By John Galt
November 8, 2011 17:45
This will be the only update I post on Tropical Storm Sean (formerly sub-tropical) which is set to impact Bermuda tomorrow. One thing for certain; even though the U.S. has escaped a direct hit from a major storm this has been one heck of an active season. Hopefully this will be the end of it.
Satellite photos will update automatically from NOAA:
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NCAR/SWFMUD MODEL PLOTS
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(click to enlarge/reduce charts)
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TROPICAL STORM ADVISORIES
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000
WTNT34 KNHC 082034
TCPAT4
BULLETIN
TROPICAL STORM SEAN ADVISORY NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011
500 PM AST TUE NOV 08 2011
…SEAN A LITTLE STRONGER…
SUMMARY OF 500 PM AST…2100 UTC…INFORMATION
———————————————-
LOCATION…27.8N 69.8W
ABOUT 430 MI…695 KM SW OF BERMUDA
MAXIMUM SUSTAINED WINDS…50 MPH…85 KM/H
PRESENT MOVEMENT…WNW OR 300 DEGREES AT 2 MPH…4 KM/H
MINIMUM CENTRAL PRESSURE…999 MB…29.50 INCHES
WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY…
NONE.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT…
A TROPICAL STORM WATCH IS IN EFFECT FOR…
* BERMUDA
A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA…GENERALLY WITHIN 48 HOURS.
INTERESTS IN BERMUDA SHOULD MONITOR PRODUCTS ISSUED BY THE BERMUDA
WEATHER SERVICE.
DISCUSSION AND 48-HOUR OUTLOOK
——————————
AT 500 PM AST…2100 UTC…THE CENTER OF TROPICAL STORM SEAN WAS
LOCATED NEAR LATITUDE 27.8 NORTH…LONGITUDE 69.8 WEST. SEAN IS
MOVING TOWARD THE WEST-NORTHWEST NEAR 2 MPH…4 KM/H…AND THIS
GENERAL MOTION IS EXPECTED TO CONTINUE OVERNIGHT. A TURN TOWARD THE
NORTHWEST IS FORECAST ON WEDNESDAY…WITH TURNS TOWARD THE NORTH AND
THEN TOWARD THE NORTHEAST ANTICIPATED ON THURSDAY.
MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 50 MPH…85 KM/H…
WITH HIGHER GUSTS. ADDITIONAL STRENGTHENING IS POSSIBLE OVER THE
NEXT COUPLE OF DAYS.
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 230 MILES…370
KM…MAINLY TO THE NORTH OF THE CENTER.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 999 MB…29.50 INCHES.
HAZARDS AFFECTING LAND
———————-
WIND…TROPICAL STORM CONDITIONS ARE POSSIBLE ON BERMUDA LATE
THURSDAY OR EARLY FRIDAY.
SURF…SWELLS GENERATED BY SEAN ARE EXPECTED TO AFFECT PORTIONS OF
THE SOUTHEASTERN COAST OF THE UNITED STATES DURING THE NEXT COUPLE
OF DAYS. THESE SWELLS WILL CAUSE LIFE-THREATENING SURF AND RIP
CURRENTS. PLEASE SEE STATEMENTS FROM YOUR LOCAL NATIONAL WEATHER
SERVICE OFFICE FOR MORE DETAILS.
NEXT ADVISORY
————-
NEXT INTERMEDIATE ADVISORY…800 PM AST.
NEXT COMPLETE ADVISORY…1100 PM AST.
$$
FORECASTER BLAKE
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TROPICAL STORM DISCUSSION
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000
WTNT44 KNHC 082035
TCDAT4
TROPICAL STORM SEAN DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011
500 PM AST TUE NOV 08 2011
CONVECTION HAS FORMED NEAR THE CENTER OF SEAN THIS AFTERNOON WITH A
BANDING FEATURE PERSISTING IN THE NORTHEASTERN QUADRANT. SINCE THE
STORM IS A LITTLE FARTHER FROM THE UPPER-LEVEL LOW…WITH A WARM
CORE APPARENT ON AMSU ANALYSES AND A SMALLER RADIUS OF MAXIMUM
WINDS AS SEEN IN ASCAT DATA…SEAN NOW HAS ENOUGH CHARACTERISTICS
TO BE CONSIDERED TROPICAL. THE MAXIMUM WINDS ARE SET TO 45 KT…IN
AGREEMENT WITH THE TAFB DVORAK ESTIMATE AND EARLIER ASCAT WINDS.
WHILE THE REGIONAL HURRICANE MODELS DO NOT SHOW MUCH
INTENSIFICATION OF SEAN…THE SHEAR REMAINS RELATIVELY LIGHT FOR
THE NEXT 36 HR OR SO WHILE THE SYSTEM IS OVER MARGINAL SSTS. SINCE
THE STORM IS EMBEDDED WITHIN COLDER-THAN-AVERAGE UPPER-AIR
TEMPERATURES…THE SST THRESHOLD FOR TROPICAL CYCLONE STRENGTHENING
IS LOWER THAN USUAL…AND SOME FURTHER STRENGTHENING IS
ANTICIPATED. THE NEW NHC FORECAST IS HIGHER THAN THE PREVIOUS
ONE…AND REMAINS IN LINE WITH THE SHIPS/LGEM MODELS AND THE
EXPERIMENTAL SPC3 ENSEMBLE SHIPS GUIDANCE. IN ABOUT TWO DAYS…
SEAN SHOULD ENCOUNTER A MORE HOSTILE UPPER-AIR ENVIRONMENT…WHICH
SHOULD INDUCE WEAKENING.
THE CENTER OF THE CYCLONE HAS BEEN WOBBLING AROUND FOR QUITE SOME
TIME…BUT IT APPEARS THAT A MOTION TOWARD THE WEST-NORTHWEST HAS
BEGUN. THIS GENERAL TRACK IS EXPECTED TO CONTINUE THROUGH TOMORROW
AS A RIDGE MOVES THROUGH THE WESTERN ATLANTIC. THEREAFTER…THE
STORM SHOULD TURN TOWARD THE NORTH AND NORTHEAST BY THURSDAY AHEAD
OF A DEEP TROUGH OVER THE EASTERN UNITED STATES. IT SEEMS THAT
BEING ON THE RIGHT SIDE OF THE GUIDANCE EARLIER WAS A GOOD CALL…
AS MOST OF THE MODELS HAVE SHIFTED IN THAT DIRECTION…APPARENTLY
BECAUSE OF FLATTER MID-LATITUDE FLOW FORECAST TO AFFECT SEAN. ONLY
COSMETIC CHANGES WERE MADE TO THE NHC TRACK FOR THE FIRST COUPLE OF
DAYS…WITH A SHIFT TO THE SOUTHEAST MADE AT DAY 3…BETWEEN THE
ECMWF AND GFS MODELS. ALL OF THE GLOBAL MODELS SHOW THE STORM
BEING ABSORBED BY A FRONTAL BOUNDARY BY DAY 4…AND THIS SCENARIO
IS REFLECTED IN THE NHC FORECAST.
FORECAST POSITIONS AND MAX WINDS
INIT 08/2100Z 27.8N 69.8W 45 KT 50 MPH
12H 09/0600Z 27.9N 70.2W 50 KT 60 MPH
24H 09/1800Z 28.4N 70.4W 50 KT 60 MPH
36H 10/0600Z 29.0N 70.5W 55 KT 65 MPH
48H 10/1800Z 29.9N 69.7W 50 KT 60 MPH
72H 11/1800Z 34.0N 64.0W 45 KT 50 MPH
96H 12/1800Z…ABSORBED
$$
FORECASTER BLAKE
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