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Tropical Storm Fred Forecast Discussion Number 24
2021-08-15 16:52:55| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Sun Aug 15 2021 000 WTNT41 KNHC 151452 TCDAT1 Tropical Storm Fred Discussion Number 24 NWS National Hurricane Center Miami FL AL062021 1100 AM EDT Sun Aug 15 2021 Satellite imagery and reports from an Air Force Reserve Hurricane Hunter aircraft indicate that the remnants of Fred have re-developed into a tropical cyclone over the eastern Gulf of Mexico. Satellite imagery shows a well-defined low-level center near the northern end of a broadly curved convective band. The Hurricane Hunters reported a central pressure of 1008 mb, along with 925-mb flight-level winds of 52 kt and SFMR wind estimates near 35 kt about 70 n mi northeast of the center. Based on these developments and data, the system was upgraded back to Tropical Storm Fred a couple of hours ago. The center re-formed northward during the redevelopment process, and the initial position is re-located to the north of the previous advisory position. While the forecast guidance is basically unchanged in calling for a north-northwest motion followed by a turn toward the north near landfall on the northern Gulf coast, the new initial position requires the forecast track to be shifted about 40 n mi to the east of the previous track through the landfall time. Fred is now expected to make landfall in the western Florida Panhandle sometime Monday afternoon or evening. Upper-level southwesterly flow between a trough to the north and northwest of Fred and an anticyclone to the southeast of the storm should keep the tropical cyclone in moderate southwesterly vertical shear until landfall. The intensity guidance forecasts gradual intensification before landfall, and the official intensity forecast follows the guidance in calling for a peak intensity of 45 kt. After landfall, Fred should quickly weaken and dissipate as it moves into the Tennessee Valley. Users are reminded not to focus on the exact forecast track of Fred, since rainfall, storm surge, and wind hazards will extend over an area well east of the center. KEY MESSAGES: 1. Today through Tuesday, heavy rainfall could lead to areal, urban, small stream and river flooding impacts across southern Florida, the Florida Big Bend and Panhandle, southern Alabama, portions of Georgia, and the western Carolinas. From Tuesday onward, heavy rain and flood impacts could continue into other portions of the Southeast and into the southern and central Appalachians and Piedmont as Fred interacts with a front in the area. 2. Dangerous storm surge inundation is possible along portions of the coast of the Florida Panhandle, and a Storm Surge Warning has been issued for this area. Interests in these areas should follow any advice given by local officials. 3. Tropical storm conditions are expected in the Tropical Storm Warning area in the Florida Panhandle beginning on Monday. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 26.1N 84.9W 35 KT 40 MPH 12H 16/0000Z 27.4N 85.8W 40 KT 45 MPH 24H 16/1200Z 28.9N 86.5W 45 KT 50 MPH 36H 17/0000Z 30.5N 86.5W 45 KT 50 MPH...INLAND 48H 17/1200Z 32.5N 86.4W 30 KT 35 MPH...INLAND 60H 18/0000Z 34.7N 85.7W 20 KT 25 MPH...POST-TROP/INLAND 72H 18/1200Z...DISSIPATED $$ Forecaster Beven
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Remnants of Fred Forecast Discussion Number 23
2021-08-15 10:59:52| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Sun Aug 15 2021 000 WTNT41 KNHC 150859 TCDAT1 Remnants Of Fred Discussion Number 23 NWS National Hurricane Center Miami FL AL062021 500 AM EDT Sun Aug 15 2021 The remnants of Fred have been undergoing some noticeable changes early this morning, with one of those features being a curved band of deep convection having developed in the northeastern quadrant of the larger cyclonic envelope. A low-level jet (925-850 mb) was noted in the 0000 UTC upper-air air data and in the Key West VAD wind profile radar data late last night and early this morning. That speed maximum produced 2-hours worth of 34-kt and higher 10-meter winds at the Sand Key (SANF1) C-MAN station south of Key West, and that is the basis for the increasing the intensity to 35 kt for this advisory. That speed maximum is also likely responsible for the large increase in convection north of the Dry Tortugas, which also has helped to spin up a small mesovortex that passed over buoy 42026 between 0500-0600 UTC, causing the pressure to decrease 3.6 mb in one hour. That small-scale feature is moving westward and could become the the low-level center farther to the north of the current alleged center within the next few hours. The initial motion estimate is an uncertain 330/07 kt. The system is expected to move north-northwestward or northwestward today and tonight through a narrow weakness in the subtropical ridge located between 85W-88W longitude based on 0000Z upper-air data. The system is forecast to turn northward on Monday as it nears the northern Gulf of coast and comes under the influence of a mid- to upper-level trough forecast to drop southward over the western Gulf of Mexico. The new NHC track forecast had to be shifted farther to the east of the previous advisory, and subsequent forecast tracks may have to be shifted even further east if a new center develops farther to the north or northeast as per what recent satellite and buoy data suggest. The official forecasts track lies a little to the left of the tightly packed consensus track models. Upper-level winds are expected to remain marginally conducive for strengthening due to at least some modest southwesterly wind shear affecting the cyclone for the next 48 hours. After landfall, Fred is forecast to weaken rapidly and the global models indicate the circulation should dissipate by around 96 hours. KEY MESSAGES: 1. Today through Monday, heavy rainfall could lead to areal, urban, and small stream flooding impacts, and cause new and renewed river flooding across southern Florida, the Big Bend, and Panhandle. From Monday onward, heavy rain and flood impacts could extend into other portions of the Southeast and into the southern and central Appalachians and Piedmont as Fred interacts with a front in the area. 2. Fred is forecast to regenerate as a tropical cyclone over the Gulf of Mexico later today, and bring a risk of tropical storm conditions to portions of the northern Gulf coast, especially from coastal Mississippi to the Florida Panhandle beginning Monday night. A Tropical Storm Warning will likely be required for a portion of this area later this morning. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 24.4N 84.6W 35 KT 40 MPH 12H 15/1800Z 25.5N 85.6W 35 KT 40 MPH...TROPICAL CYCLONE 24H 16/0600Z 27.0N 86.6W 40 KT 45 MPH 36H 16/1800Z 28.5N 87.1W 45 KT 50 MPH 48H 17/0600Z 30.3N 87.1W 45 KT 50 MPH 60H 17/1800Z 32.5N 86.8W 30 KT 35 MPH...INLAND 72H 18/0600Z 35.0N 85.8W 20 KT 25 MPH...INLAND 96H 19/0600Z...DISSIPATED $$ Forecaster Stewart
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Tropical Storm Grace Forecast Discussion Number 8
2021-08-15 10:59:18| National Hurricane Center (Atlantic)
Issued at 500 AM AST Sun Aug 15 2021 000 WTNT42 KNHC 150859 TCDAT2 Tropical Storm Grace Discussion Number 8 NWS National Hurricane Center Miami FL AL072021 500 AM AST Sun Aug 15 2021 Radar data from the Leeward Islands and Puerto Rico, as well as satellite images, indicate that Grace is still not a well-organized tropical cyclone, although over the past few hours banding features have become more evident and the outflow has improved. An earlier ASCAT-C overpass showed peak winds of 30 kt associated with Grace, and the latest Dvorak intensity estimate from TAFB was 35 kt. Assuming some undersampling from the ASCAT instrument, the initial intensity estimate remains 35 kt for this advisory. Grace continues to move fairly quickly to the west-northwest, or 285/18 kt to the south of a strong mid-level ridge. Aside from the HWRF, which is a northern outlier and has not performed particularly well for Fred or Grace, and also the Canadian model, which is a southern outlier, the track guidance has come into better agreement on the future path of Grace. The cyclone is expected to slow its forward speed today, and maintain a west-northwestward motion to the south of the ridge for the next several days. The NHC track forecast is little changed from the previous one through 72 h, and then was adjusted a little to the south of the previous one thereafter. On this path, Grace would pass just south of Puerto Rico later today, cross Hispaniola tonight through Monday night, then move along the northern coast of Cuba Tuesday and Wednesday. Grace is in an environment favorable for intensification, and the NHC intensity forecast calls for modest strengthening to 45 kt before it reaches the Dominican Republic Monday morning. This portion of the forecast is in good agreement with the various consensus models. The intensity forecast becomes highly uncertain thereafter, and is dependent on how much of the Greater Antilles the cyclone interacts with. Based on the current track forecast, Grace would cross a large portion of the rugged terrain of Hispaniola, then interact with the landmass of Cuba for a couple of days. There is a decent chance that the low-level center of Grace could dissipate over Hispaniola as the system opens back into a tropical wave. However, due to the possibility of the center remaining intact after crossing that landmass, the NHC forecast calls for weakening followed by little change in strength thereafter as it moves along the Cuban coastline. The latest NHC intensity forecast beyond 24 h is little changed from the previous one, and is close to the FSU Superensemble. Key Messages: 1. Tropical storm conditions are expected over portions of the Leewards Islands this morning and the Virgin Islands and Puerto Rico today. Tropical storm conditions are expected over eastern parts of the Dominican Republic tonight and Monday. Tropical storm conditions are possible over western portions of the Dominican Republic and Haiti Monday and Monday night. 2. Heavy rainfall could lead to flash and urban flooding over the Leeward and Virgin Islands, Haiti and the Dominican Republic. Across Puerto Rico, heavy rainfall may lead to flash, urban and small stream flooding, along with the potential for mudslides. 3. There is a risk of wind and rainfall impacts across the rest of the Dominican Republic, Haiti, the Turks and Caicos Islands, the Bahamas, Cuba, and Florida, but forecast uncertainty remains higher than usual. Interests in those areas should monitor the progress of Grace and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 16.9N 64.4W 35 KT 40 MPH 12H 15/1800Z 17.5N 66.6W 40 KT 45 MPH 24H 16/0600Z 18.3N 68.9W 45 KT 50 MPH 36H 16/1800Z 18.9N 70.6W 35 KT 40 MPH...INLAND OVER HISPANIOLA 48H 17/0600Z 19.8N 72.6W 35 KT 40 MPH...INLAND OVER HISPANIOLA 60H 17/1800Z 20.9N 75.3W 35 KT 40 MPH...OVER WATER 72H 18/0600Z 22.0N 78.0W 35 KT 40 MPH...NEAR CUBA COAST 96H 19/0600Z 23.9N 82.5W 40 KT 45 MPH 120H 20/0600Z 25.6N 86.2W 45 KT 50 MPH $$ Forecaster Latto
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Hurricane Linda Forecast Discussion Number 21
2021-08-15 10:44:53| Tropical Depression LIDIA
Issued at 200 AM PDT Sun Aug 15 2021
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Tropical Storm Grace Forecast Discussion Number 7
2021-08-15 04:58:46| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sat Aug 14 2021 000 WTNT42 KNHC 150258 TCDAT2 Tropical Storm Grace Discussion Number 7 NWS National Hurricane Center Miami FL AL072021 1100 PM AST Sat Aug 14 2021 Grace is a poorly organized tropical cyclone. Trying to pinpoint the center of the storm over the last 6-12 hours has been a challenge, even with the help of earlier NOAA aircraft, surface observations, and radar data from Guadalupe. Earlier data from the NOAA aircraft reconnaissance Twin Doppler Radar showed that the mid-level center was tilted significantly further southeast relative to the poorly-defined low-level circulation. Around 0000 UTC, multiple reporting stations in Guadalupe showed a wind shift to the west, and there were some skeletal bands seen on the nearby Guadalupe radar ahead of a convective squall propagating ahead, which is currently producing the coldest cloud tops with Grace. Given all of these data, the center of Grace is estimated to have passed by just north of Guadalupe over the last few hours. Despite the higher subjective and objective Dvorak estimates, the initial intensity was kept at 35 kt for this advisory given the lackluster wind data from the earlier NOAA aircraft reconnaissance mission. Grace appears to have reformed a bit further North tonight, and also now appears to be on a somewhat slower west-northwest heading, at 285/17 kt. There remains a large amount of spread in the guidance, even in the short-term, which is likely related to the current disorganized nature of Grace. In general, Grace is expected to maintain a west-northwestward motion and gradually slow down over the next 24-36 hours. A strong low- to mid-level ridge poleward of Grace should then maintain this west-northwest heading through the remainder of the forecast. A lot of the track uncertainty in the latter part of the forecast appears to be related to the future intensity of the storm, and both the ECMWF and GFS ensembles show a large north-to-south spread with stronger members tracking further north and weaker members tracking further south. For now, the NHC track forecast has been shifted north of the previous track, mostly related to the further north initial position, and is in close agreement with the HFIP corrected-consensus approach (HCCA) model. Grace appears to finally be slowing down a bit this evening, but will still need to slow down a bit more in order to allow the low- to mid-level centers to become better aligned. Because of this disjointed structure, only slow intensification is anticipated. The latest intensity guidance is a bit lower, and the NHC intensity guidance follows suit, with a peak intensity of 45-kt in 24 hours. Thereafter, it appears likely that Grace will have to deal with significant land interaction over Hispaniola and weakening is indicated by 48 hours. If Grace survives, it is possible some modest intensification could occur in the latter part of the forecast period. The intensity forecast remains closely tied to the track forecast, and any deviations to the north or south could allow Grace to stay stronger than indicated in this forecast. However, it also remains distinctly possible that Grace could dissipate before the end of this 5-day forecast due to the forecasted land interaction. As previously mentioned, the exact track of the center and the intensity of the system will likely not be as important as the heavy rainfall that is forecast to fall across the Leeward Islands and the Greater Antilles during the next few days. Key Messages: 1. Tropical storm conditions are expected over the Virgin Islands and Puerto Rico on Sunday. Tropical storm conditions are possible over eastern parts of the Dominican Republic Sunday night and Monday. 2. Heavy rainfall could lead to flash and urban flooding over the Leeward and Virgin Islands, Haiti and the Dominican Republic. Across Puerto Rico, heavy rainfall may lead to flash, urban and small stream flooding, along with the potential for mudslides. 3. There is a risk of wind and rainfall impacts across the rest of the Dominican Republic, Haiti, the Turks and Caicos Islands, the Bahamas, Cuba, and Florida next week, but forecast uncertainty remains higher than usual. Interests in those areas should monitor the progress of Grace and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 16.8N 62.4W 35 KT 40 MPH 12H 15/1200Z 17.3N 64.6W 40 KT 45 MPH 24H 16/0000Z 18.1N 67.0W 45 KT 50 MPH...NEAR PUERTO RICO 36H 16/1200Z 18.7N 69.1W 45 KT 50 MPH...INLAND OVER HISPANIOLA 48H 17/0000Z 19.3N 70.9W 35 KT 40 MPH...INLAND OVER HISPANIOLA 60H 17/1200Z 20.2N 73.2W 35 KT 40 MPH...OVER WATER 72H 18/0000Z 21.2N 75.8W 35 KT 40 MPH 96H 19/0000Z 23.7N 81.0W 40 KT 45 MPH 120H 20/0000Z 25.6N 84.6W 45 KT 50 MPH $$ Forecaster Papin/Brown
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