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Post-Tropical Cyclone Teddy Forecast Discussion Number 44

2020-09-23 10:41:53| National Hurricane Center (Atlantic)

Issued at 500 AM AST Wed Sep 23 2020 000 WTNT45 KNHC 230841 TCDAT5 Post-Tropical Cyclone Teddy Discussion Number 44 NWS National Hurricane Center Miami FL AL202020 500 AM AST Wed Sep 23 2020 Teddy's deep convection has been diminishing, but based on buoy observations the cyclone still has a strong circulation with a central pressure in the 950's. Assuming a gradual spindown of the system since the earlier aircraft observations, the estimated maximum winds have dropped to just below hurricane strength. The system is expected to traverse Nova Scotia today as a strong extratropical cyclone, and move near Newfoundland by tonight. After passing east of Labrador on Thursday, the global models show Teddy merging with another large extratropical low over the north Atlantic. The estimated initial motion is north-northeastward or 025/20 kt. Teddy is embedded within a deep-layer trough that is located in the vicinity of Atlantic Canada. The post-tropical cyclone should move north-northeastward on the eastern side of the trough for the next 36-48 hours before it merges with the other low. The official track forecast is very similar to the previous one and also closely follows the corrected multi-model consensus, HCCA. Even after Teddy passes Nova Scotia and Newfoundland, large swells will linger over much of the southwestern Atlantic basin for the next few days. Key Messages: 1. Teddy is expected remain a powerful post-tropical cyclone while it moves near or over portions of Atlantic Canada through tonight. The most significant hazard expected from Teddy is large destructive waves forecast along the southern coast of Nova Scotia today. 2. Very large swells produced by Teddy are expected to affect portions of Bermuda, the Leeward Islands, the Greater Antilles, the Bahamas, the east coast of the United States, and Atlantic Canada during the next few days. These swells are expected to cause life-threatening surf and rip current conditions. 3. Tropical Storm Watches and Warnings are in effect for portions of Nova Scotia, Newfoundland, Prince Edward Island and the Magdalen Islands, and heavy rainfall across Atlantic Canada is expected through Thursday. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 44.5N 62.7W 60 KT 70 MPH...POST-TROP/EXTRATROP 12H 23/1800Z 47.5N 60.6W 55 KT 65 MPH...POST-TROP/EXTRATROP 24H 24/0600Z 52.3N 56.7W 45 KT 50 MPH...INLAND 36H 24/1800Z 57.0N 53.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 25/0600Z...POST-TROP/EXTRATROP $$ Forecaster Pasch

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Tropical Storm Lowell Forecast Discussion Number 10

2020-09-23 04:44:41| Tropical Depression LIDIA

Issued at 800 PM PDT Tue Sep 22 2020

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Post-Tropical Cyclone Paulette Forecast Discussion Number 44

2020-09-23 04:36:40| National Hurricane Center (Atlantic)

Issued at 300 AM GMT Wed Sep 23 2020 000 WTNT41 KNHC 230236 TCDAT1 Post-Tropical Cyclone Paulette Discussion Number 44 NWS National Hurricane Center Miami FL AL172020 300 AM GMT Wed Sep 23 2020 Paulette has been devoid of deep convection since early Tuesday, and the shallow convection mentioned in the previous advisory has also waned. Therefore, Paulette has again become a post-tropical cyclone, and this is the last NHC advisory on this system. Recent ASCAT data showed that the system still had a small area of 35 kt winds so the initial intensity is held at that value. The post-tropical cyclone will be moving over waters of 22-23 degrees Celsius and remain within an area of moderate vertical wind shear. This should result in gradual weakening over the next couple of days. The post-tropical cyclone continues to move eastward or 080/10 kt. This motion is forecast to continue through midday Wednesday, but a reduction is forward speed is expected by Wednesday night as the system becomes vertically shallow. The remnant low is expected to turn southward in 24-36 hours, with a faster west-southwestward motion anticipated later in the forecast period when it becomes embedded within the low-level northeasterly flow. This is the last NHC advisory on Paulette. Additional information on this system can be found in High Seas Forecasts issued by Meteo France under WMO header FQNT50 LFPW and available on the web at www.meteofrance.com/previsions-meteo-marine/bulletin/grandlarge/ metarea2. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 34.8N 20.0W 35 KT 40 MPH...POST-TROPICAL 12H 23/1200Z 35.2N 18.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 24/0000Z 35.4N 17.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 24/1200Z 35.1N 17.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 25/0000Z 34.0N 19.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 25/1200Z 33.0N 21.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 26/0000Z 32.5N 26.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 27/0000Z...DISSIPATED $$ Forecaster Brown

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Post-Tropical Cyclone Teddy Forecast Discussion Number 43

2020-09-23 04:36:10| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Tue Sep 22 2020 000 WTNT45 KNHC 230236 TCDAT5 Post-Tropical Cyclone Teddy Discussion Number 43 NWS National Hurricane Center Miami FL AL202020 1100 PM AST Tue Sep 22 2020 Extratropical transition has been ongoing since last night, with the cyclone's associated rain shield expanding over a great distance in the northern semicircle. In addition, multiple dropsonde observations from the Air Force Reserve hurricane hunters and buoy data show a sharp temperature gradient of nearly 20 degrees F from northwest quadrant to the southeast, indicative of the cyclone's involvement with the strong baroclinic frontal zone. Accordingly, Teddy has become a strong post-tropical extratropical cyclone. Highest flight-level winds recorded this evening were 83 kt about 85 miles northeast of the center and the highest SFMR surface winds were 63 kt. A recent METOP-C scatterometer pass showed sustained winds no higher than 59 kt in the east quadrant. A blend of these data yields an initial intensity of 70 kt for this advisory. Further gradual weakening is forecast through the period as a result of the rapidly decreasing sea surface temperatures (less than 20C) north of the North Wall of the gulf stream. The NHC forecast indicates Teddy approaching the coast of Nova Scotia below hurricane strength, but still as a strong post-tropical extratropical low. Teddy should continue to gradually spin down as the cyclone moves north-northeastward toward Newfoundland. The initial motion is estimated to be northward, or 010/16 kt. A north-northeastward turn is forecast later tonight or early Wednesday in response to an approaching mid-latitude shortwave trough moving out of the northeast U.S. Teddy should move over Nova Scotia tomorrow and near the island of Newfoundland, and the adjacent waters of the Gulf of St. Lawrence Wednesday night. Afterward, the post-tropical cyclone will likely be absorbed by an even larger high latitude extratropical cyclone near Greenland. There has been no significant changes made to the NHC forecast track this evening, and it's in best agreement with the HFIP Corrected Consensus Approach model. Key Messages: 1. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada late today through Thursday. The most significant hazard expected from Teddy is large destructive waves forecast along the southern coast of Nova Scotia through Wednesday. 2. Very large swells produced by Teddy are expected to affect portions of Bermuda, the Leeward Islands, the Greater Antilles, the Bahamas, the east coast of the United States, and Atlantic Canada during the next few days. These swells are expected to cause life-threatening surf and rip current conditions. 3. Tropical Storm Watches and Warnings are in effect for portions of Nova Scotia, Newfoundland, Prince Edward Island and the Magdalen Islands, and heavy rainfall across Atlantic Canada is expected through Thursday. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 42.8N 63.9W 70 KT 80 MPH...POST-TROPICAL 12H 23/1200Z 45.3N 62.3W 60 KT 70 MPH...INLAND 24H 24/0000Z 49.8N 58.7W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 24/1200Z 54.7N 54.9W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 25/0000Z...ABSORBED BY A LARGER LOW $$ Forecaster Roberts

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Hurricane Teddy Forecast Discussion Number 42

2020-09-22 22:55:07| National Hurricane Center (Atlantic)

Issued at 500 PM AST Tue Sep 22 2020 000 WTNT45 KNHC 222054 TCDAT5 Hurricane Teddy Discussion Number 42 NWS National Hurricane Center Miami FL AL202020 500 PM AST Tue Sep 22 2020 Teddy is a very impressive cyclone on satellite images this afternoon, even from full-disk images. The hurricane's circulation is over 1000 miles wide, with an enormous distinct comma shape and frontal features especially in the eastern semicircle. As far as what to call the system convection has actually deepened near the center during the past several hours, and an AMSR pass around 1700 UTC showed that the system still had a low-level eye feature. For that reason and for simplicity's sake, the system will remain a hurricane on this advisory, although it is obviously a hybrid low with many characteristics of a non-tropical cyclone. The initial wind speed is lowered to 80 kt, assuming the filling trend reported by the last NOAA Hurricane Hunter mission continued. The wind radii are expanded based on ASCAT data, with tropical-storm-force winds over eastern Nova Scotia already. The hurricane is forecast to transition into a post-tropical cyclone later tonight or early tomorrow due to the cooler waters north of the Gulf Stream likely weakening any central convection. Teddy should decay below hurricane-strength before reaching Nova Scotia and steadily weaken as it moves over the even colder waters in the Gulf of St. Lawrence. The new intensity forecast is a little lower than the previous one and is closest to the GFS model. Teddy is moving northward now and should turn north-northeastward tomorrow ahead of the next trough in the mid-latitudes. This will take Post-Tropical Teddy over Nova Scotia and near Newfoundland during the next couple of days, with the cyclone likely being absorbed into a larger extratropical cyclone west of Greenland in 2-3 days. There are no significant changes to report, though there has been a slight westward shift of the track near Newfoundland. The hazards from Teddy are extending at quite a distance from the center of this hurricane. In addition to the 500-mile wind radii in the northeastern quadrant, Canadian buoy 44150 has recently reported 42 ft (13 m) significant wave heights, with the buoy still about 90 n mi from the center. Key Messages: 1. Teddy is expected to transition to a powerful post-tropical cyclone as it moves near or over portions of Atlantic Canada late today through Thursday. The most significant hazard expected from Teddy is large destructive waves forecast along the southern coast of Nova Scotia through Wednesday. 2. Very large swells produced by Teddy are expected to affect portions of Bermuda, the Leeward Islands, the Greater Antilles, the Bahamas, the east coast of the United States, and Atlantic Canada during the next few days. These swells are expected to cause life-threatening surf and rip current conditions. 3. Tropical Storm Watches and Warnings are in effect for portions of Nova Scotia, Newfoundland, Prince Edward Island and the Magdalen Islands, and heavy rainfall across Atlantic Canada is expected through Thursday. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 41.1N 64.2W 80 KT 90 MPH 12H 23/0600Z 43.1N 63.5W 65 KT 75 MPH...POST-TROPICAL 24H 23/1800Z 47.0N 60.7W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 24/0600Z 51.5N 56.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 24/1800Z 56.5N 53.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 60H 25/0600Z...DISSIPATED $$ Forecaster Blake

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