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Hurricane Teddy Forecast Discussion Number 32

2020-09-20 10:50:55| National Hurricane Center (Atlantic)

Issued at 500 AM AST Sun Sep 20 2020 000 WTNT45 KNHC 200850 TCDAT5 Hurricane Teddy Discussion Number 32 NWS National Hurricane Center Miami FL AL202020 500 AM AST Sun Sep 20 2020 The convective structure of Teddy has degraded substantially since the last advisory, with no sign of an eye in conventional satellite imagery. The most recent available microwave imagery from last night suggested that Teddy still had a very well defined low to mid-level inner-core, but this has not translated to the higher levels more apparent at night. Intensity estimates have decreased, so the initial intensity has been lowered slightly to 100 kt for this advisory. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the hurricane later this morning and should provide more information about its structure and strength. Teddy's evolution for the next few days appears to be a tale of 3 troughs. Upper-level westerly flow associated with the first upper-level trough, affecting the storm now, is the most likely reason why the hurricane's structure has degraded and has taken on a slightly sheared appearance. Teddy will begin to encounter the 2nd trough, a deep frontal system approaching from the west, later today and that should cause the hurricane to turn north. This interaction should steer the center of Teddy east of Bermuda, but tropical storm impacts from either the large hurricane, the frontal system, or both are still likely Sunday evening through Monday night. All indications are that Teddy will then continue generally northward and merge with the frontal system, nearing Nova Scotia as an extratropical cyclone early Wednesday. Teddy's maximum winds will likely decrease sharply after it becomes post-tropical, as shown by all the intensity guidance, but its gale and storm-force wind radii will likely increase at the same time. The cyclone should turn northeastward as the 3rd trough, another mid-latitude system, approaches from the west. Teddy could be absorbed by that feature in as soon as 120 h, though this is not explicitly shown in the forecast at this time. The spread in the track and intensity guidance is quite low and confidence in both aspects of the forecast is high. There is a little more uncertainty in the wind radii evolution, but it is clear that Teddy will produce strong winds over a wide area of the northwest Atlantic during the next couple of days. The extent of 12-foot or higher seas associated with Teddy continues to increase. See the Key Message below regarding swells caused by the hurricane. Key Messages: 1. The center of Teddy is forecast to move east of Bermuda late Sunday or Monday. Tropical storm conditions are likely on the island beginning this evening and could continue into Monday evening. 2. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada early next week, where there is an increasing risk of direct impacts from wind, rain, and storm surge. Residents there should closely monitor the progress of Teddy and updates to the forecast. 3. Large swells produced by Teddy are expected to affect portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, the east coast of the United States, and Atlantic Canada during the next few days. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 20/0900Z 28.0N 62.0W 100 KT 115 MPH 12H 20/1800Z 28.9N 62.7W 95 KT 110 MPH 24H 21/0600Z 30.4N 62.9W 90 KT 105 MPH 36H 21/1800Z 33.3N 62.1W 85 KT 100 MPH 48H 22/0600Z 37.5N 62.2W 85 KT 100 MPH 60H 22/1800Z 40.9N 63.2W 75 KT 85 MPH...POST-TROP/EXTRATROP 72H 23/0600Z 43.8N 62.3W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 24/0600Z 51.0N 54.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 25/0600Z 58.5N 41.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Zelinsky

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Tropical Storm Wilfred Forecast Discussion Number 8

2020-09-20 10:36:28| National Hurricane Center (Atlantic)

Issued at 500 AM AST Sun Sep 20 2020 000 WTNT43 KNHC 200836 TCDAT3 Tropical Storm Wilfred Discussion Number 8 NWS National Hurricane Center Miami FL AL232020 500 AM AST Sun Sep 20 2020 It is unclear if Wilfred still exists, and if so, exactly where it is located. Although there is clear evidence of a broad elongated circulation, the formerly small center of Wilfred is either obscured by higher clouds or has dissipated. AMSR-2 microwave imagery at 0431 UTC showed only evidence of a northwest-southeast oriented trough with one or more embedded mesoscale lows. Visible imagery and the next round of ASCAT passes will hopefully provide more information about Wilfred's status later this morning. The intensity remains 35 kt based on ASCAT data from last night, but more recent Dvorak estimates are lower. Due to the uncertainty associated with Wilfred's status and location, the motion estimate is a very uncertain 295/15 kt. In general, Wilfred or its eventual remnants should continue on a west-northwestward heading today, and then could turn westward by early Monday. The NHC forecast is very similar to the previous one and lies near the middle of the guidance suite. Virtually no change has been made to the official intensity forecast. Wilfred will likely gradually weaken until it dissipates due to a combination of increasing wind shear and a dry environment. The exact point at which Wilfred will become a trough varies from model to model, but confidence is fairly high that Wilfred won't last much longer than another day or two. The NHC forecast carries Wilfred for 48 h based on persistence from the previous advisory, but if recent trends hold, it could dissipate as soon as later today. FORECAST POSITIONS AND MAX WINDS INIT 20/0900Z 15.0N 42.0W 35 KT 40 MPH 12H 20/1800Z 15.7N 44.1W 35 KT 40 MPH 24H 21/0600Z 16.2N 46.5W 30 KT 35 MPH 36H 21/1800Z 16.5N 48.5W 30 KT 35 MPH 48H 22/0600Z 16.7N 50.3W 25 KT 30 MPH 60H 22/1800Z...DISSIPATED $$ Forecaster Zelinsky

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Tropical Storm Beta Forecast Discussion Number 10

2020-09-20 04:59:46| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Sat Sep 19 2020 000 WTNT42 KNHC 200259 TCDAT2 Tropical Storm Beta Discussion Number 10 NWS National Hurricane Center Miami FL AL222020 1000 PM CDT Sat Sep 19 2020 Beta's deep convection has been waning this evening. An Air Force Reserve Hurricane Hunter aircraft has found that the central pressure rose several millibars since this morning, but the plane also still measured surface winds around 50 kt from the SFMR instrument. The strongest winds appear to be located near on old frontal boundary which extends north and east of Beta's center, and in fact sustained tropical-storm-force winds are just grazing the coast of south-central Louisiana. The aircraft fixes indicated that Beta drifted north-northeastward during the day. Right now, the cyclone is embedded within weak steering currents between two areas of high pressure centered near the Bahamas and west Texas/southern New Mexico. The western high pressure area is expected to slide eastward across the Southern Plains into the southeastern U.S. through Sunday night, which should force Beta to move slowly toward the west-northwest toward the Texas coast. The center is now expected to reach the coast between 48-60 hours, at which point it is likely to recurve around the mid-level high and move slowly northeastward near or inland of the upper Texas coast on days 3 and 4. Because of Beta's drift today, the new guidance envelope has shifted a bit northward. For this forecast cycle, the NHC official forecast split the difference between the previous interpolated forecast and the HFIP Corrected Consensus guidance. This keeps the forecast to the east of the ECMWF, HCCA, and TVCN multi-model consensus during Beta's slow recurvature. The air mass behind the old front appears to have won out. Beta's circulation is embedded in a dry environment of mid-level relative humidities around 50 percent, and the air mass could actually become more stable as Beta moves closer to the Texas coast. On top of that, the moderate southwesterly shear is not expected to diminish much at all. As a result, the intensity guidance has continued to trend downward, and the new official forecast now flatlines Beta's intensity at 50 kt until landfall soon after 48 hours. This forecast still lies near the top end of the guidance envelope, closest to the SHIPS model. After 48 hours, weakening is expected assuming Beta's center remains over land, and it is now expected to become a remnant low over Louisiana by day 5. While the chances that Beta will become a hurricane continue to decrease, the Hurricane Watch for portions of the coast of Texas are being maintained out of an abundance of caution given the uncertainty in the forecast. Key Messages: 1. The expected slow motion of Beta has the potential to expand a long duration rainfall event from the Louisiana coast westward into southeast Texas on Sunday and northward into the Mid-South by mid next week. The potentially prolonged period of rainfall could cause flash, urban, and river flooding, especially where tide levels are above normal. 2. There is the danger of life-threatening storm surge near times of high tide from Sunday through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials. 3. Tropical storm force winds are expected to begin along portions of the northwestern Gulf Coast overnight within the tropical storm warning area in Louisiana and will spread westward to the Texas coast Sunday through Monday. Hurricane-force winds are possible along portions of the Texas coast late Monday and Monday night, where a hurricane watch is in effect. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 26.8N 92.2W 50 KT 60 MPH 12H 20/1200Z 27.1N 93.0W 50 KT 60 MPH 24H 21/0000Z 27.4N 94.1W 50 KT 60 MPH 36H 21/1200Z 27.9N 95.2W 50 KT 60 MPH 48H 22/0000Z 28.4N 96.0W 50 KT 60 MPH 60H 22/1200Z 28.9N 96.3W 40 KT 45 MPH...INLAND 72H 23/0000Z 29.3N 96.0W 35 KT 40 MPH...INLAND 96H 24/0000Z 30.2N 94.1W 30 KT 35 MPH...INLAND 120H 25/0000Z 31.4N 92.1W 25 KT 30 MPH...POST-TROP/INLAND $$ Forecaster Berg

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Hurricane Teddy Forecast Discussion Number 31

2020-09-20 04:54:45| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Sat Sep 19 2020 000 WTNT45 KNHC 200254 TCDAT5 Hurricane Teddy Discussion Number 31 NWS National Hurricane Center Miami FL AL202020 1100 PM AST Sat Sep 19 2020 Some convective cells have been developing within Teddy's large outer eye, and it is possible that this convection is forming an inner eyewall. In any event, observations from an Air Force Hurricane Hunter aircraft indicate that the maximum winds have decreased slightly, to near 100 kt. The hurricane is expected to remain in a low shear environment until tomorrow evening, and to more or less maintain its intensity for 12-24 hours. Thereafter, increasing shear associated with an upper-level trough to the west should cause weakening. Although the shear is predicted by the global models to become fairly strong after 48 hours, the system has a a very large and intense circulation so only slow weakening is expected. By 72 hours, Teddy should merge with a frontal zone to the east of New England and become a strong extratropical cyclone. The official intensity forecast is close to the model consensus. The system's wind field will likely become even larger as the wind field of Teddy interacts within a high pressure system behind a cold front during the next few days. This could prolong the period of strong winds over Bermuda into Monday night. Teddy continues on a general northwestward track or about 315/11 kt. The hurricane should move on the western side of a subtropical high pressure area for the next day or so, and then begin to accelerate northward ahead of a strong mid-tropospheric trough that develops into a cutoff low off the northeast U.S. coast in a couple of days. The interaction of Teddy with this low will likely result in a slight leftward bend of the track around days 2-3. In 4-5 days, post-tropical Teddy is likely to turn north-northeastward to northeastward in the flow on the east side of a broad 500 mb trough. The official track forecast is a blend of the simple and corrected dynamical model consensus predictions. The extent of 12-foot or higher seas associated with Teddy continues to increase. See the Key Message below regarding swells caused by the hurricane. Key Messages: 1. While the center of Teddy is forecast to move east of Bermuda late Sunday or Monday, tropical storm conditions are likely on the island beginning Sunday evening. 2. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada early next week, where there is an increasing risk of direct impacts from wind, rain, and storm surge. Residents there should closely monitor the progress of Teddy and updates to the forecast. 3. Large swells produced by Teddy are expected to affect portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, the east coast of the United States, and Atlantic Canada during the next few days. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 27.3N 61.2W 100 KT 115 MPH 12H 20/1200Z 28.3N 62.3W 100 KT 115 MPH 24H 21/0000Z 29.6N 63.0W 95 KT 110 MPH 36H 21/1200Z 31.6N 62.4W 90 KT 105 MPH 48H 22/0000Z 35.7N 61.8W 90 KT 105 MPH 60H 22/1200Z 39.7N 62.5W 80 KT 90 MPH 72H 23/0000Z 42.5N 62.8W 70 KT 80 MPH...POST-TROP/EXTRATROP 96H 24/0000Z 49.5N 56.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 25/0000Z 57.0N 42.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch

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Tropical Storm Wilfred Forecast Discussion Number 7

2020-09-20 04:34:15| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Sat Sep 19 2020 000 WTNT43 KNHC 200234 TCDAT3 Tropical Storm Wilfred Discussion Number 7 NWS National Hurricane Center Miami FL AL232020 1100 PM AST Sat Sep 19 2020 Microwave data since the previous advisory indicates that the center of Wilfred is located near the southwestern edge of the deep convection. The displacement of the center from the convection is the result of moderate westerly vertical wind shear. The initial intensity remains 35 kt, and is based on an ASCAT-B overpass from around 0000 UTC that revealed peak winds of 30-35 kt. Wilfred is headed toward an area of increasing westerly wind shear, and a drier mid-level environment. These negative factors should lead to weakening in 24 to 48 h, and the global models dissipate the cyclone within the next few days. The official forecast follows suit, but given the small size of the cyclone it could weaken and dissipate sooner than indicated below. The initial motion estimate is 295/14, a little faster than before. Wilfred is forecast to remain on a west-northwestward heading through Sunday, but should turn westward within the low-level flow by Sunday night or Monday. The latest NHC track forecast is once again similar to the previous advisory and near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 14.5N 40.5W 35 KT 40 MPH 12H 20/1200Z 15.3N 42.6W 35 KT 40 MPH 24H 21/0000Z 15.8N 45.2W 35 KT 40 MPH 36H 21/1200Z 16.2N 47.3W 30 KT 35 MPH 48H 22/0000Z 16.4N 49.2W 25 KT 30 MPH 60H 22/1200Z...DISSIPATED $$ Forecaster Brown

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