WDPN32 PGTW 110300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (DOLPHIN) WARNING 
NR 18//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 07W (DOLPHIN), LOCATED APPROXIMATELY 156 NM 
NORTH-NORTHEAST OF POHNPEI, HAS TRACKED NORTH-NORTHWESTWARD AT 08 
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY (MSI) DEPICTS FLARING DEEP CENTRAL CONVECTION OVER A 
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER. A 102257Z METOP-A 
MICROWAVE IMAGE REVEALS BROKEN CONVECTIVE BANDING WITH THE BULK OF 
THE DEEP CONVECTION SLIGHTLY DISPLACED WESTWARD. THE CURRENT 
POSITION IS BASED ON THE MSI AND THE AFOREMENTIONED METOP-A IMAGE 
WITH GOOD CONFIDENCE. THE INITIAL INTENSITY OF 40 KNOTS IS BASED ON 
A 102232Z ASCAT PASS SHOWING 35 TO 40 KNOT CIRCULATION AND HEDGED 
SLIGHTLY HIGHER THAN DVORAK INTENSITY ESTIMATE OF 35 KNOTS FROM 
PGTW. UPPER-LEVEL CONDITIONS REMAIN MARGINAL WITH EASTERLY DIFFLUENT 
FLOW ALOFT AND MODERATE (20 TO 25 KNOTS) VERTICAL WIND SHEAR (VWS). 
HOWEVER, SEA SURFACE TEMPERATURES ABOVE 29 CELSIUS REMAIN CONDUCIVE 
FOR DEVELOPMENT. TS 07W IS TRACKING SLOWLY POLEWARD TOWARDS A BREAK 
IN THE STEERING SUB-TROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM 
THE PREVIOUS PROGNOSTIC REASONING MESSAGE. HOWEVER, THE EXTENDED 
TRACK FORECAST HAS POSITIONED SLIGHTLY SOUTHWARD DUE TO A CHANGE IN 
AVAILABLE MODEL GUIDANCE. SEE PARA C FOR DETAILS.
   B. TS 07W WILL CONTINUE TO TRACK POLEWARD OVER THE NEXT 06 HOURS 
AS AN UPPER-LEVEL TROUGH PASSES TO THE NORTH CAUSING A BREAK IN 
THE STEERING STR. AFTERWARD, THE STR WILL REBUILD AND TURN TS 07W ON 
A GENERALLY WESTWARD TRAJECTORY. UPPER-LEVEL CONDITIONS WILL REMAIN 
MARGINAL OVER THE NEXT 48 HOURS LEADING TO A MODEST INTENSIFICATION. 
BEYOND TAU 48, AN IMPROVING ENVIRONMENT, WITH LOW VWS (05 TO 10 
KNOTS) AND AN INCREASING POLEWARD OUTFLOW CHANNEL WILL LEAD TO AN 
INCREASED INTENSIFICATION RATE.
   C. AFTER TAU 72, TS DOLPHIN WILL TRACK WEST-NORTHWESTWARD  UNDER 
THE STEERING INFLUENCE OF THE STR. BY TAU 96, ANOTHER APPROACHING 
MID-LATITUDE TROUGH WILL CAUSE THE STEERING STR TO WEAKEN AGAIN, 
ALLOWING TS 07W TO TURN SLIGHTLY POLEWARD TOWARDS A BREAK IN THE 
STR. ENVIRONMENTAL CONDITIONS WILL REMAIN FAVORABLE AND SUPPORT 
FURTHER INTENSIFICATION. NUMERICAL MODELS HAVE CHANGED OVER THE PAST 
SIX HOURS, BUT OVERALL REMAINS IN GOOD AGREEMENT, INDICATING A 
SOUTHWARD SHIFT IN THE TRACK DUE TO A BUILDING AFOREMENTIONED STR. 
THEREFORE, THE EXTENDED JTWC TRACK FORECAST HAS POSITIONED SOUTHWARD 
TO REFLECT THIS CHANGE. DUE TO UNCERTAINTY IN THE EXTENDED FORECAST 
INTENSITY, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST.//
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