Tropical Storm DUJUAN Advisory 2月19日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (DUJUAN) WARNING
NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 01W (DUJUAN), LOCATED APPROXIMATELY 775 NM
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 02 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY REVEALS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) POSITIONED UNDER THE SOUTHEAST EDGE OF AN AREA OF EXPANSIVE
DEEP CONVECTION. UNFORTUNATELY, THERE ARE NO USEFUL MICROWAVE IMAGES
TO HELP LOCATE THE CENTER, THEREFORE, THERE IS FAIR CONFIDENCE IN
THE INITIAL POSITION, WHICH APPEARS TO BE QUASI-STATIONARY OR SLOW
MOVING. THE INITIAL INTENSITY REMAINS ASSESSED AT 35 KNOTS BASED ON
A DVORAK ESTIMATES OF T2.5 (35 KNOTS) FROM ALL AGENCIES. UPPER-LEVEL
ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH MODERATE
(20 KNOTS) SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY
DIFFLUENT EASTERLY FLOW AND ROBUST POLEWARD OUTFLOW. SST VALUES
REMAIN CONDUCIVE AT 29-30C. TS 01W IS TRACKING ALONG THE SOUTHWEST
PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO
THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE IN THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 01W IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT SOUTH OF
A BREAK IN THE SUBTROPICAL RIDGE (STR) ASSOCIATED WITH A MAJOR
SHORTWAVE TROUGH CURRENTLY OVER AND SOUTH OF JAPAN. IN GENERAL, THE
SYSTEM WILL TRACK SLOWLY WESTWARD TO WEST-NORTHWESTWARD THROUGH TAU
36 UNTIL THE MAJOR TROUGH SHIFTS EASTWARD AND ZONAL FLOW
PREDOMINATES. THIS WILL ALLOW THE STR TO RE-BUILD NORTHEAST AND
NORTH OF THE SYSTEM, WHICH WILL ALLOW THE SYSTEM TO ACCELERATE WEST-
NORTHWESTWARD WITH LANDFALL OCCURRING NEAR TAU 48. WITH THE
EXCEPTION OF THE UKMET DETERMINISTIC AND UKMET ENSEMBLE MEAN
SOLUTIONS, NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT WITH A
175NM SPREAD IN SOLUTIONS AT TAU 72. TS 01W WILL INTENSIFY STEADILY
TO A PEAK INTENSITY OF 50 KNOTS BY TAU 36 UNDER GENERALLY FAVORABLE
CONDITIONS, ESPECIALLY STRONG POLEWARD OUTFLOW. HOWEVER, THERE IS
SOME UNCERTAINTY IN THE PEAK INTENSITY DUE TO THE PERSISTENT
MODERATE VWS.
   C. AFTER TAU 72, TS 01W WILL CONTINUE TO TRACK ACROSS THE
PHILIPPINE ARCHIPELAGO, AND BY TAU 96, WILL REACH THE SOUTH CHINA
SEA OFF THE ISLAND OF MINDORO. INTERACTION WITH THE ISLANDS AND
INCREASED VWS WILL WEAKEN THE SYSTEM DOWN TO 25 KNOTS BY TAU 120.
NUMERICAL MODEL GUIDANCE DIVERGES AND IS IN POOR AGREEMENT IN THE
EXTENDED PERIOD WITH A LARGE SPREAD OF 530NM AT TAU 120 (MINUS UKMET
AND UKMET ENSEMBLE MEAN). THESE SOLUTIONS ARE RECURVING THE SYSTEM
NORTHEASTWARD, WHICH IS UNLIKELY DUE TO THE STRONG LIKELIHOOD OF A
RE-BUILDING STR AND ZONAL UPPER-LEVEL FLOW OVER THE EAST CHINA SEA.
DUE TO THE QUASI-STATIONARY MOTION AND THE LARGE SPREAD IN MODEL
SOLUTIONS, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH
IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS.//
NNNN
NNNN