Official Discussion issued by the National Hurricane Center
SEVEN (AL072009) DATA RELEASED: 9/7/2009 5:00:00 PM UTC
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Copy of official data TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009 500 PM AST MON SEP 07 2009 SATELLITE IMAGES INDICATE THAT THE BROAD LOW PRESSURE AREA LOCATED SOUTH OF THE CAPE VERDE ISLANDS HAS ACQUIRED ENOUGH ORGANIZATION TO BE CLASSIFIED AS A TROPICAL DEPRESSION...THE SEVENTH OF THE 2009 ATLANTIC HURRICANE SEASON. THE EXACT CENTER OF THE DEPRESSION IS SOMEWHAT DIFFICULT TO LOCATE. EARLIER TODAY THE LOW-LEVEL CENTER APPEARED TO BE NEAR THE EASTERN EDGE OF THE DEEP CONVECTION. HOWEVER NOW THE THE CENTER APPEARS TO BE UNDER THE DEEP CONVECTION ...BUT DISPLACED EAST OF THE MID-LEVEL CENTER SEEN IN SATELLITE IMAGERY. DESPITE A LARGE SPREAD IN THE SATELLITE POSITION ESTIMATES FROM TAFB AND SAB...BOTH CLASSIFICATIONS WERE T2.0...YIELDING AN INITIAL INTENSITY OF 30 KT. THE HIGHLY UNCERTAIN INITIAL MOTION ESTIMATE IS 280/14. THE DEPRESSION IS CURRENTLY LOCATED SOUTH OF A NARROW EAST-TO-WEST ORIENTED RIDGE. THE RIDGE IS FORECAST TO WEAKEN AS A MID-LEVEL TROUGH MOVES INTO THE EASTERN ATLANTIC AND AN UPPER-LEVEL LOW CUTS-OFF NEAR 27N40W DURING THE NEXT DAY OR TWO. THIS IS EXPECTED TO ALLOW THE CYCLONE TO TURN NORTHWESTWARD IN A COUPLE OF DAYS... FOLLOWED BY A TURN TO THE NORTH THEREAFTER. THE TRACK GUIDANCE IS IN REASONABLY GOOD AGREEMENT ON THIS SOLUTION...AND THE OFFICIAL FORECAST IS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE. THE DEPRESSION IS CURRENTLY WITHIN AN AREA OF MODERATE EASTERLY VERTICAL SHEAR...BUT THE SHEAR IS FORECAST TO ABATE WITHIN THE NEXT DAY OR SO. SEA SURFACE TEMPERATURES ARE WARM ALONG THE FORECAST TRACK AND THE DEPRESSION IS EXPECTED TO GRADUALLY STRENGTHEN DURING THE NEXT COUPLE OF DAYS. THEREAFTER...INCREASING SOUTHERLY TO SOUTHWESTERLY SHEAR IS FORECAST TO HALT FURTHER INTENSIFICATION. THE NHC FORECAST IS CLOSEST TO THE LGEM GUIDANCE...WHICH TYPICA |