WDPN31 PGTW 292100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (KAMMURI) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. TYPHOON 29W (KAMMURI), LOCATED APPROXIMATELY 948 NM EAST
OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 06 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY REVEALS
AN ASYMMETRIC CENTRAL DENSE OVERCAST (CDO) OBSCURING THE LOW LEVEL
CIRCULATION CENTER (LLCC). THERE IS FAIR CONFIDENCE IN THE INITIAL
POSITION BASED ON A MICROWAVE EYE FEATURE REVEALING A BROAD LLCC IN
291652Z AMSR-2 AND 291826Z GMI 37GHZ MICROWAVE IMAGES. MULTI-AGENCY
DVORAK CURRENT INTENSITY ESTIMATES OF T4.5-5.0 (77-90 KNOTS) ARE WELL
ABOVE A 291810Z ADT ESTIMATE OF 61 KNOTS,GIVING LOW CONFIDENCE TO THE
INITIAL INTENSITY OF 75 KNOTS, WHICH IS BASED ON THE OBLONG CDO
STRUCTURE. MODERATE (15-20 KNOTS) VERTICAL WIND SHEAR IS CURRENTLY
HINDERING ORGANIZATION AND INTENSIFICATION, OFFSETTING FAIR WESTWARD
AND EXCELLENT POLEWARD OUTFLOW AND WARM (28-29 CELSIUS) SEA SURFACE
TEMPERATURES. TY 29W IS TRACKING ALONG THE SOUTHEASTERN PERIPHERY OF
A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHWEST, AND HAS
ACCELERATED WESTWARD OVER THE PAST 6 HOURS AS THAT STR BUILDS IN TO
WHAT WAS A WEAK STEERING ENVIRONMENT BETWEEN TWO STRS.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 36, TY 29W WILL CONTINUE WEST-SOUTHWESTWARD TO
WESTWARD WITH THE STR POSITIONED TO THE NORTHWEST AS THE PRIMARY
STEERING INFLUENCE. AFTER TAU 36, A PASSING SHORTWAVE TROUGH TO THE
NORTH ERODES THE WESTERN STR AND CAUSES A SUBTROPICAL RIDGE TO THE
NORTHEAST TO RE-ORIENT AND BECOME THE PREDOMINANT STEERING MECHANISM.
THIS BREAK IN THE STR WILL ALLOW FOR ENHANCED POLEWARD OUTFLOW AND
REDUCED VWS, AND TY 29W WILL INTENSIFY TO A PEAK OF 95 KTS BY TAU 48.
SHORTLY THEREAFTER, THE STEERING STR TO THE NORTHEAST BUILDS IN,
OUTFLOW WILL BE REDUCED, AND TY 29W WILL BEGIN TO ENCOUNTER DRY AIR
FROM THE SURFACE NORTHEASTERLY SURGE, BEGINNING A WEAKENING TREND BY
TAU 72. THERE IS STRONG AGREEMENT IN MODEL TRACK GUIDANCE, LENDING
HIGH CONFIDENCE TO THIS PORTION OF THE TRACK FORECAST. HOWEVER, THERE
IS SIGNIFICANT SPREAD IN INTENSITY FORECASTS. COAMPS-TC (GFS) AND
HWRF PEAK 29W FAR ABOVE THE MULTI-MODEL INTENSITY CONSENSUS, AS DOES
ECMWF. HOWEVER, GFS AND SHIPS DYNAMICAL-STATISTICAL GUIDANCE PRESENT
A MORE MODEST INTENSIFICATION SCENARIO. THE JTWC INTENSITY FORECAST
IS HEDGED SLIGHTLY ABOVE THE MULTI-MODEL INTENSITY FORECAST, BUT
WITHIN THE 70% PROBABILITY CURVE. THE UNCERTAINTY IN CURRENT
INTENSITY CONTRIBUTES TO UNCERTAINTY IN THE JTWC INTENSITY FORECAST
AS WELL.
   C. AFTER TAU 72, TY 29W WILL CONTINUE TO TRACK WESTWARD AND MAKE
LANDFALL EAST OF MANILA, PHILIPPINES. TY 29W WILL CONTINUE TO TRACK
WESTWARD INTO THE SOUTH CHINA SEA. TY 29W WILL WEAKEN MORE RAPIDLY
AFTER TAU 72 DUE TO FRICTIONAL EFFECTS FROM THE RUGGED TERRAIN OF
LUZON AND DRY AIR ENTRAINMENT FROM THE NORTHEASTERLY SURFACE SURGE.
MODEL TRACK GUIDANCE REMAINS IN STRONG AGREEMENT THROUGH THE
REMAINDER OF THE FORECAST AND CONFIDENCE IN THIS PORTION OF FORECAST
TRACK IS HIGH.//
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