Tropical Storm SAOLA Advisory lun, 23-10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 27W (TWENTYSEVEN)
WARNING NR 14//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 27W (TWENTYSEVEN), LOCATED APPROXIMATELY
313 NM SOUTH-SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-
NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY DEPICTS A BROAD, PARTIALLY-EXPOSED
LOW-LEVEL CIRCULATION CENTER (LLCC) WITH EXTENSIVE DEEP CONVECTION
PERSISTING OVER THE SOUTHERN SEMI-CIRCLE OF THE LLCC ASSOCIATED WITH
CONVERGENT WESTERLY FLOW. A 222053Z SSMIS 37GHZ IMAGE SHOWS BROAD
BANDING WRAPPING INTO A WEAKLY-DEFINED LLCC, HOWEVER, A 222357Z
ASCAT IMAGE SHOWS AN ELONGATED CIRCULATION WITH 25 TO 30 KNOT WINDS
AROUND THE PERIPHERY WHILE A 222314Z OSCAT BULLS-EYE IMAGE SHOWED A
MORE SYMMETRIC CIRCULATION, WHICH SUPPORTS THE INITIAL POSITION WITH
GOOD CONFIDENCE. THE INITIAL INTENSITY IS HEDGED HIGHER THAN THE
DVORAK ESTIMATES OF T1.5 (25 KNOTS) BASED ON THE ASCAT AND OSCAT
DATA. UPPER-LEVEL ANALYSIS REVEALS AN IMPROVING ENVIRONMENT WITH
DECREASING (15 TO 20 KNOTS) EASTERLY VERTICAL WIND SHEAR (VWS)
OFFSET BY STRONG EQUATORWARD OUTFLOW. RECENT SOUNDINGS FROM GUAM AND
700MB MODEL ANALYSES HAVE CONTINUED TO INDICATE A WEAKENING NEAR-
EQUATORIAL RIDGE AND A BUILDING SUBTROPICAL RIDGE (STR) TO THE NORTH
AND NORTHEAST, WHICH IS PROVIDING A WESTWARD STEERING INFLUENCE.
3. FORECAST REASONING.
   A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. AFTER TAU 18 TO 24, ENVIRONMENTAL CONDITIONS ARE FORECAST TO
IMPROVE LEADING TO A PERIOD OF SLOW INTENSIFICATION / CONSOLIDATION.
DYNAMIC AIDS ARE NOW SPLIT INTO TWO DISCRETE GROUPS WITH NVGM, JGSM
AND JENS INDICATING A SHARP RECURVE TRACK OVER IWO-TO AND THE
REMAINING TRACKERS INDICATING A MORE GRADUAL RECURVE SCENARIO OVER
AND JUST EAST OF THE RYUKYU ISLANDS. ANALYSIS OF NAVGEM FIELDS SHOWS
NAVGEM IS PUNCHING THE SYSTEM DIRECTLY INTO THE SUBTROPICAL RIDGE,
WHICH IS LIKELY ERRONEOUS, THEREFORE, THE JTWC FORECAST IS ALIGNED
WITH THE WESTERN GROUP OF MODEL TRACKERS (AVNO, AEMN, UEMN, ECMF,
EEMN, AFUM). THESE MODELS ARE IN FAIR AGREEMENT WITH A 155NM SPREAD
IN SOLUTIONS AT TAU 72.
   C. IN THE EXTENDED PERIOD, THE WESTERN GROUP OF MODELS DIVERGE
WITH INCREASED UNCERTAINTY IN THE RECURVE POINT AND TIMING OF THE
RECURVE. TD 27W IS FORECAST TO INTENSIFY TO A PEAK OF 95 KNOTS AT
TAU 120 DUE TO THE IMPROVED POLEWARD OUTFLOW. OVERALL, THERE IS LOW
CONFIDENCE IN THE JTWC FORECAST DUE TO THE BIFURCATION IN MODEL
GUIDANCE AND LARGE SPREAD IN THE WESTERN GROUP OF MODEL TRACKERS.
AFTER TAU 120, STRONG ZONAL WESTERLIES ARE FORECAST TO PERSIST OVER
JAPAN MAKING LANDFALL OVER MAINLAND JAPAN UNLIKELY.//
NNNN
NNNN