Official Discussion issued by the National Hurricane Center
NINE (AL092010) DATA RELEASED: 9/1/2010 11:00:00 AM UTC
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Copy of official data TROPICAL DEPRESSION NINE DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092010 1100 AM AST WED SEP 01 2010 THE VIGOROUS TROPICAL WAVE IN THE EASTERN TROPICAL ATLANTIC HAS BECOME BETTER ORGANIZED WITH DEEP CONVECTION WRAPPING ALMOST HALF WAY AROUND THE VORTEX. CONSEQUENTLY...DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB SUPPORT INITIATING ADVISORIES ON THIS SYSTEM AS A TROPICAL DEPRESSION. AN ASCAT PASS AT 1126Z ALONG THE EDGE OF THE CYCLONE INDICATED WINDS OF 25-30 KT. THE INITIAL INTENSITY IS SET AT 30 KT. THE MOTION OF THE DEPRESSION IS 275 DEGREES AT 15 KT AS IT IS BEING STEERED PRIMARILY BY A LARGE DEEP-LAYER SUBTROPICAL RIDGE TO ITS NORTH. AS A STRONG MID-LATITUDE SHORT WAVE MOVES ACROSS THE NORTH ATLANTIC...THE RIDGE WEAKENS SOME DURING THE NEXT TWO TO THREE DAYS. THIS SHOULD RESULT IN A SLOWING OF THE CYCLONE AND A SLIGHT TURN TOWARD THE WEST-NORTHWEST. BY DAYS FOUR AND FIVE...THE SUBTROPICAL RIDGE RESTRENGTHENS AND THE DEPRESSION SHOULD CORRESPONDINGLY ACCELERATE. THE GLOBAL MODELS ARE HAVING DIFFICULTY DISTINGUISHING THE CYCLONE FROM THE PRONOUNCED MONSOON TROUGH IN THE EASTERN ATLANTIC. THE FORECAST TRACK IS A BLEND OF THE AVAILABLE GLOBAL MODELS...THE UKMET AND CANADIAN...AND THE GFDL AND HWRF HURRICANE MODELS AND IS CLOSEST TO THE BAM-MEDIUM MODEL. THE 12Z GLOBAL MODEL GUIDANCE SHOULD PROVIDE A BETTER TRACK PREDICTION SINCE THEY WILL HOPEFULLY HAVE A MORE REALISTIC HANDLE ON THE INITIAL CONDITIONS OF THE DEPRESSION. THE INTENSITY FORECAST...AS USUAL...IS QUITE UNCERTAIN. WHILE THE DEPRESSION WILL BE TRAVERSING OVER VERY WARM WATERS...THE VERTICAL SHEAR...ESPECIALLY THE MID-LEVEL CONTRIBUTION...IS MODERATE TO STRONG. ADDITIONALLY...A LARGE OUTBREAK OF THE SAHARAN AIR LAYER IS SITUATED JUST NORTH AND WEST OF THE DEPRESSION...WHICH MAY INHIBIT SOME OF THE DEEP CONVECTIO |