Tropical Storm MEKKHALA Advisory Thu Jan 15

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (MEKKHALA) WARNING
NR 08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 01W (MEKKHALA), LOCATED APPROXIMATELY 276 NM
NORTH-NORTHWEST OF KOROR, PALAU, HAS TRACKED WESTWARD AT 10 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
REVEALS AN OVERALL UNCHANGED STRUCTURE OVER THE PAST 6 HOURS AS THE
LOW LEVEL CIRCULATION CENTER (LLCC) REMAINS PARTIALLY EXPOSED WITH
DISPLACED DEEP CONVECTION TO THE NORTHWEST. THE CURRENT POSITION IS
BASED ON THE MSI ANIMATION AND HEDGED BETWEEN THE PGTW AND RJTD
FIXES WITH FAIR CONFIDENCE. THE CURRENT INTENSITY HAS BEEN HELD AT
35 KTS BASED ON THE UNCHANGED STRUCTURE AND DVORAK INTENSITY
ESTIMATES OF THE SAME VALUE FROM PGTW AND KNES. UPPER LEVEL ANALYSIS
CONTINUES TO SHOW THAT TS 01W REMAINS IN A MARGINALLY FAVORABLE
ENVIRONMENT WITH MODERATE (15-20 KNOTS) VERTICAL WIND SHEAR (VWS)
WHICH IS BEING OFFSET BY GOOD POLEWARD OUTFLOW. TS MEKKHALA IS
TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF A LOW-
TO MID-LEVEL REFLECTION OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 01W WILL CONTINUE TO TRACK GENERALLY WEST THROUGH TAU 48
UNDER THE STEERING INFLUENCE OF THE STR LOCATED TO THE NORTH. AFTER
TAU 48, THE SYSTEM WILL TURN SLIGHTLY TO THE NORTHWEST TOWARDS A
WEAK BREAK IN THE STR. TS MEKKHALA IS FORECAST TO SLOWLY INTENSIFY
THROUGH TAU 48 REACHING A PEAK INTENSITY OF 50 KNOTS PRIOR TO MAKING
LANDFALL OVER THE CENTRAL PHILIPPINES. BEYOND TAU 48, THE SYSTEM
WILL WEAKEN AS IT MOVES ACROSS THE PHILIPPINE ISLANDS AND INTERACTS
WITH THE NORTHEASTERLY SURGE EVENT. THE DYNAMIC GUIDANCE CONTINUES
TO COME INTO BETTER AGREEMENT WITH A WESTWARD TRACK THROUGH TAU 48,
HOWEVER, THE MODELS CONTINUE TO SHOW A SIGNIFICANT DIVERGENCE
THEREAFTER AS MODELS CONTINUE TO DISAGREE IN THE STRENGTH OF THE
SYSTEM.
   C. AFTER TAU 72, TS MEKKHALA IS EXPECTED TO TRACK WEST-
NORTHWESTWARD AND WEAKEN DUE TO THE FRICTIONAL EFFECTS OF LAND,
INCREASED VWS, AND MORE STABLE AIR ASSOCIATED WITH THE PERSISTENT
NORTHEASTERLY SURGE. THE DYNAMIC MODEL GUIDANCE CONTINUES TO DIVERGE
WITH A WIDE RANGE OF SOLUTIONS AS THE JAPANESE ENSEMBLE AND EGRR
CONTINUE TO SHOW A HIGHLY UNLIKELY RE-CURVE SCENARIO AND GFDN AND
COAMPS-TC SHOW A WEAKER SYSTEM RESULTING IN A WEST-SOUTHWEST TRACK.
THE JTWC FORECAST TRACK HAS BEEN SHIFTED SLIGHTLY SOUTH TO FAVOR THE
GFS, GFS ENSEMBLE, ECMWF AND NAVGEM SOLUTIONS, ALL OF WHICH HAVE
COME INTO BETTER AGREEMENT. DUE TO THIS LARGE VARIATION IN MODEL
SOLUTIONS, THE CONFIDENCE IN THE JTWC FORECAST TRACK REMAINS LOW.//
NNNN
NNNN