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Tropical Depression Grace Forecast Discussion Number 14
2021-08-16 22:48:48| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Mon Aug 16 2021 000 WTNT42 KNHC 162048 TCDAT2 Tropical Depression Grace Discussion Number 14 NWS National Hurricane Center Miami FL AL072021 500 PM EDT Mon Aug 16 2021 Grace may have regained tropical storm status just before the center moved across the Barahona Peninsula of the Dominican Republic around midday. The Air Force Reserve Hurricane Hunters measured peak 925-mb winds of 45 kt very near the coast, which would equate to an intensity right at the threshold of tropical storm. Since then, however, land interaction has likely weakened these winds, and Grace is still estimated to be a 30-kt depression. The center appears to have moved back over water just to the south of the Haitian coast. Grace has been moving a little slower today, possibly due to interaction with the terrain of Hispaniola, and the initial motion is estimated to be 285/11 kt. A mid-level high centered over the western Atlantic is forecast to build westward over the southeastern United States and northern Gulf of Mexico in the coming days. This pattern should keep Grace on a westward to west-northwestward trajectory for the entire 5-day forecast period, moving across the northwestern Caribbean Sea, across the northern Yucatan Peninsula, and into the southwestern Gulf of Mexico. The most significant model trends are on days 4 and 5, when many of the track models are indicating a slight west-southwest bend as the cyclone approaches mainland Mexico. The NHC track forecast has been nudged southward at most forecast times, but that may be within the noise level of typical model run-to-run variability. Once the center of Grace moves away from Hispaniola tomorrow, the deep, warm waters of the northwestern Caribbean Sea and relatively light deep-layer shear should be conducive for strengthening. Model data suggest that some mid-level shear could come into play at times, so it's not a sure bet that conditions will be ideal for significant strengthening. Partly for that reason, the NHC intensity forecast is near or just below the intensity consensus. However, even this new forecast is a little higher than the previous forecast, and many of the models indicate that Grace could be near or at hurricane strength when it approaches the Yucatan Peninsula in about 60 hours. After passing the Yucatan Peninsula, additional strengthening is likely, and the new forecast now explicitly shows Grace reaching hurricane intensity over the southwestern Gulf of Mexico. Key Messages: 1. Heavy rainfall across the Dominican Republic, Haiti, Cuba, Jamaica, and the Cayman Islands may lead to flash, urban, and small stream flooding, with the potential for mudslides highest in Haiti and the Dominican Republic. 2. Tropical storm conditions are possible over portions of Hispaniola this evening and tonight, and over Jamaica on Tuesday. Tropical storm conditions are expected over portions of the southern coast of Cuba on Tuesday, spreading westward to the Cayman Islands and possibly other portions of the southern coast of Cuba Tuesday evening through Wednesday morning. 3. There is a increasing risk of wind, rainfall, and storm surge impacts on the Yucatan Peninsula of Mexico Wednesday night and Thursday. Interests there areas should monitor the progress of Grace and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 17.9N 72.4W 30 KT 35 MPH 12H 17/0600Z 18.3N 74.4W 30 KT 35 MPH...NEAR SW TIP OF HAITI 24H 17/1800Z 18.9N 77.2W 35 KT 40 MPH 36H 18/0600Z 19.6N 80.4W 40 KT 45 MPH...NEAR CAYMAN ISLANDS 48H 18/1800Z 20.2N 83.5W 50 KT 60 MPH 60H 19/0600Z 20.9N 86.7W 60 KT 70 MPH...NEAR YUCATAN COAST 72H 19/1800Z 21.6N 89.9W 60 KT 70 MPH 96H 20/1800Z 22.4N 95.1W 65 KT 75 MPH 120H 21/1800Z 22.4N 98.8W 65 KT 75 MPH...INLAND $$ Forecaster Berg
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Tropical Storm Fred Forecast Discussion Number 29
2021-08-16 22:46:41| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Mon Aug 16 2021 000 WTNT41 KNHC 162046 TCDAT1 Tropical Storm Fred Discussion Number 29 NWS National Hurricane Center Miami FL AL062021 400 PM CDT Mon Aug 16 2021 Radar data indicate that the center of Fred made landfall in the eastern Florida Panhandle a little while ago, and it is currently moving farther inland. Observations from the Air Force Hurricane Hunters indicate that the storm reached a peak intensity of 55 kt just before landfall. Assuming some weakening since crossing the coast, the current intensity estimate is 50 kt. Fairly rapid weakening will occur while the center moves over land, and the cyclone will probably be reduced to tropical depression status by tomorrow morning. The official intensity forecast for the next day or so is close to the latest Decay-SHIPS model guidance. Radar fixes indicate that the motion is north-northeastward, or 020/8 kt. During the next day or two Fred should move, with increasing forward speed, between a mid-level subtropical high pressure area over the southwestern Atlantic and a weak trough over the east-central United states. The official track forecast is quite close to the latest NOAA corrected consensus model prediction, HCCA. Although it is weakening, Fred is likely to bring flooding rains over portions of the southeastern and eastern United States during the next couple of days. KEY MESSAGES: 1. Through Tuesday, heavy rainfall may lead to considerable flash, urban, small stream, and isolated river flooding impacts across portions of the Florida Big Bend and Panhandle. By the middle of the week as Fred lifts north and inland, heavy rainfall and flooding will impact the southern and central Appalachians, the Piedmont of the Southeast and Mid-Atlantic. Landslides are possible across the mountains of North Carolina and Blue Ridge Escarpment on Tuesday. 2. Dangerous storm surge inundation is ongoing along portions of the coast of the Florida Panhandle and the Florida Big Bend region. 3. Tropical storm conditions will continue along the coastline within the warning area over the next few hours and will continue to spread farther inland later today and tonight across portions of the Florida Panhandle, southwestern Georgia, and southeastern Alabama. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 29.9N 85.3W 50 KT 60 MPH...INLAND 12H 17/0600Z 31.5N 85.1W 35 KT 40 MPH...INLAND 24H 17/1800Z 34.0N 84.3W 30 KT 35 MPH...INLAND 36H 18/0600Z 37.0N 82.5W 25 KT 30 MPH...POST-TROP/INLAND 48H 18/1800Z 39.5N 80.0W 20 KT 25 MPH...POST-TROP/INLAND 60H 19/0600Z...DISSIPATED $$ Forecaster Pasch
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Tropical Storm Henri Forecast Discussion Number 4
2021-08-16 22:46:40| National Hurricane Center (Atlantic)
Issued at 500 PM AST Mon Aug 16 2021 000 WTNT43 KNHC 162046 TCDAT3 Tropical Storm Henri Discussion Number 4 NWS National Hurricane Center Miami FL AL082021 500 PM AST Mon Aug 16 2021 Deep convection has persisted near and southeast of the center of the small tropical cyclone today, and subjective Dvorak intensity estimates were a consensus T2.5 (35 kt) at 1800 UTC. Objective estimates from ADT and SATCON also support tropical storm status, therefore the depression has been upgraded to a 35-kt tropical storm with this advisory. Henri (ahn-REE) becomes the eighth named storm of the 2021 Atlantic hurricane season. This is the fourth-earliest eighth storm on record with only 2020, 2005, and 1936 having the eighth-named storm form earlier in the season. Henri is located over warm waters, but is currently being affected by light to moderate northerly shear and dry mid-level air in the surrounding environment. Although these conditions are not overly conducive for strengthening, most of the intensity guidance supports gradual intensification over the next 24 to 48 hours. After that time, a significant increase in northeasterly upper-level winds is depicted by the global models over the system, which is likely to halt further strengthening. In fact, given the small size of Henri, it is likely to be more susceptible to the increase in shear, and it could weaken faster than indicated below. The HWRF remains more aggressive, but given the expected increase in shear, that solution still does not seem likely. The NHC intensity forecast is in best agreement with the LGEM model, and is slightly below the IVCN intensity consensus. The tropical storm is moving south-southwestward or 200/6 kt. Henri is forecast to move west-southwestward during the next 12-24 hours around the southeastern side of a mid-tropospheric high over the western Atlantic. After that time, Henri should turn westward as the ridge shifts eastward to the north of the tropical cyclone, and after 72 hours Henri is expected to approach the western extent of the ridge and should turn northward and then north-northeastward. The dynamical model guidance is in somewhat better agreement during the next 48-72 hours, but there remains some spread later in the period as to how sharp of northward turn occurs. The new NHC track forecast is similar to the previous advisory and lies near the center of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 31.0N 62.9W 35 KT 40 MPH 12H 17/0600Z 30.5N 63.4W 40 KT 45 MPH 24H 17/1800Z 30.3N 64.2W 45 KT 50 MPH 36H 18/0600Z 30.2N 65.4W 50 KT 60 MPH 48H 18/1800Z 30.2N 66.9W 50 KT 60 MPH 60H 19/0600Z 30.3N 68.5W 50 KT 60 MPH 72H 19/1800Z 30.5N 69.9W 45 KT 50 MPH 96H 20/1800Z 31.8N 70.2W 45 KT 50 MPH 120H 21/1800Z 34.2N 68.4W 45 KT 50 MPH $$ Forecaster Brown
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Tropical Storm Fred Forecast Discussion Number 28
2021-08-16 17:00:43| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Mon Aug 16 2021 000 WTNT41 KNHC 161500 TCDAT1 Tropical Storm Fred Discussion Number 28 NWS National Hurricane Center Miami FL AL062021 1000 AM CDT Mon Aug 16 2021 Fred became better organized on satellite and radar images this morning, with the center fairly well embedded within a small CDO and a large convective band over the eastern portion of the circulation. The Air Force Hurricane Hunters found flight-level winds that supported an intensity of 50 kt, and data from the aircraft also found that the central pressure had fallen to 993 mb, although the most recent pressures appeared to have leveled off. The satellite and radar data also show a dry slot over the southeastern quadrant. Fred is over very warm waters of near 30 deg C and within a fairly moist mid-level atmosphere. A little more strengthening is possible prior to landfall, but significant southwesterly shear is likely to limit strengthening. Also, the storm has little time remaining over water. The latest official intensity forecast is similar to the LGEM guidance. Center fixes from the Hurricane Hunters and WSR-88D data from Tallahassee and Eglin AFB indicate that Fred is a little east of the previous track. It is not certain whether this is due to a slight reformation of the center nearer to the strongest convection, but that is certainly a possibility. Based on the most recent fixes, the current motion estimate is just slightly east of north, or 010/9 kt. Fred is moving between the western side of a mid-level subtropical high pressure area over the southwestern Atlantic and a weak trough over the east-central United States. A slight bend of the track toward the north-northeast with a little acceleration is expected during the next couple of days. The official forecast is just a bit to the east of the previous one, and follows the most recent multi-model consensus. 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. Through Tuesday, heavy rainfall may lead to flash, urban, small stream, and isolated river flooding impacts across the Southeast. By the middle of the week as Fred lifts north and inland, heavy rainfall and flooding will impact the southern and central Appalachians, the Piedmont of the Southeast and Mid-Atlantic. Landslides are possible across the mountains of North Carolina and Blue Ridge Escarpment on Tuesday. 2. Dangerous storm surge inundation is expected along portions of the coast of the Florida Panhandle and the Florida Big Bend region. Preparations to protect life and property should be rushed to completion in the Storm Surge Warning area. 3. Tropical storm conditions are occurring in the warning area and will spread farther inland later today and tonight across portions of the Florida Panhandle, southwestern Georgia, and southeastern Alabama. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 29.2N 85.7W 50 KT 60 MPH 12H 17/0000Z 30.5N 85.5W 55 KT 65 MPH...INLAND 24H 17/1200Z 32.6N 85.0W 30 KT 35 MPH...INLAND 36H 18/0000Z 35.0N 84.3W 25 KT 30 MPH...POST-TROP/INLAND 48H 18/1200Z 38.0N 82.5W 15 KT 15 MPH...POST-TROP/INLAND 60H 19/0000Z...DISSIPATED $$ Forecaster Pasch
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Tropical Depression Grace Forecast Discussion Number 13
2021-08-16 16:55:41| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Mon Aug 16 2021 000 WTNT42 KNHC 161455 TCDAT2 Tropical Depression Grace Discussion Number 13 NWS National Hurricane Center Miami FL AL072021 1100 AM EDT Mon Aug 16 2021 Air Force Reserve and NOAA Hurricane Hunters were both able to locate a center for Grace--probably the most well-defined center observed over the past few days. That center now appears to be moving onshore along the Barahona Peninsula of the Dominican Republic as we speak. The planes measured several possible areas of tropical-storm-force winds from the SFMR, however these observations have not been supported by the more reliable 925-mb flight-level winds for weaker systems, which were only as high as 38 kt, and warrant maintaining the 30-kt initial intensity. Dropsonde data indicate that the central pressure has fallen to 1007 mb. The aircraft fixes confirm that Grace is moving westward, or 280/13 kt. High pressure over the western Atlantic is forecast to slide westward over the southeastern United States during the next several days, which should keep Grace on a westward to west- northwestward trajectory for the entire 5-day forecast period. This scenario is agreed upon by all of the available track models, and the new NHC track forecast has only been nudged slightly southward from the previous forecast based on the latest consensus aids. Grace's intensity forecast remains complicated by interaction with land and the possibility of some westerly shear during the forecast period. However, the southern shift in the forecast track takes the center of Grace more definitively over very warm 30 degrees Celsius waters in the northwestern Caribbean Sea. Therefore, gradual strengthening is anticipated while Grace approaches the Yucatan coast of Mexico. Once the system reaches the Gulf of Mexico, the shear appears to decrease, and conditions there will likely be conducive for additional strengthening. In fact, many of the models, including the consensus aids, bring Grace to hurricane intensity, and the NHC intensity forecast has therefore been bumped upward, bringing Grace very near hurricane strength by the end of the forecast period. Key Messages: 1. Heavy rainfall across the Dominican Republic, Haiti, Cuba, Jamaica, and the Cayman Islands may lead to flash, urban, and small stream flooding, with the potential for mudslides highest in Haiti and the Dominican Republic. 2. Tropical storm conditions are possible over portions of Hispaniola today and tonight, and over Jamaica on Tuesday. Tropical storm conditions are expected over portions of the southern coast of Cuba on Tuesday, spreading westward to the Cayman Islands and other portions of the southern coast of Cuba Tuesday evening through Wednesday morning. 3. There is a increasing risk of wind and rainfall impacts over the Yucatan Peninsula of Mexico Wednesday night and Thursday. Interests there areas should monitor the progress of Grace and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 17.7N 71.4W 30 KT 35 MPH 12H 17/0000Z 18.2N 73.4W 30 KT 35 MPH...S COAST OF HAITI 24H 17/1200Z 18.8N 76.2W 35 KT 40 MPH 36H 18/0000Z 19.4N 79.0W 40 KT 45 MPH 48H 18/1200Z 20.1N 82.1W 45 KT 50 MPH 60H 19/0000Z 20.9N 85.2W 50 KT 60 MPH 72H 19/1200Z 21.6N 88.4W 50 KT 60 MPH...N COAST OF YUCATAN 96H 20/1200Z 22.5N 94.0W 60 KT 70 MPH 120H 21/1200Z 23.0N 98.0W 60 KT 70 MPH...INLAND $$ Forecaster Berg
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