Tropical Storm NANGKA Advisory Tue Jul 07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (NANGKA) WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (NANGKA), LOCATED APPROXIMATELY 181 NM NORTHWEST
OF UJELANG, HAS TRACKED WESTWARD AT 11 KNOTS OVER THE PAST SIX
HOURS. THE CURRENT POSITION IS BASED ON RECENT MULTISPECTRAL
SATELLITE IMAGERY SHOWING A 15 NM EYE WITH HIGH CONFIDENCE. THE
INTENSITY HAS BEEN RAISED TO 70 KNOTS AS THE STRUCTURE HAS IMPROVED
AS SHOWN IN A 060658Z SSMIS PASS SHOWING VERY GOOD BANDING WRAPPING
INTO THE LLCC AND DEEP CONVECTION AS WELL AS A PGTW FIX OF 4.0 WITH
A DT OF 4.5. THE INTENSIFICATION OF THE SYSTEM IS PARTIALLY DUE TO
THE CONDUCIVE UPPER-LEVEL ENVIRONMENT WITH LOW TO MODERATE (15
KNOTS) VWS AND GOOD RADIAL OUTFLOW. TY 11W IS TRACKING ALONG THE
SOUTHWESTERN PERIPHERY OF A STR.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 11W WILL CONTINUE TRACKING TO THE NORTHWEST UNDER THE
INFLUENCE OF THE STR. AS THE RIDGE BACKS TO THE EAST, AN EXTENSION
WILL REMAIN THROUGH TAU 72, KEEPING TY NANGKA ON ITS NORTHWEST
TRACK. THE UPPER LEVEL ENVIRONMENT WILL REMAIN FAVORABLE OVER THE
NEXT 36 HOURS, WITH POTENTIAL FOR NEAR RI INCREASE IN INTENSITY.
BEYOND THAT, EXPECT STEADY GROWTH IN THE TYPHOONS INTENSITY AS IT
NEARS THE MARIANA ISLAND CHAIN.
   C. BEYOND TAU 72, TY 11W IS EXPECTED TO SLOW ITS TRACK SPEED AS A
MID-LATITUDE TROUGH WEAKENS THE STR EXTENSION, CREATING A WEAKER
STEERING ENVIRONMENT. INTENSIFICATION IN THE EXTENDED FORECAST
PERIOD WILL CONTINUE, ALTHOUGH AT A SLIGHTLY SLOWER RATE AS SSTS
BEGIN TO DROP. DYNAMIC MODEL GUIDANCE REMAINS IN GENERALLY GOOD
AGREEMENT REGARDING THE FORECAST TRACK WITH THE CURRENT TRACK
FORECAST LAID CLOSE TO THE MULTI-MODEL CONSENSUS.//
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