Tropical Storm MALAKAS Advisory 14 Σεπ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (MALAKAS) WARNING
NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 18W (MALAKAS), LOCATED APPROXIMATELY 387 NM
NORTH-NORTHWEST OF YAP, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY REVEALS
THAT ALTHOUGH THE STORM STRUCTURE CONTINUES TO STRUGGLE DUE TO THE
OUTFLOW OF STY 16W, THE CONVECTION HAS DEEPENED AND WRAPPED TIGHTER
INTO THE LOW LEVEL CIRCULATION CENTER (LLCC). A 131847Z SSMIS 91GHZ
MICROWAVE IMAGE DEPICTS DEEP CONVECTIVE BANDING WRAPPING INTO THE
MICROWAVE EYE FROM THE SOUTHERN PERIPHERY. THE CURRENT POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE EYE IN THE SSMIS
IMAGE AND IS SUPPORTED BY A SATELLITE FIX CLUSTER FROM PGTW AND
RJTD. THE INITIAL INTENSITY HAS BEEN INCREASED TO 60 KNOTS BASED ON
AN ASSESSMENT OF DVORAK INTENSITY ESTIMATES OF T3.5 TO T4.0 (55-65
KNOTS) AND RECENT SATCON INTENSITY TRENDS. ENVIRONMENTAL PARAMETERS
REMAIN MARGINAL DUE TO THE NEGATIVE IMPACTS FROM THE OUTFLOW FROM
STY 16W INCLUDING MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS)
AND CONVERGENCE OVER THE NORTHERN PORTION OF THE CYCLONE. HOWEVER,
WATER VAPOR IMAGERY SHOWS A SLIGHT EXPANSION OF MOISTURE TO THE
NORTH INDICATING THAT THE IMPACTS OF STY 16W MAY BE REDUCING. SEA
SURFACE TEMPERATURES (SSTS) REMAIN FAVORABLE NEAR 29 CELSIUS. TS 18W
IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 18W WILL TRACK WEST-NORTHWESTWARD THEN NORTHWESTWARD
THROUGH TAU 72. WITH THE NEGATIVE IMPACTS OF STY 16W REDUCING, TS
MALAKAS WILL BEGIN TO RAPIDLY INTENSIFY IN THE NEXT 12 HOURS AS
ENVIRONMENTAL CONDITIONS BECOME INCREASINGLY MORE FAVORABLE. DYNAMIC
MODEL GUIDANCE IS IN PRETTY GOOD AGREEMENT WITH THE FORECAST TRACK
UP TO TAU 36. AFTERWARDS, THE MODELS BEGIN TO SPREAD REGARDING THE
TIMING AND DEGREE OF THE RECURVE. HOWEVER, THE CONSENSUS TREND OVER
THE PAST 24 HOURS HAS CONTINUED TO SHIFT THE TRACK TO THE WEST,
CLOSER TO TAIWAN.
   C. IN THE EXTENDED FORECAST, TS 18W WILL REACH THE WESTERN EXTENT
OF THE STEERING STR AND TURN NORTHEASTWARD INTO THE STRONG MID-
LATITUDE WESTERLIES, MAKING LANDFALL IN KYUSHU JUST AFTER TAU 96.
STRONG VWS WILL GRADUALLY WEAKEN THE CYCLONE AS IT ACCELERATES
NORTHEASTWARD. DYNAMIC MODEL GUIDANCE IMPROVES IN THE EXTENDED
FORECAST DUE TO THE SETUP OF THE ZONAL MID-LATITUDE WESTERLIES WITH
ONLY DIFFERENCES IN THE FORWARD SPEED OF THE CYCLONE. HOWEVER, DUE
TO THE LARGE SPREAD DURING THE RECURVE PHASE AND THE CHANGES IN THE
MODEL TREND, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.//
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