Tropical Storm SAOLA Advisory czw., 26.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (SAOLA)
WARNING NR 26//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 27W (SAOLA), LOCATED APPROXIMATELY 589 NM SOUTH-
SOUTHEAST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 11 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
ILLUSTRATES THAT THE SYSTEM IS STRUGGLING TO CONSOLIDATE, WITH
FLARING DEEP CONVECTION COALESCING INTO WELL-DEFINED BANDS ON THE
SOUTHWEST SIDE, WITH LITTLE TO NO CONVECTIVE ACTIVITY ON THE NORTH
SIDE. THE LOW LEVEL CIRCULATION CENTER (LLCC) IS WELL-DEFINED BY THE
LOW LEVEL CLOUD LINES BUT IS PARTIALLY EXPOSED ALONG THE NORTHERN
PORTION OF THE CIRCULATION. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE ANIMATED IMAGERY AND EXTRAPOLATION FROM A
252152Z 37GHZ SSMIS MICROWAVE FIX POSITION. HINTS OF A MICROWAVE EYE
SEEN IN EARLIER IMAGERY APPEARS TO HAVE DISSIPATED OR WEAKENED AND
IS NO LONGER EVIDENT IN AVAILABLE MICROWAVE IMAGERY. THE INITIAL
INTENSITY IS ASSESSED AT 45 KNOTS BASED ON MULTI-AGENCY DVORAK
INTENSITY OF ESTIMATES OF T3.0 (45 KTS), SATELLITE CONSENSUS
(SATCON) ESTIMATES OF 46 KNOTS AND AUTOMATED DVORAK ESTIMATES OF
T2.2 (32 KTS). ENVIRONMENTAL ANALYSIS INDICATES MARGINALLY FAVORABLE
CONDITIONS WITH LOW TO MODERATE (10-15 KNOTS) VERTICAL WIND SHEAR
(VWS) AND HIGH SEA SURFACE TEMPERATURES (31 CELSIUS). THESE
FAVORABLE CONDITIONS ARE BEING OFFSET BY WEAK, THOUGH IMPROVING,
EQUATORWARD OUTFLOW, PROVIDED BY A WEAK POINT SOURCE NEAR THE SYSTEM
WHICH IS ITSELF BEING OFFSET BY A STRONG ANTICYCLONE TO THE NORTH,
LIMITING CONSOLIDATION OF THE SYSTEM ON THE NORTHERN PERIPHERY. THE
SYSTEM IS ALSO TRANSITING OVER A POOL OF LOW OCEAN HEAT CONTENT
(OHC) VALUES, WHICH IS SERVING TO HINDER INTENSIFICATION. TS SAOLA
IS TRACKING TO THE NORTHWEST ALONG THE SOUTHWESTERN EXTENT OF A DEEP
LAYERED SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THIS FORECAST REPRESENTS A SHIFT IN THE OVERALL TRACK
PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THE
TRACK HAS SLOWED SIGNIFICANTLY AFTER TAU 72 AND SHIFTED SOUTHWARD IN
RESPONSE TO A ROBUST COLD SURGE ASSOCIATED WITH PASSAGE OF A STRONG
COLD FRONT ACROSS JAPAN NEAR TAU 96.
   B. TS 27W IS FORECAST TO CONTINUE TO TRACK WEST-NORTHWEST THEN
NORTHWESTWARD THROUGH TAU 48, ALONG THE SOUTHWESTERN PERIPHERY OF
THE STR. TS 27W WILL BEGIN TO SLOW ITS FORWARD SPEED AFTER TAU 36,
AS IT ENTERS A COMPETING STEERING ENVIRONMENT AND APPROACHES THE
RIDGE AXIS, IN THE VICINITY OF OKINAWA. THE SYSTEM WILL ROUND THE
RIDGE AFTER TAU 48 AND BEGIN TO TRACK EAST-NORTHEASTWARD BY TAU 72.
SLOW INTENSIFICATION IS FORECAST THROUGH TAU 36 AS THE MARGINALLY
FAVORABLE ENVIRONMENT PERSISTS. THE SYSTEM WILL UNDERGO A BRIEF
SPURT OF INTENSIFICATION NEAR TAU 48 AS IT NEARS THE RIDGE AXIS AND
TAPS INTO DUAL CHANNEL OUTFLOW, PEAKING AT 75 KNOTS. DYNAMIC
MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 24, BUT SHOWS
INCREASING SPREAD THEREAFTER, WITH A 350NM SPREAD IN SOLUTIONS AT
THE RECURVE POINT NEAR OKINAWA. SINCE THE PREVIOUS FORECAST, THE
NAVGEM, GFS, JGSM AND GALWEM TRACKERS HAVE ALL SHIFTED WEST, NOW
SHOWING EITHER LANDFALL AT OKINAWA OR A TRACK TO THE WEST OF OKINAWA
BY TAU 48 AND A SHARP SHIFT TO THE EAST BY TAU 72 AHEAD OF THE
PREVIOUSLY MENTIONED COLD FRONT. NAVGEM SHOWS THE SYSTEM BECOMING
QUASI-STATIONARY IN THE EAST CHINA SEA THROUGH THE END OF THE
FORECAST. THE REMAINDER OF THE MODELS INDICATES A MORE RAPID RECURVE
AND ACCELERATION ALONG THE JAPANESE COAST. THE WESTERN GROUPING OF
MODEL TRACKERS HAS BEEN CONSISTENT OVER THE PAST THREE MODEL RUNS,
LENDING INCREASING CONFIDENCE IN THIS SOLUTION, THOUGH THE SCENARIO
REMAINS HIGHLY UNCERTAIN. THE JTWC TRACK HAS BEEN ADJUSTED TO
REFLECT THE INCREASING CONFIDENCE, SLOWING THE SYSTEM AND TAKING IT
MORE WESTWARD TOWARDS OKINAWA. WITH THE LARGE AMOUNT OF UNCERTAINTY
IN THE TIMING AND STRENGTH OF THE APPROACHING COLD FRONTAL SYSTEM
AND LARGE SPREAD IN THE MODELS, THERE IS LOW CONFIDENCE IN THE JTWC
TRACK FORECAST.
   C. AFTER TAU 72, THE FORECAST HAS BECOME HIGHLY UNCERTAIN. THE
WESTERN GROUPING OF MODELS ALL INDICATE A SHARP TURN TO A SLOW,
NEARLY DUE EAST TRACK AFTER TAU 72, DISSIPATING THE SYSTEM TO THE
WEST OF IWO TO BY TAU 120 IN RESPONSE TO THE STRONG SURGE OF COLD,
DRY AIR FROM THE NORTH, BLOCKING ANY NORTHWARD MOVEMENT. THE
REMAINDER OF THE MODELS (ALL SECOND INTERPOLATIONS) TO INCLUDE THE
UKMET, EGRR, ECMWF AND HWRF, CONTINUE WITH A TRADITIONAL RECURVE
SCENARIO AND RAPIDLY TRACK THE SYSTEM NORTHEAST ALONG THE COAST OF
JAPAN, AHEAD OF THE COLD SURGE. THESE MODELS HAVE, HOWEVER,
SIGNIFICANTLY SLOWED FORWARD TRACK SPEED SINCE THE PREVIOUS RUN,
WHICH MAY INDICATE A GRADUAL DRIFT MORE TOWARDS THE OTHER MODELS.
BEYOND TAU 72, THE JTWC TRACK HAS BEEN SLOWED SIGNIFICANTLY, WITH
THE TAU 120 POSITION NOW PLACED NEAR THE SAME LATITUDE AS THE
PREVIOUS TAU 96 POSITION AND SHIFTED SOUTH. IN EITHER SCENARIO, THE
SYSTEM WILL BEGIN TO UNDERGO EXTRA-TROPICAL TRANSITION (ETT) NEAR
TAU 72, AS IT BEGINS TO INTERACT WITH UPPER-LEVEL WESTERLY FLOW AND
THE BAROCLINIC ZONE ASSOCIATED WITH THE APPROACHING COLD FRONT. ETT
SHOULD BE COMPLETE BY TAU 120 AS THE SYSTEM MOVES OFF THE EAST COAST
OF JAPAN, BECOMING A COLD CORE LOW WITH AN EXPANSIVE GALE FORCE WIND
FIELD. DUE TO THE HIGH DEGREE OF UNCERTAINTY ASSOCIATED WITH THE
MULTIPLE MODEL SOLUTIONS THERE IS OVERALL LOW CONFIDENCE IN JTWC
TRACK FORECAST.//
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