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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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Post-Tropical Cyclone Teddy Wind Speed Probabilities Number 43

2020-09-23 04:35:09| National Hurricane Center (Atlantic)

Issued at 0300 UTC WED SEP 23 2020 000 FONT15 KNHC 230235 PWSAT5 POST-TROPICAL CYCLONE TEDDY WIND SPEED PROBABILITIES NUMBER 43 NWS NATIONAL HURRICANE CENTER MIAMI FL AL202020 0300 UTC WED SEP 23 2020 AT 0300Z THE CENTER OF POST-TROPICAL CYCLONE TEDDY WAS LOCATED NEAR LATITUDE 42.8 NORTH...LONGITUDE 63.9 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 75 KTS...85 MPH...140 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) ATLANTIC STANDARD TIME (AST)...SUBTRACT 4 HOURS FROM Z TIME EASTERN DAYLIGHT TIME (EDT)...SUBTRACT 4 HOURS FROM Z TIME CENTRAL DAYLIGHT TIME (CDT)...SUBTRACT 5 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 00Z WED AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 00Z WED 12Z WED 00Z THU 12Z THU 00Z FRI 00Z SAT 00Z SUN PERIODS TO TO TO TO TO TO TO 12Z WED 00Z THU 12Z THU 00Z FRI 00Z SAT 00Z SUN 00Z MON FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT CAPE RACE NFLD 34 X 8( 8) X( 8) X( 8) X( 8) X( 8) X( 8) ILE ST PIERRE 34 40 14(54) X(54) X(54) X(54) X(54) X(54) BURGEO NFLD 34 58 21(79) X(79) X(79) X(79) X(79) X(79) BURGEO NFLD 50 X 7( 7) X( 7) X( 7) X( 7) X( 7) X( 7) PTX BASQUES 34 80 18(98) X(98) X(98) X(98) X(98) X(98) PTX BASQUES 50 4 52(56) X(56) X(56) X(56) X(56) X(56) PTX BASQUES 64 X 5( 5) X( 5) X( 5) X( 5) X( 5) X( 5) EDDY POINT NS 34 99 X(99) X(99) X(99) X(99) X(99) X(99) EDDY POINT NS 50 99 X(99) X(99) X(99) X(99) X(99) X(99) EDDY POINT NS 64 18 5(23) X(23) X(23) X(23) X(23) X(23) SYDNEY NS 34 99 1(99) X(99) X(99) X(99) X(99) X(99) SYDNEY NS 50 64 9(73) X(73) X(73) X(73) X(73) X(73) SYDNEY NS 64 1 6( 7) X( 7) X( 7) X( 7) X( 7) X( 7) SABLE ISLAND 34 99 X(99) X(99) X(99) X(99) X(99) X(99) SABLE ISLAND 50 21 X(21) X(21) X(21) X(21) X(21) X(21) HALIFAX NS 34 99 X(99) X(99) X(99) X(99) X(99) X(99) HALIFAX NS 50 99 X(99) X(99) X(99) X(99) X(99) X(99) HALIFAX NS 64 53 X(53) X(53) X(53) X(53) X(53) X(53) YARMOUTH NS 34 99 X(99) X(99) X(99) X(99) X(99) X(99) YARMOUTH NS 50 99 X(99) X(99) X(99) X(99) X(99) X(99) MONCTON NB 34 99 X(99) X(99) X(99) X(99) X(99) X(99) MONCTON NB 50 51 X(51) X(51) X(51) X(51) X(51) X(51) ST JOHN NB 34 99 X(99) X(99) X(99) X(99) X(99) X(99) ST JOHN NB 50 19 X(19) X(19) X(19) X(19) X(19) X(19) EASTPORT ME 34 99 X(99) X(99) X(99) X(99) X(99) X(99) BAR HARBOR ME 34 99 X(99) X(99) X(99) X(99) X(99) X(99) AUGUSTA ME 34 4 X( 4) X( 4) X( 4) X( 4) X( 4) X( 4) NANTUCKET MA 34 3 X( 3) X( 3) X( 3) X( 3) X( 3) X( 3) $$ FORECASTER ROBERTS

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Summary for Post-Tropical Cyclone Teddy (AT5/AL202020)

2020-09-23 04:34:41| National Hurricane Center (Atlantic)

...POST-TROPICAL CYCLONE TEDDY FORECAST TO PRODUCE DESTRUCTIVE WAVES, HEAVY RAIN AND STRONG WINDS FOR PORTIONS OF NOVA SCOTIA TONIGHT THROUGH WEDNESDAY... As of 11:00 PM AST Tue Sep 22 the center of Teddy was located near 42.8, -63.9 with movement N at 18 mph. The minimum central pressure was 957 mb with maximum sustained winds of about 80 mph.

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Post-Tropical Cyclone Teddy Graphics

2020-09-23 01:38:49| National Hurricane Center (Atlantic)

5-Day Uncertainty Track last updated Tue, 22 Sep 2020 23:38:49 GMT Wind Speed Probabilities last updated Tue, 22 Sep 2020 21:33:10 GMT

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Summary for Post-Tropical Cyclone Teddy (AT5/AL202020)

2020-09-23 01:35:08| National Hurricane Center (Atlantic)

...POST-TROPICAL CYCLONE TEDDY HEADING TOWARD THE NOVA SCOTIA COAST... ...DESTRUCTIVE WAVES, HEAVY RAIN AND STRONG WINDS ARE EXPECTED FOR PORTIONS OF NOVA SCOTIA TONIGHT THROUGH WEDNESDAY... As of 8:00 PM AST Tue Sep 22 the center of Teddy was located near 41.9, -64.2 with movement N at 18 mph. The minimum central pressure was 955 mb with maximum sustained winds of about 85 mph.

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