Tropical Storm SAOLA Advisory Thu Oct 26

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (SAOLA)
WARNING NR 23//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 27W (SAOLA), LOCATED APPROXIMATELY 385 NM NORTH-
NORTHWEST OF YAP, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
A POORLY ORGANIZED SYSTEM WITH FLARING DEEP CONVECTION LOCATED TO
THE SOUTH OF A BROAD LOW LEVEL CIRCULATION CENTER (LLCC). THE
INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE
ANIMATED MULTISPECTRAL LOOP AND A 250526Z 37GHZ SSMI MICROWAVE
IMAGE. THE MICROWAVE IMAGE REVEALS CONVECTIVE BANDING WRAPPING INTO
A LLCC THAT IS ELONGATED AND LACKS DEFINITIVE ORGANIZATION. THE
INITIAL INTENSITY IS ASSESSED AT 40 KNOTS WHICH IS HEDGED SLIGHTLY
ABOVE MULTI-AGENCY DVORAK INTENSITY OF ESTIMATES OF T2.5 (35 TO 45
KTS) FROM PGTW AND RJTD, AND IS SUPPORTED BOTH BY A SATCON ESTIMATE
OF 43 KNOTS AND A 250055Z METOP-A ASCAT IMAGE SHOWING AN AREA OF 35
TO 40 KNOT WIND BARBS IN THE SOUTHERN SEMI-CIRCLE. ENVIRONMENTAL
ANALYSIS REVEALS MARGINALLY FAVORABLE CONDITIONS WITH MODERATE (15-
20 KNOTS) VERTICAL WIND SHEAR (VWS) AND HIGH SEA SURFACE
TEMPERATURES (31 CELSIUS). THE SYSTEM CONTINUES TO EXPERIENCE
WEAK OUTFLOW BOTH EQUATORWARD AND POLEWARD AS AN UPPER LEVEL TROUGH
LOCATED TO THE EAST CONTINUES TO INTRODUCE SUBSIDENCE TO THE AREA.
TS SAOLA IS TRACKING TO THE NORTHWEST ALONG THE SOUTHWESTERN
PERIPHERY OF A DEEP SUBTROPICAL RIDGE (STR) LOCATED TO THE
NORTHEAST. THE TRACK HAS SHIFTED MORE NORTHERLY IN THE PAST SIX
HOURS AS AN EXTENSION OF THE STR SHIFTS EAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 27W IS FORECAST TO CONTINUE TO TRACK NORTHWEST FOR THE
NEXT 48 HOURS ALONG THE SOUTHWESTERN PERIPHERY OF THE STR. AFTER
TAU 48, THE SYSTEM WILL ROUND THE RIDGE AXIS AND BEGIN RECURVING,
ESTABLISHING A NORTHEAST TRACK DIRECTION BY TAU 72. THE SYSTEM WILL
MAINTAIN INTENSITY THROUGH TAU 12 AS IT CONTINUES TO ORGANIZE AND
CONSOLIDATE. WEAK OUTFLOW CONDITIONS WILL PREVENT RAPID
INTENSIFICATION THROUGH TAU 48. AFTER TAU 48, A BRIEF PERIOD OF
INTENSIFICATION WILL OCCUR AS OUTFLOW CONDITIONS ARE IMPROVED
THROUGH INTERACTION WITH THE MID-LATITUDE WESTERLIES. AVAILABLE
DYNAMIC MODEL GUIDANCE IS IN STRONG AGREEMENT THROUGH TAU 48. AFTER
TAU 48, THERE IS INCREASING UNCERTAINTY DUE TO DIFFERENCES IN THE
EXACT TIME AND SHARPNESS OF THE TURN TO THE NORTHEAST. THE
PRINCIPLE OUTLIERS ARE NAVGEM, RECURVING TO THE WEST OF OKINAWA,
AND COAMPS-TC, TRACKING CONSIDERABLY FARTHER EAST THAN THE REST OF
THE CONSENSUS MEMBERS. GIVEN THE STRENGTH OF THE STEERING STR, THE
COAMPS-TC TRACK SCENARIO IS CONSIDERED UNLIKELY. THERE IS OVERALL
HIGH CONFIDENCE IN THE JTWC TRACK FORECAST THROUGH TAU 48, THEN LOW
CONFIDENCE THEREAFTER DUE TO THE HIGH DEGREE OF UNCERTAINTY IN THE
MODEL GUIDANCE.
   C. AFTER TAU 72, TS SAOLA WILL RAPIDLY ACCELERATE TO THE
NORTHEAST. ALSO, AFTER TAU 72, THE SYSTEM WILL BEGIN TO INTERACT
WITH AN APPROACHING MID-LATITUDE TROUGH, BRINGING INCREASING VWS
AND DECREASING SSTS, CAUSING THE SYSTEM TO BEGIN EXTRATROPICAL
TRANSITION (ET) BY TAU 96. TS 27W IS FORECAST TO COMPLETE
EXTRATROPICAL TRANSITION PRIOR TO TAU 120, BECOMING A COLD CORE LOW
WITH AN EXPANSIVE GALE FORCE WIND FIELD. DYNAMIC MODEL GUIDANCE IS
IN FAIR AGREEMENT AS TO THE TRACK DIRECTION BUT POOR AGREEMENT WITH
THE SPEED OF THE SYSTEM. THE JTWC TRACK IS PLACED NEAR THE
CONSENSUS WITH GREATER SPEED, HOWEVER, THE HIGH DEGREE OF
UNCERTAINTY LENDS LOW CONFIDENCE IN THIS PORTION OF THE JTWC TRACK
FORECAST.//
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