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Tropical Storm Vicky Forecast Discussion Number 9

2020-09-16 10:26:55| National Hurricane Center (Atlantic)

Issued at 500 AM AST Wed Sep 16 2020 000 WTNT41 KNHC 160826 TCDAT1 Tropical Storm Vicky Discussion Number 9 NWS National Hurricane Center Miami FL AL212020 500 AM AST Wed Sep 16 2020 Vicky remains a strongly sheared and poorly organized tropical storm. The low-level center is displaced to the west-southwest of the main area of deep convection due to strong westerly vertical wind shear. The initial intensity is held at 45 kt based on the earlier ASCAT data, which is well above the Dvorak estimates. Vicky is expected to remain in hostile wind shear conditions while traversing 26 C waters, so it seems likely that weakening should occur. The NHC intensity forecast follows the trend of the model guidance and shows gradual weakening during the next few days. Vicky is expected to become a remnant low in a couple of days, but it is always tricky to figure out when these systems will lose all of its convection since it is forecast to stay over relatively warm waters. The storm continues to more west-northwestward, a little to the left of the previous track at 285/9. Vicky should gradually turn westward later today and west-southwestward in a couple of days when it becomes a shallow cyclone and moves in the low-level flow. The new track forecast is just a little south of the previous one to be closer to the latest consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 21.6N 33.9W 45 KT 50 MPH 12H 16/1800Z 21.9N 35.3W 40 KT 45 MPH 24H 17/0600Z 22.0N 36.9W 35 KT 40 MPH 36H 17/1800Z 22.0N 38.7W 30 KT 35 MPH 48H 18/0600Z 21.7N 40.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 18/1800Z 21.4N 42.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 19/0600Z 20.8N 44.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 20/0600Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Storm Karina Forecast Discussion Number 14

2020-09-16 10:23:53| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Wed Sep 16 2020 000 WTPZ41 KNHC 160823 TCDEP1 Tropical Storm Karina Discussion Number 14 NWS National Hurricane Center Miami FL EP162020 200 AM PDT Wed Sep 16 2020 Karina is weakening in a hurry. Deep convection near the center has largely dissipated, and the only area of lingering convection is in the northeastern quadrant. An ASCAT overpass from around 0500 UTC showed maximum winds in the 30-35 kt range, and based on that data the initial intensity is lowered to 35 kt. The tropical storm is already in unfavorable conditions of cool 25 C waters and a dry and stable airmass. Since Karina will be moving over even cooler waters and into an environment of stronger southerly wind shear, continued weakening is expected. Karina is now forecast to become a remnant low by 24 hours and dissipate within a few days. Karina is moving west-northwestward at about 9 kt as it remains steered by a mid-level ridge to its northeast. A continued west-northwest to northwest motion should continue for about another day, but after Karina becomes a shallow remnant low it is expected to turn westward within the low-level trade winds. The NHC track forecast lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 21.7N 123.7W 35 KT 40 MPH 12H 16/1800Z 22.4N 124.8W 30 KT 35 MPH 24H 17/0600Z 23.1N 126.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 17/1800Z 23.5N 127.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 18/0600Z 23.4N 128.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 18/1800Z 23.1N 129.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 19/0600Z...DISSIPATED $$ Forecaster Cangialosi

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Hurricane Teddy Forecast Discussion Number 15

2020-09-16 08:46:25| National Hurricane Center (Atlantic)

Issued at 300 AM AST Wed Sep 16 2020 000 WTNT45 KNHC 160646 TCDAT5 Hurricane Teddy Special Discussion Number 15 NWS National Hurricane Center Miami FL AL202020 300 AM AST Wed Sep 16 2020 Teddy has rapidly intensified overnight. Satellite images show an eye has formed, and satellite intensity estimates are between 77- 90 kt. The initial wind speed is set to 80 kt as a blend of these data. Further strengthening is expected and Teddy could become a major hurricane later today or Thursday. The intensity forecast has been raised considerably in the short-term based on current trends, and could have to revised upward on the regular 5 am advisory. No changes to the track forecast are needed. FORECAST POSITIONS AND MAX WINDS INIT 16/0700Z 15.5N 48.7W 80 KT 90 MPH 12H 16/1200Z 16.0N 49.2W 90 KT 105 MPH 24H 17/0000Z 17.3N 50.5W 95 KT 110 MPH 36H 17/1200Z 18.8N 52.0W 100 KT 115 MPH 48H 18/0000Z 20.2N 53.4W 105 KT 120 MPH 60H 18/1200Z 21.6N 54.8W 100 KT 115 MPH 72H 19/0000Z 23.0N 56.2W 100 KT 115 MPH 96H 20/0000Z 26.5N 60.0W 100 KT 115 MPH 120H 21/0000Z 29.5N 62.5W 95 KT 110 MPH $$ Forecaster Blake

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Hurricane Sally Forecast Discussion Number 20

2020-09-16 08:43:26| National Hurricane Center (Atlantic)

Issued at 130 AM CDT Wed Sep 16 2020 000 WTNT44 KNHC 160643 TCDAT4 Hurricane Sally Special Discussion Number 20 NWS National Hurricane Center Miami FL AL192020 130 AM CDT Wed Sep 16 2020 Justification for this special advisory is to increase the initial intensity and the 12-h forecast intensity at landfall. Observations from an Air Force Hurricane Hunter aircraft and Mobile Alabama WSR-88D Doppler radar data indicate that Sally has continued to strengthen this morning. Radar data show that Sally's eye has become better defined and Doppler velocities in the northern eyewall have reached average values of at least 110 kt between 5000-6000 ft ASL, which supports an equivalent surface wind speed of about 89 kt. The reconnaissance aircraft has recently measured peak 700-mb flight-level winds of 103 kt, which equates to about 93 kt using a standard 90 percent adjustment factor, while peak SFMR surface wind speed have been 85 kt. In addition, a recent dropsonde in the northeast eyewall measured an average wind speed of 113 kt in the lowest 150 meters, which equates to about a 94-kt surface wind. However, those winds appeared to be possibly contaminated by wind gusts. Based on the above data, the initial intensity has been increased to 90 kt. Some additional slight strengthening is possible until landfall occur, and Sally could peak at 95 kt. Rapid weakening will occur after the center moves inland, and the system should become a remnant low in a couple of days. This is consistent with the latest model guidance. Radar and aircraft center fixes indicate that Sally's motion is north-northeastward, or 030/02 kt. No changes were made to the previous track forecast. Sally should continue to move north-northeastward this morning, and then turn northeastward with a gradual increase in forward speed by tonight. That motion will then continue for the next day or so. Then, as Sally approaches the westerly flow at higher latitudes, the cyclone should turn toward the east-northeast with a slight further increase in forward speed until becoming a dissipating remnant low near the southeast U.S. coast in 2-3 days. The official forecast is close to the latest corrected dynamical model consensus, HCCA, prediction. KEY MESSAGES: 1. Historic, life-threatening flash flooding due to rainfall is likely through Wednesday along and just inland of the coast from the Florida Panhandle west of the Apalachicola River to the Alabama/Mississippi border. Widespread moderate to major river flooding is forecast across the Florida Panhandle and southern Alabama. Significant flash and urban flooding, as well as widespread minor to moderate river flooding, is likely across inland portions of Mississippi and Alabama, and into Georgia and the western Carolinas this week. 2. Life-threatening storm surge is expected along portions of the coastline from Alabama to the western Florida Panhandle, including Mobile Bay. 3. Hurricane conditions are expected this morning and then continue into this afternoon within portions of the Hurricane Warning area along the Mississippi and Alabama coastlines and the western Florida Panhandle. FORECAST POSITIONS AND MAX WINDS INIT 16/0630Z 29.9N 87.8W 90 KT 105 MPH 12H 16/1200Z 30.3N 87.5W 95 KT 110 MPH 24H 17/0000Z 31.2N 86.8W 40 KT 45 MPH...INLAND 36H 17/1200Z 32.0N 85.7W 30 KT 35 MPH...INLAND 48H 18/0000Z 32.9N 83.9W 25 KT 30 MPH...INLAND 60H 18/1200Z 33.6N 81.5W 20 KT 25 MPH...INLAND 72H 19/0000Z 34.0N 79.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 20/0000Z...DISSIPATED $$ Forecaster Stewart

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Hurricane Sally Forecast Discussion Number 19

2020-09-16 04:57:52| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Tue Sep 15 2020 000 WTNT44 KNHC 160257 TCDAT4 Hurricane Sally Discussion Number 19 NWS National Hurricane Center Miami FL AL192020 1000 PM CDT Tue Sep 15 2020 Observations from an Air Force Hurricane Hunter aircraft and WSR-88D Doppler radar data indicate some strengthening. The eye has become a little better defined on the radar, and the central pressure has fallen to 972 mb. The eye has also become evident on recent IR imagery. Using a blend of flight-level and SFMR-observed surface winds, along with the Doppler velocities, gives a current intensity estimate of 75 kt. Given the recent trends, the official forecast allows for some more intensification before landfall, which is likely to occur in less than 12 hours. Rapid weakening will occur after the center moves inland, and the system should become a remnant low in a couple of days. This is consistent with the model guidance. Radar and aircraft center fixes indicate that the motion is now north-northeastward, or 020/2 kt. Sally should move north-northeastward, and then northeastward, with a gradual increase in forward speed, along the northwestern side of a weak mid-level high pressure area for the next couple of days. Then, as the system approaches the westerly flow at higher latitudes, the cyclone should turn toward the east-northeast with a slight further increase in forward speed until becoming a dissipating remnant low near the southeast U.S. coast in 2-3 days. The official forecast is close to the latest corrected dynamical model consensus, HCCA, prediction. KEY MESSAGES: 1. Historic, life-threatening flash flooding due to rainfall is likely through Wednesday along and just inland of the coast from the Florida Panhandle west of the Apalachicola River to the Alabama/Mississippi border. Widespread moderate to major river flooding is forecast across the Florida Panhandle and southern Alabama. Significant flash and urban flooding, as well as widespread minor to moderate river flooding, is likely across inland portions of Mississippi and Alabama, and into Georgia and the western Carolinas this week. 2. Life-threatening storm surge is expected along portions of the coastline from Alabama to the western Florida Panhandle, including Mobile Bay. 3. Hurricane conditions are expected this evening and overnight within portions of the Hurricane Warning area along the Mississippi and Alabama coastlines and the western Florida Panhandle. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 29.8N 87.8W 75 KT 85 MPH 12H 16/1200Z 30.3N 87.5W 80 KT 90 MPH...ON THE COAST 24H 17/0000Z 31.2N 86.8W 40 KT 45 MPH...INLAND 36H 17/1200Z 32.0N 85.7W 30 KT 35 MPH...INLAND 48H 18/0000Z 32.9N 83.9W 25 KT 30 MPH...INLAND 60H 18/1200Z 33.6N 81.5W 20 KT 25 MPH...INLAND 72H 19/0000Z 34.0N 79.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 20/0000Z...DISSIPATED $$ Forecaster Pasch

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