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Tropical Storm Teddy Forecast Discussion Number 9

2020-09-14 22:33:09| National Hurricane Center (Atlantic)

Issued at 500 PM AST Mon Sep 14 2020 000 WTNT45 KNHC 142033 TCDAT5 Tropical Storm Teddy Discussion Number 9 NWS National Hurricane Center Miami FL AL202020 500 PM AST Mon Sep 14 2020 Teddy is strengthening this afternoon. Recent satellite imagery shows a growing convective band south and west of the center and a CDO feature developing over the estimated low-level center position. The initial intensity is set to 45 kt based on the latest Dvorak estimates of T3.0/45 kt from TAFB and SAB. The environment along Teddy's forecast track features increasing SSTs and low shear for the next several days, and with the improved convective structure of the cyclone, steady strengthening is forecast. The NHC intensity prediction has been increased from the previous advisory, and shows a 25-kt increase in the next 24 hours, which is supported by the SHIPS model and some of the RII indices. Beyond that time, Teddy is forecast to reach major hurricane intensity in about 3 days. The new NHC forecast is near HCCA through the forecast period. Microwave and geostationary satellite fixes suggest an initial motion of 275/12. The track forecast reasoning is similar to that of the previous advisory. Teddy will initially be steered westward and then west-northwestward by a deep-layer ridge located over the central Atlantic. As the ridge shifts eastward through the forecast period, Teddy is forecast to turn more northwestward as it moves around the western edge of the ridge. There is a fair amount of across track spread in the guidance, with the ECMWF on the right and the GFS and HWRF on the left. Overall the guidance envelope has shifted to the left since this morning. The new NHC track has been adjusted in that direction, and lies near or a little to the right of the latest consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 14/2100Z 13.0N 44.0W 45 KT 50 MPH 12H 15/0600Z 13.6N 45.8W 55 KT 65 MPH 24H 15/1800Z 14.5N 47.7W 70 KT 80 MPH 36H 16/0600Z 15.4N 49.3W 75 KT 85 MPH 48H 16/1800Z 16.6N 50.8W 85 KT 100 MPH 60H 17/0600Z 17.9N 52.2W 95 KT 110 MPH 72H 17/1800Z 19.3N 53.6W 100 KT 115 MPH 96H 18/1800Z 22.0N 56.0W 105 KT 120 MPH 120H 19/1800Z 24.5N 58.5W 100 KT 115 MPH $$ Forecaster Brennan

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Remnants of Rene Forecast Discussion Number 31

2020-09-14 22:32:42| National Hurricane Center (Atlantic)

Issued at 500 PM AST Mon Sep 14 2020 000 WTNT43 KNHC 142032 TCDAT3 Remnants Of Rene Discussion Number 31 NWS National Hurricane Center Miami FL AL182020 500 PM AST Mon Sep 14 2020 Visible satellite imagery during the past few hours shows that Rene has opened into a trough of low pressure and is no longer a tropical cyclone. Therefore, this is the last advisory. The remnants of Rene will likely move generally southwestward for the next day or two while the associated winds slowly subside. Although the trough may continue to produce occasional showers and thunderstorms, no redevelopment of the system is expected. Additional information on this system can be found in High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php FORECAST POSITIONS AND MAX WINDS INIT 14/2100Z 26.9N 49.3W 25 KT 30 MPH...REMNANTS OF RENE 12H 15/0600Z...DISSIPATED $$ Forecaster Zelinsky

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Hurricane Sally Forecast Discussion Number 13

2020-09-14 18:31:30| National Hurricane Center (Atlantic)

Issued at 1130 AM CDT Mon Sep 14 2020 000 WTNT44 KNHC 141631 TCDAT4 Hurricane Sally Special Discussion Number 13 NWS National Hurricane Center Miami FL AL192020 1130 AM CDT Mon Sep 14 2020 A NOAA Hurricane Hunter aircraft investigating Sally recently measured peak flight-level winds of 88 kt at 700 mb and SFMR winds of 78 kt north of the center, and an Air Force reconnaissance aircraft just measured 79 kt flight-level winds at 700 mb. These data indicate that Sally has rapidly strengthened into a hurricane with an intensity of around 80 kt. In addition, data from the KEVX WSR-88D show an eye forming at around 16,000 ft altitude. This special advisory has been issued to increase the initial and forecast intensity. Additional adjustments to the intensity forecast could be required this afternoon. Only a slight adjustment was made to the 12-h track forecast position based on the more northward and eastward initial position. KEY MESSAGES: 1. It is too early to determine where Sally's center will move onshore given the uncertainty in the timing and location of Sally's northward turn near the central Gulf Coast. Users should not focus on the details of the official forecast track, since NHC's average forecast error at 48 hours is around 80 miles, and dangerous storm surge, rainfall, and wind hazards will extend well away from the center. 2. An extremely dangerous and life-threatening storm surge is expected for areas outside the southeastern Louisiana Hurricane and Storm Damage Risk Reduction System from Port Fourchon, Louisiana, to the Alabama/Florida border, where a Storm Surge Warning is in effect. Residents in these areas should follow any advice given by local officials. 3. Hurricane conditions are expected tonight within the Hurricane Warning area in southeastern Louisiana and are expected by late Tuesday within the Hurricane Warning area along the Mississippi and Alabama coastline. Tropical storm conditions are likely to begin later today and this evening in these areas and preparations should be rushed to completion. 4. Life-threatening flash flooding is likely, as well as widespread minor to isolated major flooding, on area rivers along and just inland of the Central Gulf Coast. Significant flash and urban flooding, as well as widespread minor to moderate river flooding is likely across Mississippi and Alabama through the middle of the week. Flooding impacts are expected to spread farther across the Southeast through the week. Sally could continue to produce flash flooding across the Florida peninsula and prolong existing minor river flooding across west-central Florida through today. FORECAST POSITIONS AND MAX WINDS INIT 14/1630Z 28.7N 87.0W 80 KT 90 MPH 12H 15/0000Z 28.8N 87.8W 85 KT 100 MPH 24H 15/1200Z 29.2N 88.8W 90 KT 105 MPH 36H 16/0000Z 29.8N 89.1W 90 KT 105 MPH 48H 16/1200Z 30.8N 88.7W 65 KT 75 MPH...INLAND 60H 17/0000Z 31.8N 87.7W 30 KT 35 MPH...INLAND 72H 17/1200Z 32.6N 86.5W 25 KT 30 MPH...INLAND 96H 18/1200Z 33.1N 84.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 19/1200Z...DISSIPATED $$ Forecaster Brown

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Hurricane Paulette Forecast Discussion Number 31

2020-09-14 16:55:01| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Mon Sep 14 2020 000 WTNT42 KNHC 141454 TCDAT2 Hurricane Paulette Discussion Number 31 NWS National Hurricane Center Miami FL AL172020 1100 AM AST Mon Sep 14 2020 The 53rd Air Force Reserve hurricane hunter aircraft observed a peak 700 mb flight-level wind of 93 kt and a SFMR wind of 80 kt 25 miles to the northeast of the center of the 35 mile wide eye. The central pressure, also reported by the aircraft, has fallen to 970 mb. Based on these data, the initial intensity is increased to 85 kt for this advisory. Additional strengthening is expected as Paulette moves away from Bermuda and accelerates northeastward over the North Atlantic. Paulette should be at or near major hurricane strength within the next 24 hours. At the 48 hour forecast period, weakening will commence as the cyclone becomes involved with a mid-latitude shortwave trough approaching from the Canadian Maritimes. Paulette should begin losing its tropical characteristics toward the end of the week. The peak intensity is increased a little at the 24 hour period to agree with the HCCA and IVCN intensity multi-models and follows these aids through the remaining portion of the forecast period. The initial motion estimate is 355/12 kt. Paulette will begin accelerating northeastward by Tuesday morning then turn east-northeastward with a further increased in forward motion early Wednesday morning. A slower eastward to southeastward motion is forecast on Friday in response to a larger mid- to upper tropospheric cut-off low approaching the eastern Atlantic. The NHC forecast is a little faster than the previous one beyond the 36 hour period and basically lies down the middle of the tightly clustered deterministic and regional model guidance. Key Messages: 1. The eye of Paulette will gradually move away from Bermuda today, however, hurricane and tropical storm conditions, storm surge, and very heavy rainfall will likely continue into this afternoon. 2. Swells produced by Paulette are affecting portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, and the east coast of the United States. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 33.4N 64.7W 85 KT 100 MPH 12H 15/0000Z 35.1N 63.6W 95 KT 110 MPH 24H 15/1200Z 37.5N 59.8W 110 KT 125 MPH 36H 16/0000Z 40.1N 54.2W 110 KT 125 MPH 48H 16/1200Z 42.9N 47.6W 90 KT 105 MPH 60H 17/0000Z 45.5N 41.1W 75 KT 85 MPH 72H 17/1200Z 47.1N 36.8W 65 KT 75 MPH 96H 18/1200Z 45.5N 33.2W 50 KT 60 MPH 120H 19/1200Z 40.1N 32.1W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Roberts

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Hurricane Sally Forecast Discussion Number 12

2020-09-14 16:51:58| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Mon Sep 14 2020 000 WTNT44 KNHC 141451 TCDAT4 Tropical Storm Sally Discussion Number 12 NWS National Hurricane Center Miami FL AL192020 1000 AM CDT Mon Sep 14 2020 An intense burst of deep convection with cloud tops colder than -80 degrees Celsius has developed over and the to east of the center this morning. A recent fix from an Air Force Reserve Hurricane Hunter aircraft indicates that the center has reformed to the east of the previous estimated location, beneath the burst of deep convection. NWS WSR-88D radar imagery shows an increase in banding around the eastern and southeastern portion of new center found by the aircraft and it appears that an eye is in its formative stage. The aircraft has reported believable SFMR winds of 55 kt, and that is the basis for the initial intensity. The most recent minimum pressure estimated from the aircraft data is 991 mb, down several millibars from the first fix on this flight. Sally is located within a conducive environment of low wind shear, warm waters, and a moist atmosphere. These conditions are likely to lead to steady strengthening over the next 24 hours or so. With the recent increase in organization of the inner core, there is more confidence that Sally will strengthen to a hurricane later today or tonight. Additional strengthening is possible on Tuesday while the storm moves slowly northwestward near the coast of southeast Louisiana. Increasing westerly wind shear and land interaction will probably slow the intensification rate by late tomorrow. The new NHC intensity forecast is similar to the previous advisory and is near the upper-end of the guidance envelope. Since Sally is forecast to be moving very slowly around the time of landfall a slower rate of weakening is indicated since a large portion of the circulation will remain over water for some time. Given the recent re-formation of the center, the initial motion is a somewhat uncertain west-northwestward at 5 kt. Weak ridging over the southeastern United State should steer Sally slowly west- northwestward through tonight. After that time, a northwestward to northward turn is anticipated but the exact timing and location of the turn remains uncertain. The general trend in the guidance has been eastward for the past few cycles, and the NHC forecast has been nudged in that direction and lies between the GFS and ECMWF models but a little west of the various consensus aids. Regardless of the exact forecast track and intensity of Sally, the slow-moving storm is expected to cause a life-threatening storm surge and freshwater flooding event. KEY MESSAGES: 1. It is too early to determine where Sally's center will move onshore given the uncertainty in the timing and location of Sally's northward turn near the central Gulf Coast. Users should not focus on the details of the official forecast track, since NHC's average forecast error at 48 hours is around 80 miles, and dangerous storm surge, rainfall, and wind hazards will extend well away from the center. 2. An extremely dangerous and life-threatening storm surge is expected for areas outside the southeastern Louisiana Hurricane and Storm Damage Risk Reduction System from Port Fourchon, Louisiana, to the Alabama/Florida border, where a Storm Surge Warning is in effect. Residents in these areas should follow any advice given by local officials. 3. Hurricane conditions are expected tonight within the Hurricane Warning area in southeastern Louisiana and are expected by late Tuesday within the Hurricane Warning area along the Mississippi and Alabama coastline. Tropical storm conditions are likely to begin later today and this evening in these areas and preparations should be rushed to completion. 4. Life-threatening flash flooding is likely, as well as widespread minor to isolated major flooding, on area rivers along and just inland of the Central Gulf Coast. Significant flash and urban flooding, as well as widespread minor to moderate river flooding is likely across Mississippi and Alabama through the middle of the week. Flooding impacts are expected to spread farther across the Southeast through the week. Sally could continue to produce flash flooding across the Florida peninsula and prolong existing minor river flooding across west-central Florida through today. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 28.4N 86.9W 55 KT 65 MPH 12H 15/0000Z 28.7N 88.0W 65 KT 75 MPH 24H 15/1200Z 29.2N 88.8W 75 KT 85 MPH 36H 16/0000Z 29.8N 89.1W 80 KT 90 MPH 48H 16/1200Z 30.8N 88.7W 60 KT 70 MPH...INLAND 60H 17/0000Z 31.8N 87.7W 30 KT 35 MPH...INLAND 72H 17/1200Z 32.6N 86.5W 25 KT 30 MPH...INLAND 96H 18/1200Z 33.1N 84.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 19/1200Z...DISSIPATED $$ Forecaster Brown

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