Tropical Storm NAKRI Advisory 11月7日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (NAKRI)
WARNING NR 05//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
06NOV19. TROPICAL STORM 25W (NAKRI), LOCATED APPROXIMATELY 235 NM
WEST-SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED NORTHEASTWARD
AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS PERSISTENT DEEP CONVECTION DISPLACED TO
THE WEST OF A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER. THE
INITIAL POSITION IS PLACED WITH MODERATE CONFIDENCE BASED ON THE
ANIMATED INFRARED IMAGERY, SUPPORTED BY A 061746Z ATMS MICROWAVE
IMAGE, WHICH SHOWS A CENTRAL LOW REFLECTIVITY FEATURE SURROUNDED BY
A NOTCH IN DEEP CONVECTION. THE INITIAL INTENSITY IS ASSESSED AT
40KTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF T2.5 (40 KTS)
FROM RJTD AND PGTW AND IS SUPPORTED BY BOTH AN EARLIER ASCAT PASS
SHOWING A SWATH OF 40 KNOT WINDS TO THE SOUTHWEST OF THE CENTER, AND
SUPPORTED BY A SATELLITE CONSENSUS ESTIMATE OF 41 KNOTS. THE SYSTEM
LIES IN AN OVERALL FAVORABLE ENVIRONMENT WITH A POLEWARD OUTFLOW
CHANNEL, MODERATE (20-25 KNOTS) VWS AND WARM SSTS AROUND 29-30
DEGREES CELSIUS. TS 25W IS QUASI-STATIONARY IN THE SOUTH CHINA SEA
IN A WEAK STEERING ENVIRONMENT BETWEEN A SUBTROPICAL RIDGE (STR)
LOCAST TO THE NORTH EAST AND A WEAKER STR ANCHORED OVER THE
INDOCHINA PENINSULA.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 25W IS FORECAST TO REMAIN QUASI-STATIONARY, DRIFTING SLOWLY
UNDER THE INFLUENCE OF A WEAK STEERING PATTERN OVER THE NEXT 24
HOURS. AFTER TAU 24, A STR BUILDING OVER NORTHERN LAOS WILL EXTEND
EASTWARD, BECOMING THE DOMINANT STEERING MECHANISM BY TAU 36. ONCE
STEERING SHIFTS TO THE STR, TS 25W WILL TURN SOUTH, THEN WEST AND
ACCELERATE TOWARDS VIETNAN THROUGH TAU 72. GOOD OUTLFOW, WARM SSTS
AND HIGH OHC VALUES WILL OFFSET MODERATE VWS OVER THE NEXT 24 HOURS
BEFORE LEVELING OFF BY TAU 36 AS OUTFLOW WEAKENS AND OHC VALUES
BEGIN TO DECREASE. THERE IS HIGH UNCERTAINTY IN THE FIRST 36 HOURS
OF THE FORECAST DUE TO THE WEAK STEERING ENVIRONMENT. THERE ARE TWO
DIVERGENT MODEL SOLUTIONS WITH THE GFS ENSEMBLE, UKMET ENSEMBLE,
HWRF AND NAVGEM SOLUTIONS FAVOR A NORTHWARD LOOP BEFORE MOVING
SOUTHWEST AND THEN WEST. THE ALTERNATIVE SOLUTION FAVORED BY THE
ECMWF, ECMWF ENSEMBLE, JGSM, EGRR AND GFS TURN THE SYSTEM SOUTHWARD
THROUGH TAU 24 BEFORE ACCELERATING WEST. HOWEVER, ALL MODELS AGREE
ON SLOW AND DRIFTING MOTION DURING THE INITIAL FORECAST TAUS
FOLLOWED BY WESTWARD ACCELERATION. THE JTWC FORECAST TRACK FAVORS
THE SOUTHERN TURN AND IS PLACED NEAR THE MULTIMODEL CONSENSUS, WITH
LOW CONFIDENCE.
C. AFTER TAU 72, ALL MODELS AGREE ON A WESTWARD TRACK TOWARDS
VIETNAM AND SHOW LANDFALL AROUND TAU 96. THE EXTENDED RANGE FORECAST
HAS SLOWED SOME FROM THE PREVIOUS FORECASTS. THE SYSTEM IS FORECAST
TO REACH A PEAK IN INTENSITY AT TAU 48 OF 55 KNOTS BEFORE WEAKENING
STEADILY DUE TO COOLER SSTS AND UPPER LEVEL CONVERGENCE OVER THE
SYSTEM. AFTER LANDFALL, THE SYSTEM WILL RAPIDLY DISSIPATE DUE TO THE
FRICTIONAL EFFECTS OF THE MOUNTAINOUS TERRAIN OF WESTERN VIETNAM.
MOST CONSENSUS MEMBERS ARE TIGHTLY CLUSTERED NEAR THE JTWC TRACK
FROM TAU 72 TO 120 WITH THE EXCEPTION NAVGEM WHICH TRACKS
CONSIDERABLY FURTHER NORTH THAN THE REST OF THE CONSENSUS MEMBERS.
WITH THE MAJORITY OF CONSENSUS MEMBERS BEING IN GOOD AGREEMENT,
THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST
TRACK.//
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