Tropical Storm SAUDEL Advisory pon., 19.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W
(NINETEEN) WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION
(TD) 19W (NINETEEN), LOCATED APPROXIMATELY 356 NM
EAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD
AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED
ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A BROAD
SYSTEM WITH CONVECTIVE BANDS SPIRALING INTO A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER. DEEP CONVECTION
APPEARS TO BE LIMITED TO THE WESTERN HALF OF THE
CIRCULATION, WITH THE BANDING FEATURES ON THE WEST
SIDE BECOMING INCREASINGLY WELL ORGANIZED OVER THE PAST
COUPLE OF HOURS, WHILE THE EASTERN HALF OF THE SYSTEM
REMAINS RELATIVELY FREE OF DEEP CONVECTION AND THE
SPIRAL BANDS ARE SOMEWHAT MORE ILL-DEFINED. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANALYSIS
OF THE EXPOSED OUTER BANDS EVIDENT IN ANIMATED INFRARED
IMAGERY. THE INITIAL INTENSITY OF 30 KNOTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON ANALYSIS OF MULTI-AGENCY
DVORAK CURRENT INTENSITY ESTIMATES OF T2.0 (30 KNOTS)
FROM PGTW, T2.5 (35 KNOTS) FROM KNES AND T1.5 (25 KNOTS)
FROM RJTD, AS WELL AS AN ADVANCED DVORAK TECHNIQUE
ESTIMATE OF T2.3 (32 KNOTS). TD 19W CONTINUES TO TRACK
ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE
EXTENDING SOUTHWESTWARD FROM A CENTER NEAR 30N 155E TO
NORTHERN VIETNAM. THE SYSTEM IS TRACKING THROUGH A
GENERALLY FAVORABLE ENVIRONMENT WITH WARM SSTS (29-30
DEG CELSIUS), LOW (10-15 KNOTS) VWS AND MODERATE UPPER-
LEVEL OUTFLOW ON THE DIVERGENT SOUTHWEST QUADRANT OF
AN UPPER LEVEL ANTICYCLONE.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 19W WILL TRACK WEST-NORTHWESTWARD THROUGH TAU
72 UNDER THE STEERING INFLUENCE OF THE DEEP-LAYER STR TO
THE NORTH. THE SYSTEM IS EXPECTED TO MAKE LANDFALL ALONG
THE EAST COAST OF CENTRAL LUZON SHORTLY AFTER TAU 24, THEN
REEMERGE INTO THE SOUTH CHINA SEA BY TAU 36. WHILE A
WEAKNESS IS STILL EXPECTED TO DEVELOP IN THE STEERING
RIDGE AROUND TAU 48, THE VAST MAJORITY OF THE MODEL
GUIDANCE INDICATES THAT THE MAIN IMPACT ON THE TRACK OF
TD 19W WILL BE TO SLOW ITS FORWARD SPEED, WITH ONLY A
VERY SMALL JOG TO A MORE NORTHWESTWARD TRACK BETWEEN TAUS
48 AND 72. THE SYSTEM IS CURRENTLY EXPERIENCING A BIT OF
EASTERLY SHEAR, PUSHING THE MAJORITY OF THE CONVECTION
OFF TO THE WEST OF THE CENTER, AND THIS PATTERN IS
EXPECTED TO CONTINUE THROUGH TAU 72, ALLOWING FOR ONLY
SLOW BUT STEADY INTENSIFICATION. AFTER MAKING LANDFALL
ON LUZON, THE SYSTEM MAY WEAKEN SLIGHTLY BUT ONCE BACK
OVER WATER WILL QUICKLY REGAIN INTENSITY AND THEREAFTER
RESUME SLOW BUT STEADY INTENSIFICATION, REACHING A PEAK OF
55 KNOTS BY TAU 72. NUMERICAL TRACK GUIDANCE HAS COME INTO
MUCH BETTER AGREEMENT SINCE THE PREVIOUS RUN, WITH ALL
CONSENSUS MEMBERS WITHIN THE EXCEPTION OF NAVGEM AND THE
UKMET ENSEMBLE FORMING A VERY TIGHT ENVELOPE WITH LESS
THAN 60 NM AT TAU 72. HOWEVER THIS SPREAD INCREASES TO
195 NM IF THE NAVGEM IS INCLUDED. THE ALTERNATE SCENARIO
OF A MORE NORTHWARD TRACK INTO THE STR WEAKNESS IS STILL
A POSSIBILITY, IF AN INCREASINGLY LESS LIKELY ONE, WITH
ONLY THE TWO PREVIOUSLY MENTIONED MODELS SUPPORTING THAT
SCENARIO AND EVEN THE HWRF NOW SIGNIFICANTLY CHANGING AND
COMING IN LINE WITH THE REMAINDER OF THE TRACKERS. THE
JTWC TRACK LIES JUST SOUTH OF THE MULTI-MODEL CONSENSUS
TRACK THROUGH TAU 72 WITH HIGH CONFIDENCE.
   C. IN THE EXTENDED FORECAST, TD 19W IS EXPECTED TO TRACK
WESTWARD THROUGH TAU 120 UNDER THE STEERING INFLUENCE OF A
REFORMED AND STRENGTHENED STR IN THE NORTHERN SOUTH CHINA
SEA. AS THE SYSTEM MOVES WEST IT WILL INCREASINGLY COME
UNDER CONFLUENT UPPER-LEVEL FLOW, CHOKING OFF THE OUTFLOW,
WHICH COMBINED WITH INCREASING VWS WILL LEAD TO A SLOW
WEAKENING TREND THROUGH TAU 120. NUMERICAL GUIDANCE IS IN
GOOD AGREEMENT WITH THE EXCEPTION OF NAVGEM, WITH ONLY A
65 NM SPREAD AT TAU 120 IF NAVGEM IS DISCOUNTED, AND 190 NM
IF IT IS INCLUDED. THE JTWC FORECAST LIES TO THE SOUTH OF
THE MULTI-MODEL CONSENSUS WITH FAIR CONFIDENCE IN LIGHT OF
THE ALTERNATE SCENARIO AS REPRESENTED BY THE NAVGEM TRACKER.//
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