Tropical Storm NANGKA Advisory Sun Jul 05

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NANGKA) WARNING NR
07//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 11W (NANGKA), LOCATED APPROXIMATELY 136 NM EAST-
SOUTHEAST OF ENEWETAK, HAS TRACKED WESTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS. THE CURRENT POSITION IS BASED ON MICROWAVE IMAGERY
AND ASCAT SCATTEROMETER DATA FROM A 042311Z METOP-B PASS. THE
CURRENT INTENSITY OF 50 KNOTS IS CONSISTENT WITH THE AFOREMENTIONED
ASCAT PASS AND DVORAK SATELLITE INTENSITY ESTIMATES FROM MULTIPLE
REPORTING AGENCIES. RECENT MULTISPECTRAL SATELLITE IMAGERY SHOWS A
TIGHTLY-WRAPPED LOW LEVEL CIRCULATION WITH LIMITED DEEP CONVECTION
FLARING TO THE NORTH AND EAST OF THE CENTER. TS 11W LIES IN AN AREA
OF LOW VERTICAL WIND SHEAR AND IMPROVING UPPER LEVEL OUTFLOW. THE
SYSTEM IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF A
SUBTROPICAL STEERING RIDGE TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO MAJOR CHANGE TO FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 11W WILL CONTINUE TRACKING ALONG THE PERIPHERY OF THE
CURRENT SUBTROPICAL STEERING RIDGE THROUGH THE NEXT 72 HOURS, TURNING
GRADUALLY NORTHWESTWARD FROM ITS CURRENT WESTWARD TRACK AS THE
STEERING RIDGE REORIENTS. LOW VERTICAL WIND SHEAR, INCREASING RADIAL
OUTFLOW, AND PASSAGE OVER VERY WARM WATER WILL ALLOW THE SYSTEM TO
STEADILY INTENSIFY DURING THIS PERIOD. DYNAMIC MODEL GUIDANCE IS IN
GOOD AGREEMENT REGARDING THE FORECAST TRACK THROUGH TAU 72. THE
CURRENT TRACK FORECAST LIES CLOSE TO THE MULTI-MODEL CONSENSUS
DURING THIS PERIOD.
   C. IN THE TAU 96 THROUGH TAU 120 PERIOD, TS 11W IS EXPECTED TO
CONTINUE TRACKING GENERALLY NORTHWESTWARD ALONG THE SUBTROPICAL
RIDGE PERIPHERY. INTENSIFICATION SHOULD CONTINUE AS ENVIRONMENTAL
CONDITIONS REMAIN MOSTLY FAVORABLE, ALTHOUGH RESTRICTED POLEWARD
OUTFLOW MAY LIMIT THE INTENSIFICATION RATE AS REFLECTED IN THE
CURRENT FORECAST. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT
IN THE EXTENDED RANGE, LENDING HIGH CONFIDENCE TO THE CURRENT TRACK
FORECAST.//
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