Tropical Depression SEVEN-E

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TROPICAL DEPRESSION SEVEN-E DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP072007
200 PM PDT SUN JUL 22 2007
 
SATELLITE IMAGERY SHOWS TROPICAL DEPRESSION SEVEN-E IS COMPRISED OF
A LARGE CYCLONIC SWIRL OF LOW CLOUDS WITH ABUNDANT...BUT
DISORGANIZED...CONVECTION NEAR THE CENTER IN THE NORTHWEST
SEMICIRCLE AND IN A LARGE BAND AWAY FROM THE CENTER IN THE
SOUTHEASTERN SEMICIRCLE.  SATELLITE INTENSITY ESTIMATES AND THE
OVERALL ORGANIZATION OF THE SYSTEM ARE UNCHANGED SINCE THIS
MORNING...SO THE INITIAL INTENSITY REMAINS 30 KT.  THE CYCLONE
REMAINS UNDER 20-25 KT OF NORTHEASTERLY VERTICAL WIND SHEAR.

THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/7.  THE DEPRESSION IS
ON THE SOUTHWEST SIDE OF A RIDGE OVER MEXICO...WHICH SHOULD PERSIST
WITH SOME FLUCTUATIONS IN STRENGTH DURING THE NEXT 5 DAYS.  THE
MODELS INDICATE THAT A MID-LEVEL SHORTWAVE TROUGH OVER NORTHEASTERN
MEXICO WILL MOVE SOUTHWESTWARD AROUND THE RIDGE AND INTERACT WITH
THE TROPICAL CYCLONE IN 36 HR OR SO.  THIS EVOLUTION WOULD ALLOW
THE DEPRESSION TO MOVE WEST-NORTHWESTWARD FOR 24 HR OR SO FOLLOWED
BY A NORTHWESTWAR MOTION.  THE TRACK GUIDANCE GENERALLY AGREES ON
THIS...WITH THE SPREAD DECREASING SINCE THE PREVIOUS MODEL RUNS. 
THE NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK AND IS IN
BEST AGREEMENT WITH THR GFDL AND THE GUNA CONSENSUS MODELS.  IT
SHOULD BE NOTED THAT THE SHORTWAVE TROUGH IS STILL NOT READILY
APPARENT IN WATER VAPOR IMAGERY...AS IT MAY BE MASKED BY CLOUDS AND
MOISTURE AT HIGHER LEVELS.
 
LARGE-SCALE MODELS FORECAST THE CURRENT STRONG UPPER-LEVEL WINDS TO
CONTINUE FOR 36-48 HR...AFTER WHICH THEY FORECAST A GRADUAL DECREASE
IN THE SHEAR.  THE INTENSITY GUIDANCE MODELS CONTINUE TO FORECAST
STRENGTHENING IN SPITE OF THE SHEAR...WITH THE GFDL AND THE HRWF
BOTH FORECASTING A 50 KT INTENSITY IN 24 HR.  THIS LOOKS A BIT
UNLIKELY GIVEN THE CURRENT TRENDS.  THE INTENSITY FORECAST CALLS
FOR SLOW STRENGTHENING FOR 48 HR WHILE THE SHEAR LASTS...A FASTER
DEVELOPMENT RATE FROM 48-96 HR AS THE SHEAR DECREASES...AND A
WEAKENING TREND AFTER 96 HR AS THE SYSTEM REACHES COOLER SEA
SURFACE TEMPERATURES.  IT IS POSSIBLE THAT THE CYCLONE MAY NOT
STRENGTHEN MUCH THROUGH 48 HR DUE TO THE SHEAR.    
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/2100Z 12.9N 107.2W    30 KT
 12HR VT     23/0600Z 13.2N 108.3W    30 KT
 24HR VT     23/1800Z 13.8N 109.7W    35 KT
 36HR VT     24/0600Z 14.3N 110.5W    40 KT
 48HR VT     24/1800Z 15.1N 111.1W    45 KT
 72HR VT     25/1800Z 17.0N 112.5W    55 KT
 96HR VT     26/1800Z 19.0N 114.5W    60 KT
120HR VT     27/1800Z 21.0N 117.5W    50 KT
 
$$
FORECASTER BEVEN
 
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