Tropical Storm John

Tropical Storm John Track 0200 Hours August 10 2018
Tropical Storm John Track 0200 Hours August 10 2018
Tropical Storm John Satellite 0800 Hours August 10 2018
Tropical Storm John Satellite 0800 Hours August 10 2018

NWS National Hurricane Center Miami FL 800 AM PDT Fri Aug 10 2018

John’s convection vanished around 0430 UTC, and the cyclone now consists of a tight swirl of low clouds moving over a 22 degree Celsius ocean. Given the lack of convection, the system has been classified as a remnant low with 30-kt winds in this last advisory. The low is moving toward the northwest at 9 kt, and this general motion will likely continue until dissipation in a couple of days.

Swells associated with the remnants of John continue to affect portions of the coasts of the Baja California peninsula and southern California, but will soon begin to subside. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

This is the last NHC advisory on John.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 26.8N 121.1W   30 KT  35 MPH...POST-TROPICAL - (SE of Campamento Militar Isla Guadalupe , Mx)
 12H  11/0000Z 27.5N 122.5W   25 KT  30 MPH...POST-TROP/REMNT LOW - (SE of Campamento Militar Isla Guadalupe , Mx)
 24H  11/1200Z 28.2N 123.7W   25 KT  30 MPH...POST-TROP/REMNT LOW - (SE of Campamento Militar Isla Guadalupe , Mx)
 36H  12/0000Z 28.5N 124.5W   25 KT  30 MPH...POST-TROP/REMNT LOW - (SE of Campamento Militar Isla Guadalupe , Mx)
 48H  12/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 AM PDT Fri Aug 10 2018

Convection associated with John has decreased significantly during the past several hours as the cyclone moves over progressively cooler water. Recent scatterometer data suggests that the maximum sustained winds have decreased to near 40 kt. Continued weakening is forecast as John moves over even colder water, and the system is now forecast to weaken to a depression in less than 24 h and to a remnant low in 24-36 h. After that, the remnant low will gradually spin down until it dissipates early next week.

The initial motion is now 310/9. This motion should continue with a decrease in forward speed during the next couple of days, followed by a turn toward the north before the system dissipates. The new forecast track is near the consensus models through 48 h and is a little to the west of them from 48-72 h.

Swells associated with John continue to affect portions of the coast of the Baja California peninsula and are beginning to reach portions of the southern California coast. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0900Z 25.9N 119.9W   40 KT  45 MPH - Tropical Storm - (SE of San Juanico, Mx)
 12H  10/1800Z 26.7N 121.3W   35 KT  40 MPH - Tropical Storm - (SE of Bahía Asunción, Mx)
 24H  11/0600Z 27.4N 122.8W   30 KT  35 MPH - Tropical Storm - (SE of Campamento Militar Isla Guadalupe, Mx)
 36H  11/1800Z 28.0N 123.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  12/0600Z 28.6N 124.4W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  13/0600Z 30.5N 124.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  14/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 AM PDT Fri Aug 10 2018

Convection associated with John has decreased significantly during the past several hours as the cyclone moves over progressively cooler water. Recent scatterometer data suggests that the maximum sustained winds have decreased to near 40 kt. Continued weakening is forecast as John moves over even colder water, and the system is now forecast to weaken to a depression in less than 24 h and to a remnant low in 24-36 h. After that, the remnant low will gradually spin down until it dissipates early next week. The initial motion is now 310/9. This motion should continue with a decrease in forward speed during the next couple of days, followed by a turn toward the north before the system dissipates. The new forecast track is near the consensus models through 48 h and is a little to the west of them from 48-72 h. Swells associated with John continue to affect portions of the coast of the Baja California peninsula and are beginning to reach portions of the southern California coast. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

NWS National Hurricane Center Miami FL 800 AM PDT Thu Aug 09 2018

John’s structure hasn’t changed much over the past few hours. A combination of cool SSTs and stable air appear to be causing convection to erode in the southern portion of the cyclone’s circulation. A blend of objective and subjective Dvorak classifications was used to determine the initial intensity of 60 kt. The tropical storm will be moving over progressively cooler SSTs for the next couple of days, and further weakening is inevitable. The intensity models are in good agreement on the forecast weakening rate, and John is still forecast to become a remnant low within the next 48 h.

The initial motion continues near 305/14 kt. There is no change to the reasoning behind the track forecast, and the new NHC forecast is merely an update of the previous advisory. All of the guidance remains in good agreement that the cyclone should will gradually turn west-northwestward as it moves around a mid-level ridge centered over the southwestern U.S. for the next few days. By the end of the forecast period, the remnant low is likely to slow down to a drift within an area of weak low-level steering flow.

Large swells associated with John are already affecting portions of the coast of the Baja California peninsula and are forecast to spread northward and reach portions of the southern California coast by tonight. These swells are likely to cause life- threatening surf and rip current conditions. Please consult products from your local weather office.

FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 24.5N 117.3W   60 KT  70 MPH - Tropical Storm - (E of Puerto San Carlos, Mx)
 12H  10/0000Z 25.5N 119.1W   50 KT  60 MPH - Tropical Storm - (SE of San Juanico, Mx)
 24H  10/1200Z 26.6N 121.1W   40 KT  45 MPH - Tropical Storm - (SE of Bahía Asunción, Mx)
 36H  11/0000Z 27.4N 122.8W   35 KT  40 MPH - Tropical Storm - (SE of Bahía Tortugas, Mx)
 48H  11/1200Z 27.9N 124.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  12/1200Z 28.6N 125.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  13/1200Z 29.5N 125.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  14/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 AM PDT Thu Aug 09 2018

The satellite presentation of John continues to degrade, with the central dense overcast decreasing in both size and intensity. Scatterometer data also indicate that the low-level center is southwest of the mid-level center, hinting that the circulation could be decoupling. The initial wind speed is set to 60 kt, near the latest TAFB and CIMSS-ADT estimates. John is rapidly moving over cool waters into a dry stable airmass, which should cause further weakening. The new NHC wind speed prediction follows the trend of the HFIP corrected-consensus guidance (a top performer this year), leading to a small reduction in the forecast. Remnant low status is forecast after 36 hours when the cyclone moves over sub-22C waters with little environmental instability.

John has turned leftward, now estimated at 305/14 kt. The tropical cyclone should continue to gradually turn toward the west-northwest over the next few days as it moves around a ridge situated over the southwestern United States. John’s remnants are likely to drift northward or northwestward at long range in a region of weak steering currents. The track guidance is in very good agreement and the official forecast is close to the previous one.

John is producing large swells that are already affecting portions of the coast of the southern Baja California peninsula. These swells are predicted to spread northward along the west coast of the peninsula today and reach portions of the coast of southern California by tonight. These swells are likely to cause life- threatening surf and rip current conditions. Please consult products from your local weather office.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0900Z 23.7N 115.9W   60 KT  70 MPH- Tropical Storm - (W of Puerto San Carlos, Mexico)
 12H  09/1800Z 24.8N 117.8W   50 KT  60 MPH- Tropical Storm - (SW of San Juanico, Mx)
 24H  10/0600Z 25.9N 119.9W   40 KT  45 MPH- Tropical Storm - (SW of Punta Abreojos, Mx)
 36H  10/1800Z 26.9N 121.8W   35 KT  40 MPH- Tropical Storm - (SW of Campamento Militar Isla Guadalupe, Mx)
 48H  11/0600Z 27.5N 123.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  12/0600Z 28.1N 125.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  13/0600Z 29.0N 126.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  14/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 300 PM MDT Wed Aug 08 2018

John has shown some improved organization since the last advisory as the system has formed a 20 n mi wide cloud-filled eye. Satellite intensity estimates remain in the 65-77 kt range, so the initial intensity will be held at 75 kt for this advisory. Other than this temporary break in the weakening, there is little change to the intensity forecast, as the forecast track takes John over progressively colder sea surface temperatures and into a more stable air mass. The new intensity forecast is in the center of the intensity guidance, with John expected to weaken to a tropical storm in 24 h or less and to a remnant low between 48-72 h.

The initial motion is 325/13, a bit faster than earlier. A combination of an upper-level low near 19N 124W and a mid- to upper-level ridge over northwestern Mexico should steer John northwestward for the next 36 h or so. After that, the cyclone or its remnants is forecast to turn west-northwestward in the low-level trade wind flow. Near the end of the forecast period, a slow motion is expected as the remnants of John move into an area of light steering currents. The guidance envelope has shifted a little to the north from the previous advisory, and the new forecast track is north of and faster than the previous forecast.

Although the center of John is forecast to remain well offshore of the Baja California Peninsula, a surge of moisture around John’s outer circulation is expected to bring some locally heavy rainfall to portions of Baja California Sur during the next couple of days. Therefore, interests in the southern portion of the Baja California Peninsula should monitor the progress of John.

John is also producing large swells that are already affecting portions of the coast of the southern Baja California peninsula. These swells are predicted to spread northward along the west coast of the peninsula today and reach portions of the coast of southern California by late Thursday. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 22.0N 113.5W   75 KT  85 MPH - Category 1 - (SW of Cabo San Lucas, Mexico)
 12H  09/0600Z 23.2N 115.0W   65 KT  75 MPH - Category 1 - (E of Todos Santos. Mx)
 24H  09/1800Z 24.6N 117.2W   55 KT  65 MPH - Tropical Storm - (E of Puerto San Carlos, Mx)
 36H  10/0600Z 25.8N 119.3W   45 KT  50 MPH - Tropical Storm - (SE of San Juanico, Mx)
 48H  10/1800Z 26.7N 121.4W   40 KT  45 MPH - Tropical Storm - (E of Punta Abreojos, Mx)
 72H  11/1800Z 27.5N 124.5W   30 KT  35 MPH...POST-TROP/REMNT LOW - (SE of Campamento Militar Isla Guadalupe. Mx)
 96H  12/1800Z 28.0N 126.0W   25 KT  30 MPH...POST-TROP/REMNT LOW - (SE of Campamento Militar Isla Guadalupe. Mx)
120H  13/1800Z 29.0N 126.0W   15 KT  15 MPH...POST-TROP/REMNT LOW - (E of Campamento Militar Isla Guadalupe. Mx)

NWS National Hurricane Center Miami FL 900 AM MDT Wed Aug 08 2018

The satellite presentation of John has degraded over the past 12 hours or so, with the eye no longer present in conventional satellite data. The CDO has also become considerably less symmetric than noted yesterday. Satellite intensity estimates range from 65 to 77 kt, and the initial intensity has been lowered to 75 kt for this advisory. John will be moving over cooler waters within the next 6-12 hours and into a more stable atmosphere, which should cause gradual weakening through tonight. By Thursday, John will be moving over much colder SSTs and a more rapid rate of filling is expected by that time. John is predicted to become a remnant low in 2 to 3 days as it reaches SSTs of around 21C.

The hurricane is moving northwestward or 320/10 kt. John should continue moving northwestward while it remains a vertically deep cyclone, but once it weakens and becomes a more shallow system it is expected to turn west-northwestward in the low-level trade wind flow. The dynamical model guidance remains in excellent agreement and little change was required to the previous NHC track forecast.

Although the center of John is forecast to remain well offshore of the Baja California Peninsula, a surge of moisture around John’s outer circulation is expected to bring some locally heavy rainfall to portions of Baja California Sur during the next couple of days. Therefore, interests in the southern portion of the Baja California Peninsula should monitor the progress of John.

John is also producing large swells that are already affecting portions of the coast of the southern Baja California peninsula. These swells are predicted to spread northward along the west coast of the peninsula today and reach portions of the coast of southern California by late Thursday. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 20.7N 112.3W   75 KT  85 MPH - Category 1 - (SW of Cabo San Lucas, Mexico)
 12H  09/0000Z 22.0N 113.7W   65 KT  75 MPH - Category 1 - (SW of Cabo San Lucas, Mexico)
 24H  09/1200Z 23.5N 115.9W   60 KT  70 MPH - Tropical Storm - (SW of Puerto San Carlos, Mx)
 36H  10/0000Z 24.9N 118.1W   50 KT  60 MPH - Tropical Storm - (SW of San Juanico, Mx)
 48H  10/1200Z 25.9N 120.2W   40 KT  45 MPH - Tropical Storm - (SW of Campamento Militar Isla Guadalupe, Mx)
 72H  11/1200Z 26.9N 123.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  12/1200Z 27.0N 126.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  13/1200Z 27.5N 126.8W   15 KT  15 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 300 AM MDT Wed Aug 08 2018

As mentioned in the previous discussion, the eye of John passed about 9 nmi northeast of Socorro Island around 0030 UTC, with the island possibly being within or just outside the eyewall. Additional data from an automated station on the island indicate that the highest sustained wind reported in 15-minute intervals was 48 kt at 0230 UTC, with another 70-kt gust reported at 0200 UTC. The lowest pressure measured was 970 mb at 0015 UTC, which is probably a 4-5 mb too low. Since that time, John’s eye has occasionally become cloud-filled, but deep convection has recently developed in the eyewall. The initial intensity is only decreased slightly to 85 kt based on a UW-CIMSS ADT estimate of 87 kt and due to the recent uptick in eyewall convection.

Although John should remain over warm waters for another 12 hours or so, the general trend calls for steady weakening due to the ingestion of more stable air to the north, which is expected to decrease the instability and inner-core convection. The official intensity forecast is lower than the previous intensity forecast, and is similar to a blend of the FSSE and HCCA models.

The initial motion estimate is north-northwestward or 330/10 kt. John is expected to return to a northwestward motion at a slightly faster forward speed later this morning, and then continue that motion for the next 72 hours. After that time, a turn toward the west-northwestward is forecast due to the weakening and shallow cyclone being steered by the low-level trade wind flow. The new official forecast remains in close agreement with the previous advisory, and lies down the middle of the guidance envelope.

Although the core of John is forecast to remain well offshore of the Baja California Peninsula, a surge of moisture around John’s outer circulation is expected to bring some locally heavy rainfall to portions of Baja California Sur during the next couple of days. Therefore, interests in the southern portion of the Baja California Peninsula should monitor the progress of John.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 20.0N 111.6W   85 KT 100 MPH - Category 2 -(NW of Socorro Island, Mx)
 12H  08/1800Z 21.1N 112.8W   80 KT  90 MPH - Category 1 -(SW of Cabo San Lucas, Mexico)
 24H  09/0600Z 22.8N 114.8W   75 KT  85 MPH - Category 1 -(W of Cabo San Lucas, Mexico)
 36H  09/1800Z 24.2N 116.8W   65 KT  75 MPH - Tropical Storm -(W of Puerto San Carlos, Mx)
 48H  10/0600Z 25.3N 119.0W   50 KT  60 MPH - Tropical Storm -(W of San Juanico, Mx)
 72H  11/0600Z 26.8N 122.9W   35 KT  40 MPH...POST-TROPICAL
 96H  12/0600Z 27.0N 125.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  13/0600Z 27.3N 127.2W   15 KT  15 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 900 PM MDT Tue Aug 07 2018

The eye of John passed a short distance east of Socorro Island a few hours ago, and it is estimated that the radius of maximum winds narrowly missed the island. An automated station at Socorro recorded a wind gust to 70 kt at 2300 UTC. Although John’s inner core convection has weakened somewhat, Dvorak Current Intensity numbers from TAFB and SAB still support an intensity of 90 kt for this advisory. Although John should remain over warm waters for the next day or so, the deterioration of its convection suggests it is now in a somewhat less favorable atmospheric environment, so no further strengthening is expected. The official intensity forecast is somewhat above the model consensus for the first 1-2 days and near the consensus thereafter.

The initial motion estimate remains northwestward or 315/9 kt. The hurricane should continue to move northwestward along the southwestern side of a mid-tropospheric ridge for the next couple of days. Later, the weakening cyclone is likely to turn to the left and eventually move westward following the low-level flow. The new official forecast is in close agreement with the previous one and much of the track model guidance, which remains in good agreement.

Although the core of John is forecast to remain well offshore of the Baja California Peninsula, an eastward shift of the forecast track or an unexpected increase in the size of the outer wind field of the hurricane could bring tropical-storm-force winds close to the west coast of the peninsula. In addition, a surge of moisture around John’s outer circulation is expected to bring some locally heavy rainfall to portions of Baja California Sur during the next couple of days. Therefore, interests in the southern portion of the Baja California Peninsula should monitor the progress of John.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0300Z 19.2N 111.1W   90 KT 105 MPH - Category 2 (N of Socorro Island, Mx)
 12H  08/1200Z 20.4N 112.3W   90 KT 105 MPH - Category 2 (W of Cabo San Lucas, Mx)
 24H  09/0000Z 22.0N 114.0W   90 KT 105 MPH - Category 2 (ESE of Cabo San Lucas, Mx)
 36H  09/1200Z 23.5N 116.0W   80 KT  90 MPH - Category 1 (SE of Puerto San Carlos, Mx)
 48H  10/0000Z 24.9N 118.1W   60 KT  70 MPH - Category 1 (ESE of San Juanico, Mx)
 72H  11/0000Z 26.6N 122.0W   40 KT  45 MPH - Tropical Storm (ESE of Campamento Militar Isla Guadalupe, Mx)
 96H  12/0000Z 27.0N 125.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  13/0000Z 27.0N 127.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 300 PM MDT Tue Aug 07 2018

The eye of John has become more distinct in visible and infrared satellite imagery during the past few hours, however the surrounding convective clouds tops have warmed, and a 1642 UTC AMSU microwave overpass indicated that the eyewall was open over the northwestern portion of the circulation. Although objective Dvorak T-numbers have increased to T5.6, subjective estimates from TAFB and SAB are unchanged so the initial intensity is kept at 90 kt. There is still an opportunity for John to become a major hurricane tonight or early Wednesday while it remains over warm water and in a low shear environment. After that time, the hurricane will be moving over decreasing SSTs and into a less favorable thermodynamic environment. These conditions should result in steady to rapid weakening and John is forecast to become a post-tropical cyclone by day 4 when it is over SSTs of 20-21C. There is significant spread in the intensity guidance as to how rapid John will spin down. The NHC forecast is a little higher than the ICON consensus model, but shows a faster rate of weakening than the statistical guidance.

John is moving northwestward or 320/9 kt. The hurricane should continue moving northwestward around the western side of a mid-level ridge over northern Mexico during the next 2-3 days. After that time, the system should turn westward as it weakens and comes under the influence of the low-level flow. The track guidance remains in excellent agreement and the new NHC track is essentially an update of the previous advisory.

Although the core of John is forecast to remain well offshore of the Baja California Peninsula, an eastward shift of the forecast track or an unexpected increase in the size of the outer wind field of the hurricane could bring tropical-storm-force winds close to the west coast of the peninsula. In addition, a surge of moisture around John’s outer circulation is expected to bring some locally heavy rainfall to portions of Baja California Sur during the next couple of days. Therefore, interests in the southern portion of the Baja California Peninsula should monitor the progress of John.

FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 18.7N 110.5W   90 KT 105 MPH
 12H  08/0600Z 19.9N 111.6W  100 KT 115 MPH
 24H  08/1800Z 21.5N 113.3W   95 KT 110 MPH
 36H  09/0600Z 23.0N 115.2W   80 KT  90 MPH
 48H  09/1800Z 24.4N 117.3W   65 KT  75 MPH
 72H  10/1800Z 26.6N 121.3W   45 KT  50 MPH
 96H  11/1800Z 27.0N 124.7W   35 KT  40 MPH...POST-TROPICAL
120H  12/1800Z 27.0N 127.3W   25 KT  30 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 900 AM MDT Tue Aug 07 2018

Visible and infrared satellite images have continued to show the ragged eye of John this morning, but the surrounding convective cloud tops have become more symmetric and cooled since the previous advisory. The latest Dvorak satellite intensity estimates from TAFB and SAB were T5.0/90 kt, which support increasing the initial wind speed to that value. John has about another 24 hours over warm water in which to intensify, and the NHC intensity forecast calls for John to attain major hurricane strength later today or tonight. After that time, decreasing SSTs and a more stable environment should lead to steady or rapid weakening, and John is expected to become a post-tropical cyclone by day 4. The NHC intensity forecast is near the SHIPS and HCCA models for the first 12 to 24 hours, and then is between the aforementioned models and the intensity consensus thereafter.

John is moving northwestward or 320/8 kt. The track guidance is in good agreement on taking the hurricane northwestward around the western portion of a mid-level ridge centered over northern Mexico. Once John weakens and becomes a vertically shallow system it should turn westward in the low-level flow. The NHC track forecast is near the middle of the tightly clustered guidance envelope.

The dangerous core of John is forecast to remain well offshore of the Baja California Peninsula. However, an eastward shift of the forecast track or an unexpected increase in the size of the outer wind field of the hurricane could bring tropical-storm-force winds to portions of the west coast of the peninsula. Therefore, interests in the southern portion of the Baja California Peninsula should monitor the progress of this hurricane.

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 17.9N 109.8W   90 KT 105 MPH - Category 2 (SE of Socorro Island, Mx)
 12H  08/0000Z 18.9N 110.7W  100 KT 115 MPH - Category 3 (NE of Socorro Island, Mx)
 24H  08/1200Z 20.5N 112.2W  105 KT 120 MPH - Category 3 (SW of Cabo San Lucas, Mx)
 36H  09/0000Z 22.0N 114.0W   90 KT 105 MPH - Category 2 (SW of Cabo San Lucas, Mx)
 48H  09/1200Z 23.5N 116.1W   80 KT  90 MPH - Category 1 (SW of Puerto San Carlos, Mx)
 72H  10/1200Z 26.2N 120.2W   50 KT  60 MPH - Tropical Storm (SW of Punta Abreojos, Mexico
 96H  11/1200Z 27.0N 123.8W   40 KT  45 MPH...POST-TROPICAL (E of Bahía Asunción, Mexico)
120H  12/1200Z 27.0N 126.8W   30 KT  35 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 300 PM MDT Mon Aug 06 2018

John has continued to intensify since the previous advisory. Visible satellite images continue to indicate an increase in banding and very recent pictures show the formation of a banding eye. As a result, the initial intensity is increased to 65 kt, which is based on a TAFB Dvorak T-number of 4.0 and UW/CIMSS objective Dvorak estimates that are close to 65 kt. John becomes the fifth hurricane of the 2018 eastern North Pacific hurricane season.

John is forecast to remain within a very favorable environment for strengthening during the next day or so. Although some of the intensity guidance is not quite as aggressive as this morning, the various rapid intensification indices still show a high likelihood of rapid strengthening during the next 24 hours. The NHC forecast once again calls for rapid intensification and brings John to major hurricane strength within 36 h. The updated NHC intensity forecast is near the upper-end of the guidance in best agreement with the latest SHIPS, HCCA, and FSSE models. After 48 h, John will be moving over much cooler waters and into a less conducive thermodynamic environment. This should result in rapid weakening, and John is forecast to become a remnant low by day 5.

John is moving northwestward at about 7 kt. The hurricane is forecast to move northwestward around the western periphery of a mid-level ridge over northern Mexico during the next few days. Once the system weakens and becomes a more shallow cyclone late in the forecast period, it should turn westward in the low-level flow. The overall track envelope has shifted eastward this cycle, with the GFS and HWRF along the eastern edge of the track guidance envelope while the ECMWF and UKMET are along the western side. The new NHC forecast has been adjusted eastward and lies between the ECMWF and the various consensus aids. Due to the eastward shift in the forecast track and the predicted increase in the size of John, interests in the southern portion of the Baja California peninsula should monitor the progress of this system.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 16.0N 108.0W   65 KT  75 MPH - Category 1 (SW of Zihuatanejo, Mx)
 12H  07/0600Z 16.8N 108.7W   80 KT  90 MPH - Category 1 (SE of Socorro Island, Mx)
 24H  07/1800Z 18.1N 109.9W   95 KT 110 MPH - Category 2 (NE of San Benedicto Island, Mx)
 36H  08/0600Z 19.6N 111.3W  110 KT 125 MPH - Category 3 (NE of San Benedicto Island, Mx)
 48H  08/1800Z 21.0N 112.8W  105 KT 120 MPH - Category 3 (SW of Cabo San Lucas, Mx)
 72H  09/1800Z 24.3N 117.0W   70 KT  80 MPH - Category 1 (SW of Puerto San Carlos, Mx)
 96H  10/1800Z 26.6N 121.2W   45 KT  50 MPH - Tropical Storm (E of Bahía Asunción
120H  11/1800Z 27.2N 124.8W   30 KT  35 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 900 AM MDT Mon Aug 06 2018

Corrected to remove the percent symbols in the text

Early morning visible satellite images and recent microwave data show that John continues to quickly become better organized. Banding features now wrap nearly completely around the center, with the development of a fairly symmetric CDO. One-minute GOES-16 imagery also show several overshooting convective cloud tops near and to the east of the center. A TAFB Dvorak estimate of T3.5 was the basis of the 1200 UTC intensity of 55 kt, but with the increase in organization since that time, and raw objective T-numbers above 4.0 for the past few hours, the advisory intensity has been increased to 60 kt.

John is within a very favorable environment for intensification. The hurricane will be moving over SSTs around 30C, and in a low shear and moist environment. These conditions are expected to allow for rapid strengthening during the next day or so. The SHIPS Rapid Intensification Index shows a nearly 80 percent chance of RI over the the next 24 h, and DTOPS gives an 80 percent chance of a 40 kt increase in intensity during the next 24 h. Based on these data and the very aggressive guidance, the NHC forecast calls for a 40 kt increase in strength from 1200 this morning through 1200 UTC Tuesday. The NHC forecast calls for a peak intensity that is close to the FSSE and HCCA models in 36 to 48 hours. After that time, John will be moving over cooler waters and into a more stable environment which is expected to cause rapid weakening.

John is moving west-northwestward at about 7 kt. The tropical storm should turn northwestward and accelerate over the next day or so as it is steered around the western portion of a mid-level ridge that is centered over northern Mexico. As noted in the previous discussion, some interaction with Ileana is likely, which could cause some slow down of the forward speed of John. However since John is the larger system, it should remain the dominant tropical cyclone. The latest dynamical model guidance was similar to the previous cycle and no significant change to the NHC forecast was required. The NHC forecast is in best agreement with the ECMWF and is close to the HFIP corrected consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 15.5N 107.9W   60 KT  70 MPH - Category 1 (SW of Acapulco, Mx)
 12H  07/0000Z 16.0N 108.6W   75 KT  85 MPH - Category 1 (W of Acapulco, Mx)
 24H  07/1200Z 17.0N 109.6W   95 KT 110 MPH - Category 2 (SE of Socorro Island, Mx)
 36H  08/0000Z 18.3N 111.0W  110 KT 125 MPH - Category 3 (S of Socorro Island, Mx)
 48H  08/1200Z 19.8N 112.7W  110 KT 125 MPH - Category 3 (SW of Cabo San Lucas, Mx)
 72H  09/1200Z 22.9N 116.6W   85 KT 100 MPH - Category 2 (W of Todos Santos, Mx)
 96H  10/1200Z 25.5N 120.7W   55 KT  65 MPH
120H  11/1200Z 26.8N 125.0W   35 KT  40 MPH...POST-TROPICAL

National Hurricane Center Miami FL 400 PM CDT Sun Aug 05 2018

Tropical Depression Twelve-E : The low pressure area located a few hundred miles south of the southwest coast of Mexico has become better defined today and the associated deep convection has enough organization to classify the system as a tropical depression, the twelfth tropical cyclone of the 2018 eastern Pacific hurricane season. The initial intensity is set at 30 kt, which is in agreement with Dvorak satellite intensity estimates from both TAFB and SAB.

The initial motion estimate is northwestward at about 6 kt. The track and intensity forecast for the depression is complicated due to the close proximity of Tropical Storm Ileana to its east-southeast. Somewhat surprisingly, however, the track guidance is in relatively good agreement on a general northwestward motion around the western portion of a mid-level ridge over northern Mexico during the next several days. Since the depression is larger than Ileana, most of the global models suggest that Ileana will move around the northeastern portion of the new tropical cyclone’s circulation and weaken and dissipate. The NHC track forecast is near the middle of the guidance envelope between the slower ECMWF solution, and the faster GFS, HWRF, and HMON tracks.

The depression is currently over very warm SSTs, within low shear, and a moist atmosphere. These factors suggest that the depression will steadily strengthen and the intensity guidance is quite aggressive in intensifying the system. The NHC forecast is slightly more conservative during the first 36 h since the system is still quite broad and lacks an inner core. Regardless, the NHC forecast brings the system to hurricane strength within 36 h, and shows a peak intensity of 90 kt in 3 days, which is in agreement with the HFIP corrected consensus model. Cool waters and less favorable thermodynamic conditions should lead to steady to rapid weakening late in the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 14.6N 105.8W   30 KT  35 MPH 
 12H  06/0600Z 15.2N 106.5W   40 KT  45 MPH
 24H  06/1800Z 16.0N 107.4W   50 KT  60 MPH
 36H  07/0600Z 16.9N 108.3W   65 KT  75 MPH - Category 1 (SW of Manzanillo, Mx)
 48H  07/1800Z 17.9N 109.6W   75 KT  85 MPH - Category 1 (SE of Socorro Island, Mx)
 72H  08/1800Z 20.5N 112.8W   90 KT 105 MPH - Category 2 (SW of Cabo San Lucas, Mx)
 96H  09/1800Z 23.2N 117.0W   65 KT  75 MPH - Category 1 ( SW of Puerto San Carlos, Mx)
120H  10/1800Z 25.5N 121.5W   45 KT  50 MPH - (SW of Campamento Militar Isla Guadalupe, Mx)

NWS National Hurricane Center Miami FL 1100 AM PDT Sun Aug 5 2018

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

The National Hurricane Center is issuing advisories on Hurricane Hector, located well east-southeast of the Big Island of Hawaii, and on Tropical Depression Eleven-E, located south of Puerto Escondido,
Mexico.

NWS National Hurricane Center Miami FL 1100 AM PDT Sun Aug 5 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Hurricane Hector, located well east-southeast of the Big Island of Hawaii, and on Tropical Depression Eleven-E, located south of Puerto Escondido, Mexico.

Satellite images indicate that the low pressure area located about 400 miles southwest of Acapulco, Mexico, has become better defined, and a tropical depression appears to be forming. If the current development trend continues, advisories will likely be issued this afternoon or evening on this system. The low is forecast to move slowly northwestward off the southwest coast of Mexico during the next few days. * Formation chance through 48 hours…high…near 100 percent. * Formation chance through 5 days…high…near 100 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sun Aug 5 2018

Showers and thunderstorms associated with an elongated area of low pressure located about 900 miles southwest of the southern tip of the Baja California peninsula have changed little in organization overnight. Environmental conditions appear favorable for development, and a tropical depression is expected to form within the next day or two while this system moves slowly westward. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sat Aug 4 2018

Satellite data indicate that a broad low pressure area has formed several hundred miles south-southwest of Acapulco, Mexico. Environmental conditions are conducive for significant development, and a tropical depression or tropical storm is expected to form tonight or tomorrow while the system moves west-northwestward off the coast of Mexico. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…near 100 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sat Aug 4 2018

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

The National Hurricane Center is issuing advisories on Hurricane Hector, located well southwest of Baja California Sur.

A large area of disturbed weather centered several hundred miles south of Acapulco, Mexico, has become better organized overnight. Environmental conditions are conducive for signficant development, and a tropical depression or tropical storm is expected to form within the next day or two while the system moves west-northwestward off the coast of Mexico. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Fri Aug 3 2018

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

The National Hurricane Center is issuing advisories on Hurricane Hector, located well southwest of Baja California Sur.

A large area of disturbed weather centered several hundred miles southwest of the Gulf of Tehuantepec has become a little better organized since yesterday. Environmental conditions are expected to be conducive for development during the next several days, and a tropical depression or tropical storm is expected to form by early next week while it moves west-northwestward off the coast of Mexico.
* Formation chance through 48 hours…medium…50 percent.
* Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Fri Aug 3 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Hurricane Hector, located well southwest of Baja California Sur.

Satellite images indicate that a low pressure area has formed about 700 miles southwest of Manzanillo, Mexico, and is already showing some signs of organization. Environmental conditions appear conducive for further development, and a tropical depression is likely to form over the weekend or early next week. The low is forecast to move slowly westward over the next few days. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high…70 percent.

If this storm system is named, it will be Tropical Storm John.

NWS National Hurricane Center Miami FL 500 AM PDT Fri Aug 3 2018

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

The National Hurricane Center is issuing advisories on Hurricane Hector, located well southwest of Baja California Sur.

A tropical wave is producing disorganized showers and thunderstorms several hundred miles south-southwest of Manzanillo, Mexico. Environmental conditions appear marginally conducive for gradual development of this system during the next few days as it moves slowly west-northwestward or northwestward. By early next week, proximity to another low pressure system could limit further development of this disturbance.
* Formation chance through 48 hours…low…30 percent.
* Formation chance through 5 days…medium...50 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Thu Aug 2 2018

Disorganized showers and thunderstorms centered several hundred miles south-southwest of Manzanillo, Mexico, are associated with a tropical wave. Environmental conditions appear marginally conducive for gradual development of this system during the next few days as it moves generally westward across the tropical eastern Pacific. By early next week, proximity to another low pressure system could limit further development of this disturbance. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...30 percent.

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