Tropical Depression EIGHT-E

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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
 
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