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Tropical Storm Fred Forecast Discussion Number 6
2021-08-11 04:55:50| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Tue Aug 10 2021 000 WTNT41 KNHC 110255 TCDAT1 Tropical Storm Fred Discussion Number 6 NWS National Hurricane Center Miami FL AL062021 1100 PM AST Tue Aug 10 2021 Data from satellites, the San Juan NOAA Doppler weather radar, and an Air Force Reserve Unit reconnaissance aircraft indicate that the low-level circulation has become better defined since the previous advisory and,thus, the disturbance has been upgraded to Tropical Storm Fred. Although the surface and low-level circulations are vertically aligned, radar data indicate that the mid-level circulation is still tilted about 40 n mi to the south. However, that mid-level feature has been steadily gaining ground from its earlier 100-nmi southeastward displacement. Radar Doppler velocity data, aircraft 850-mb flight-level wind data of 43 kt and SFMR surface winds of 33 kt, plus earlier surface observations of sustained 33-kt winds, support an initial intensity of 35 kt. The initial motion estimate is westward or 270/15 kt. However, this should be a short-term motion overnight due to interaction with the mountainous terrain of Puerto Rico to the north. By early Wednesday morning, Fred is expected to resume a west-northwestward motion and pass through the Mona Passage, reaching the eastern Dominican Republic shortly after sunrise. A strong subtropical ridge to the north of the cyclone is forecast by the global models to basically remain static across the central and western Atlantic Ocean for the next five days. Given this pattern, Fred is expected to maintain a west-northwestward motion through 96 hours, remaining just offshore the north coast of Haiti and Cuba during that time. After emerging over the southeastern Gulf of Mexico on day 4, Fred is forecast to gradually turn more north-northwestward as the cyclone rounds the southwestern periphery of the aforementioned ridge. The latest NHC track forecast models strongly support this track scenario, although there was a slight northward shift in the guidance envelope on this cycle. The new official track forecast was shifted a little north of the previous one through 72 hours, and then lies down the middle of the tightly packed track consensus models. Conditions remain favorable for some strengthening before Fred reaches Hispaniola in about 12 h, but the intensity likely won't be much stronger than 40-45 kt at landfall. Interaction with the mountainous terrain of Hispaniola on Wednesday should result in some weakening, but tropical-storm-force winds could occur along the the north coast of the island if the center shifts a little more to right of the forecast track. After emerging back over water by late Wednesday, only slow strengthening is forecast in the 36-60-h time period due to westerly vertical wind shear of about 20 kt expected to affect the cyclone. On days 4 and 5, however, Fred is expected to be moving over warmer sea-surface temperatures and into a much weaker wind shear regime, which would favor more robust strengthening. As a result, some of the regional and statistical- dynamical intensity models bring Fred near or to hurricane strength during that time. However, there is uncertainty Fred's structure after interaction with Hispaniola and possibly Cuba, and continued disagreement between the global models on how the upper-level wind flow pattern near the cyclone will evolve, which ranges from favorable anticyclonic outflow to strong southwesterly shear. Given these factors, the NHC intensity forecast was only nudged slightly higher than the previous advisory, and lies between the consensus models HCCA and IVCN, and the SHIPS and LGEM models. KEY MESSAGES: 1. Tropical storm conditions are expected in portions of the U.S. Virgin Islands and Puerto Rico tonight, and are expected to begin in the Dominican Republic Wednesday morning. Tropical storm conditions are possible in northern Haiti and the southeastern Bahamas by late Wednesday. 2. Heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises and the potential for mudslides across the U.S. Virgin Islands, Puerto Rico, and the Dominican Republic. The greatest threat for flooding impacts will be across eastern and southern Puerto Rico. 3. There is a risk of wind and rainfall impacts elsewhere in portions of Hispaniola, the Bahamas, and Cuba during the next several days, although the forecast is more uncertain than usual since Fred is forecast to interact with Hispaniola on Wednesday. Interests in these areas should monitor Fred's progress and updates to the forecast. 4. There is a risk of wind and rainfall impacts in Florida beginning Friday in the Keys and spreading northward through portions of the Peninsula and the Panhandle this weekend. However, it is too soon to determine the exact timing, location, and magnitude of any potential impacts. Interests throughout Florida should monitor Fred's progress and check updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 17.4N 66.8W 35 KT 40 MPH 12H 11/1200Z 18.6N 68.9W 40 KT 45 MPH...INLAND 24H 12/0000Z 19.9N 71.4W 35 KT 40 MPH...INLAND 36H 12/1200Z 20.9N 73.7W 35 KT 40 MPH...OVER WATER 48H 13/0000Z 21.8N 76.0W 35 KT 40 MPH 60H 13/1200Z 22.8N 78.0W 35 KT 40 MPH 72H 14/0000Z 23.8N 79.9W 40 KT 45 MPH 96H 15/0000Z 26.5N 82.8W 45 KT 50 MPH 120H 16/0000Z 29.3N 84.6W 55 KT 65 MPH $$ Forecaster Stewart
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Tropical Storm Kevin Forecast Discussion Number 15
2021-08-11 04:36:17| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Tue Aug 10 2021 000 WTPZ41 KNHC 110236 TCDEP1 Tropical Storm Kevin Discussion Number 15 NWS National Hurricane Center Miami FL EP112021 800 PM PDT Tue Aug 10 2021 Tracking the center of Kevin this evening has been a challenge, as multiple low-level swirls appear to be rotating cyclonically around a broader mean circulation. The deeper convection remains mostly south of the estimated circulation center, though some cooler cloud tops did attempt to build northward, following a mesovortex seen on visible satellite imagery. Subjective Dvorak intensity estimates from SAB and TAFB at 0000 UTC were T2.5/35 kt and T3.0/45 kt, respectively, and the latest UW-CIMSS SATCON estimate was hovering between these values at 42 kt. The initial intensity is held at 45 kt for this advisory, favoring the higher intensity estimates given the earlier ASCAT data. The initial motion is estimated at 315/7 kt, attempting to follow the mean center that has several mesovorticies rotating around. A general northwest to west-northwestward motion is expected to continue over the next several days as the large cyclone is steered by a deep-layer ridge located to its northeast. The latest track guidance was a bit more poleward compared to the previous cycle, and the latest NHC track forecast has been shifted a bit more poleward in the short term, choosing to remain close to the track guidance consensus. Moderate to strong northeasterly wind shear continues to keep Kevin's deepest convection downshear in the southern semicircle of the large circulation envelope. Over the next 24 hours, Kevin will also be crossing a sharp sea-surface temperature (SST) gradient, with sub 26 C SSTs not far away to the north. As the cyclone moves over these progressively cooler waters, gradual weakening should commence. Simulated IR brightness temperature data from both the GFS and ECMWF suggest that Kevin will lose its remaining organized convection by 48-60 hours, and the latest NHC intensity forecast shows Kevin becoming a remnant low by that time. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 19.5N 115.4W 45 KT 50 MPH 12H 11/1200Z 20.7N 116.5W 40 KT 45 MPH 24H 12/0000Z 21.9N 118.3W 35 KT 40 MPH 36H 12/1200Z 23.0N 120.3W 30 KT 35 MPH 48H 13/0000Z 24.0N 122.5W 25 KT 30 MPH 60H 13/1200Z 25.1N 124.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 14/0000Z 26.3N 126.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 15/0000Z 28.4N 130.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 16/0000Z...DISSIPATED $$ Forecaster Papin/Stewart
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Potential Tropical Cyclone Six Forecast Discussion Number 5
2021-08-10 23:07:49| National Hurricane Center (Atlantic)
Issued at 500 PM AST Tue Aug 10 2021 965 WTNT41 KNHC 102107 CCA TCDAT1 Potential Tropical Cyclone Six Discussion Number 5...Corrected NWS National Hurricane Center Miami FL AL062021 500 PM AST Tue Aug 10 2021 Corrected speed of motion in second paragraph. Satellite imagery this afternoon continues to show that the disturbance has an organized convective pattern, with satellite intensity estimates of tropical-storm strength from SAB and TAFB. However, the circulation still appears to not be well defined, with the San Juan WSR-88D Doppler radar showing multiple mid-level centers and several convective cells with small-scale rotation. Based on this, the system will not be upgraded to a tropical cyclone at this time. The initial intensity remains 30 kt based on mainly on continuity from earlier data. It should be noted that squalls with short-lived winds to tropical-storm force have been reported in bands over the northern Leeward Islands. The initial motion remains west-northwestward or 295/15 kt. A strong low- to mid-level ridge to the north should steer the system generally west-northwestward for the next 72 h with some decrease in forward speed after 24 h. Beyond that time, a turn toward the northwest with an further decrease in forward speed is likely while the system moves near the western periphery of the ridge. There has been some increase in the spread of the track guidance from 72-120 h, with the GFS shifting to the right and the other models not changing very much. The new NHC forecast track has only minor changes from the previous one and lies near the various consensus models. Conditions continue to appear favorable for strengthening before the system reaches Hispaniola in about 18 h, although there may be dry air entraining into the system in the southeastern quadrant. The intensity forecast will follow the previous prediction in calling for the disturbance to become a tropical storm before landfall, followed by weakening to a depression. From 24-60 h, the models have come into better agreement that the system will encounter westerly vertical wind shear, and based on that and the possibility of land interaction the intensity forecast shows little re-intensification during that time. After 60 h, the models still disagree on the evolution of the upper-level winds near the system, but they are in better agreement that conditions over the eastern Gulf will become more conducive for development. Thus, the intensity forecast calls for intensification during that time. The new intensity forecast is almost the same as the previous one. KEY MESSAGES: 1. The system is forecast to become a tropical storm as it moves over the northeastern Caribbean Sea tonight. Tropical storm conditions are expected in portions of the U.S. Virgin Islands and Puerto Rico tonight, and are expected to begin in the Dominican Republic by Wednesday. Tropical storm conditions are possible in northern Haiti and the southeastern Bahamas by late Wednesday. 2. Heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises and the potential for mudslides across the U.S. Virgin Islands, Puerto Rico, and the Dominican Republic. The greatest threat for flooding impacts will be across the eastern and southern portions of Puerto Rico. 3. There is a risk of wind and rainfall impacts elsewhere in portions of Hispaniola, the Bahamas, and Cuba during the next several days, although the forecast is more uncertain than usual since the system is still in its formative stage. Interests in these areas should monitor the system's progress and updates to the forecast. 4. There is a risk of wind and rainfall impacts in portions of Florida beginning Friday through the weekend. However, given the uncertainty in the long-range forecast it is too soon to determine the timing, location, and magnitude of any potential impacts. Interests in Florida should monitor updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 16.9N 65.5W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 11/0600Z 17.8N 67.8W 35 KT 40 MPH...TROPICAL CYCLONE 24H 11/1800Z 19.0N 70.4W 35 KT 40 MPH...INLAND 36H 12/0600Z 20.2N 72.8W 30 KT 35 MPH...OVER WATER 48H 12/1800Z 21.2N 75.0W 30 KT 35 MPH 60H 13/0600Z 22.1N 77.2W 35 KT 40 MPH 72H 13/1800Z 23.1N 79.1W 35 KT 40 MPH 96H 14/1800Z 25.5N 82.5W 40 KT 45 MPH 120H 15/1800Z 28.5N 84.5W 50 KT 60 MPH $$ Forecaster Beven
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Tropical Storm Linda Forecast Discussion Number 3
2021-08-10 22:49:24| Tropical Depression LIDIA
Issued at 400 PM CDT Tue Aug 10 2021
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Tropical Storm Kevin Forecast Discussion Number 14
2021-08-10 22:42:44| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Tue Aug 10 2021 000 WTPZ41 KNHC 102042 TCDEP1 Tropical Storm Kevin Discussion Number 14 NWS National Hurricane Center Miami FL EP112021 200 PM PDT Tue Aug 10 2021 Kevin is a poorly defined tropical cyclone. A recent scatterometer pass shows a small enclosed low embedded in a larger, elongated cyclonic gyre. This satellite wind data also indicated that the strongest winds associated with the cyclone are located well to the south of the center. Some of this data was questionable, and the wind retrievals greater than 45 kt were in an area of deep convection and likely rain contaminated. However, there were a few believable wind vectors outside of the convection between 40-45 kt, so Kevin's initial intensity has been adjusted to 45 kt, despite the disorganized satellite presentation. The scatterometer data along with surface observations from Clarion Island revealed that the mean center of Kevin is farther to the southwest than previously estimated, and therefore the initial motion is a somewhat uncertain 305/08kt. There is no change to the forecast track philosophy. A general northwestward to west-northwestward motion is expected over the next several days as Kevin moves along the southwestern periphery of a deep-layer ridge. Other than an adjustment to the short-term track based on the shift in the initial position, the latest NHC track forecast is little changed from the previous one. Moderate to strong northeasterly wind shear is forecast to persist over Kevin for the next 18-24 h, which should limit the cyclone's ability to strengthen despite favorable SSTs and abundant mid-level moisture. By 24 h, the cyclone will begin to pass over progressively cooler waters and into a drier, more stable environment. Based on this scenario, the latest NHC intensity forecast shows no change in strength through tonight, followed by weakening beginning Wednesday. By 72 h, CMC and ECMWF model simulated satellite imagery continue to suggest that Kevin will be devoid of organized convection, and so the official NHC forecast shows Kevin as a remnant low by that time. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 19.1N 115.5W 45 KT 50 MPH 12H 11/0600Z 19.9N 116.5W 45 KT 50 MPH 24H 11/1800Z 21.2N 118.0W 40 KT 45 MPH 36H 12/0600Z 22.2N 120.0W 30 KT 35 MPH 48H 12/1800Z 23.3N 122.0W 25 KT 30 MPH 60H 13/0600Z 24.3N 124.4W 25 KT 30 MPH 72H 13/1800Z 25.3N 126.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 14/1800Z 27.1N 130.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 15/1800Z...DISSIPATED $$ Forecaster Latto
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