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Tropical Storm Kevin Forecast Discussion Number 18

2021-08-11 22:55:06| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Wed Aug 11 2021 000 WTPZ41 KNHC 112054 TCDEP1 Tropical Storm Kevin Discussion Number 18 NWS National Hurricane Center Miami FL EP112021 200 PM PDT Wed Aug 11 2021 Satellite imagery this afternoon shows that Kevin continues to have a large circulation, but that the deep convection is well-removed from the tropical storm's center. A blend of the Dvorak classifications from SAB and TAFB suggest that the system remains with an intensity of 40 kt, which is also supported by 1723Z SATCON estimate of 38 kt. Kevin's short-term movement has been a bit more westward, perhaps due to pulling by the remaining deep convection restricted to its southwestern quadrant. The longer-term initial motion is estimated as 290 degrees at 9 kt. The tropical storm is primarily being steered along the southwestern periphery of a deep tropospheric ridge. However, as the deep convection ceases completely in a day or two, the system will increasingly be steered by the lower tropospheric flow. A motion toward the west-northwest or northwest at a slightly faster forward speed is anticipated until dissipation. The official track forecast is based upon the HFIP Corrected Consensus Approach (HCCA), which is midway between the GFS and ECMWF global model solutions but substantially faster than the mesoscale hurricane model output. This new forecast is slightly westward of the previous advisory, due to the somewhat more westward position at the initial time. The tropical storm has already moved across the 26C SST isotherm and is moving toward even cooler water, drier air, and a more stable atmosphere. Additionally, Kevin is being affected by moderate NE tropospheric vertical wind shear. The large system should gradually weaken under these increasingly hostile conditions and it's likely that Kevin will become a remnant low by late Thursday. The official intensity forecast is based upon the IVCN statistical scheme and is nearly the same as the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 21.1N 117.8W 40 KT 45 MPH 12H 12/0600Z 22.2N 119.3W 35 KT 40 MPH 24H 12/1800Z 23.4N 121.6W 30 KT 35 MPH 36H 13/0600Z 24.7N 124.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 13/1800Z 26.2N 126.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 14/0600Z 27.9N 128.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 14/1800Z 29.5N 129.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 15/1800Z...DISSIPATED $$ Forecaster Landsea

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Tropical Storm Linda Forecast Discussion Number 7

2021-08-11 22:41:35| Tropical Depression LIDIA

Issued at 300 PM MDT Wed Aug 11 2021

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Tropical Storm Fred Forecast Discussion Number 9

2021-08-11 22:40:25| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Wed Aug 11 2021 000 WTNT41 KNHC 112040 TCDAT1 Tropical Storm Fred Discussion Number 9 NWS National Hurricane Center Miami FL AL062021 500 PM EDT Wed Aug 11 2021 During the past several hours, the center of Fred has moved inland over the Dominican Republic. The storm continues to produce an area of convection near and southeast of the center. However, the low-level circulation is losing some organization as it passes over mountainous terrain. There have been no observations near the center recently, so the initial intensity of 35 kt is based mainly on weakening from the previous over water intensity. The initial motion is a somewhat uncertain 290/13. Some erratic motion is expected during the next 12 h or so as the center moves over the mountains of Hispaniola. After reaching the water, the cyclone is expected to moves west-northwestward on the south side of the subtropical ridge through about 60 h. After that, a northwestward motion is expected through the end of the forecast period as Fred moves toward a weakness in the ridge. The track guidance becomes a bit divergent during this time, with the ECMWF, Canadian, and HWRF models showing a track near or over the Florida Peninsula, while the GFS, UKMET, and HMON models show the center passing south and west of the Florida Keys, followed by a more northward motion over the Gulf of Mexico. The new forecast track is between these extremes, and it has only minor adjustments from the previous NHC track. Fred is expected to weaken to a depression over Hispaniola during the next 12 h. Once back over water, the cyclone is expected to be in a moderate westerly shear environment through at least 60 h. Due to that, and the uncertainty in how well organized the system will be after crossing Hispaniola, the intensity forecast shows only modest intensification during this time. After that time, the global models forecast that an upper-level trough over Florida will gradually move to the north, with an large upper-level anticyclone following near or to the southeast of Fred. How close this anticyclone gets to Fred will determine how much the shear decreases while the system is over the eastern Gulf of Mexico, and the global models are not in great agreement on this. The GFS and Canadian keep the high far enough to the east to expose Fred to southwesterly upper-level winds, while the UKMET and ECMWF move it closer to the storm. The intensity forecast will show a slightly faster rate of strengthening after 72 h to match the guidance and the previous forecast. However, there is lower than normal confidence in this part of the intensity forecast. KEY MESSAGES: 1. Tropical storm conditions are ongoing across portions of the Dominican Republic. Tropical storm conditions are possible in northern Haiti and the southeastern Bahamas this evening, and in portions of Cuba by tonight. 2. Through early Thursday morning, heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises and potential mudslides in the Dominican Republic. 3. There is a risk of wind and rainfall impacts elsewhere in portions of Hispaniola, the Bahamas, and Cuba during the next few days, although the forecast is more uncertain than usual since Fred is forecast to interact with Hispaniola through tonight. 4. There is an increasing risk of wind and rainfall impacts in Florida beginning Friday night or early Saturday in the Keys and spreading northward through portions of the Peninsula and the Panhandle Saturday through Monday. Beginning Friday, heavy rainfall could lead to areal, urban, and small stream flooding, and possible rapid river rises across southern Florida. Interests throughout Florida should monitor Fred's progress and check updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 18.9N 71.0W 35 KT 40 MPH...INLAND 12H 12/0600Z 19.8N 72.7W 30 KT 35 MPH...INLAND 24H 12/1800Z 20.9N 75.0W 30 KT 35 MPH...OVER WATER 36H 13/0600Z 21.9N 77.1W 35 KT 40 MPH 48H 13/1800Z 22.9N 79.2W 35 KT 40 MPH 60H 14/0600Z 23.9N 80.6W 40 KT 45 MPH 72H 14/1800Z 25.3N 82.0W 40 KT 45 MPH 96H 15/1800Z 28.5N 84.0W 50 KT 60 MPH 120H 16/1800Z 31.0N 85.0W 45 KT 50 MPH...INLAND $$ Forecaster Beven

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Tropical Storm Fred Forecast Discussion Number 8

2021-08-11 16:56:34| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Wed Aug 11 2021 000 WTNT41 KNHC 111456 TCDAT1 Tropical Storm Fred Discussion Number 8 NWS National Hurricane Center Miami FL AL062021 1100 AM AST Wed Aug 11 2021 Morning satellite imagery and reports from a NOAA Hurricane Hunter aircraft indicate that the circulation of Fred has become better defined south of the eastern Dominican Republic. The NOAA plane reported maximum flight-level winds of 40-45 kt, and SFMR winds of up to 50 kt, although these were measured near the coast and the reliability is unknown. The central pressure is near 1006 mb. Based on these data and a dropsonde northeast of the center, the initial intensity is increased to 40 kt. The low-level center is partly exposed near the western edge of the convection, which has decreased in coverage since yesterday. The center has been moving more westward for the past few hours. However, the longer term motion is 290/14. There is no change in the track forecast philosophy since the previous advisory. Fred should continue moving generally west-northwestward for the next 72 h or so, followed by a turn toward the northwest as the cyclone nears the western periphery of the ridge. The new forecast track is little changed from the previous advisory and lies near the various consensus models. However, some adjustments to the track may be necessary as the center interacts with the mountains of Hispaniola during the next 12-24 hours. Fred is now in an environment of 15-20 kt of westerly vertical shear produced in part by an upper-level trough near the Florida Peninsula, and the global models suggests that moderate shear should persist for at least the next 48-60 h. This, combined with land interaction, should cause Fred to weaken as it crosses Hispaniola, and then at best slowly re-intensify after it emerges over the water. After that time, the global models suggest the trough should weaken as a large upper-level anticyclone forms near or just southeast of Fred. This evolution could let the shear decrease a little and allow a little more strengthening, particularly when Fred is over the Gulf of Mexico. The new intensity forecast is similar to the previous forecast and follows the overall trend of the intensity guidance. KEY MESSAGES: 1. Tropical storm conditions are spreading across portions of the Dominican Republic. Tropical storm conditions are possible in northern Haiti and the southeastern Bahamas by late today, and in portions of Cuba by tonight. 2. Heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises and the potential for mudslides in the Dominican Republic. Heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises across southern Florida. 3. There is a risk of wind and rainfall impacts elsewhere in portions of Hispaniola, the Bahamas, and Cuba during the next few days, although the forecast is more uncertain than usual since Fred is forecast to interact with Hispaniola today and tonight. Interests in these areas should monitor Fred's progress and updates to the forecast. 4. There is an increasing risk of wind and rainfall impacts in Florida beginning Friday night or early Saturday in the Keys and spreading northward through portions of the Peninsula and the Panhandle Saturday through Monday. Interests throughout Florida should monitor Fred's progress and check updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 11/1500Z 18.2N 69.7W 40 KT 45 MPH 12H 12/0000Z 19.2N 71.4W 30 KT 35 MPH...INLAND 24H 12/1200Z 20.3N 73.7W 30 KT 35 MPH...OVER WATER 36H 13/0000Z 21.4N 76.0W 35 KT 40 MPH 48H 13/1200Z 22.3N 78.1W 35 KT 40 MPH 60H 14/0000Z 23.3N 79.9W 40 KT 45 MPH 72H 14/1200Z 24.6N 81.4W 40 KT 45 MPH 96H 15/1200Z 27.5N 83.5W 50 KT 60 MPH 120H 16/1200Z 30.5N 85.5W 55 KT 65 MPH...INLAND $$ Forecaster Beven

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