Tropical Storm WIPHA Advisory Thu Oct 10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (TWENTYFIVE)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 25W (TWENTYFIVE), LOCATED APPROXIMATELY 696
NM SOUTH OF IWO TO, HAS TRACKED WEST-SOUTHWESTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY DEPICTS
CENTRAL CONVECTION THAT HAS RAPIDLY DEVELOPED AS THE LOW-LEVEL
CIRCULATION CENTER HAS BECOME INCREASINGLY MORE CONSOLIDATED JUST
SOUTHWEST OF GUAM. A 100959Z SSMIS MICROWAVE IMAGE DEPICTS A BROAD,
ALBEIT FRAGMENTED, CONVECTIVE BANDING FEATURE LOCATED ALONG THE
SOUTHERN SEMI-CIRCLE THAT HAS PERSISTED OVER THE PAST 24 HOURS. THE
INITIAL POSITION IS BASED ON THE IR ANIMATION AS WELL AS LOCAL RADAR
FIXES FROM GUAM WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS
ASSESSED AT 25 BASED AGENCY DVORAK ESTIMATES AND LOCAL OBSERVATIONS
FROM GUAM AND ROTA. UPPER LEVEL ANALYSIS INDICATES A FAVORABLE
ENVIRONMENT WITH LOW TO MODERATE (10 TO 20 KTS) VERTICAL WIND SHEAR
(VWS), DIFFLUENT EASTERLY OUTFLOW, AND A TUTT CELL TO THE NORTHEAST.
TD 25W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY
OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
   B. TD 25W IS EXPECTED TO TRACK GENERALLY NORTHWESTWARD ALONG THE
SOUTHWEST PERIPHERY OF THE STR OVER THE NEXT 72 HOURS. WARM SEA
SURFACE TEMPERATURES (SSTS) AND FAVORABLE UPPER LEVEL CONDITIONS
WILL AID THE SYSTEM IN A GRADUAL INTENSIFICATION TO 80 KNOTS BY TAU
72. DYNAMIC MODEL GUIDANCE IS TIGHT AGREEMENT THROUGH TAU 48, WITH
ONLY SLIGHT VARIATIONS IN POSITION TO THE EAST AND WEST. BY TAU 72,
AS TD 25W APPROACHES THE STR AXIS, THE UNCERTAINTY BETWEEN MODEL
TRACKERS INCREASES IN BOTH POSITION AND SPEED. THE CONFIDENCE IN
THIS PORTION OF THE FORECAST IS LOW.
   C. IN THE LATER TAUS, TD 25W IS EXPECTED TO CREST THE STR AXIS
NEAR TAU 96 AND BEGIN RECURVING MORE POLEWARD BY TAU 120. INCREASING
VWS AND COOLING SSTS WILL BEGIN TO DEGRADE THE SYSTEM AS THE
INTENSITY IS EXPECTED TO BEGIN TO SLIGHTLY WEAKEN BY TAU 120.
DYNAMIC MODEL GUIDANCE IS SIGNIFICANTLY SPREAD IN THIS PORTION OF
THE FORECAST AND THE JTWC FORECAST TRACK LAID CLOSE TO THE MULTI-
MODEL CONSENSUS. DUE TO THE DYNAMIC MODEL UNCERTAINTY AND THIS BEING
THE FIRST WARNING THERE IS OVERALL LOW CONFIDENCE IN THE JTWC
FORECAST.//
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