Tropical Storm NEOGURI Advisory 19 Οκτ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (NEOGURI) WARNING
NR 010//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 21W (NEOGURI), LOCATED APPROXIMATELY 344 NM
SOUTH OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT
08 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY SHOWS A COMPACT SYSTEM THAT CONTINUES TO
SLOWLY CONSOLIDATE AS SHORT RAIN BANDS, EMANATING FROM THE NORTH,
WRAPPED TIGHTER INTO THE CENTER. THE EIR LOOP ALSO INDICATES THE
SYSTEM HAS DEFINITELY BEGUN TO MOVE FROM A QUASI-STATIONARY STATE.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A
FORMATIVE MICROWAVE PINHOLE EYE IN THE 181801Z GMI 37GHZ PASS. THE
INITIAL INTENSITY OF 50KTS IS HELD SLIGHTLY HIGHER THAN AGENCY AND
OBJECTIVE DVORAK ESTIMATES RANGING FROM T2.5 TO T3.1 AND REFLECTS THE
IMPROVED EIR SIGNATURE AND IS CONSISTENT WITH A FORMATIVE MICROWAVE
EYE. UPPER LEVEL ANALYSIS INDICATES MODERATE (15-20KT) VERTICAL
WIND SHEAR (VWS) THAT IS OFFSET BY POLEWARD OUTFLOW AND THE STORM
MOTION THAT IS IN-PHASE WITH UPPER LEVEL WIND FLOW. SEA SURFACE
TEMPERATURES (SSTS) ARE ALSO CONDUCIVE AT 28-29C, HOWEVER THIS IS
TEMPERED BY A COLD DRY SURGE IN THE PHILIPPINE SEA. OVERALL, THE
ENVIRONMENT IS MARGINALLY FAVORABLE. THE CYCLONE IS TRACKING ALONG
THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE; HOWEVER, THE EXTENDED
FORECAST ALONG TRACK SPEEDS WERE INCREASED.
   B. TS 21W WILL CONTINUE IN ITS CURRENT TRACK, STEERED BY THE STR,
AND WILL CREST THE STR AXIS BY TAU 24. AFTERWARD, IT WILL RECURVE
NORTHEASTWARD ON THE POLEWARD SIDE OF THE STR AND GRADUALLY
ACCELERATE. THE OVERALL FAVORABLE CONDITIONS, ENHANCED BY STRONG
POLEWARD OUTFLOW AS THE SYSTEM APPROACHES THE PREVAILING WESETRLIES,
WILL PROMOTE MODERATE INTENSIFICATION TO A PEAK OF 60KTS BY TAU TW.
AFTERWARD, INCREASING VWS AND COOLING SSTS WILL GRADUALLY ERODE THE
SYSTEM DOWN TO 35KTS BY TAU 72.  THE NUMERICAL MODELS ARE IN GENERAL
AGREEMENT TO THIS TRACK WITH ECMWF THE NOTABLE OUTLIER BRINGING THE
VORTEX MORE WESTWARD AND SLOWER. THERE IN FAIR CONFIDENCE IN THIS
PORTION OF THE JTWC TRACK FORECAST THAT IS LAID JUST TO THE EAST OF
AND SLOWER THAN MODEL CONSENSUS TO OFFSET ECMWF.
   C. BEYOND TAU 72, TS 21W IS EXPECTED TO CONTINUE ACCELERATING
NORTHEASTWARD. CONCURRENTLY IT WILL BEGIN EXTRA-TROPICAL TRANSITION
AS IT ENTERS THE BAROCLINIC ZONE. INCREASING VWS AND COOLING SSTS
WILL DEGRADE THE SYSTEM TO 25KTS AS IT TRANSFORMS INTO A COLD-CORE
LOW BY TAU 120. NUMERICAL MODELS SIGNIFICANTLY SPREAD OUT AND DEVIATE
IN ALONG-TRACK SPEEDS BEYOND TAU 72, LENDING LOW CONFIDENCE IN THE
EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
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