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TROPICAL DEPRESSION SEVEN-E DISCUSSION NUMBER 2
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT SUN AUG 26 2001
TROPICAL DEPRESSION SEVEN-E HAS BECOME BETTER ORGANIZED THIS MORNING
AND IS VERY NEAR TROPICAL STORM STRENGTH. THE INITIAL INTENSITY OF
30 KT IS BASED ON SATELLITE DVORAK INTENSITY ESTIMATES OF 35 KT...30
KT...AND 25 KT FROM TAFB...SAB...AND AFWA...RESPECTIVELY. THE
EARLIER POSITION ESTIMATES WERE ON THE EAST SIDE OF THE CONVECTIVE
CLOUD SHIELD...WHICH HAS SINCE DISSIPATED. A NEW CENTER APPEARS TO
HAVE REFORMED FURTHER WEST NEAR A CONVECTIVE CLOUD MASS THAT IS
BEGINNING TO TAKE ON THE APPEARANCE OF A CDO. OUTFLOW IS GOOD TO
THE SOUTHEAST AND FAIR ELSEWHERE.
INITIAL MOTION ESTIMATE IS 300/9. THE MAJORITY OF THE NHC MODEL
GUIDANCE TAKES THE DEPRESSION IN A GENERAL WEST-NORTHWEST OR
WESTWARD DIRECTION THROUGH 36 HOURS AND THEN GRADUALLY TURNS THE
SYSTEM SLIGHTLY SOUTH OF DUE WEST. THE OUTLIERS ARE THE
GFDL...WHICH TAKES THE CYCLONE DUE NORTH INTO THE GULF OF CALIFORNIA
AND THEN ACROSS CENTRAL BAJA...AND NOGAPS WHICH HOLDS THE DEPRESSION
NEARLY STATIONARY JUST SOUTH OF BAJA THROUGH THE PERIOD. BOTH
SOLUTIONS HAVE BEEN DISCOUNTED GIVEN THE STRENGTH OF THE LARGE MID-
TO UPPER-LEVEL RIDGE ACROSS THE SOUTHWEST U.S. AND NORTHERN
MEXICO...WHICH SHOULD ACT TO KEEP THE SYSTEM ON A GENERAL WESTWARD
TRACK THROUGHOUT THE PERIOD. AFTER 36 HOURS...THE STEERING FLOW
WEAKENS AS A STRONG TROUGH OVER THE CENTRAL PACIFIC OCEAN IS
FORECAST TO MOVE EASTWARD TO THE U.S. WEST COAST AND ERODE THE
SUBTROPICAL RIDGE TO THE NORTH OF T.D. 7-E.
THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS INTENSITY FORECAST OR
REASONING. SLOW BUT STEADY INTENSIFICATION IS FORECAST THROUGHOUT
THE PERIOD. OUTFLOW SHOULD CONTINUE TO IMPROVE AS THE CYCLONE
TRACKS WESTWARD AND BECOMES EMBEDDED BETWEEN AN UPPER-LEVEL LOW TO
ITS WEST AND A DIGGING UPPER-TROUGH TO ITS EAST. MY MAIN CONCERN IS
HOW MUCH INFLUENCE THE COOLER WATER TO THE NORTHWEST WILL HAVE ON
THE CYCLONE. T.D. 7-E IS CURRENTLY OVER 29C SSTS AND IS FORECAST
TO REMAIN OVER 26C OR HIGHER SSTS THROUGHOUT THE PERIOD. IF MOST OF
THE INFLOW COMES FROM THE SOUTH AND A CDO DEVELOPS OVER THE CENTER
WITHIN THE NEXT 12 HOURS...THEN THE INTENSITY FORECAST WILL HAVE TO
BE INCREASED SIGNIFICANTLY AND THE SYSTEM COULD BECOME A HURRICANE
IN 36 TO 48 HOURS.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 26/1500Z 19.9N 110.1W 30 KTS
12HR VT 27/0000Z 20.3N 111.4W 40 KTS
24HR VT 27/1200Z 20.4N 113.2W 45 KTS
36HR VT 28/0000Z 20.3N 114.4W 50 KTS
48HR VT 28/1200Z 20.2N 115.5W 55 KTS
72HR VT 29/1200Z 20.0N 117.0W 65 KTS
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