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Tropical Depression Vicente Forecast Discussion Number 16

2018-10-23 10:38:30| National Hurricane Center (East Pacific)

Issued at 400 AM CDT Tue Oct 23 2018 000 WTPZ43 KNHC 230838 TCDEP3 Tropical Depression Vicente Discussion Number 16 NWS National Hurricane Center Miami FL EP232018 400 AM CDT Tue Oct 23 2018 Cells of heavy showers and thunderstorms are still forming near Vicente's center, but overall the convective organization has continued to deteriorate. Scatterometer data from 0418 UTC showed maximum winds of around 25 kt, so assuming some undersampling of the small circulation, the initial intensity is lowered to 30 kt. WindSat and ASCAT data revealed that Vicente's center had moved a little to the east of earlier fixes, and the depression's initial motion estimate is north-northwestward, or 330/10 kt. This motion should continue as Vicente gets drawn up between Hurricane Willa's circulation and a low- to mid-level ridge over the Gulf of Mexico, and the depression is therefore forecast to move inland over the Mexican state of Michoacan later today. Once inland, the tiny circulation is likely to dissipate quickly over mountainous terrain. A 12-hour remnant low position is provided for continuity to show a track moving inland, but in all likelihood Vicente will have dissipated by that time. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 17.2N 102.0W 30 KT 35 MPH 12H 23/1800Z 19.2N 103.2W 20 KT 25 MPH...POST-TROP/INLAND 24H 24/0600Z...DISSIPATED $$ Forecaster Berg

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Hurricane Willa Forecast Discussion Number 13

2018-10-23 10:38:30| National Hurricane Center (East Pacific)

Issued at 300 AM MDT Tue Oct 23 2018 000 WTPZ44 KNHC 230838 TCDEP4 Hurricane Willa Discussion Number 13 NWS National Hurricane Center Miami FL EP242018 300 AM MDT Tue Oct 23 2018 Willa's overall satellite presentation has continued to slowly degrade since the previous advisory, with the exception of a few brief attempts at redevelopment of an inner-core ring of deep convection. However, dry intrusions from the moat region between the larger outer eyewall and the smaller inner core have thus far prevented the reformation of an inner eyewall. Satellite intensity estimates have been steadily decreasing, and the advisory intensity is set at 115 kt, based on a average of the subjective T- and CI-numbers from TAFB and a UW-CIMSS ADT objective estimate of T6.0/115 kt. An Air Force Reserve Unit reconnaissance aircraft is scheduled to reconnoiter Hurricane Willa later this morning, providing more detailed intensity information. The initial motion estimate remains northward, but at a slower forward speed, or 360/04 kt. There are no significant changes to the previous track forecast or reasoning. Willa is expected to move slowly northward this morning around the western periphery of a deep-layer ridge located over central Mexico, and then recurve toward the north-northeast and northeast at a faster forward speed by this afternoon ahead of an approaching mid-latitude trough, with that motion continuing into this evening and Wednesday. The new NHC track forecast is near the eastern edge of the tightly packed guidance envelope, near the FSSE and GFS model tracks. There has been no microwave imagery since around 0100Z to provide information on the eyewall replacement cycle (ERC). However, conventional infrared satellite imagery suggests that the ERC is still ongoing based on the appearance of a partial moat or clear region in the northern semicircle of the inner core. Willa is currently moving over warmer and deeper water as indicated by upper-ocean heat content (UOHC) values greater than 50 units. This favorable ocean condition is expected to continue along the forecast track for another 12 hours or so, which could help to offset the weakening rate due to the gradual increase in the southwesterly wind shear. By 18 h, or just before landfall, the shear is forecast to increase to more than 20 kt and the warm water beneath the hurricane is expected to become more shallow, a combination that could lead to significant upwelling and weakening. However, the official intensity forecast follows the consensus of the various intensity models, keeping Willa's intensity near 100 kt at landfall, which is similar to the FSSE and HCCA corrected-consensus models. Despite the forecast decrease in the peak winds, Willa is expected to remain a dangerous major hurricane through landfall, bringing life-threatening storm surge, wind, and rainfall hazards to Las Islas Marias and portions of west-central and southwestern Mexico later today. After moving inland, Willa will rapidly weaken, with dissipation forecast by Wednesday over the high terrain of Mexico. However, deep moisture from the remnants of Willa is forecast to spread northeastward over northern Mexico and portions of Texas where a swath of heavy rainfall is expected midweek. Key Messages: 1. A life-threatening storm surge is expected today along the coasts of the Isla Marias, and along the coast of southern Sinaloa and Nayarit states in west-central and southwestern Mexico near the path of Willa. Residents should rush preparations to completion to protect life and property and follow any advice given by local officials. 2. Everyone in the Isla Marias, and within the hurricane warning area along the coast of west-central Mexico should prepare for life- threatening major hurricane winds associated with the core of Willa. Hurricane force winds will also extend inland across the mountainous areas of west-central Mexico as Willa moves inland. 3. Heavy rainfall from Willa is likely to produce life-threatening flash flooding and landslides over much of southwestern and west-central Mexico. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 20.8N 107.3W 115 KT 130 MPH 12H 23/1800Z 22.0N 106.5W 100 KT 115 MPH 24H 24/0600Z 23.8N 104.5W 40 KT 45 MPH...INLAND 36H 24/1800Z 25.8N 102.3W 20 KT 25 MPH...POST-TROP/INLAND 48H 25/0600Z...DISSIPATED INLAND $$ Forecaster Stewart

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Tropical Storm Vicente Forecast Discussion Number 15

2018-10-23 04:49:54| National Hurricane Center (East Pacific)

Issued at 1000 PM CDT Mon Oct 22 2018 000 WTPZ43 KNHC 230249 TCDEP3 Tropical Storm Vicente Discussion Number 15 NWS National Hurricane Center Miami FL EP232018 1000 PM CDT Mon Oct 22 2018 Although conventional satellite imagery is unimpressive tonight, a pair of microwave passes indicate there is probably still a low-level circulation remaining with Vicente. The center is located between the main convective band to the south, and sporadic cells north of the center. All of the intensity estimates that I have suggest the intensity is no lower than 35 kt, so the initial wind speed will stay 35 kt. Continued northeasterly shear will very likely cause Vicente to weaken soon, and this is the solution presented by most of the guidance. The new NHC track forecast shows Vicente coming ashore as a tropical depression tomorrow over Mexico, most similar to the GFS model. Vicente is moving northwestward, or 320/11 kt. The system should move a little faster and to the right between the mid-level ridge over the Gulf of Mexico and the southeastern portion of the circulation of Willa. The official track forecast is a bit east of the previous one, in line with the latest guidance. The 24-hour position is simply a placeholder to get Vicente inland because the cyclone will probably dissipate not long after it reaches land due to the high terrain. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 16.4N 102.0W 35 KT 40 MPH 12H 23/1200Z 17.9N 103.1W 30 KT 35 MPH 24H 24/0000Z 19.5N 104.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 24/1200Z...DISSIPATED $$ Forecaster Blake

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Hurricane Willa Forecast Discussion Number 12

2018-10-23 04:34:54| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Mon Oct 22 2018 000 WTPZ44 KNHC 230234 TCDEP4 Hurricane Willa Discussion Number 12 NWS National Hurricane Center Miami FL EP242018 900 PM MDT Mon Oct 22 2018 Willa's eye is no longer apparent in geostationary imagery, but an SSMIS overpass from 0049 UTC showed a remnant inner eye along the northern edge of a larger outer eyewall that has taken shape over the past few hours. The initial intensity has been lowered to 125 kt based on a blend of the latest Dvorak Final-T and CI numbers from TAFB. Given that the eyewall replacement cycle is well underway and that moderate southwesterly shear now affecting the hurricane is expected to increase, continued gradual weakening is forecast through landfall, and the new NHC intensity forecast through 24 hours is near or a bit above the FSU Superensemble. Despite the forecast decrease in the peak winds, Willa is expected to remain a dangerous major hurricane through landfall, and will bring life- threatening storm surge, wind, and rainfall hazards to Las Islas Marias and portions of west-central and southwestern Mexico on Tuesday. After moving inland, Willa will rapidly weaken, with dissipation forecast by Wednesday over the high terrain of Mexico. Moisture from the remnants of Willa is forecast to spread northeastward over northern Mexico and portions of Texas where a swath of heavy rainfall is expected midweek. The initial motion estimate remains northward, or 360/08. The track forecast reasoning remains unchanged, as Willa is expected to gradually recurve as it is steered by a large mid-level ridge centered to the east and a shortwave trough approaching from the northwest. The new NHC track forecast has been adjusted slightly left of the previous one due to the initial position and motion and lies along the eastern edge of the guidance envelope near the HCCA consensus aid. There continue to be differences in the forward speed of the cyclone as it approaches the coast, and the NHC forecast remains close to the forward speed of the consensus aids. Key Messages: 1. A life-threatening storm surge is expected Tuesday along the coasts of the Isla Marias, and along the coast of southern Sinaloa and Nayarit states in west-central and southwestern Mexico near the path of Willa. Residents should rush preparations to completion to protect life and property and follow any advice given by local officials. 2. Everyone in the Isla Marias, and within the hurricane warning area along the coast of west-central Mexico should prepare for life- threatening major hurricane winds associated with the core of Willa. Hurricane force winds will also extend inland across the mountainous areas of west-central Mexico as Willa moves inland. 3. Heavy rainfall from Willa is likely to produce life-threatening flash flooding and landslides over much of southwestern and west-central Mexico. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 20.5N 107.2W 125 KT 145 MPH 12H 23/1200Z 21.5N 106.9W 115 KT 130 MPH 24H 24/0000Z 23.0N 105.8W 85 KT 100 MPH...INLAND 36H 24/1200Z 25.3N 102.7W 30 KT 35 MPH...INLAND 48H 25/0000Z...DISSIPATED $$ Forecaster Brennan

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Hurricane Willa Forecast Discussion Number 11

2018-10-22 22:39:21| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Mon Oct 22 2018 000 WTPZ44 KNHC 222039 TCDEP4 Hurricane Willa Discussion Number 11 NWS National Hurricane Center Miami FL EP242018 300 PM MDT Mon Oct 22 2018 Willa continues to exhibit an impressive presentation in satellite imagery, however the small eye has become cloud filled this afternoon and and earlier microwave data indicated that an eyewall replacement cycle had begun. Subjective and objective data T-numbers are a little lower than this morning, and the initial intensity has been set at 135 kt for this advisory. The Air Force Reserve Hurricane Hunter aircraft that was en route to Willa around midday was struck by lightning in one of the outer rain bands and had to return to base due to safety issues regarding some of the onboard equipment. The hurricane has been moving due northward today at about 7 kt. The track forecast reasoning remains unchanged from the previous advisory as Willa is currently moving around the western portion of a deep-layer ridge. An approaching shortwave trough should turn Willa north-northeastward, then northward toward the west-central coast of Mexico on Tuesday, and the hurricane is forecast to make landfall within the hurricane warning area between San Blas and Mazatlan Tuesday afternoon or evening. There are still some model differences regarding the timing of landfall, and the NHC track forecast is near the various consensus aids to account for these variations in forward speed. The rapid intensification phase that Willa has gone through since its formation on Saturday appears to have ended now that an eyewall replacement has begun. Although the hurricane is forecast to remain in a low to moderate wind shear environment and over warm SSTs through tonight, some weakening is likely due to internal dynamics of the eyewall replacement. Increasing southwesterly shear on Tuesday is likely to cause some additional weakening, and the NHC intensity forecast has been adjusted accordingly, however, Willa is forecast to remain a dangerous major hurricane through landfall. Rapid weakening will occur Tuesday night as Willa moves over the mountainous terrain of Mexico, and the cyclone is expected to dissipate on Wednesday. Moisture from the remnants of Willa are forecast to spread northeastward over northern Mexico and portions of Texas where a swath of heavy rainfall is expected midweek. Key Messages: 1. A life-threatening storm surge is expected Tuesday along the coasts of the Isla Marias, and west-central and southwestern Mexico near the path of Willa. Residents should rush preparations to completion to protect life and property and follow any advice given by local officials. 2. Everyone in Isla Marias, and within the hurricane warning area along the coast of west-central Mexico should prepare for life- threatening major hurricane winds associated with the core of Willa. Hurricane force winds will also extend inland across the mountainous areas of west-central Mexico as Willa moves inland. 3. Heavy rainfall from Willa is likely to produce life-threatening flash flooding and landslides over much of southwestern and west-central Mexico. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 19.7N 107.2W 135 KT 155 MPH 12H 23/0600Z 20.7N 107.1W 125 KT 145 MPH 24H 23/1800Z 22.0N 106.5W 110 KT 125 MPH 36H 24/0600Z 23.9N 104.7W 60 KT 70 MPH...INLAND 48H 24/1800Z 26.2N 101.5W 25 KT 30 MPH...INLAND 72H 25/1800Z...DISSIPATED $$ Forecaster Brown

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