500 PM HST WED OCT 15 2014 ANA HAS DETERIORATED OVER THE PAST FEW HOURS AND THERE IS SIGNIFICANT UNCERTAINTY OVER THE POSITION OF THE LOW LEVEL CENTER. AN AMSU-B PASS FROM 2303 UTC SUGGESTS THAT THE CENTER REMAINS DISPLACED NORTH OF THE DEEPEST CONVECTION...AND CENTER FIXES FROM SAB AND JTWC AT 2330 UTC BOTH CAME IN AT 14.3N 148.0W. HOWEVER...LOW CLOUD LINES IN THE VISIBLE IMAGES INDICATE THAT THE CENTER MAY HAVE SHIFTED SLIGHTLY SOUTH CLOSER TO THE DEEP CONVECTION WITH PHFO PLACING THE CENTER AT 13.9N 148.0W. THE INITIAL POSITION USES A BLEND OF BOTH ESTIMATES...BUT THE CONFIDENCE IS RATHER LOW. IN ADDITION TO THE CENTER UNCERTAINTIES...ANA/S APPEARANCE HAS BECOME QUITE RAGGED IN THE LATEST SATELLITE IMAGES AND HAS BECOME MUCH LESS SYMMETRIC. DVORAK INTENSITY ESTIMATES CAME IN AT 55 KT FROM ALL THREE FIX AGENCIES. AS A RESULT...THE INITIAL INTENSITY HAS BEEN LOWERED TO 55 KT FOR THIS FORECAST PACKAGE...AND THIS MAY BE GENEROUS. THE INITIAL MOTION REMAINS UNCHANGED FROM THE PREVIOUS PACKAGE AT 270/8 KT. A DEEP LAYER RIDGE PROVIDING THE STEERING CURRENT IS EXPECTED TO SHIFT AND PRODUCE A NORTHWESTWARD STEERING FLOW WHICH WILL TURN ANA TOWARD THE HAWAIIAN ISLANDS. THE LATEST OBJECTIVE AIDS REMAINS TIGHTLY CLUSTERED BUT HAVE SHIFTED TO THE WEST. AS A RESULT...THE FORECAST HAS BEEN ADJUSTED SLIGHTLY WEST FROM THE PREVIOUS FORECAST AND IS PARALLEL TO AND SLIGHTLY TO THE RIGHT OF THE CONSENSUS. THE TRACK TAKES THE CENTER OF ANA SOUTH AND WEST OF THE BIG ISLAND THEN NEAR KAUAI LATE THIS WEEKEND. FORWARD MOTION OF THE CYCLONE IS EXPECTED TO SLOW LATE FRIDAY AND INTO SATURDAY AS STEERING CURRENTS WEAKEN DUE TO THE PASSAGE OF A LOW PRESSURE SYSTEM NORTH OF THE HAWAIIAN ISLANDS. THE NOAA GULFSTREAM IV SAMPLED THE NEAR-STORM ENVIRONMENT EARLIER TODAY. DATA COLLECTED DURING THE FLIGHT SHOULD HELP IMPROVE THIS EVENING/S MODEL GUIDANCE. THE INTENSITY FORECAST IS A CHALLENGE. ON ONE HAND...MORE THAN ADEQUATE SEA SURFACE TEMPERATURES AND FAVORABLE FORECASTED VERTICAL SHEAR CONDITIONS WOULD SUPPORT INTENSIFICATION TO A HURRICANE THROUGH 48 HOURS. HWRF AND GHM ARE CONSISTENT WITH THIS REASONING. HOWEVER...SHIPS AND LGEM ARE NO LONGER FORECASTING ANA TO BECOME A HURRICANE. THE CURRENT DETERIORATION OF THE TROPICAL STORM IN THE SATELLITE IMAGES DOES LEND CREDENCE TO THIS POSSIBILITY. THE INTENSITY FORECAST FOR THIS PACKAGE LEANS TOWARD THE HWRF/GHM SOLUTION AND STILL CALLS FOR ANA TO REACH HURRICANE INTENSITY WITHIN 24 HOURS. HOWEVER...THE PEAK INTENSITY HAS BEEN LOWERED TO 70 KT INSTEAD OF 80 KT IN THE PREVIOUS FORECAST. IF ANA FAILS TO REORGANIZE SOON...SUBSEQUENT INTENSITY FORECASTS MAY NEED TO BE NUDGED DOWNWARD FURTHER. NOTE THAT IT IS IMPORTANT FOR PEOPLE IN THE MAIN HAWAIIAN ISLANDS NOT TO FOCUS TOO CLOSELY ON THE EXACT FORECAST TRACK OF ANA. WITH AN AVERAGE 48 HOUR TRACK ERROR OF APPROXIMATELY 80 MILES...IT IS STILL TOO SOON TO SAY WITH MUCH CERTAINTY WHICH ISLANDS WILL BE MOST LIKELY TO EXPERIENCE THE WORST WEATHER. EVERYONE SHOULD BE PREPARED FOR THE POSSIBILITY OF DIRECT IMPACTS FROM ANA. IT IS ALSO IMPORTANT TO KEEP IN MIND THAT SIGNIFICANT IMPACTS FROM TROPICAL CYCLONES CAN EXTEND WELL AWAY FROM THE CENTER. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 14.1N 148.4W 55 KT 65 MPH 12H 16/1200Z 14.5N 149.8W 60 KT 70 MPH 24H 17/0000Z 15.3N 151.6W 65 KT 75 MPH 36H 17/1200Z 16.1N 153.4W 70 KT 80 MPH 48H 18/0000Z 17.2N 155.2W 70 KT 80 MPH 72H 19/0000Z 19.8N 157.1W 60 KT 70 MPH 96H 20/0000Z 21.0N 158.5W 55 KT 65 MPH 120H 21/0000Z 22.5N 160.5W 50 KT 60 MPH $$ FORECASTER KODAMA MC
Posted on: Thu, 16 Oct 2014 03:07:15 +0000
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