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Tropical Storm Leslie Forecast Discussion Number 49
2018-10-08 16:38:51| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Mon Oct 08 2018 000 WTNT43 KNHC 081438 TCDAT3 Tropical Storm Leslie Discussion Number 49 NWS National Hurricane Center Miami FL AL132018 1100 AM AST Mon Oct 08 2018 For the fourth (and hopefully final) time as a tropical or subtropical cyclone, Leslie has crossed 48W. The convective pattern of the tropical storm hasn't changed significantly over the past several hours, though there is some evidence of a convective band attempting to wrap around the western side of the storm. The initial intensity is still 45 kt, based on a blend of the most recent current intensity estimates from TAFB, SAB, and the UW-CIMSS SATCON. There has been little change in the intensity forecast. Just about all of the typically reliable intensity models still call for Leslie to gradually strengthen over the next 3 days, despite marginal SSTs. All of the dynamical models call for Leslie to become a hurricane once again by 72 h, but SHIPS and LGEM are a little lower. The official intensity forecast remains near the HCCA and IVCN consensus aids, and calls for Leslie to become a hurricane by the end of the week. Leslie has continued to move east-southeastward, now at 12 kt, and the global models are in good agreement that this motion will continue through today. After that time, most of the guidance generally shows that Leslie will separate from a mid-latitude trough, causing the tropical storm to turn toward the southeast or south-southeast and slow down. A day or so after that, another mid-latitude trough will approach from the west and cause Leslie to accelerate toward the east-northeast. The timing of Leslie's acceleration is still very uncertain, and the model spread beyond 72 h remains very high. Until the spread decreases, I don't feel confident making a big change to the forecast, so the official track forecast has only been slightly tweaked to bring it closer to HCCA and TVCN. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 34.6N 47.0W 45 KT 50 MPH 12H 09/0000Z 33.6N 45.2W 50 KT 60 MPH 24H 09/1200Z 32.0N 43.5W 50 KT 60 MPH 36H 10/0000Z 30.2N 42.2W 55 KT 65 MPH 48H 10/1200Z 29.1N 41.2W 60 KT 70 MPH 72H 11/1200Z 29.5N 37.0W 65 KT 75 MPH 96H 12/1200Z 33.0N 28.0W 70 KT 80 MPH 120H 13/1200Z 39.0N 18.0W 65 KT 75 MPH $$ Forecaster Zelinsky
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Hurricane Michael Forecast Discussion Number 8
2018-10-08 16:38:51| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Mon Oct 08 2018 000 WTNT44 KNHC 081438 TCDAT4 Hurricane Michael Discussion Number 8 NWS National Hurricane Center Miami FL AL142018 1100 AM EDT Mon Oct 08 2018 The satellite presentation of Michael has continued to improve overnight and this morning, with the center well embedded within an area of cold cloud tops. An eye is becoming apparent in visible imagery, and this was also confirmed by a recent SSMIS microwave overpass and the Air Force Reserve reconnaissance aircraft. The aircraft reported a minimum pressure around 982 mb during the most recent pass through the center, and also found flight-level winds that support upgrading Michael to a a 65-kt hurricane for this advisory. Although the outflow is still somewhat restricted over the western portion of the circulation, it has been expanding in that direction. The global models suggest that the shear will relax a little more while the hurricane moves over the very warm waters of the southeastern Gulf of Mexico. Now that Michael has developed an inner core, steady to rapid strengthening is predicted during the next 24 to 36 hours. The SHIPS Rapid Intensification Index and DTOPS give a 55-60 percent chance of rapid intensification during the next 24 hours. The updated NHC forecast is near the upper-end of the guidance and calls for rapid strengthening over the next 24 hours, and brings Michael to major hurricane status. After that time, most of the intensity guidance slows down the rate of intensification, perhaps due to a slight increase in southwesterly shear. Weakening is expected after landfall, but the forecast track keeps a portion of the circulation over water along the southeast U.S. coast, so Michael is predicted to remain a tropical storm through 72 hours. The system should become a powerful extratropical low off the U.S. Mid-Atlantic coast in about 4 days. Reconnaissance aircraft fixes indicate that Michael is still moving a little east of due north. The hurricane should move northward or north-northwestward over the next couple of days while the storm crosses the eastern Gulf of Mexico. By 48 hours, Michael should turn northeastward ahead of a trough moving into the central United States. The cross-track spread in the guidance has decreased since yesterday, but there continue to be differences in how fast Michael moves northward over the Gulf of Mexico. The HWRF and GFS remain among the faster models, while the ECMWF is still much slower. The NHC track is along the eastern side of the guidance through 24 hours due to the recent motion of the storm, and is remains near the various consensus aids after that time. The post-tropical portion of the track and intensity forecast is based on guidance provided by the Ocean Prediction Center. Key Messages: 1. Michael is forecast to be a dangerous major hurricane when it reaches the northeastern Gulf Coast on Wednesday, and life- threatening storm surge is possible along portions of the Florida Gulf Coast regardless of the storm's exact track or intensity. Residents in the storm surge and hurricane watch areas should follow any advice given by local officials, as storm surge and hurricane warnings will likely be issued later today. 2. Heavy rainfall from Michael could produce life-threatening flash flooding from the Florida Panhandle and Big Bend region into portions of the Carolinas through Thursday. 3. Hurricane conditions will spread over portions of western Cuba this afternoon, where a hurricane warning is now in effect. Tropical storm conditions are expected over the northeastern Yucatan Peninsula and the Isle of Youth today. 4. Michael is expected to produce heavy rainfall and flash flooding over portions of western Cuba and the northeastern Yucatan Peninsula of Mexico during the next couple of days. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 21.2N 84.9W 65 KT 75 MPH 12H 09/0000Z 22.6N 85.3W 85 KT 100 MPH 24H 09/1200Z 24.4N 85.9W 95 KT 110 MPH 36H 10/0000Z 26.4N 86.4W 105 KT 120 MPH 48H 10/1200Z 28.6N 86.1W 105 KT 120 MPH 72H 11/1200Z 33.0N 82.5W 45 KT 50 MPH...INLAND 96H 12/1200Z 37.8N 73.6W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 13/1200Z 42.8N 59.0W 55 KT 65 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown
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Tropical Storm Michael Forecast Discussion Number 7
2018-10-08 10:58:42| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Mon Oct 08 2018 000 WTNT44 KNHC 080858 TCDAT4 Tropical Storm Michael Discussion Number 7 NWS National Hurricane Center Miami FL AL142018 400 AM CDT Mon Oct 08 2018 Michael has become better organized this morning, with the deep convection migrating westward on top of the low-level center and upper-level outflow beginning to increase within the western semicircle. An Air Force Reserve Hurricane Hunter aircraft made several passes through the system during the past few hours, and somewhat surprisingly, found that the central pressure has fallen to about 983 mb and maximum winds have increased to near 60 kt. This increase in intensity indicates that despite the shear which has been affecting Michael, the system has, by definition, rapidly intensified during the past 24 hours. With the increase in the initial wind speeds, the official intensity forecast is higher than in the previous forecast. Decreasing vertical shear and very warm sea surface temperatures are expected to support continued strengthening, and due to the favorable conditions, the NHC intensity forecast follows a blend of the IVCN consensus and the HCCA model. This new official forecast brings the intensity to just below major hurricane strength in 48 hours, and since the storm will still be over water for a time between 48 and 72 hours, there is a real possibility that Michael will strengthen to a major hurricane before landfall. Weakening is expected after landfall, but the system will likely maintain tropical storm strength after day 4 when it moves off the east coast of the United States. Michael should then become an extratropical low by day 5. The reconnaissance fixes indicate that Michael's center is moving northward, or 360 degrees at 6 kt. A general northward motion with some increase in forward speed is expected during the next 48 hours as Michael enters the southerly flow between high pressure over the western Atlantic and a deep-layer trough over the western and central United States. After 48 hours, Michael is expected to turn northeastward toward and across the southeastern United States, exiting over the western Atlantic between days 4 and 5. Nearly all of the track models have shifted westward after 24 hours, which left the previous forecast near the eastern edge of the guidance envelope. Due to this shift, the new NHC track forecast has also been adjusted westward close to the consensus aids. Overall the track guidance is in fairly good agreement up until landfall along the Florida Panhandle or Florida Big Bend, which has yielded a fairly confident track forecast. Key Messages: 1. Hurricane conditions are expected over portions of western Cuba, where a hurricane warning is now in effect. Tropical storm conditions are expected over the northeastern Yucatan Peninsula and the Isle of Youth today. 2. Michael is expected to produce heavy rainfall and flash flooding over portions of western Cuba and the northeastern Yucatan Peninsula of Mexico during the next couple of days. 3. Michael is forecast to be a hurricane, and possibly a major hurricane, when it reaches the northeastern Gulf Coast by mid-week, and storm surge and hurricane watches are now in effect for portions of the area. Some areas along the Florida Gulf Coast are especially vulnerable to storm surge, regardless of the storm's exact track or intensity. Residents in the watch areas should monitor the progress of this system and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 20.6N 85.5W 60 KT 70 MPH 12H 08/1800Z 21.7N 85.6W 70 KT 80 MPH 24H 09/0600Z 23.5N 86.1W 85 KT 100 MPH 36H 09/1800Z 25.2N 86.7W 90 KT 105 MPH 48H 10/0600Z 27.2N 86.7W 95 KT 110 MPH 72H 11/0600Z 31.2N 84.5W 55 KT 65 MPH...INLAND 96H 12/0600Z 35.5N 77.5W 50 KT 60 MPH...INLAND 120H 13/0600Z 40.5N 64.5W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Berg
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Hurricane Sergio Forecast Discussion Number 36
2018-10-08 10:50:45| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Mon Oct 08 2018 000 WTPZ41 KNHC 080850 TCDEP1 Hurricane Sergio Discussion Number 36 NWS National Hurricane Center Miami FL EP212018 200 AM PDT Mon Oct 08 2018 Sergio continues to have a large 60 nmi diameter eye with several mesovorticies within it. Although the cloud pattern is quite symmetric around the eye, the cloud tops are not very cold, likely due to some ocean upwelling beneath the hurricane. The Dvorak estimates are largely unchanged from earlier and still support an initial intensity of 80 kt. Sergio is now drifting northwestward in weak steering currents. A shortwave trough is expected to approach Sergio from the north, and that feature, and a large trough over the southwestern United States should cause Sergio to turn northeastward tonight. This motion with an increase in forward speed is expected through the remainder of the week. The models are in good agreement overall, and the NHC track forecast lies near the middle of the guidance envelope. Based on this forecast, Sergio is expected to be very near the Baja California peninsula in about 4 days. Sergio is expected to hold its strength or weaken only slightly during the next day or so while it remains in a favorable atmospheric environment. However, steady weakening is expected after that time due to increasing shear, drier air, and progressively cooler waters along the forecast track. Based on the intensity guidance and environmental conditions, Sergio is expected to be a tropical storm by the time it nears the Baja California peninsula. The cyclone should weaken quickly once it moves inland. The NHC intensity forecast is an update of the previous one and near the HCCA and IVCN guidance. Recent ASCAT data was very helpful in analyzing the 34- and 50-kt wind radii. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 15.2N 128.1W 80 KT 90 MPH 12H 08/1800Z 15.7N 128.3W 75 KT 85 MPH 24H 09/0600Z 16.4N 127.9W 75 KT 85 MPH 36H 09/1800Z 17.2N 126.6W 70 KT 80 MPH 48H 10/0600Z 18.2N 124.8W 65 KT 75 MPH 72H 11/0600Z 21.4N 120.0W 60 KT 70 MPH 96H 12/0600Z 26.5N 114.0W 45 KT 50 MPH...NEAR BAJA CALIFORNIA 120H 13/0600Z 33.0N 106.5W 25 KT 30 MPH...INLAND $$ Forecaster Cangialosi
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Tropical Storm Leslie Forecast Discussion Number 48
2018-10-08 10:46:40| National Hurricane Center (Atlantic)
Issued at 500 AM AST Mon Oct 08 2018 000 WTNT43 KNHC 080846 TCDAT3 Tropical Storm Leslie Discussion Number 48 NWS National Hurricane Center Miami FL AL132018 500 AM AST Mon Oct 08 2018 There has not been a lot of change with Leslie overnight. Deep convection is still organized in curved bands near and to the north of the center, but there is some dry air entraining into the western side of the circulation. A blend of the latest satellite intensity estimates supports holding the initial intensity at 45 kt. Leslie is over cool 24 deg C waters, but it will be headed over slightly warmer waters during the next few days while remaining in low wind shear conditions. Therefore, slow strengthening is expected and most of the intensity models show Leslie reaching hurricane strength once again within the next 3 to 4 days. By the end of the period, cooler waters and an increase in shear could cause some weakening. The NHC intensity forecast is a little higher than the previous one, to trend toward the latest IVCN and HCCA guidance. Leslie is moving east-southeastward at 11 kt steered by the flow on the south side of a broad mid- to upper-level trough over the north Atlantic. An east-southeast to southeast motion is expected during the next couple of days as the trough passes by to the north of Leslie. After that time, another large-scale trough will approach Leslie from the northwest and that should cause the storm to turn east-northeastward at a faster pace in the 4 to 5 day time frame. The models have come into a better agreement this cycle showing a faster and more northward motion at the end of the period, and the NHC forecast has been adjusted accordingly. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 35.2N 47.9W 45 KT 50 MPH 12H 08/1800Z 34.3N 46.2W 45 KT 50 MPH 24H 09/0600Z 32.9N 44.0W 50 KT 60 MPH 36H 09/1800Z 31.1N 42.4W 55 KT 65 MPH 48H 10/0600Z 29.6N 41.3W 60 KT 70 MPH 72H 11/0600Z 28.8N 38.3W 65 KT 75 MPH 96H 12/0600Z 31.2N 30.4W 70 KT 80 MPH 120H 13/0600Z 36.8N 20.0W 65 KT 75 MPH $$ Forecaster Cangialosi
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