Tropical Storm Olivia

Tropical Storm Olivia Track 2300 Hours September 11 2018

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Thu Sep 13 2018

Olivia (see Thurs video below)continues to move rapidly toward the west-southwest away from the main Hawaiian Islands this morning. Southwesterly vertical wind shear of over 30 kt remains in the vicinity of Olivia. Scattered thunderstorms continue to develop far northeast, southeast, and south of the low-level circulation center (LLCC), but the core of the system remains completely devoid of deep convection. An ASCAT pass over Olivia’s outer circulation at 0810Z showed a swath of 30 kt winds. The latest subjective Dvorak current intensity estimate was 1.5/25 kt from PHFO and JTWC. The UW-CIMSS ADT was also 1.5/25 kt. We will keep the initial intensity 30 kt for this advisory based on the earlier scatterometer data. Olivia is expected to remain a tropical depression into tonight. However, we continue to indicate it will become a post-tropical remnant low starting late tonight or on Friday. This intensity forecast is close to the IVCN guidance.

The initial motion for this advisory is 255/16 kt. The LLCC is being steered by the low-level trade wind flow. A general west-southwest motion with a slight decrease in forward speed is forecast through this morning. Olivia will likely turn toward the west later today, and then the west-northwest tonight and Friday as the system increasingly interacts with the upper-level low responsible for the wind shear. The latest track forecast has been adjusted to the left during the first 24 hours, which takes into account the faster initial motion. This track forecast remains close to the previous forecast for the 36 through 72 hour time period. This forecast track closely follows the TVCE and HCCA, and remains near the middle of the guidance envelope.

Lingering moisture from Olivia continues to cause heavy rainfall across portions of the main Hawaiian Islands this morning. These wet conditions will likely persist through tonight. Since many areas are already saturated, any additional heavy rainfall could produce life-threatening flash flooding.

Tropical Storm Olivia Distances 0500 Hours September 13 2018
Tropical Storm Olivia Distances 0500 Hours September 13 2018
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/1500Z 19.5N 162.2W   30 KT  35 MPH - Tropical Storm (WSW Puʻuwai, Hawaii)
 12H  14/0000Z 19.1N 164.2W   30 KT  35 MPH - Tropical Storm (WSW Puʻuwai, Hawaii)
 24H  14/1200Z 19.4N 167.0W   30 KT  35 MPH - Tropical Storm (WSW Puʻuwai, Hawaii)
 36H  15/0000Z 20.0N 169.4W   30 KT  35 MPH - Tropical Storm (ENE Johnson Atoll)
 48H  15/1200Z 21.0N 171.7W   30 KT  35 MPH - Tropical Storm (ENE Johnson Atoll)
 72H  16/1200Z 23.0N 176.5W   25 KT  30 MPH - Tropical Storm (ESE Midway Atoll)
 96H  17/1200Z...DISSIPATED

NWS Central Pacific Hurricane Center Honolulu HI 1100 PM HST Tue Sep 11 2018

Olivia’s  low level circulation center (LLCC) continues to be exposed, with deep convection primarily located in the eastern semicircle due to strong westerly vertical wind shear. Subjective Dvorak current intensity estimates from PHFO/SAB/PGTW ranged from 2.0/30 kt to 3.0/45 kt. A blend of this data and an earlier ASCAT pass support lowering the initial intensity to 40 kt for this advisory.

The motion has been very erratic over the past 12 to 18 hours, and although unclear as to why, it appears to have been modulated by pulses in deep convection. When Olivia accelerated westward this morning, associated deep convection had dissipated, allowing the LLCC to be steered by the low-level trade winds. When deep convection redeveloped this afternoon, the forward motion slowed markedly, allowing a deeper-layer flow to lead to a slower forward speed. The motion estimate for this advisory is 250/7 kt.

Erratic motion is likely to continue overnight as Olivia encounters terrain, but a general west-southwest motion is expected, with an increase in forward speed. If Olivia’s LLCC survives the passage near the island terrain, the center is expected to continue moving toward the west-southwest through 48 hours. A more westward motion is expected to begin by 72 hours and beyond as the deep layer ridge west of Olivia weakens and an mid-level low digs southwest toward the cyclone.

Our intensity forecast operates under the assumption that the LLCC will be intact after emerging to the southwest of Maui and the Big Island. If this occurs, gradual weakening is expected to continue in line with all the guidance, which shows moderate to strong shear continuing through the forecast period. Olivia is still expected to become a remnant low within 72 hours, with dissipation expected by day 5, but there is a decent chance this will happen even sooner.

Key Messages:Tropical Storm Olivia Distances 0200 Hours September 12 2018

1. Although Olivia is weakening, flooding rainfall, high surf, and damaging winds are expected in the warning area. Significant impacts can occur well away from the center, especially when considering that the mountainous terrain of Hawaii can produce localized areas of strongly enhanced wind gusts and rainfall.

FORECAST POSITIONS AND MAX WINDS
 
INIT  12/0900Z 20.8N 154.6W   40 KT  45 MPH - Tropical Storm (ENE Hāna, Hawaii)
 12H  12/1800Z 20.2N 156.7W   40 KT  45 MPH - Tropical Storm (WSW Kaho‘olawe, Hawaii)
 24H  13/0600Z 19.8N 159.3W   35 KT  40 MPH - Tropical Storm (WNW Kailua-Kona, Hawaii)
 36H  13/1800Z 19.3N 161.8W   30 KT  35 MPH - Tropical Storm (WSW Puʻuwai, Hawaii)
 48H  14/0600Z 19.0N 164.4W   30 KT  35 MPH - Tropical Storm (WSW Puʻuwai, Hawaii)
 72H  15/0600Z 19.5N 170.0W   30 KT  35 MPH - Tropical Storm (WNW Johnson Atoll)
 96H  16/0600Z 21.0N 174.5W   30 KT  35 MPH - Tropical Storm (WNW Johnson Atoll)
120H  17/0600Z...DISSIPATED

NWS Central Pacific Hurricane Center Honolulu HI  500 AM HST Tue Sep 11 2018

Hurricane Hunters from the 53rd Weather Reconnaissance Squadron spent most of the night flying through Olivia , sampling the core as well the periphery. Maximum flight level winds of 78 kt were observed in the northwest quadrant fairly early in the evening, but subsequent observations indicated that Olivia is well below hurricane intensity. The surface pressure was gradually rising, and the system exhibited tilt with height, with the low-level center on the south side of the cold cloud tops seen in satellite. Additionally, the observed wind field was rather asymmetric, with winds fairly weak in the southern semicircle. The initial intensity for this advisory is deemed to be 55 kt, and given current satellite trends, this may be slightly generous.

The aircraft center fixes add confidence to the initial motion estimate of 270/9 kt. Olivia is being steered by a mid-level ridge centered to the distant northeast, but a mid-level ridge building to the northwest of Olivia will induce a motion toward the west- southwest later today. Once this occurs, this motion is expected to persist as Olivia crosses the Hawaiian Islands. The updated track forecast is very close to the previous, especially over the first 48 hours. In 48 to 72 hours, a low aloft is expected to develop north of Olivia, and this development is expected to impart a motion toward the west-northwest on days 4 and 5. The official forecast is now near the center of the guidance envelope, and is close to the multi-model consensus TVCE and GFEX. The along-track differences between the GFS and ECMWF were reduced with the arrival of the 06Z GFS, adding confidence to the short term forecast track, which indicates a slightly faster speed of motion than the previous forecast.Tropical Storm Olivia Distances 0500 Hours September 11 2018

Moderate shear is expected to continue over the next 48 hours while SSTs increase to 28C. The shear is expected to induce slow weakening as indicated by nearly all intensity guidance, with interaction with island terrain potentially contributing to weakening as well. After Olivia exits the Hawaiian Islands to the west in 48 to 72 hours, a cold core low aloft is expected to develop north of Olivia. By 96 hours the cold core low and Olivia become vertically stacked, potentially resulting in Olivia becoming post-tropical. The official intensity forecast indicates this will occur by day 5, and closely follows IVCN through the bulk of the forecast.

Key Messages:

1. Although Olivia is expected to move over the islands as a tropical storm, it could still bring significantly worse impacts than recent Hurricane Lane. Those impacts could include intense flooding rainfall, damaging winds, and large and dangerous surf.

2. It is important to not focus on the exact forecast track and intensity when planning for Olivia. Regardless of the track that Olivia takes as it approaches the islands, significant impacts can be expected away from the center. In particular, the mountainous terrain of Hawaii can produce localized areas of strongly enhanced wind gusts and rainfall.

FORECAST POSITIONS AND MAX WINDS
 
INIT  11/1500Z 21.9N 151.1W   55 KT  65 MPH - Tropical Storm (ENE Kailua, Hawaii)
 12H  12/0000Z 21.6N 152.9W   50 KT  60 MPH - Tropical Storm (ENE Kahului, Hawaii)
 24H  12/1200Z 21.1N 155.3W   45 KT  50 MPH - Tropical Storm (ENE Hāna, Hawaii)
 36H  13/0000Z 20.3N 157.8W   45 KT  50 MPH - Tropical Storm (WSW Kaho‘olawe, Hawaii)
 48H  13/1200Z 19.7N 160.2W   40 KT  45 MPH - Tropical Storm (ENE Kailua-Kona, Hawaii)
 72H  14/1200Z 19.3N 164.7W   40 KT  45 MPH - Tropical Storm (WSW Puʻuwai, Hawaii)
 96H  15/1200Z 20.5N 169.5W   35 KT  40 MPH - Tropical Storm (ENE Johnson Atoll)
120H  16/1200Z 21.6N 174.0W   30 KT  35 MPH - Tropical Depression (ESE Midway Atoll)

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Sun Sep 09 2018

Hurricane Olivia remains poorly organized early this morning. There continue to be hints of an eye in satellite imagery, but the feature has not been consistent for any length of time. A timely AMSR microwave image from 1140z confirms the initial location used for this advisory, plus it showed a closed eyewall structure a few hours ago. The latest subjective Dvorak current intensity estimates from the satellite fix agencies ranged from 4.0/65 kt at PHFO to 3.5/55 kt at SAB and JTWC. The latest UW-CIMSS ADT estimate is also 3.5/55 kt.

The U.S. Air Force Reserves 53rd Weather Reconnaissance Squadron will be conducting missions in and around Olivia later today. The first mission, which will depart from Oahu shortly, will be making direct measurements in Olivia. This will help us determine the track, intensity, and size of the system. The second mission by the 53rd will sample the environment around Olivia to provide valuable data for improved initialization of the forecast models that will run later today. This is expected to improve the track and intensity forecasts as Olivia approaches the Hawaiian Islands this week. Since there is so much uncertainty for the moment in the initial intensity, we will only weaken Olivia to a 65 kt hurricane for this advisory.Hurricane Olivia Distances 0500 Hours September 9 2018

Olivia continues to move due west, and the initial motion estimate is 270/14 kt. The hurricane is being steered to the south of a strong deep layer ridge situated north through west of the system. Olivia is expected to continue moving westward at a slightly slower forward speed during the next 36 hours, since the ridging is forecast to build westward in tandem with the tropical cyclone’s movement. Beyond 36 hours, the portion of the ridge to the west of Olivia is forecast to build, which will likely shunt the tropical cyclone on a more west-southwest motion. The track guidance remains fairly tightly clustered, but has started to shift southward. As a result, the latest forecast track has been nudged to the left from days 2 through 4. This track still brings the center of Olivia across the main Hawaiian Islands between 72 and 96 hours. A more westward motion is expected to resume after Olivia’s passage through the islands, as the upper ridge retreats westward and the circulation center becomes increasingly steered by the low-level trade wind flow.

Olivia remains in an environment with relatively weak vertical wind shear, but it is moving over marginal sea surface temperatures (SSTs) of 25.5C. The hurricane has likely already traversed the coolest water along its track. Note that the Ocean Heat Content (OHC) analysis from CIRA shows this parameter may increase starting around 24 or 36 hours, so this may help Olivia maintain its intensity longer than is currently forecast. However, vertical wind shear is expected to begin increasing after 48 hours, which will likely result in a gradual weakening trend. Despite this trend, Olivia is forecast to remain a strong tropical storm during 72 to 96 hours, which could cause significant impacts in the main Hawaiian Islands. The latest intensity forecast closely follows the previous advisory.

KEY MESSAGES:

1. It is important to recognize that errors in both forecast track and intensity, particularly at longer time ranges, can be large. While it is too soon to determine the location and magnitude of the worst impacts, all interests in Hawaii should continue to monitor the progress of Olivia, and use this time to prepare for the increasing likelihood of direct impacts from this system this week.

2. Regardless of the exact track and intensity that Olivia takes as it approaches the islands, significant effects often extend far from the center. In particular, the mountainous terrain of Hawaii can produce localized areas of strongly enhanced winds and rainfall, even well away from the tropical cyclone center.

FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 21.8N 143.9W   65 KT  75 MPH - Category 1 (ESE Honolulu, Hawaii)
 12H  10/0000Z 21.8N 145.5W   70 KT  80 MPH - Category 1 (ESE Honolulu, Hawaii)
 24H  10/1200Z 21.8N 147.6W   70 KT  80 MPH - Category 1 (ESE Honolulu, Hawaii)
 36H  11/0000Z 21.7N 149.4W   70 KT  80 MPH - Category 1 (ESE Honolulu, Hawaii)
 48H  11/1200Z 21.3N 151.2W   65 KT  75 MPH - Category 1 (ESE Honolulu, Hawaii)
 72H  12/1200Z 20.3N 155.5W   55 KT  65 MPH - Tropical Storm (ESE Honolulu, Hawaii)
 96H  13/1200Z 19.5N 160.0W   45 KT  50 MPH - Tropical Storm (ESE Honolulu, Hawaii)
120H  14/1200Z 19.5N 165.0W   35 KT  40 MPH - Tropical Storm (ESE Honolulu, Hawaii)

NWS National Hurricane Center Miami FL 200 PM PDT Sat Sep 08 2018

The satellite presentation of Olivia has remained about the same for the past several hours, as eyewall convection stays mostly solid around the eye. Dvorak estimates are basically unchanged, so the initial wind speed is kept at 75 kt. Olivia should stay a hurricane for the next couple of days while it is experiencing light shear, balanced by very dry air aloft and marginal but warming SSTs. After the weekend, most of the guidance continue to indicate that westerly shear should increase, and weakening is forecast while Olivia approaches the Hawaiian Islands. No significant changes were made to the intensity forecast.

Olivia is moving westward at 13 kt. There is no change to the synoptic reasoning. A building subtropical ridge should steer the hurricane basically due westward for the next couple of days. Thereafter, a mid-level ridge over Hawaii should cause Olivia to lose some latitude and move west-southwestward toward the main Hawaiian Islands. The models are in better agreement on this cycle, with the UKMET and GFS models trending more to the north, resulting in a smaller guidance spread. The official forecast is shifted a bit northward to match the guidance trend. A C-130 plane is currently conducting a synoptic surveillance mission around Olivia, which should hopefully aid later forecasts, which will be issued by the Central Pacific Hurricane Center.

KEY MESSAGES:

1. Olivia is forecast to approach the main Hawaiian Islands from the east on Tuesday, and pass close to or over the Islands on Wednesday. It is too soon to determine the exact location and magnitude of any impacts, but interests in Hawaii should continue to monitor the progress of Olivia, and use this time to enact your hurricane action plan.

2. Do not focus on the exact track or intensity forecast, or any specific landfall location, as errors can be large at extended time ranges. Tropical storm or hurricane conditions could be felt anywhere in the islands as significant impacts could extend well away from the center.Hurricane Olivia Distances 1100 Hours September 8 2018

FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 21.7N 139.4W   75 KT  85 MPH - Category 1 (ESE Honolulu, Hawaii)
 12H  09/0600Z 21.9N 141.4W   70 KT  80 MPH - Category 1 (ESE Honolulu, Hawaii)
 24H  09/1800Z 22.0N 144.0W   65 KT  75 MPH - Category 1 (ESE Honolulu, Hawaii)
 36H  10/0600Z 22.0N 146.2W   65 KT  75 MPH - Category 1 (ESE Honolulu, Hawaii)
 48H  10/1800Z 22.0N 148.1W   65 KT  75 MPH - Category 1 (ESE Honolulu, Hawaii)
 72H  11/1800Z 21.4N 152.1W   55 KT  65 MPH - Tropical Storm (ESE Honolulu, Hawaii)
 96H  12/1800Z 20.4N 156.8W   50 KT  60 MPH - Tropical Storm (WSW Kaho‘olawe, Hawaii)
120H  13/1800Z 19.5N 162.0W   40 KT  45 MPH - Tropical Storm (WSW Kailua-Kona , Hawaii)

NWS National Hurricane Center Miami FL 200 AM PDT Sat Sep 08 2018

The satellite presentation of Olivia has continued to degrade overnight with the surrounding ring of deep convection warming and the eye becoming less distinct. Dvorak T-numbers have decreased and a blend of current intensity (CI) numbers from TAFB and SAB, and ADT and SATCON estimates from UW/CIMSS yields an initial wind speed of 80 kt. Although the vertical wind shear is expected to remain low over Olivia, the hurricane will be moving over marginal sea surface temperatures of 25-26C, and into a dry mid-level environment. These factors are expected to cause gradual weakening over the next 24 hours. After that time, slightly warmer SSTs along the forecast track should slow or halt the weakening process, and little change in strength is expected between 24 and 72 hours. Increasing southwesterly shear by day 3 is likely to result in additional weakening later in the forecast period. The NHC intensity forecast is similar to the previous advisory and is between the HFIP corrected consensus model and the IVCN consensus aid.

Olivia is moving west-northwestward or 285/13 kt. A strong deep-layer ridge that is building westward across the central Pacific should steer Olivia generally westward over the next 2-3 days. After that time, most of the track guidance takes Olivia west-southwestward as it comes under the influence of the northeasterly trade wind flow. Although the track models are fairly unanimous in taking Olivia west-southwestward, there is large cross-track spread in the guidance at 72 hours and beyond. The HWRF and ECMWF are along the northern side of the guidance envelope while the GFS and UKMET bracket the southern side. Given the large amount of spread, the official forecast is again near the TVCN and HFIP consensus models at 72-120 h. On the forecast track, Olivia is expected to cross into the central Pacific basin later today and approach the Hawaiian Islands early next week.

KEY MESSAGES

1. Olivia is forecast to approach the main Hawaiian Islands from the east early next week, but it is too soon to determine the exact location and magnitude of any impacts. Interests in Hawaii should monitor the progress of Olivia this weekend and use this time to enact your hurricane action plan.

2. Do not focus on the exact track or intensity forecast, or any specific landfall location, as errors can be large at extended time ranges. Tropical storm or hurricane conditions could be felt anywhere in the islands as significant impacts could extend well away from the center.

Tropical Storm Olivia Distances 2300 Hours September 7 2018

FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 21.2N 136.6W   80 KT  90 MPH - Category 1 (ESE Hilo, Hawaii)
 12H  08/1800Z 21.5N 138.7W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 24H  09/0600Z 21.7N 141.5W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 36H  09/1800Z 21.8N 144.0W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 48H  10/0600Z 21.8N 146.2W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  11/0600Z 21.5N 150.0W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  12/0600Z 20.5N 154.0W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)
120H  13/0600Z 19.2N 159.0W   45 KT  50 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 PM PDT Fri Sep 07 2018

Olivia  continues to slowly weaken. Deep convection in the eyewall has been gradually decreasing in intensity and coverage, but it still completely surrounds the eye. A blend of the latest satellite intensity estimates supports lowering the initial wind speed to 95 kt. Olivia still has an annular appearance with the cloud pattern consisting of an inner core with little to no outer bands.

The hurricane is moving west-northwestward at 14 kt. There has been no change to the track forecast reasoning. Olivia is forecast to move west-northwestward for another day or so before turning to the west, or even west-southwest, as ridging builds to the north of the system. The NHC track forecast remains near the middle of the guidance envelope, and in best agreement with the consensus aids. Based on this forecast, Olivia is expected to cross into the central Pacific basin by late Saturday and approach the Hawaiian Islands in 4 to 5 days.Hurricane Olivia Distances 1100 Hours September 7 2018

Although Olivia remains in low wind shear conditions, the cyclone is over fairly cool 25-26 deg C waters. These marginal SSTs and an increasingly drier and more stable air mass should cause the slow weakening trend to continue through the forecast period. However, as mentioned in previous discussions, annular hurricanes like Olivia often weaken slower than normal in these conditions, so it is possible Olivia won’t weaken as fast as some of the guidance suggests.

FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 20.5N 133.9W   95 KT 110 MPH - Category 2 (ENE Hilo, Hawaii)
 12H  08/0600Z 21.1N 135.9W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
 24H  08/1800Z 21.6N 138.5W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 36H  09/0600Z 21.8N 141.2W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 48H  09/1800Z 22.0N 143.7W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  10/1800Z 22.0N 148.0W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  11/1800Z 21.6N 151.8W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)
120H  12/1800Z 20.5N 156.0W   50 KT  60 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 AM PDT Fri Sep 07 2018

Although Olivia  is still a major hurricane, the cloud tops have warmed some over the past several hours and the eye is not quite as distinct as it was overnight. All of the satellite intensity estimates have decreased this cycle, and the initial intensity is lowered to 100 kt using that data. Satellite data indicate that Olivia is an annular hurricane with a well organized inner core, but with a lack of outer banding features.

The hurricane is moving west-northwestward at 14 kt. The track forecast philosophy appears fairly straightforward. Olivia is expected to move westward to west-northwestward during the next few days as it remains steered by a subtropical ridge to its north. By the end of the forecast period, a turn to the west-southwest is expected as ridging builds to the northwest of the cyclone. The NHC track forecast remains near the middle of the guidance envelope, in best agreement with the consensus aids. Based on this forecast, Olivia is expected to cross into the central Pacific basin by late Saturday.

Olivia is over cool 25-26 deg C waters, and it will remain over these waters during the next several days. These marginal SSTs combined with drier air should cause a slow weakening trend through the forecast period. However, as mentioned in previous discussions, research has proven that annular hurricanes like Olivia weaken slower than normal in these types of conditions. Therefore, the NHC intensity forecast shows a slower rate of weakening than the IVCN and HCCA models.Hurricane Olivia Distances 0500 Hours September 7 2018

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 20.1N 132.5W  100 KT 115 MPH - Category 3 (ESE Hilo, Hawaii)
 12H  08/0000Z 20.7N 134.5W   90 KT 105 MPH - Category 2 (ESE Hilo, Hawaii)
 24H  08/1200Z 21.3N 137.0W   80 KT  90 MPH - Category 1 (ESE Hilo, Hawaii)
 36H  09/0000Z 21.7N 139.7W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 48H  09/1200Z 22.0N 142.3W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  10/1200Z 22.3N 146.9W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  11/1200Z 22.0N 150.5W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)
120H  12/1200Z 21.0N 155.0W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 PM PDT Thu Sep 06 2018

Olivia  has continued to strengthen since the previous advisory, with the eye becoming better defined inside of the central dense overcast. The various satellite intensity estimates range from 100-120 kt, and the initial intensity is nudged upward to 110 kt in agreement with the CIMSS satellite consensus. The hurricane remains in a light vertical shear environment and is showing good cirrus outflow, especially in the southwestern semicircle.

Olivia should remain in a light shear environment during the forecast period, so sea surface temperatures and environmental moisture should be the main controls on the intensity. The hurricane should reach the 26C sea surface temperature isotherm in about 12 h, and this should finally cause the hurricane to weaken. The forecast track keeps the cyclone over 25-26C sea surface temperatures through about the 72 h point as it also encounters a drier airmass, and thus the intensity forecast shows weakening consistent with the trend of the intensity guidance. After 72 h, the waters along the forecast track begin to warm, but the airmass near Olivia gets even drier. The guidance shows continued weakening during this time, so the intensity forecast follows suit. However, there is lower confidence in this portion of the forecast.Hurricane Olivia Distances 1100 Hours September 6 2018

Water vapor imagery continues to show a large deep-layer ridge to the north of Olivia, and the large-scale models forecast the western end of the ridge to build westward during the next several days. This pattern should steer the cyclone west-northwestward for the next 48 h or so, followed by a westward motion from 72-120 h. The tightly clustered track guidance supports this scenario, and the new forecast track is changed little from the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 18.6N 128.5W  110 KT 125 MPH - Category 3 (ESE Hilo, Hawaii)
 12H  07/0600Z 19.2N 130.5W  110 KT 125 MPH - Category 3 (ESE Hilo, Hawaii)
 24H  07/1800Z 20.0N 133.0W  100 KT 115 MPH - Category 3 (ESE Hilo, Hawaii)
 36H  08/0600Z 20.7N 135.6W   90 KT 105 MPH - Category 2 (ESE Hilo, Hawaii)
 48H  08/1800Z 21.2N 138.2W   80 KT  90 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  09/1800Z 21.5N 143.5W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  10/1800Z 21.5N 147.5W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
120H  11/1800Z 21.5N 151.5W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 AM PDT Thu Sep 06 2018

Satellite imagery indicates that Olivia  has a well-defined 20 n mi wide eye, although the eye is not quite as distinct as it was at the time of the previous special advisory. The eye is inside of a central dense overcast with eyewall cloud tops as cold as -80C. Satellite intensity estimates are currently in the 100-115 kt range. Based on these, the initial intensity is set at 105 kt, and it is possible that this is a little conservative. The hurricane is now in a light vertical shear environment and is showing good cirrus outflow in the southwestern semicircle.

The intensity guidance has been consistent in saying that Olivia should weaken due to a combination of decreasing sea surface temperatures along the forecast track and entrainment of dry air. The hurricane has not yet followed the guidance, and the current structure and convective trends suggest that this round of intensification may not be finished. After 12 h, Olivia should move north of the 26C isotherm, and the cyclone should mostly traverse sea-surface temperatures of 25-26C for the remainder of the forecast period. This development should start a weakening trend. The new intensity forecast allows for 12 h of additional strengthening, followed by a gradual weakening that follows the overall trend of the intensity guidance. However, the new forecast lies at the upper edge of the guidance, and thus most of the forecast intensities are higher than those in both the previous special and regular advisories.

Hurricane Olivia Distances 0500 Hours September 6 2018

Water vapor imagery shows a large deep-layer ridge to the north of Olivia, and the large-scale models forecast the western end of the ridge to build westward during the next several days. This pattern should steer the cyclone west-northwestward for the next 48 h or so, followed by a westward motion from 72-120 h. The track guidance is in good agreement with this scenario, and the guidance is more tightly clustered than it was 24 h ago. The new forecast track is similar to the previous track through 48 h, then it is nudged a little to the south of the previous track from 72-120 h. The new track lies close to the various consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 18.4N 127.2W  105 KT 120 MPH - Category 3 (ESE Hilo, Hawaii)
 12H  07/0000Z 18.9N 129.2W  110 KT 125 MPH - Category 3 (ESE Hilo, Hawaii)
 24H  07/1200Z 19.8N 131.8W  100 KT 115 MPH - Category 3 (ESE Hilo, Hawaii)
 36H  08/0000Z 20.5N 134.4W   90 KT 105 MPH - Category 2 (ESE Hilo, Hawaii)
 48H  08/1200Z 21.2N 137.0W   80 KT  90 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  09/1200Z 21.5N 142.0W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  10/1200Z 21.5N 146.5W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
120H  11/1200Z 21.5N 150.5W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 PM PDT Tue Sep 04 2018

Olivia  is displaying a well-defined eye this evening embedded within a circular central dense overcast. The rapid intensification seems to have leveled off, since Dvorak estimates have increased only slightly, but still support a higher wind speed of 110 kt.

Moderate easterly shear, gradually decreasing sea surface temperatures, and dry air aloft along the forecast track of Olivia will likely cause the hurricane to slowly weaken by late Wednesday. The new intensity forecast is slightly higher than the last one, near or a bit above the model consensus. The forecast is on the higher side of the guidance because I don’t feel particularly confident about this weakening, given the poor performance of the guidance for this hurricane so far.

Olivia is moving a little south of due west, 265/10. A building subtropical ridge over the eastern Pacific is forecast to cause the hurricane to move westward and west-northwestward with increasing forward speed during the next several days. Near the end of the forecast, model guidance is showing a stronger ridge, and a westward turn is possible. The guidance envelope has shifted southward on this cycle, and the official NHC prediction is adjusted in that direction.Hurricane Olivia Distances 1700 Hours September 4 2018

FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 16.7N 120.1W  110 KT 125 MPH - Category 3 (ESE Hilo, Hawaii)
 12H  05/1200Z 16.9N 121.7W  110 KT 125 MPH - Category 3 (ESE Hilo, Hawaii)
 24H  06/0000Z 17.5N 124.2W  105 KT 120 MPH - Category 3 (ESE Hilo, Hawaii)
 36H  06/1200Z 18.2N 126.8W  100 KT 115 MPH - Category 3 (ESE Hilo, Hawaii)
 48H  07/0000Z 19.1N 129.7W   90 KT 105 MPH - Category 2 (ESE Hilo, Hawaii)
 72H  08/0000Z 20.9N 135.2W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  09/0000Z 22.0N 140.5W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
120H  10/0000Z 22.5N 145.5W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 AM PDT Tue Sep 04 2018

Olivia  has become better organized since the last advisory, with conventional satellite imagery indicating the formation of a 25 n mi wide eye and a surrounding cold ring of cloud tops in the eyewall. Satellite intensity estimates from TAFB and SAB have increased to 90 kt, and that will be the initial intensity for this advisory. This burst of rapid intensification has occurred even though the analyzed easterly shear in the SHIPS model and analyses from CIMSS is in the 15-20 kt range.

How much additional intensification will occur is uncertain. The intensity guidance suggests that continued shear and decreasing sea surface temperatures along the forecast track will allow only about 12 h of additional strengthening, and most of the guidance forecasts only modest strengthening during this time. However, it is unlikely that the current rapid intensification will stop that quickly. Based on this, the new intensity forecast calls for a peak intensity of 100 kt in 12 h at the upper edge of the intensity guidance, and it is possible Olivia could get stronger. After 24 h, the cooler sea surface temperatures and entrainment of dry air should cause a gradual weakening even though the shear is forecast to decrease.Hurricane Olivia Distsnces 0500 Hours September 4 2018

The initial motion remains 275/10. As noted previously, a building subtropical ridge over the eastern Pacific is forecast to induce a westward and west-northwestward motion with increasing forward speed during the next several days. The model guidance supports this scenario with a tight clustering, and the new NHC track forecast is again an update of the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 17.0N 118.2W   90 KT 105 MPH - Category 2 (ESE Hilo, Hawaii)
 12H  05/0000Z 17.2N 119.9W  100 KT 115 MPH - Category 3 (ESE Hilo, Hawaii)
 24H  05/1200Z 17.4N 122.1W  100 KT 115 MPH - Category 3 (ESE Hilo, Hawaii)
 36H  06/0000Z 18.0N 124.5W   95 KT 110 MPH - Category 3 (ESE Hilo, Hawaii)
 48H  06/1200Z 18.8N 127.2W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
 72H  07/1200Z 20.5N 133.0W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  08/1200Z 22.0N 138.5W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)
120H  09/1200Z 23.0N 143.5W   50 KT  60 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 PM PDT Mon Sep 03 2018

Olivia   continues to strengthen with convection deepening near the center, and the latest microwave passes show a nearly complete eyewall underneath the central dense overcast. Dvorak estimates from TAFB/SAB are a consensus 65 kt, and that will be the initial wind speed.

A bit surprisingly, Olivia has intensified 25 kt over the past 24 hours. The current northeasterly shear apparently has not been enough to cause the strengthening rate to decrease, although some models are still suggesting the shear will disrupt the hurricane over the next couple of days. After inspecting the environmental winds, it appears that most of the shear will avoid the inner core, so the official forecast is raised from the previous one, lying near the upper edge of the guidance. This forecast still feels a bit conservative, given the explosive nature of many of the 2018 eastern Pacific cyclones. Olivia should move over more marginal waters in a few days, and a gradual weakening is indicated at long range.

A gradual acceleration continues with Olivia, now moving westward at about 8 kt. A strengthening ridge over the eastern Pacific should steer the cyclone westward and west-northwestward at an increasing forward pace over the next several days. The model guidance is tightly packed on this solution, and the latest NHC track forecast is basically just an update of the previous prediction.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 16.8N 116.0W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 12H  04/1200Z 16.9N 117.4W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 24H  05/0000Z 17.1N 119.5W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
 36H  05/1200Z 17.4N 121.8W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
 48H  06/0000Z 18.0N 124.2W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
 72H  07/0000Z 19.7N 129.7W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  08/0000Z 21.5N 135.3W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
120H  09/0000Z 23.0N 140.5W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 900 AM MDT Mon Sep 03 2018

There has been a pretty significant change with Olivia overnight, with the center either moving into or reforming southward under the central dense overcast. Microwave data indicate that a developing inner core is present as well, along with a notable increase in curved banding. Subjective Dvorak estimates have risen to 55 kt, which agrees well with the latest CIMSS-SATCON estimates, so the initial wind speed is raised to that value.

While the cyclone remains over warm water for the next couple of days, northeasterly shear is forecast to persist, which should keep the intensification rates of the cyclone in check, along with some mid-level dry air. Slow strengthening seems most likely, and the official forecast is raised from the previous one, mostly due to the higher initial intensity. It should be noted that the corrected- consensus guidance is even higher, so the intensity forecast could be conservative. Olivia should move over more marginal waters in a few days, and a gradual weakening is indicated at long range.

Tropical Storm Olivia Tropical Storm Force Wind Speeds September 3-8 2018

Olivia appears to be moving westward at about 6 kt, but this is pretty uncertain due to the recent center jump. The storm should move faster toward the west and eventually toward the west- northwest during the next several days as it encounters a strong ridge over the eastern Pacific Ocean. Almost all of the guidance is south of the previous model cycle, which is consistent with a stronger cyclone feeling the effects of a deep-layer ridge, so the latest NHC forecast is shifted in that direction.

FORECAST POSITIONS AND MAX WINDS

INIT  03/1500Z 16.5N 114.5W   55 KT  65 MPH - Tropical Storm (WSW Clarion Island, Mexico)
 12H  04/0000Z 16.5N 115.6W   60 KT  70 MPH - Tropical Storm (WSW Clarion Island, Mexico)
 24H  04/1200Z 16.6N 117.4W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 36H  05/0000Z 16.9N 119.4W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 48H  05/1200Z 17.3N 121.7W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  06/1200Z 18.6N 126.6W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)
 96H  07/1200Z 20.3N 132.2W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)
120H  08/1200Z 22.0N 138.0W   50 KT  60 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 300 AM MDT Mon Sep 03 2018

10 to 15 kt of northeasterly shear, noted by the UW-CIMSS shear analysis and the Decay SHIPS Intensity model, continues to impede Olivia’s   cloud pattern. A blend of the Dvorak satellite intensity estimates from TAFB and SAB, and an earlier SATCON estimate support holding the initial intensity at 40 kt.

Only modest short-term strengthening is expected over the next day or so due to the persistent shear. Afterwards, a weakening trend should commence as a result of stronger shear, decreasing sea surface temperatures, and a less than favorable thermodynamic environment. It’s worth noting, however, that the Decay SHIPS indicates a longer, slower intensification period through day 3, while the better performing IVCN and NOAA-HCCA intensity consensus guidance reflect a shorter period of intensification, only 24 hours, followed by a weakening trend through day 5. Subsequently, these models no longer indicate that Olivia will become a hurricane, and neither does the official forecast. A compromise of the previous advisory, and a blend of the consensus models was used as a basis for this advisory.

The initial motion is estimated to be westward, or 280/6 kt. Olivia should continue moving westward during the next couple of days within the mid-level steering flow of a strengthening ridge to the north. By day 3, Olivia should turn back toward the west-northwest as it rounds the southwestern periphery of the ridge. Only a minor adjustment to the south of the previous advisory was made in accord with the various consensus models.Tropical Storm Olivia Distances 2300 Hours September 2 2018

FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 17.1N 114.2W   40 KT  45 MPH - Tropical Storm (WSW Clarion Island, Mexico)
 12H  03/1800Z 17.2N 115.1W   45 KT  50 MPH - Tropical Storm (WSW Clarion Island, Mexico)
 24H  04/0600Z 17.3N 116.6W   55 KT  65 MPH - Tropical Storm (WSW Clarion Island, Mexico)
 36H  04/1800Z 17.5N 118.4W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)
 48H  05/0600Z 17.9N 120.3W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)
 72H  06/0600Z 19.1N 124.8W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)
 96H  07/0600Z 20.7N 130.0W   45 KT  50 MPH - Tropical Storm (ESE Hilo, Hawaii)
120H  08/0600Z 22.1N 135.6W   35 KT  40 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 300 AM MDT Sun Sep 02 2018

The tropical cyclone’s  convection is still not well organized, and the cloud pattern consists of an irregularly shaped CDO-like feature with limited banding. Nonetheless, a couple of scatterometer overpasses showed that the cyclone had winds to around 40 kt over the southern semicircle of the circulation. Therefore the system is being named, and the aforementioned wind speed will be used for the advisory intensity. The north-northeasterly shear that has been affecting the storm is expected to abate somewhat, which would allow for further strengthening. The official intensity forecast is in line with the latest numerical model consensus, IVCN. Some of the models show more rapid strengthening during the next day or two, but this does not seem likely at this time since the system is still not very well organized and some shear is expected to continue affecting it.

The center was somewhat elongated in the scatterometer data, but appeared to be located a little north of the previous working best track. The initial motion is a rather uncertain 300/8 kt. A weak mid-level ridge to the north of Olivia should lead to a slow west-northwestward to northwestward motion over the next day or two. Thereafter, a strengthening ridge is likely to cause a turn toward the west with some increase in forward speed. Late in the forecast period, the dynamical model consensus indicates a turn back to the west-northwest. The official track forecast is a little north of the previous one, mainly due to the recent re-positioning of the center.Tropical Storm Olivia Distances 0500 Hours September 2 2018

FORECAST POSITIONS AND MAX WINDS

INIT  02/0900Z 16.0N 112.2W   40 KT  45 MPH - Tropical Storm (ESE Hilo, Hawaii)
 12H  02/1800Z 16.6N 112.7W   45 KT  50 MPH - Tropical Storm (ESE Hilo, Hawaii)
 24H  03/0600Z 17.2N 113.6W   50 KT  60 MPH - Tropical Storm (ESE Hilo, Hawaii)
 36H  03/1800Z 17.5N 114.8W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)
 48H  04/0600Z 17.6N 116.6W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  05/0600Z 17.7N 120.2W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
 96H  06/0600Z 19.0N 124.5W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
120H  07/0600Z 20.5N 130.0W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)

Tropical Depression Seventeen-E 300 PM MDT Sat Sep 01 2018

ASCAT scatterometer overpasses at 1625Z and 1704Z indicated that the depression’s inner-core wind field remains elongated northeast-to-southwest, with a second fully exposed low-level swirl located near the northeastern end of the wind field. There was also a fairly large field of 27-29 kt surface wind vectors located in the southern quadrant. Various Dvorak satellite intensity estimates have remained unchanged since the previous advisory, so the initial intensity is being held at 30 kt for this advisory.

The initial motion estimate is an uncertain 285/10 kt. Most of the global and regional models take the cyclone west-northwestward for the next 24 h or so, and then move it westward thereafter. The exception is the new GFS model run, which takes the system northward for 36 h before turning it back westward. The GFS appears to have keyed in on the aforementioned exposed low-level swirl noted in the ASCAT and recent visible satellite data, and makes it the primary circulation center. The official forecast track calls for the main low-level center to remain/develop closer to the stronger deep convection and strongest low-level winds and associated vorticity. The more northern track of the GFS model is being discounted, but it has strongly skewed the various consensus tracks farther to the north. As a result, the new official forecast track lies south of the consensus model HCCA, and is close to the previous advisory track and a blend of the more westerly HWRF and ECMWF models.Tropical Storm Olivia Distances 1500 Hours September 1 2018

Due to the GFS model’s more northerly track, the GFS-based shear computations have a high bias. In contrast, the more southerly ECMWF model has continued to forecast much weaker shear of 10-15 kt for the next 72 h, followed by decreasing shear after that. These more modest shear conditions, combined with very warm SSTs greater than 28.5 deg C, should allow for at least steady strengthening to occur. The only hindering factor early on remains when the inner-core wind field contracts down and becomes better defined, which would result in sooner and more significant intensification to occur than is indicated by the official forecast. For now, the intensity forecast remains above the consensus models HCCA and IVCN due to the very low bias induced by the GFS-based SHIPS and LGEM intensity models.

FORECAST POSITIONS AND MAX WINDS

INIT  01/2100Z 14.9N 111.1W   30 KT  35 MPH - Tropical Storm (ESE Hilo, Hawaii)
 12H  02/0600Z 15.3N 111.6W   35 KT  40 MPH - Tropical Storm (ESE Hilo, Hawaii)
 24H  02/1800Z 15.7N 112.5W   40 KT  45 MPH - Tropical Storm (ESE Hilo, Hawaii)
 36H  03/0600Z 16.0N 113.7W   45 KT  50 MPH - Tropical Storm (ESE Hilo, Hawaii)
 48H  03/1800Z 16.2N 115.1W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)
 72H  04/1800Z 16.3N 118.3W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  05/1800Z 16.9N 122.4W   85 KT 100 MPH - Category 1 (ESE Hilo, Hawaii)
120H  06/1800Z 18.3N 127.3W   95 KT 110 MPH - Category 2 (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 900 AM MDT Sat Sep 01 2018

A 0914Z AMSR microwave pass indicated that the low-level circulation remains elongated northeast-to-southwest, with the alleged center positioned northeast of the deepest convection. Although cloud tops have cooled significant since the previous advisory, microwave data indicate that the convection remains loosely organized underneath the dense cirrus canopy. The initial intensity remains 30 kt for this advisory, which is just below the various satellite intensity estimates.

The initial motion estimate is 290/08 kt. Although the center is somewhat ill-defined, the models remain remarkably in good agreement on the cyclone moving west-northwestward for the next 24-36 h, and then turning westward as the system encounters a strong subtropical ridge extending westward from central Mexico across the eastern North Pacific. The NHC new track forecast is similar to the previous advisory track, and lies close to the HCCA and FSSE consensus models.

The ECMWF model is forecasting the shear along the cyclone’s track to decrease to less than 10 kt by 12 h and beyond. The combination of the low shear and warm waters beneath the cyclone supports at least steady strengthening. The only hindering factor early on is when the inner-core wind field finally contracts and becomes better defined to allow for more significant intensification to begin. The intensity forecast follows the consensus models HCCA and IVCN.Tropical Storm Olivia Distances 0500 Hours September 1 2018

FORECAST POSITIONS AND MAX WINDS

INIT  01/1500Z 14.9N 110.0W   30 KT  35 MPH - (E Socorro Island, Mexico)
 12H  02/0000Z 15.3N 110.7W   35 KT  40 MPH - Tropical Storm (ESE Hilo, Hawaii)
 24H  02/1200Z 15.7N 111.5W   40 KT  45 MPH - Tropical Storm (ESE Hilo, Hawaii)
 36H  03/0000Z 16.2N 112.6W   45 KT  50 MPH - Tropical Storm (ESE Hilo, Hawaii)
 48H  03/1200Z 16.4N 113.7W   55 KT  65 MPH - Tropical Storm (ESE Hilo, Hawaii)
 72H  04/1200Z 16.4N 116.8W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  05/1200Z 16.8N 120.6W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
120H  06/1200Z 18.0N 125.2W   95 KT 110 MPH - Category 2 (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 300 AM MDT Sat Sep 01 2018

Recent microwave data and GOES-16 shortwave infrared imagery have indicated that the depression consists of a broad low-level circulation with the center exposed to the northeast of the associated deep convection. Since the system is still rather disorganized, and T-numbers have not increased, the maximum winds remain 30 kt. Based on the 00Z suite of global models, it may be another day or two before the depression becomes organized enough to start strengthening. In fact, the GFS and ECMWF models in particular show the center jumping around or re-forming during the next 24 hours, with more significant deepening not occurring until after 48 hours. Once the cyclone is able to consolidate, a more robust intensification phase should occur since it will be located over warm waters and in a relatively low-shear environment. To account for the possible slow initial organization process, the NHC intensity forecast has been decreased during the first 3 days or so and is a little below the intensity consensus. After day 3, the official forecast is largely unchanged from the previous one and is closer to the intensity consensus and the HCCA model.Tropical Storm Olivia Depression 17-e 2300 Hours August 31 2018

The depression still appears to be moving west-northwestward, or 285/9 kt, but that motion is uncertain given the poor organization. As noted above, the center could jump around or re-form during the next 24 hours, but overall the cyclone should move slowly toward the west-northwest for the next 2 days, south of the subtropical ridge. After that time, the ridge is expected to strengthen, which should cause the system to move faster toward the west on days 3 through 5. Since the model trackers are bouncing around so much during the first 2 days of the forecast period, the NHC track forecast is not much different from the previous forecast to maintain continuity, although it is a little slower to be in line with the latest HCCA solution.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 14.7N 109.3W   30 KT  35 MPH
 12H  01/1800Z 15.2N 110.2W   30 KT  35 MPH - (E Socorro Island, Mexico)
 24H  02/0600Z 15.6N 111.0W   35 KT  40 MPH - Tropical Storm (ESE Hilo, Hawaii)
 36H  02/1800Z 16.0N 111.9W   40 KT  45 MPH - Tropical Storm (ESE Hilo, Hawaii)
 48H  03/0600Z 16.4N 113.0W   50 KT  60 MPH - Tropical Storm (ESE Hilo, Hawaii)
 72H  04/0600Z 16.6N 115.8W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  05/0600Z 17.0N 119.5W   85 KT 100 MPH - Category 2 (ESE Hilo, Hawaii)
120H  06/0600Z 18.0N 123.5W   90 KT 105 MPH - Category 2 (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 500 AM PDT Fri Aug 31 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Hurricane Norman, located more than 700 miles west-southwest of the southern tip of the Baja California peninsula.

1. Showers and thunderstorms continue in association with a low pressure system located several hundred miles south-southwest of Manzanillo, Mexico. Gradual development of this system is anticipated, and a tropical depression is likely to form within the next couple of days while the system moves generally west-northwestward, away from the coast of Mexico. * 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 Thu Aug 30 2018

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

The National Hurricane Center is issuing advisories on Hurricane Norman, located several hundred miles west-southwest of the southern tip of the Baja California peninsula.

1. Disorganized showers and thunderstorms located several hundred miles southwest of the southwestern coast of Mexico are associated with an area of low pressure. Environmental conditions are expected to be conducive for gradual development, and a tropical depression is likely to form this weekend or early next week while the system moves west-northwestward away from the coast of Mexico. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Thu Aug 30 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Hurricane Norman, located several hundred miles southwest of the southern tip of the Baja California peninsula.

1. Disorganized showers and thunderstorms located several hundred miles southwest of the southwestern coast of Mexico are associated with a broad area of low pressure. Environmental conditions are expected to be conducive for gradual development over the next several days, and a tropical depression is likely to form this weekend or early next week while the system moves west-northwestward away from the coast of Mexico. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high…70 percent

NWS National Hurricane Center Miami FL 500 AM PDT Wed Aug 29 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located about 1200 miles east-southeast of the Hawaiian Islands , and on Tropical Storm Norman, located several hundred miles southwest of the southern tip of the Baja California peninsula.

1. Disorganized showers and thunderstorms located several hundred miles south of the southern coast of Mexico are associated with a tropical wave. An area of low pressure is forecast to form well southwest of the coast of Mexico in association with this wave over the next day or two. Environmental conditions are expected to be conducive for development, and a tropical depression could form this weekend or early next week while the system moves west-northwestward away from the coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Tue Aug 28 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located more than 1000 miles east-southeast of the Hawaiian Islands, and on recently formed Tropical Depression Sixteen-E, located several hundred miles south-southwest of the southern tip of the Baja California peninsula.

1. Another area of low pressure is forecast to form well southwest of the coast of southwestern Mexico in a few days. Some gradual development of this system is possible by the end of the week while it moves west-northwestward or northwestward farther away from the coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...30 percent.

If this system forms, it will be Tropical Storm Olivia.

NWS National Hurricane Center Miami FL 500 AM PDT Mon Aug 28 2018

The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located about 1500 miles east-southeast of the Hawaiian Islands.

An area of low pressure is forecast to form well southwest of the coast of southwestern Mexico in a few days. Some gradual development of this system is possible by the end of the week while it moves west-northwestward or northwestward farther away from the coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Mon Aug 27 2018

An area of low pressure is forecast to form well south or southwest of the coast of southwestern Mexico in a few days. Some gradual development of this system is possible by the end of the week. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Mon Aug 27 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located more than 1400 miles west-southwest of the southern tip of the Baja California peninsula.

2. Another area of low pressure is forecast to form well south or southwest the coast of southwestern Mexico later this week. Conditions are expected to be conducive for gradual development of this system this weekend. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

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