu Sep 27 2018

For the central North Pacific…between 140W and 180W:

Tropical Storm Sergio forming  – Showers and thunderstorms associated with a low level circulation center located about 700 miles southeast of Hilo, Hawaii continues to become better organized. Environmental conditions remain conducive for this system to become a tropical depression this week while it moves west 10 to 15 mph. * Formation chance through 48 hours…Medium…60 percent. * Formation chance through 5 days…High…90 percent.

NWS Central Pacific Hurricane Center Honolulu HI 200 AM HST Thu Sep 27 2018

For the central North Pacific…between 140W and 180W:

Showers and thunderstorms associated with a low level circulation center located about 860 miles southeast of Hilo, Hawaii  are becoming more organized. Environmental conditions remain conducive for gradual development of this system over the next few days as it moves westward across the central Pacific. * Formation chance through 48 hours…low…40 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Tue Sep 25 2018

For the eastern North Pacific…east of 140 degrees west longitude:

The National Hurricane Center is issuing advisories on newly formed Tropical Depression Twenty-E, located several hundred miles south-southwest of Manzanillo, Mexico.

A trough of low pressure located a little over 1400 miles east-southeast of Hilo, Hawaii, is producing disorganized shower activity. Some gradual development of this system is possible through the end of the week while it moves westward into the central Pacific. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…medium...50 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Fri Sep 21 2018

For the eastern North Pacific…east of 140 degrees west longitude:

An area of low pressure is expected to form in a couple of days well to the south of the southern coast of Mexico. Some slow development is possible early next week while the system moves nearly parallel and well offshore of the southwestern coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.

Tropical Storm Sergio Forming – NWS National Hurricane Center Miami FL 500 PM PDT Wed Sep 19 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Depression Nineteen-E located over the Gulf of California.

1. An elongated area of low pressure located about 850 miles southwest of the southern tip of the Baja California peninsula continues to produce disorganized showers and thunderstorms. Some slow development of this system is possible before upper-level winds become unfavorable for development late this weekend. This disturbance is expected to move west-northwestward during the next several days. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…30 percent.

2. An area of disturbed weather is expected to form in a couple of days well to the south of the Gulf of Tehuantepec. Some slow development of this system is possible late this weekend and early next week while the disturbance moves nearly parallel to the southwestern coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS Weather Prediction Center College Park MD 1100 AM PDT Wed Sep 19 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on newly formed Tropical Depression Nineteen-E located over the southern Gulf of California.

1. An elongated area of low pressure located about 850 miles southwest of the southern tip of the Baja California peninsula has become less organized today. Environmental conditions could be conducive for some gradual development of this system during the next few days while it moves slowly west-northwestward or northwestward. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…30 percent.

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