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Hurricane Henri Forecast Discussion Number 25

2021-08-22 04:49:45| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Sat Aug 21 2021 000 WTNT43 KNHC 220249 TCDAT3 Hurricane Henri Discussion Number 25 NWS National Hurricane Center Miami FL AL082021 1100 PM EDT Sat Aug 21 2021 The convective pattern associated with Henri is less ragged than it was 6 h ago, as the convection has increased near the center and a NOAA Hurricane Hunter aircraft reported a 25 n mi wide eye has formed However, the hurricane has not yet strengthened significantly, as the maximum winds remain about 65 kt in the southeastern eyewall and the central pressure is near 987 mb. Henri has moved a little to the right of the previous track at 18-20 kt during the past several hours. However, the cyclone now seems to be moving northward with an initial motion of 355/18 kt. There is no change to the forecast track philosophy. A cut-off low located over the central Appalachians and a ridge building to the east and northeast of Henri should cause the storm to move generally northward tonight. A turn toward the north-northwest and a slower forward speed are expected on Sunday, which should bring the center near or over southern New England or Long Island between 18-24 h. With the more eastward initial position, the forecast track is shifted a bit to the east of the previous forecast. However, there is still some uncertainty of the landfall point, as several of the guidance models are to the left of the official forecast. After landfall, Henri should slow its forward speed and turn eastward as it become steered by the mid-latitude westerlies. Users are reminded to not focus on the exact forecast track, as the average 24-hour track uncertainty is around 40 miles and impacts will extend well away from the center. Henri is almost out of time to strengthen, as the center will be moving north of the north wall of the Gulf Stream during the next several hours. The intensity forecast will call for modest strengthening during the first 12 h based on the premise that strengthening will occur before Henri reaches the cooler waters. After that, while the cyclone should start to weaken before landfall, it should still be near or at hurricane strength when it reaches southern New England. Rapid weakening is expected after landfall, and Henri is again forecast to become post-tropical in about 48 hours and dissipate in 3 to 4 days. Key Messages: 1. Dangerous storm surge inundation is expected to begin late tonight or Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Residents in these areas should follow any advice given by local officials. 2. Hurricane conditions are expected to begin late tonight or Sunday in portions of Long Island, Connecticut, and Rhode Island, where a Hurricane Warning is in effect. Tropical storm conditions will begin in these areas late tonight. 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor to isolated moderate river flooding over portions of Long Island, New England, eastern New York and New Jersey. 4. Swells from Henri will continue to affect much of the east coast of the U.S. during the next day or two. These swells could cause life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 22/0300Z 38.6N 71.0W 65 KT 75 MPH 12H 22/1200Z 40.3N 71.2W 70 KT 80 MPH 24H 23/0000Z 41.9N 71.8W 55 KT 65 MPH...INLAND 36H 23/1200Z 43.1N 71.7W 30 KT 35 MPH...INLAND 48H 24/0000Z 43.9N 70.5W 25 KT 30 MPH...POST-TROP/INLAND 60H 24/1200Z 44.4N 68.3W 25 KT 30 MPH...POST-TROPICAL 72H 25/0000Z 44.8N 63.5W 25 KT 30 MPH...POST-TROP/INLAND 96H 26/0000Z...DISSIPATED $$ Forecaster Beven

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Remnants of Grace Forecast Discussion Number 34

2021-08-21 22:45:09| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Sat Aug 21 2021 000 WTNT42 KNHC 212045 TCDAT2 Remnants Of Grace Discussion Number 34 NWS National Hurricane Center Miami FL AL072021 400 PM CDT Sat Aug 21 2021 The mountainous terrain of Mexico has taken its toll on Grace. Surface observations and high-resolution visible satellite images indicate that the system no longer has a definite surface circulation, and Grace has degenerated into a trough to the west of Mexico City. Therefore, this is the last advisory on this system. Although the surface center has dissipated, the mid-tropospheric remnants of Grace are expected to continue westward, and to emerge into the eastern Pacific Ocean by late Sunday. There is high likelihood that this will lead to the formation of a new tropical cyclone over that basin by early next week. For additional information on this possibility, see the eastern North Pacific Tropical Weather Outlook under AWIPS header MIATWOEP, WMO header ABPZ20 KNHC and on the web at hurricanes.gov. Key Messages: 1. Through tonight, lingering heavy rainfall from the remnants of Grace may result in additional areas of flash and urban flooding, along with mudslides, over central Mexico. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 19.6N 100.1W 20 KT 25 MPH...REMNANTS 12H 22/0600Z...DISSIPATED $$ Forecaster Pasch

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Hurricane Henri Forecast Discussion Number 24

2021-08-21 22:33:37| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Sat Aug 21 2021 000 WTNT43 KNHC 212033 TCDAT3 Hurricane Henri Discussion Number 24 NWS National Hurricane Center Miami FL AL082021 500 PM EDT Sat Aug 21 2021 Visible satellite images and microwave data indicate that a tight inner core has formed in association with Henri, but the convective pattern appears ragged in infrared images. An ASCAT pass from earlier today indicated that the 34- and 50-kt winds continue to expand in the southeastern quadrant, and that data was used to update the initial wind radii. The latest Dvorak estimates range from 55 to 77 kt, and based on that data, the initial intensity is held at 65 kt. The NOAA Hurricane Hunters will be investigating Henri this evening. Henri is moving faster to the north-northeast, or 020 degrees, at 16 kt. There continues to be little change to the forecast track philosophy. A cut-off low located over the central Appalachians and a ridge building to the east and northeast of Henri should cause the storm to continue moving north-northeastward through tonight. A decresae in forward speed and a slight bend to the left is then forecast to occur on Sunday. The latest model guidance has shifted slightly to the right, and the NHC official track forecast has been nudged in that direction. This forecast shows landfall over eastern Long Island and southern Connecticut in about 24 hours. Users are reminded to not focus on the exact forecast track, as the average 24-hour track uncertainty is around 40 miles and impacts will extend well away from the center. The environment looks favorable for Henri to strengthen through tonight with low shear, upper-level divergence associated with the upper-level trough, and warm SSTs. In fact, SST analyses indicate that Henri will be passing over a patch of very warm 30 deg C waters this evening. By early Sunday Henri is predicted to cross the north wall of the Gulf Stream. That should result in some weakening, but Henri is forecast to be at or near hurricane strength at landfall. Once the center moves inland over the northeast United States, rapid weakening is expected. Henri is forecast to become post-tropical in about 48 hours and dissipate in 3 to 4 days. Key Messages: 1. Dangerous storm surge inundation is expected to begin late tonight or Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Residents in these areas should follow any advice given by local officials. 2. Hurricane conditions are expected to begin late tonight or Sunday in portions of Long Island, Connecticut, and Rhode Island, where a Hurricane Warning is in effect. Tropical storm conditions will begin in these areas tonight. 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor to isolated moderate river flooding over portions of Long Island, New England, eastern New York and New Jersey. 4. Swells from Henri will continue to affect much of the east coast of the U.S. during the next day or two. These swells could cause life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 36.3N 71.4W 65 KT 75 MPH 12H 22/0600Z 38.8N 71.4W 70 KT 80 MPH 24H 22/1800Z 40.8N 72.1W 60 KT 70 MPH 36H 23/0600Z 42.1N 72.4W 40 KT 45 MPH...INLAND 48H 23/1800Z 43.3N 71.9W 25 KT 30 MPH...INLAND 60H 24/0600Z 43.6N 69.9W 25 KT 30 MPH...POST-TROP/INLAND 72H 24/1800Z 44.3N 68.1W 25 KT 30 MPH...POST-TROP/INLAND 96H 25/1800Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Storm Grace Forecast Discussion Number 33

2021-08-21 16:54:55| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Sat Aug 21 2021 000 WTNT42 KNHC 211454 TCDAT2 Tropical Storm Grace Discussion Number 33 NWS National Hurricane Center Miami FL AL072021 1000 AM CDT Sat Aug 21 2021 Grace has continued to move over east-central Mexico since making landfall around 0600 UTC. Visible satellite images show that the system's organization is degrading, but there is still some deep convection near the center with a few showers and thunderstorms near the coast. Assuming a slightly faster rate of weakening than given by the Decay-SHIPS output to account for the mountainous terrain, the advisory intensity is set to 60 kt. Additional rapid weakening should occur while the cyclone moves over the mountains of central and west-central Mexico today and tonight. Grace is likely to weaken below tropical storm strength tonight and dissipate tomorrow morning. After making a southwestward turn just after landfall, the current motion is just a little south of west, or 250/11 kt. A mid-level ridge to the north of Grace should cause a generally westward motion until dissipation on Sunday. The mid-level remnants of Grace are expected to continue westward after the surface center dissipates, and to emerge into the eastern Pacific Ocean by late Sunday. There is a good chance that this will lead to the formation of a new tropical cyclone over that basin by early next week. Key Messages: 1. Through the weekend, heavy rainfall across Veracruz, Puebla, Tlaxcala, Hidalgo, Queretaro, and eastern San Luis Potosi will lead to significant flash and urban flooding, along with the likelihood of mudslides. FORECAST POSITIONS AND MAX WINDS INIT 21/1500Z 19.7N 98.9W 60 KT 70 MPH 12H 22/0000Z 19.4N 100.6W 40 KT 45 MPH...INLAND 24H 22/1200Z 19.0N 102.5W 25 KT 30 MPH...POST-TROP/INLAND 36H 23/0000Z...DISSIPATED $$ Forecaster Pasch

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Hurricane Henri Forecast Discussion Number 23

2021-08-21 16:42:06| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Sat Aug 21 2021 000 WTNT43 KNHC 211442 TCDAT3 Hurricane Henri Discussion Number 23 NWS National Hurricane Center Miami FL AL082021 1100 AM EDT Sat Aug 21 2021 The Air Force Reserve and NOAA Hurricane Hunters have been investigating Henri this morning and continue to provide very valuable data. The Air Force aircraft measured a peak flight-level wind of 82 kt at 700 mb, which easily supports hurricane strength, but the initial intensity is set at 65 kt as a blend of these data and somewhat lower SFMR winds. In addition, aircraft data indicate that the minimum pressure has fallen to 991 mb. The NOAA tail Doppler radar data indicate that the storm is becoming more vertically aligned and that a more symmetric eyewall appears to be forming. In addition, dropsonde data from the NOAA Gulfstream IV aircraft flying around Henri indicate that the 34- and 50-kt wind radii are a little larger than previously estimated in the southeastern quadrant. NOAA buoy 41001 located in the northeastern quadrant of the hurricane has recently reported 18 ft. seas. Henri is moving north-northeastward, or 020 degrees, at 12 kt. The steering pattern appears fairly well established now with a cut off low located over the central Appalachians and a ridge building to the east and northeast of Henri. This pattern should cause the storm to accelerate to the north or north-northeast today followed by a slight bend to the left on Sunday. The latest run of the GFS has shifted to the east, but overall the models are focused in on landfall being between central Long Island and Rhode Island on Sunday. However, users are reminded to not focus on the center itself, as impacts will extend well away from the center, especially to the east. The new NHC track forecast is a little to the east of the previous one and very near the best-performing models, the consensus aids. The environment looks favorable for Henri to continue to gain strength through tonight with low shear, upper-level divergence associated with the upper-level trough, and warm SSTs. In fact, the GFS and HWRF models show the minimum pressure dropping by 15 mb or more during that time period. By early Sunday, Henri is predicted to cross the north wall of the Gulf Stream and that should cause some weakening, but Henri is forecast to be at or near hurricane strength at landfall. Once the center moves inland over the northeast United States, rapid weakening is expected. Henri is forecast to become post-tropical in 48-60 hours and dissipate in 3 to 4 days. Key Messages: 1. Dangerous storm surge inundation is expected to begin late tonight or Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Dangerous storm surge is possible beginning late tonight or Sunday in western portions of Long Island and Connecticut in the Storm Surge Watch area. Residents in these areas should follow any advice given by local officials. 2. Hurricane conditions are expected to begin late tonight or Sunday in portions of Long Island, Connecticut, and Rhode Island, where a Hurricane Warning is in effect. Tropical storm conditions will begin in these areas tonight. 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor and isolated moderate river flooding, over portions of Long Island, New England, southeast New York and northern New Jersey. 4. Swells from Henri will continue to affect much of the east coast of the U.S. during the next day or two. These swells could cause life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 21/1500Z 34.4N 72.5W 65 KT 75 MPH 12H 22/0000Z 36.9N 71.9W 75 KT 85 MPH 24H 22/1200Z 39.7N 71.9W 70 KT 80 MPH 36H 23/0000Z 41.3N 72.6W 60 KT 70 MPH...INLAND 48H 23/1200Z 42.4N 72.9W 35 KT 40 MPH...INLAND 60H 24/0000Z 43.1N 71.9W 25 KT 30 MPH...POST-TROP/INLAND 72H 24/1200Z 43.8N 69.2W 25 KT 30 MPH...POST-TROP/INLAND 96H 25/1200Z...DISSIPATED $$ Forecaster Cangialosi

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