Tropical Storm MALAKAS Advisory Tue Sep 13

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (MALAKAS) WARNING
NR 06//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 18W (MALAKAS), LOCATED APPROXIMATELY 289 NM
NORTH OF YAP, HAS TRACKED WESTWARD AT 12 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS SOME
IMPROVED ORGANIZATION AND STRENGTHENING IN THE CONVECTIVE STRUCTURE.
A 130111Z GPM 89GHZ MICROWAVE IMAGE SHOWS DEEP CONVECTIVE BANDING
WRAPPING INTO AN IMPROVED LOW LEVEL CIRCULATION CENTER (LLCC). THE
CURRENT POSITION IS BASED ON THE LLCC IN THE GPM IMAGE WITH GOOD
CONFIDENCE. THE INTENSITY HAS BEEN INCREASED BASED ON THE IMPROVED
STRUCTURE OF ALL IMAGERY AND IS SUPPORTED BY A DVORAK INTENSITY
ESTIMATE OF T3.0 (45 KNOTS) FROM PGTW. ENVIRONMENTAL ANALYSIS
REVEALS A MARGINAL ENVIRONMENT DUE TO THE NEGATIVE IMPACTS OF THE
OUTFLOW FROM STY 16W PRODUCING MODERATE (15-20 KNOTS) VWS AND
RESTRICTED 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.
   B. TS 18W IS FORECAST TO TRACK WEST-NORTHWESTWARD THEN
NORTHWESTWARD THROUGH TAU 72. 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 OF TS 18W AS THE VWS DECREASES AND THE OUTFLOW
GREATLY IMPROVES. DYNAMIC MODEL GUIDANCE IS IN BETTER AGREEMENT
DURING THIS PORTION OF THE FORECAST WITH THE BULK OF GUIDANCE
SUPPORTING THE CURRENT TRACK. EGRR IS AN OUTLIER TO THE WEST TAKING
THE CYCLONE OVER TAIWAN. GFS AND ITS ENSEMBLE CONTINUE TO SHOW AN
EARLIER RECURVE TO THE EAST OF THE CURRENT TRACK.
   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
SHOWING MULTIPLE SOLUTIONS, ESPECIALLY AFTER TAU 48, THERE IS LOW
CONFIDENCE IN THE JTWC TRACK FORECAST.//
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