Tropical Storm DOLPHIN Advisory Sun May 10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (DOLPHIN) WARNING
NR 16//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 07W (DOLPHIN), LOCATED APPROXIMATELY 115 NM
EAST-NORTHEAST OF POHNPEI HAS TRACKED NORTH-NORTHWESTWARD AT 05
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY AND A 101021Z MHS MICROWAVE IMAGE DEPICT AN ELONGATED AND
FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH LIMITED
CONVECTIVE BANDING SHEARED TO THE WEST. THE INITIAL POSITION AND
INTENSITY IS BASED ON A 101022Z SCATTEROMETER BULLSEYE WITH 40 KNOT
WINDS ALONG THE SOUTHEASTERN PERIPHERY. UPPER LEVEL ENVIRONMENTAL
CONDITIONS REMAIN MARGINAL, WITH TS DOLPHIN UNDER EASTERLY DIFFLUENT
FLOW ALOFT AND MODERATE (20 TO 25 KNOTS) VERTICAL WIND SHEAR (VWS)
WHICH IS PREVENTING CONVECTION FROM BUILDING OVER THE LLCC. 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.
   B. TS 07W WILL CONTINUE TO TRACK POLEWARD OVER THE NEXT 24 HOURS
AS AN UPPER LEVEL TROUGH PASSES TO THE NORTH CAUSING THE BREAK IN
THE STEERING STR. AFTER TAU 24, THE STR WILL REBUILD AND TURN TS 07W
ON A WEST-NORTHWESTWARD TRAJECTORY. UPPER LEVEL ENVIRONMENTAL
CONDITIONS WILL REMAIN MARGINAL OVER THE NEXT 48 HOURS LEADING TO A
MODEST INTENSIFICATION. BEYOND TAU 48, AN IMPROVING ENVIRONMENT,
WITH LOW VWS (5-10 KNOTS) AND AN INCREASING POLEWARD OUTFLOW CHANNEL
WILL LEAD TO AN INCREASED INTENSIFICATION RATE.
   C. IN THE EXTENDED TAUS, TS DOLPHIN WILL REMAIN ON A WEST-
NORTHWESTWARD TRACK UNDER THE STEERING INFLUENCE OF THE STR. BY THE
END OF THE FORECAST PERIOD 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. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT
REGARDING THE TRACK AND OVERALL SPEED, LEADING TO HIGH CONFIDENCE IN
THE JTWC FORECAST.//
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