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Hurricane Teddy Forecast Discussion Number 17

2020-09-16 16:38:02| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Wed Sep 16 2020 000 WTNT45 KNHC 161437 TCDAT5 Hurricane Teddy Discussion Number 17 NWS National Hurricane Center Miami FL AL202020 1100 AM AST Wed Sep 16 2020 Teddy's overall appearance has changed little over the past several hours. Microwave and infrared satellite images depict a well-defined inner core with an eye evident in the microwave imagery. However, visible imagery reveals that the eye remains cloud filled. Over the past few hours, the coldest cloud tops and have become confined to the western portion of the circulation, which could be the early signs of the cyclone experiencing some westerly wind shear. The latest satellite intensity estimates remain unchanged from 6 h ago, and therefore the initial intensity will remain 85 kt. Environmental conditions appear favorable for additional strengthening over the next 18-24 h, and with the inner-core well defined, rapid intensification could resume shortly. By 36 h, increasing westerly wind shear and drier air should limit any further intensification, and possibly induce some weakening. Later on in the forecast period, Teddy could encounter some cooler waters due to upwelling caused by Paulette. This could also attribute to additional weakening. The latest NHC forecast is largely unchanged from the previous one, and is on the high end of the guidance. It should be noted that if the rapid intensification that has paused recently doe not resume soon, adjustments to the intensity forecast will be necessary. Teddy continues to move northwestward at about 10 kt. This motion is forecast to continue for the next few days, as the cyclone is steered by a mid-level ridge to its north and northeast. Late in the forecast period, the portion of the ridge north of Teddy is expected to erode as a mid-latitude trough digs across the northeastern United States. This evolution should cause the cyclone to turn north-northwest and possibly north by day 5. The track guidance is tightly clustered through day 3, then the spread increases after that time, likely due to how the models are handling the approaching trough. The NHC track forecast is close to the previous one and is near the various multi-model track consensus aids. On the forecast track, Teddy could make a close to approach to Bermuda in about 5 days. However, based on average 5-day track and intensity errors, it is too soon to know what type of impacts the cyclone could have on the island. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 16.5N 49.7W 85 KT 100 MPH 12H 17/0000Z 17.5N 50.8W 95 KT 110 MPH 24H 17/1200Z 19.0N 52.3W 110 KT 125 MPH 36H 18/0000Z 20.4N 53.8W 115 KT 130 MPH 48H 18/1200Z 21.9N 55.3W 115 KT 130 MPH 60H 19/0000Z 23.5N 56.9W 110 KT 125 MPH 72H 19/1200Z 25.1N 58.7W 105 KT 120 MPH 96H 20/1200Z 28.3N 62.7W 95 KT 110 MPH 120H 21/1200Z 31.7N 64.1W 90 KT 105 MPH $$ Forecaster Latto

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Tropical Storm Karina Forecast Discussion Number 15

2020-09-16 16:36:32| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Wed Sep 16 2020 000 WTPZ41 KNHC 161436 TCDEP1 Tropical Storm Karina Discussion Number 15 NWS National Hurricane Center Miami FL EP162020 800 AM PDT Wed Sep 16 2020 Very little deep convection with cloud tops of -40C remains this morning, and what's left is located well to the west-northwest of the center of circulation. There could still be a few 35-kt winds remaining in that particular area, which was identified earlier by a scatterometer pass, so the initial intensity is held at a generous 35 kt for this advisory. Karina is expected to continue traversing cooler waters while moving farther into an inhibiting thermodynamic environment and unfavorable upper-level winds. Therefore, weakening is forecast and Karina should degenerate to a remnant low tonight. The initial motion is estimated to be northwestward, or 310/7 kt. A turn back toward the west-northwest is expected later today and the cyclone should continue on this general motion through Thursday night. A westward turn is forecast on Friday as Karina degenerates to a remnant low and is steered by the low-level tradewind flow. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 22.6N 123.9W 35 KT 40 MPH 12H 17/0000Z 23.2N 125.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 17/1200Z 23.8N 126.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 18/0000Z 24.0N 127.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 18/1200Z 23.9N 128.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 19/0000Z 23.6N 129.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 19/1200Z...DISSIPATED $$ Forecaster Roberts

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Tropical Storm Vicky Forecast Discussion Number 10

2020-09-16 16:35:01| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Wed Sep 16 2020 000 WTNT41 KNHC 161434 TCDAT1 Tropical Storm Vicky Discussion Number 10 NWS National Hurricane Center Miami FL AL212020 1100 AM AST Wed Sep 16 2020 Hostile vertical shear of 50 to 60 kt has finally taken a toll on Vicky. A 1227 UTC ASCAT-B overpass showed peak winds of 35 kt north of the center, and that is the basis for the advisory intensity. The strong shear is expected to continue while Vicky moves over marginal 26-27C SSTs, so additional weakening is forecast. Vicky should become a tropical depression in around 24 hours before weakening to a remnant low in about 2 days, with dissipation expected by day 3. However, the timing of when organized deep convection will finally cease is difficult to determine, so its is possible Vicky could weaken faster than indicated here or hang on a bit longer. The initial motion estimate is more westward, or 270/08. Vicky should continue moving westward for the next day or two before turning west-southwestward in the low-level flow. The new NHC track forecast is south of the previous one and is close to the new multi-model consensus aids. The ASCAT data were also used to modify the initial 34-kt wind radii. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 21.5N 34.7W 35 KT 40 MPH 12H 17/0000Z 21.6N 36.0W 35 KT 40 MPH 24H 17/1200Z 21.7N 37.7W 30 KT 35 MPH 36H 18/0000Z 21.5N 39.5W 30 KT 35 MPH 48H 18/1200Z 21.0N 41.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 19/0000Z 20.5N 42.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 19/1200Z...DISSIPATED $$ Forecaster Brennan

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Hurricane Sally Forecast Discussion Number 21

2020-09-16 10:58:22| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Wed Sep 16 2020 632 WTNT44 KNHC 160858 TCDAT4 Hurricane Sally Discussion Number 21 NWS National Hurricane Center Miami FL AL192020 400 AM CDT Wed Sep 16 2020 There has been little change in Sally's convective structure during the past few hours as seen in radar and satellite data. The initial intensity of 90 kt is based on previous reconnaissance SFMR surface wind data of 88 kt in the northeastern quadrant, along with average Doppler radar values of 114 kt between 4500-5000 ft ASL, which supports an equivalent surface wind speed of about 90 kt. The reconnaissance aircraft has recently measured peak 700-mb flight-level winds of 110 kt, but those winds may not be making it down to the surface based on earlier buoy wind reports underneath the eyewall. Although the northern eyewall has moved onshore between Mobile Bay and Pensacola Bay, some slight strengthening is still possible until the center of Sally's eye makes landfall later this morning. Rapid weakening is forecast 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 020/03 kt. No significant changes were required to the previous track forecast. The latest NHC model guidance continues to show Sally moving slowly north-northeastward this morning, and then turn northeastward with a gradual increase in forward speed by tonight. That motion should then continue for the next day or so. As Sally approaches the mid-latitude westerlies at higher latitudes, the tropical cyclone should turn toward the east-northeast with some slight increase in forward speed until it becomes a dissipating remnant low near the southeastern 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 and catastrophic flooding is unfolding along and just inland of the coast from west of Tallahassee, Florida, to Mobile Bay, Alabama. In addition, widespread moderate to major river flooding is forecast. Significant flash and urban flooding, as well as widespread minor to moderate river flooding, is likely across inland portions Alabama into central Georgia. Widespread flash and urban flooding is possible, as well as widespread minor to moderate river flooding, across western South Carolina into western and central North Carolina. Scattered flash and urban flooding is possible, as well as scattered minor river flooding in southeast Virginia. 2. Life-threatening storm surge is occurring along portions of the coastline from Alabama to the western Florida Panhandle, including Pensacola Bay and southern portions of 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 16/0900Z 30.1N 87.7W 90 KT 105 MPH 12H 16/1800Z 30.7N 87.2W 70 KT 80 MPH...INLAND 24H 17/0600Z 31.5N 86.3W 35 KT 40 MPH...INLAND 36H 17/1800Z 32.6N 84.7W 30 KT 35 MPH...INLAND 48H 18/0600Z 33.5N 82.4W 25 KT 30 MPH...INLAND 60H 18/1800Z 34.1N 79.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 19/0600Z...DISSIPATED $$ Forecaster Stewart

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Hurricane Teddy Forecast Discussion Number 16

2020-09-16 10:38:58| National Hurricane Center (Atlantic)

Issued at 500 AM AST Wed Sep 16 2020 000 WTNT45 KNHC 160838 TCDAT5 Hurricane Teddy Discussion Number 16 NWS National Hurricane Center Miami FL AL202020 500 AM AST Wed Sep 16 2020 Teddy continues to quickly intensify. The latest satellite images shows that a ragged eye is present, although microwave images show it is closed in the low-levels. Satellite intensity estimates earlier were between 77- 90 kt, and the initial wind speed is set to 85 with the increasing organization. The environment appears to be ripe for rapid intensification with light shear, warm water, and a solid ring present on overnight 37 GHz microwave data. Thus a 30-kt wind increase will be forecast for the first 24 hours from the 6Z initial wind speed of 80 kt. After that time, there could be an increase in shear from the mid-oceanic trough, which should level off the wind speed, along with possibly an increase in mid-level dry air. At long range, Teddy could also be affected by the cold wake from Paulette. The intensity forecast is also uncertain considering the guidance is still catching up to the higher current intensity, but most everything shows a large major hurricane for the bulk of the forecast period, and so does the official forecast. Teddy is moving northwestward at about 10 kt. A mid-tropospheric high should steer the hurricane in that general direction and speed throughout the forecast period until early next week when a turn to the north-northwest is possible ahead of a mid-latitude trough. The biggest change to note that guidance has almost unanimously shifted westward at long range, seemingly due to a stronger central Atlantic ridge, and the NHC forecast is also moved in that direction. Unfortunately, this change does increase the threat to Bermuda, which was just hit by Hurricane Paulette, but remember the average track error at 5 days is roughly 200 miles. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 15.8N 49.0W 85 KT 100 MPH 12H 16/1800Z 16.8N 50.0W 95 KT 110 MPH 24H 17/0600Z 18.3N 51.5W 110 KT 125 MPH 36H 17/1800Z 19.7N 52.9W 115 KT 130 MPH 48H 18/0600Z 21.3N 54.6W 115 KT 130 MPH 60H 18/1800Z 22.7N 56.1W 110 KT 125 MPH 72H 19/0600Z 24.2N 57.8W 105 KT 120 MPH 96H 20/0600Z 27.5N 62.0W 100 KT 115 MPH 120H 21/0600Z 31.0N 64.0W 95 KT 110 MPH $$ Forecaster Blake

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