ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM HURRICANE DANIEL DISCUSSION NUMBER 26 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP052006 200 AM PDT SUN JUL 23 2006 INFRARED SATELLITE IMAGERY SHOWS THAT CLOUD TOP TEMPERATURES OVER THE WESTERN SEMICIRCLE CONTINUE TO GRADUALLY WARM AND THE OVERALL CONVECTIVE PATTERN HAS BECOME ASYMMETRIC ABOUT THE EYE. IT WOULD APPEAR THAT DANIEL IS BEGINNING TO FEEL THE INFLUENCE OF COOLER WATERS. THE INITIAL INTENSITY IS LOWERED TO 115 KT WHICH IS A COMPROMISE BETWEEN 102 KT FROM SAB AND 127 KT FROM TAFB. THREE- HOUR AVERAGE ADT VALUES HAVE ALSO BEEN STEADY AT 115 KT. BEING AT OR VERY NEAR THE 26C ISOTHERM...DANIEL IS EXPECTED TO CONTINUE WEAKENING THROUGH THE FORECAST PERIOD. MODERATE VERTICAL SHEAR MAY ALSO BEGIN CONTRIBUTING TO THE WEAKENING IN THE 36-48 HOUR TIME FRAME. STILL...DANIEL DISPLAYS CHARACTERISTICS OF AN ANNULAR HURRICANE AND THE OFFICIAL FORECAST SHOWS WEAKENING AT A SLOWER RATE THAN USUAL GIVEN THE AFOREMENTIONED ENVIRONMENTAL CONDITIONS. THIS FORECAST IS ALSO HIGHER THAN THE SHIPS MODEL...WHICH STUDIES HAVE SHOWN WEAKENS CYCLONES TOO QUICKLY IN THESE SITUATIONS. DANIEL IS CURRENTLY BEING STEERED BY A STRONG MID-TO-UPPER TROPOSPHERIC RIDGE TO ITS NORTH RESULTING IN A WEST TO WEST-NORTHWESTWARD MOTION OR 280/12. THIS OVERALL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 12-24 HOURS. THEREAFTER...MOST OF THE DYNAMICAL MODELS INDICATE A PRONOUNCED WEAKNESS DEVELOPING WITHIN THE RIDGE BETWEEN 135W-140W. THIS EVOLUTION IS EXPECTED TO RESULT IN A REDUCTION IN FORWARD SPEED AS THE CYCLONE MOVES INTO THE WEAKNESS. AS WOULD BE EXPECTED IN LIGHT STEERING FLOW CONDITIONS...DYNAMICAL MODELS BEGIN TO DIVERGE WITH THE GFS AND GFS ENSEMBLE MEAN SHOWING DANIEL BECOMING...TEMPORARILY..NEARLY STATIONARY AT 48 HOURS WHILE THE UKMET KEEPS THE CYCLONE MOVING ALONG AT A STEADY CLIP. THE OFFICIAL FORECAST SPLITS THE DIFFERENCE BETWEEN THESE TWO SCENARIOS BY SHOWING DANIEL SLOWING AS IT MOVES INTO THE WEAKNESS WITHIN THE RIDGE BETWEEN 36 AND 48 HOURS. AS DANIEL BECOMES INCREASINGLY SHALLOW DURING THE LATER PARTS OF THE FORECAST...THE STEERING IS EXPECTED TO BECOME DOMINATED BY THE LOW LEVEL EASTERLIES WHICH SHOULD ALLOW THE CYCLONE TO SPEED UP AGAIN AND TURN MORE TOWARDS THE WEST. FORECAST POSITIONS AND MAX WINDS INITIAL 23/0900Z 14.7N 134.6W 115 KT 12HR VT 23/1800Z 15.0N 135.9W 100 KT 24HR VT 24/0600Z 15.6N 137.7W 90 KT 36HR VT 24/1800Z 16.0N 139.2W 80 KT 48HR VT 25/0600Z 16.4N 140.2W 70 KT 72HR VT 26/0600Z 17.2N 142.0W 60 KT 96HR VT 27/0600Z 18.5N 145.0W 50 KT 120HR VT 28/0600Z 20.0N 150.0W 40 KT $$ FORECASTER RHOME NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:40 UTC