ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM SUBTROPICAL DEPRESSION TWENTY-TWO DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT SAT OCT 08 2005 CONVECTION ASSOCIATED WITH SUBTROPICAL DEPRESSION TWENTY-TWO HAS DECREASED SOMEWHAT DURING THE DAY...WITH THE OUTER BAND SEEN EARLIER DISSIPATING AND THE LOW-LEVEL CENTER BECOMING FULLY EXPOSED FOR A TIME. DURING THE PAST COUPLE OF HOURS...A NEW BURST HAS FORMED JUST WEST-NORTHWEST OF THE CENTER. SATELLITE INTENSITY ESTIMATES ARE SUBTROPICAL 35-40 KT FROM SAB...SUBTROPICAL 25-30 KT FROM TAFB...AND TROPICAL 25 KT FROM AFWA. THE INITIAL INTENSITY WILL REMAIN 30 KT BASED ON A BLEND OF THESE ESTIMATES AND THE OVERALL ORGANIZATION BEING SIMILAR TO THAT OF 6 HR AGO. THE INITIAL MOTION IS NOW 300/17. OTHER THAN THAT...THERE IS LITTLE CHANGE IN THE FORECAST PHILOSOPHY FROM THE PREVIOUS PACKAGE. BEFORE 36 HR...THE CYCLONE SHOULD MOVES GENERALLY WEST-NORTHWESTWARD WITH SOME DECELERATION BETWEEN A LARGE DEEP-LAYER RIDGE TO THE NORTH AND A LARGE MID/ UPPER-LEVEL LOW TO THE SOUTH. AFTER 36-48 HR...THE TRACK FORECAST BECOMES LOW CONFIDENCE AS A SIGNIFICANT SPREAD APPEARS IN THE GUIDANCE. IF THE LARGE-SCALE MODELS ARE RIGHT...A SECOND LOW PRESSURE AREA WILL FORM SOUTH AND SOUTHEAST OF THE SUBTROPICAL DEPRESSION...WHICH COULD STEER THE SYSTEM MORE WESTWARD. ON THE OTHER HAND...IF THE NEW LOW IS SLOWER TO FORM OR TROUGHING CONTINUES ALONG THE EAST COAST OF THE UNITED STATES AS SUGGESTED BY THE LARGE-SCALE MODELS...THE CYCLONE COULD TURN MORE TOWARD THE NORTH. THE TRACK FORECAST AFTER 48 HR CONTINUES TO CALL FOR A GRADUAL NORTHWARD TURN AT A DECREASING FORWARD SPEED ON THE PREMISE THAT THE U. S. MID/UPPER-LEVEL TROUGH WILL BE THE DOMINANT STEERING MECHANISM. THE DEPRESSION REMAINS IN DEEP-LAYER EASTERLY FLOW NORTH OF THE MID/UPPER-LEVEL LOW WITH ABOUT 15 KT OF SHEAR. THE SHIPS MODEL SUGGESTS THAT THE SYSTEM WILL UNDERGO PULSES OF SHEAR DURING THE NEXT THREE DAYS...AND THEN UNDERGO SIGNIFICANT SHEAR AFTER THREE DAYS. THE GFDL AND THE LARGE-SCALE MODELS ALL LOSE THE SYSTEM IN 36-72 HR. ALL OF THIS...COMBINED WITH SEA SURFACE TEMPERATURES OF 26C-27C ALONG THE FORECAST TRACK...SUGGEST THE CYCLONE COULD STRUGGLE TO INTENSIFY. THE INTENSITY FORECAST CALLS FOR MODEST STRENGTHENING A LITTLE ABOVE THAT OF THE SHIPS MODEL... WITH A PEAK INTENSITY OF 50 KT IN 48 KT. THE NEW INTENSITY FORECAST CALLS FOR A FASTER WEAKENING AFTER 72 HR THAN THE PREVIOUS PACKAGE. IF THE LARGE-SCALE MODELS ARE CORRECT ON THE FORMATION OF THE SECOND LOW...OR IF THE SHIPS MODEL IS RIGHT ABOUT THE SHEAR... THE CYCLONE COULD WEAKEN EVEN FASTER. THERE IS STILL A CHANCE THE SYSTEM COULD FULLY TRANSITION TO A TROPICAL CYCLONE DURING THE NEXT 36-48 HR. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 08/2100Z 29.1N 60.8W 30 KT 12HR VT 09/0600Z 30.1N 62.8W 35 KT 24HR VT 09/1800Z 31.1N 65.5W 40 KT 36HR VT 10/0600Z 31.9N 67.9W 45 KT 48HR VT 10/1800Z 33.0N 69.8W 50 KT 72HR VT 11/1800Z 34.5N 72.0W 50 KT 96HR VT 12/1800Z 36.0N 72.5W 40 KT 120HR VT 13/1800Z 37.5N 72.5W 30 KT $$ NNNN
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Page last modified: Saturday, 08-Oct-2005 21:10:11 UTC