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Tropical Storm Vicente Forecast Discussion Number 14

2018-10-22 22:33:23| National Hurricane Center (East Pacific)

Issued at 400 PM CDT Mon Oct 22 2018 000 WTPZ43 KNHC 222033 TCDEP3 Tropical Storm Vicente Discussion Number 14 NWS National Hurricane Center Miami FL EP232018 400 PM CDT Mon Oct 22 2018 Satellite imagery indicates that Vicente continues to lose organization. Deep convection has been sporadic and is generally limited to the east and south of the storm's center. Unfortunately, the most recent ASCAT pass missed the center of the system, so we are unable to verify if Vicente's circulation is still closed. Due to Vicente's deteriorating satellite presentation, the initial intensity has been lowered to 35 kt, which is a blend of Dvorak Current Intensity estimates from TAFB and SAB. This intensity estimate may be generous, however. Although sea-surface temperatures near Vicente are quite warm (29 degrees C), the storm continues to be negatively affected by northeasterly vertical wind shear. Moreover, the cyclone's small size has likely made it more susceptible to shear. Although the shear is forecast to weaken slightly over the the next day or so, the influence of the large circulation of Hurricane Willa and the interaction with land is likely to cause the storm to dissipate in 24-36 hours, or less. The majority of the dynamical guidance models dissipate Vicente by tomorrow afternoon and the official forecast calls for dissipation by 36 h. It should be noted that, given the current tenuous state of Vicente, the system could dissipate at any time. Vicente's current motion is west-northwestward, or 300/10 kt. The system is forecast to turn toward the northwest and north-northwest while moving 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 little faster than the previous one and roughly in the middle of the model guidance. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 15.4N 101.5W 35 KT 40 MPH 12H 23/0600Z 16.8N 102.7W 30 KT 35 MPH 24H 23/1800Z 19.0N 104.0W 25 KT 30 MPH...INLAND 36H 24/0600Z...DISSIPATED $$ Forecaster Pasch

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Hurricane Willa Forecast Discussion Number 10

2018-10-22 17:15:48| National Hurricane Center (East Pacific)

Issued at 900 AM MDT Mon Oct 22 2018 000 WTPZ44 KNHC 221515 CCA TCDEP4 Hurricane Willa Discussion Number 10...corrected NWS National Hurricane Center Miami FL EP242018 900 AM MDT Mon Oct 22 2018 Corrected wording in Key Messages number 2 Willa is an extremely impressive hurricane in infrared and visible satellite imagery this morning. The small, but very distinct, eye is embedded within a symmetric central dense overcast with cloud tops of -70 to -80 degrees Celsius. A very recent SSMIS microwave overpass is the first to indicate that an outer eyewall has formed, suggesting that an eyewall replacement cycle has started. The latest objective T-numbers from UW-CIMSS are T7.0/140 kt, and subjective Dvorak intensity estimates from TAFB and SAB are 140 kt and 127 kt, respectively. Based on these data the initial intensity has been increased to 140 kt. An Air Force Reserve Hurricane Hunter aircraft is currently en route to Wilma and should provide a better assessment of the storm's intensity by early this afternoon. Willa is moving northward 6 kt. The hurricane is forecast to continue to move northward today around the western flank of a deep-layer ridge that is located over the Gulf of Mexico. A short wave trough that is seen in water vapor imagery near 130W longitude is forecast to deepen as it moves eastward toward Baja California. This should cause Willa to turn north-northeastward tonight, then accelerate northeastward on Tuesday, bringing the center of the hurricane onshore along the west-central coast of Mexico Tuesday afternoon or evening. As mentioned in the previous advisory, the track guidance is good agreement on the overall scenario but there are still some notable differences in the predicted forward speed of the hurricane. The NHC track forecast leans toward the faster solutions of the GFS and GFS ensemble mean, which have been handling Willa's track the best so far. The environment of low wind shear and water temperatures of 28 to 29.5 degrees Celsius suggest some additional strengthening is possible but with the evidence that an eyewall replacement has begun, some fluctuations intensity are possible during the next 12 to 24 hours. After that time, increasing southwesterly shear is forecast to induce weakening, but Willa is likely to remain an extremely dangerous major hurricane when it makes landfall along the west-central coast of Mexico. After landfall, shear and the mountainous terrain of Mexico will cause rapid weakening and dissipation of the cyclone. 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 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 22/1500Z 19.1N 107.2W 140 KT 160 MPH 12H 23/0000Z 20.1N 107.2W 140 KT 160 MPH 24H 23/1200Z 21.4N 106.9W 135 KT 155 MPH 36H 24/0000Z 23.1N 105.6W 90 KT 105 MPH...INLAND 48H 24/1200Z 25.4N 102.5W 30 KT 35 MPH...INLAND 72H 25/1200Z...DISSIPATED $$ Forecaster Brown

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Tropical Storm Vicente Forecast Discussion Number 13

2018-10-22 16:45:21| National Hurricane Center (East Pacific)

Issued at 1000 AM CDT Mon Oct 22 2018 000 WTPZ43 KNHC 221445 TCDEP3 Tropical Storm Vicente Discussion Number 13 NWS National Hurricane Center Miami FL EP232018 1000 AM CDT Mon Oct 22 2018 Satellite imagery and microwave data this morning are indicating that the early morning re-strengthening of Vicente has ended. The system appears elongated, with the low-level center becoming increasingly difficult to locate. Radar imagery from Acapulco, Mexico, does not suggest a well-organized tropical cyclone at this time. The averages of the subjective Dvorak analyses from SAB and TAFB support an initial intensity of 40 kt, which may be a little generous. Moderate northeasterly shear is forecast to continue over the cyclone the next couple of days which should support ongoing steady weakening. The GFS, HWRF, and HMON models show the cyclone dissipating tonight, with some of the other global model guidance showing little change in intensity until landfall. Given the current disorganized appearance, a weakening trend appears to be the most realistic scenario, with Vicente forecast to weaken to a tropical depression before it makes landfall over southwestern Mexico in about 36 hours. Regardless of the forecast intensity, the primary hazard will be heavy rainfall across portions of southern and southwestern Mexico, which could cause life-threatening flash flooding. Vicente appears to have begun a turn to the west-northwest, and the initial motion is now estimated to be 290/10 kt as the system begins to round the southwestern periphery of a mid-level ridge over Mexico. As the cyclone rounds the western periphery of the ridge later today and Tuesday, a turn to the northwest and then north-northwest is expected. The latest NHC forecast track is similar, and just slightly to the right of the previous one, and is near the tightly clustered model guidance. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 14.9N 100.8W 40 KT 45 MPH 12H 23/0000Z 15.8N 101.8W 35 KT 40 MPH 24H 23/1200Z 17.4N 103.0W 30 KT 35 MPH 36H 24/0000Z 18.9N 104.0W 30 KT 35 MPH...NEAR THE COAST 48H 24/1200Z 20.3N 104.8W 20 KT 25 MPH...POST-TROP/INLAND 72H 25/1200Z...DISSIPATED $$ Forecaster Pasch/Latto

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Hurricane Willa Forecast Discussion Number 9

2018-10-22 10:38:46| National Hurricane Center (East Pacific)

Issued at 300 AM MDT Mon Oct 22 2018 000 WTPZ44 KNHC 220838 TCDEP4 Hurricane Willa Discussion Number 9 NWS National Hurricane Center Miami FL EP242018 300 AM MDT Mon Oct 22 2018 Willa is an impressive hurricane with rapid to explosive deepening having occurred over the past 48 hours, and yielding a 105-kt intensity increase during that time. Satellite intensity estimates range from subjective Dvorak T-numbers of T6.5/127 kt from TAFB and SAB to objective T-numbers of T7.0/140 kt from UW-CIMSS ADT and NHC. The most recent UW-CIMSS SATCON value around 0437Z was 127 kt. Based on these data and the slightly more ragged appearance of the CDO over the past couple of hours, the intensity is raised to 135 kt, which is just below category 5 strength. Willa is now moving northward and the initial motion estimate is 360/06 kt. Willa is forecast to continue moving northward today as the hurricane rounds the western portion of a deep-layer ridge located over central Mexico and which extends westward along 20N latitude to near the Pacific coast of Mexico. On Tuesday, a turn toward the north-northeast and northeast at a slightly faster forward speed is expected as the hurricane gets caught up in southwesterly flow ahead of an approaching mid-/upper-level trough. The latest 00Z NHC model guidance is in decent agreement on this general track scenario, but with noticeable differences in the forward speed. Internal statistical analyses show that the ECMWF and UKMET models have had a slow westward bias over the past 48 hours, which has significantly affected the consensus models. As a result, the new NHC forecast is a little to the right of and slightly faster the previous advisory track and the consensus models, and lies close to GFS model which has verified the best thus far. On the forecast track, Willa is expected to move over Las Islas Marias on Tuesday and then move inland over southwestern and west-central Mexico Tuesday night or early Wednesday. A 72-hour position has been provided only for continuity purposes beyond the 48-hour period, and Willa will likely have dissipated by then. Water temperatures ahead of the powerful hurricane are forecast to increase from 28 deg C to near 29.5 deg C, and the depth of the warm water is also expected to increase, which would tend to offset any cold upwelling beneath Willa. The deep-layer shear is forecast to increase to a little more than 10 kt during the next 36 hours, and remain at that level during the duration of that time period. These conditions would favor at least slight strengthening before the internal dynamics of the hurricane in the form of an eyewall replacement cycle (ERC) induces some weakening. With the eye diameter already at 10-15 nmi, an ERC could begin at any time during the next 12 hours. Shortly after 36 hours, the shear is expected to increase sharply to more than 20 kt, which will cause more significant weakening. However, Willa is still expected to be near major hurricane strength when it makes landfall along the west-central coast of Mexico. After landfall, the mountainous terrain along with strong southwesterly wind shear of more than 30 kt will cause rapid weakening and dissipation of the cyclone inland over north-central Mexico. Key Messages: 1. Willa is forecast to be a dangerous hurricane when it reaches the Islas Marias and the coast of southwestern Mexico by late Tuesday or Wednesday morning, bringing a life-threatening storm surge and flash flooding along with damaging hurricane-force winds. A Hurricane Warning is in effect for these areas, and residents should rush preparations to completion to protect life and property and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 18.2N 107.1W 135 KT 155 MPH 12H 22/1800Z 19.2N 107.2W 135 KT 155 MPH 24H 23/0600Z 20.4N 107.2W 125 KT 145 MPH 36H 23/1800Z 21.8N 106.5W 115 KT 130 MPH 48H 24/0600Z 23.8N 104.6W 50 KT 60 MPH...INLAND WNCTRL MEXICO 72H 25/0600Z 27.0N 99.5W 20 KT 25 MPH...POST-TROP/INLAND 96H 26/0600Z...DISSIPATED INLAND $$ Forecaster Stewart

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Tropical Storm Vicente Forecast Discussion Number 12

2018-10-22 10:36:20| National Hurricane Center (East Pacific)

Issued at 400 AM CDT Mon Oct 22 2018 000 WTPZ43 KNHC 220836 TCDEP3 Tropical Storm Vicente Discussion Number 12 NWS National Hurricane Center Miami FL EP232018 400 AM CDT Mon Oct 22 2018 Vicente's cloud pattern has become better organized during the past several hours. A burst of deep convection has developed near the surface center, and a developing curved band with associated cold cloud tops of -80C is wrapping around nearly 70 percent of the cyclone's circulation. A SATCON analysis, subjective and objective satellite intensity estimates from TAFB and SAB, and an earlier 0325 UTC ISRO ScatSAT-1 overpass support an initial intensity increase to 40 kt for this advisory. Despite this temporary strengthening interlude, modest northeasterly shear as indicated by the statistical intensity aids and the UW-CIMSS shear product should induce weakening soon. In fact, most of the large-scale models agree with dissipation in 36 hours, or show the cyclone reaching the Mexico coastline around the 48-hour period as a depression. Although the majority of the models support dissipation over water, the NHC forecast will reflect landfall as a tropical depression for continuity purposes. Regardless of the forecast intensity scenarios, the primary hazard will be heavy rainfall across portions of southern and southwestern Mexico, which could cause life-threatening flash flooding. The initial motion is estimated to be westward, or 275/9 kt, within southeast to easterly steering flow produced by a mid-tropospheric ridge extending westward over southern Mexico from the central Gulf of Mexico. Vicente is expected to round the southwestern to western periphery of the aforementioned ridge during the next 36 hours, or prior to dissipation. The track forecast is a little slower than the previous advisory, and is based on a blend of the Florida State Superensemble and the TVCN multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 14.1N 99.7W 40 KT 45 MPH 12H 22/1800Z 14.8N 100.8W 40 KT 45 MPH 24H 23/0600Z 16.1N 102.3W 35 KT 40 MPH 36H 23/1800Z 17.7N 103.5W 30 KT 35 MPH 48H 24/0600Z 19.5N 104.4W 20 KT 25 MPH...POST-TROP/INLAND 72H 25/0600Z...DISSIPATED $$ Forecaster Roberts

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