| http://www.weather.bm/ForecastDiscussion.asp Bermuda Weather Service Forecast Discussion For Friday, September 17, 2010 21:00 UTC (this is the most recent posted) FORECASTER - Nick Camizzi CURRENT HURRICANE IGOR HAS WEAKENED SOMEWHAT, BUT IS STILL A CATEGORY THREE HURRICANE WITH WINDS OF 100 KT WITH GUSTS TO 120 KT. A HURRICANE WARNING WAS ISSUED AT 3PM DUE TO THE EXPECTED ONSET OF 34 KT (TROPICAL STORM FORCE WINDS) IN ABOUT 36 HOURS NEAR 2 AM IN THE MARINE AREA. FOR THE TIME BEING, MODERATE TO STRONG EAST-NORTHEASTERLY WINDS ARE EXPECTED IN ADVANCE OF IGOR TONIGHT ALONG WITH ROUGH TO VERY ROUGH SEAS AND LARGE WAVES ON THE SOUTH AND EAST FACING BEACHES. SHORT TERM CONDITIONS WILL CONTINUE TO DETERIORATE TOMORROW AS SHOWERS INCREASE ON THE FORWARD EDGE OF HURRICANE IGOR. IT DOES NOT LOOK LIKE A WASHOUT BY ANY MEANS. HOWEVER, THE OCCASIONAL SHOWERS SHOULD CONTAIN GUSTY WINDS AND THE POSSIBILITY OF THUNDER. THE ONSET OF TROPICAL STORM FORCE WINDS ON THE LATEST NHC FORCAST IS AROUND 2 AM SUNDAY ON THE ISLAND AND 11PM SATURDAY IN THE MARINE AREA. FOR THIS REASON, THE HURRICANE WARNING WAS ISSUED GIVEN THE ONSET OF TROPICAL STORM FORCE WINDS BEFORE THE HURRICANE FORCE WINDS DEVELOP ON LATE SUNDAY AFTERNOON/SUNDAY EVENING. AS WITH ANY TROPICAL SYSTEM, TORNADOES AND THUNDERSTORMS ARE POSSIBLE. IT APPEARS ABOUT 5-8" OF RAIN IS LIKELY WITH IGOR AS IT PASSES, GIVEN IT'S LARGE SIZE AND RELATIVELY SLOW MOVEMENT. AT THIS POINT, THE FORECAST TRACK TAKES THE EYE OF IGOR VERY CLOSE IF NOT OVER BERMUDA, GIVING A PERIOD OF LIGHT AND VARIABLE WINDS. HOWEVER, IT IS TOO SOON TO SAY WHETHER IGOR WILL PASS DIRECTLY OVER THE ISLAND, JUST EAST, OR JUST WEST. A JUST EAST TRACK WILL PRODUCE THE STRONGEST WINDS OUT OF THE NORTH WHILE A JUST WEST TRACK WILL PRODUCE THE STRONGEST WINDS OUT OF THE SOUTH. A TRACK THAT GOES RIGHT OVER THE ISLAND PRODUCES THE STRONGEST WINDS OUT OF THE EAST. THE FURTHER WEST TRACK ALSO PRODUCES THE WORST STORM SURGE AND THE HIGHEST WAVES. WE ARE LOOKING AT ABOUT A 42 HOUR PERIOD OF TROPICAL STORM FORCE WINDS IN THE MARINE AREA AND A 40 HOUR PERIOD OF TROPICAL STORM FORCE WINDS ON THE ISLAND. LONG TERM MONDAY AND TUESDAY, THE HURRICANE MOVES AWAY. HOWEVER, IT APPEARS THAT ISLAND IS STILL WITHIN STORM FORCE WINDS ON MONDAY MORNING WHICH EASE TO TROPICAL STORM FORCE WINDS IN THE AFTERNOON THEN LESS THAN TROPICAL STORM FORCE WINDS BY EVENING. THE RAIN AND POSSIBLE MORNING THUNDER SHOULD EASE THROUGH THE DAY AS WELL. http://www.nhc.noaa.gov/text/refresh/MIATCDAT1+shtml/181448.shtml 000 WTNT41 KNHC 181448 TCDAT1 HURRICANE IGOR DISCUSSION NUMBER 42 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010 1100 AM AST SAT SEP 18 2010 THERE HAS BEEN LITTLE CHANGE IN THE STRUCTURE OF IGOR DURING THE PAST SEVERAL HOURS. RECENT MICROWAVE OVERPASSES SUGGEST THE HURRICANE IS UNDERGOING AN EYEWALL REPLACEMENT CYCLE...WITH THE 20 NM WIDE INNER EYE SEEN IN THE PREVIOUS AIRCRAFT MISSION GRADUALLY WEAKENING. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN 102 KT...AND THE INITIAL INTENSITY REMAINS 95 KT. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS CURRENTLY EN ROUTE TO INVESTIGATE IGOR. THE INITIAL MOTION IS 310/10. DURING THE NEXT 36-72 HR...IGOR WILL ROUND THE WESTERN END OF A DEEP-LAYER RIDGE OVER THE CENTRAL AND EASTERN ATLANTIC AND ENTER THE WESTERLIES TO THE EAST OF A SHORTWAVE TROUGH MOVING OFF THE COAST OF EASTERN NORTH AMERICA. THE TRACK GUIDANCE IS IN GOOD AGREEMENT WITH THIS SCENARIO AND HAS CHANGED LITTLE SINCE THE PREVIOUS ADVISORY. THIS PART OF THE THE NEW FORECAST TRACK IS THUS AN UPDATE OF THE PREVIOUS ONE...WITH THE CENTER OF IGOR PASSING NEAR OR OVER BERMUDA IN 36-48 HR. AFTER 72 HR...THERE IS SOME SPREAD IN THE GUIDANCE AS IGOR UNDERGOES EXTRATROPICAL TRANSITION. THE ECMWF TURNS THE CYCLONE SHARPLY TO THE NORTH...WHILE THE OTHER DYNAMICAL MODELS SHOW A MORE NORTHEASTWARD TO EASTWARD MOTION. THIS PART OF THE TRACK IS SHIFTED TO THE EAST OF THE PREVIOUS FORECAST BASED ON A BLEND OF THE DYNAMICAL MODELS...BUT LIES TO THE NORTH OF THE CENTER OF THE GUIDANCE ENVELOPE. IGOR IS IN AN ENVIRONMENT OF LIGHT SOUTHERLY VERTICAL SHEAR...AND THIS IS FORECAST TO CONTINUE FOR THE NEXT 24 HR OR SO. AFTER THAT...THE HURRICANE IS FORECAST TO ENCOUNTER INCREASING SHEAR. IT IS UNCERTAIN IF THE CURRENT EYEWALL REPLACEMENT CYCLE WILL BE COMPLETE ENOUGH TO ALLOW STRENGTHENING BEFORE THE SHEAR INCREASES...BUT CURRENT TRENDS SUGGEST IT WILL NOT. MOST OF THE INTENSITY GUIDANCE NOW SHOWS LITTLE CHANGE IN STRENGTH OR SLOW WEAKENING DURING THE FIRST 36 HR...WITH ONLY THE SHIPS MODEL SHOWING MODEST STRENGTHENING. THE NEW INTENSITY FORECAST CALLS FOR IGOR TO MAINTAIN A 95 KT INTENSITY FOR 36 HR OR SO... FOLLOWED BY WEAKENING DUE TO SHEAR. IT CANNOT BE RULED OUT THAT IGOR COULD REGAIN MAJOR HURRICANE STATUS BEFORE REACHING BERMUDA...BUT IT APPEARS LESS LIKELY THAN PREVIOUSLY THOUGHT. EXTRATROPICAL TRANSITION SHOULD BE UNDERWAY BY 72 HR AND BE COMPLETE BY 96 HR. IGOR IS EXPECTED TO REMAIN A LARGE AND POWERFUL CYCLONE AFTER EXTRATROPICAL TRANSITION. IGOR CONTINUES TO HAVE A VERY LARGE WIND FIELD...AND CONDITIONS WILL BEGIN TO DETERIORATE ON BERMUDA BY TONIGHT WELL IN ADVANCE OF THE CENTER. FORECAST POSITIONS AND MAX WINDS INITIAL 18/1500Z 26.0N 63.6W 95 KT 12HR VT 19/0000Z 27.1N 64.6W 95 KT 24HR VT 19/1200Z 28.9N 65.3W 95 KT 36HR VT 20/0000Z 31.1N 65.2W 95 KT 48HR VT 20/1200Z 33.9N 64.2W 90 KT 72HR VT 21/1200Z 40.5N 56.0W 75 KT 96HR VT 22/1200Z 47.5N 44.0W 65 KT...POST-TROP/EXTRATROP 120HR VT 23/1200Z 50.0N 36.5W 50 KT...POST-TROP/EXTRATROP $$ FORECASTER BEVEN |