Tropical Storm MALAKAS Advisory 13 Σεπ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (MALAKAS) WARNING
NR 05//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 18W (MALAKAS), LOCATED APPROXIMATELY 287 NM
NORTH OF YAP, HAS TRACKED WEST-NORTHWESTWARD AT 15 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS
BUILDING CENTRAL CONVECTION SHEARED JUST SOUTH OF A CONSOLIDATING
LOW LEVEL CIRCULATION CENTER (LLCC) DUE TO MODERATE (15-20 KNOT)
NORTHERLY VERTICAL WIND SHEAR (VWS). A 121707Z SSMI 37GHZ MICROWAVE
IMAGE SHOWS A DEEP CONVECTIVE BAND WRAPPING TIGHTLY INTO THE LLCC
WHICH SUPPORTS THE CURRENT POSITION WITH GOOD CONFIDENCE. THE
INITIAL INTENSITY IS HELD AT 40 KNOTS BASED ON AN AVERAGE OF DVORAK
INTENSITY ESTIMATES RANGING FROM T2.5 TO T3.0 (35-45 KNOTS). TS
MALAKAS IS TRACKING IN A MARGINAL ENVIRONMENT DUE TO THE IMPACTS OF
THE OUTFLOW FROM STY 16W PRODUCING THE AFOREMENTIONED VWS AND
RESTRICTING POLEWARD OUTFLOW. HOWEVER, WATER VAPOR IMAGERY SHOWS A
TUTT CELL LOCATED TO THE NORTHEAST PRODUCING ENHANCED EASTERLY
OUTFLOW WHICH IS PROVIDING SUFFICIENT VENTILATION FOR THE INCREASED
CONVECTION. SEA SURFACE TEMPERATURES 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; HOWEVER, THE TRACK HAS SHIFTED
WESTWARD.
   B. TS 18W IS FORECAST TO TRACK WEST-NORTHWESTWARD THEN
NORTHWESTWARD THROUGH TAU 72. THE SHORTWAVE TROUGH APPROACHING FROM
THE WEST IS FORECAST TO FILL AND FLATTEN OUT; THEREFORE, NOT HAVING
THE DYNAMIC REQUIREMENTS TO BREAK DOWN THE STEERING RIDGE AND TURN
THE SYSTEM POLEWARD AS SOON AS PREVIOUSLY DISCUSSED. AS A RESULT THE
FORECAST TRACK HAS BEEN SHIFTED WESTWARD WHICH IS SUPPORTED BY THE
EUROPEAN AND JAPANESE MODELS. THE NAVGEM AND GFS SUITES CONTINUE TO
SHOW A SHARPER RECURVE CLOSER TO OKINAWA AND ALONG THE EASTERN COAST
OF MAINLAND JAPAN. TS MALAKAS WILL GRADUALLY INTENSIFY OVER THE NEXT
24 HOURS, BUT AT A SLOW RATE, DUE TO THE CONTINUED NEGATIVE EFFECTS
FROM THE OUTFLOW OF STY 16W. BY TAU 36, STY 16W WILL MOVE WEST OF
TAIWAN WHICH WILL ALLOW FOR INCREASED INTENSIFICATION AS THE VWS
DECREASES AND THE OUTFLOW GREATLY IMPROVES.
   C. IN THE EXTENDED FORECAST, TS 18W WILL REACH THE WESTERN EXTENT
OF THE STEERING STR AND TURN POLEWARD INTO THE MID-LATITUDE
WESTERLIES. THE STRONG ZONAL FLOW WILL RAPIDLY INCREASE THE VWS
CREATING ADVERSE EFFECTS FOR THE STORM. THE SYSTEM WILL CONTINUE TO
WEAKEN AS IT APPROACHES KYUSHU. DUE TO THE SPREAD IN MODEL GUIDANCE,
ESPECIALLY AFTER TAU 48, THERE IS LOW CONFIDENCE IN THE JTWC TRACK
FORECAST.//
NNNN
NNNN