ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION EIGHT-E DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP082007 200 PM PDT TUE JUL 31 2007 SHEARED BUT STRONG CONVECTION HAS PERSISTED FOR ABOUT 12 HR NEAR AND TO THE WEST OF THE LOW PRESSURE AREA CENTERED ABOUT 1125 MILES SOUTHWEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA. SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM BOTH TAFB AND SAB. BASED ON THIS...ADVISORIES ARE INITIATED ON TROPICAL DEPRESSION EIGHT-E WITH AN INITIAL INTENSITY OF 30 KT...A LITTLE MORE CONSERVATIVE THAN THE SATELLITE ESTIMATES. THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/12. WATER VAPOR IMAGERY AND LARGE-SCALE MODEL SHOW A LARGE DEEP-LAYER RIDGE NORTH OF THE DEPRESSION...ALBEIT A RIDGE WITH A WEAKNESS CAUSED BY DEEP-LAYER TROUGHING TO ITS NORTH JUST WEST OF CALIFORNIA. THE MODELS FORECAST THE RIDGE TO PERSIST WITH LITTLE CHANGE IN STRENGTH THROUGH 120 HR. THIS SHOULD CAUSE THE DEPRESSION TO MOVE WESTWARD OR WEST-NORTHWESTWARD AT A SPEED A SLIGHTLY BELOW CLIMATOLOGY. NHC TRACK GUIDANCE AGREES ON THIS SCENARIO EXCEPT FOR THE NOGAPS... WHICH MERGES THE DEPRESSION WITH ANOTHER CYCLONE FORMING TO THE EAST. WHILE THERE IS A BROAD DISTURBANCE EAST OF THE DEPRESSION... IT CURRENTLY APPEARS UNLIKELY THAT IT WILL DEVELOP FAST ENOUGH FOR THE NOGAPS TO VERIFY. THUS...THE FORECAST TRACK CALLS FOR A GENERAL WESTWARD MOTION AT ABOUT 10 KT THROUGH THE FORECAST PERIOD. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE ABOUT 20 KT OF NORTHEASTERLY VERTICAL WIND SHEAR...AND WATER VAPOR IMAGERY SHOWS UPPER-LEVEL DRY AIR IMPINGING ON THE DEPRESSION. THE LARGE-SCALE MODELS ARE NOT IN GOOD AGREEMENT ON THE EVOLUTION OF THE UPPER-LEVEL WINDS. THE GFS...THE ECMWF...AND THE NOGAPS FORECAST THE SHEAR TO DECREASE IN LESS THAN 24 HR...WHILE THE CANADIAN AND THE UKMET FORECAST HOSTILE CONDITIONS TO CONTINUE BEYOND THAT TIME. FOR NOW...THE INTENSITY FORECAST WILL LEAN MORE TOWARD THE CANADIAN/UKMET SOLUTIONS AND CALL FOR SLOW STRENGTHENING AFTER 24 HR. THERE IS A CHANCE THAT THE DEPRESSION WILL NOT SURVIVE THE FIRST 24 HR DUE TO THE SHEAR AND DRY AIR. FORECAST POSITIONS AND MAX WINDS INITIAL 31/2100Z 13.3N 123.8W 30 KT 12HR VT 01/0600Z 13.6N 125.6W 30 KT 24HR VT 01/1800Z 13.9N 127.6W 30 KT 36HR VT 02/0600Z 14.1N 129.8W 35 KT 48HR VT 02/1800Z 14.1N 132.0W 35 KT 72HR VT 03/1800Z 14.0N 136.0W 40 KT 96HR VT 04/1800Z 14.0N 140.0W 45 KT 120HR VT 05/1800Z 14.5N 144.0W 45 KT $$ FORECASTER BEVEN NNNN
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Page last modified: Friday, 02-Nov-2007 21:20:59 UTC