Tropical Storm NANGKA Advisory Mon Jul 06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (NANGKA) WARNING NR 13//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (NANGKA), LOCATED APPROXIMATELY 242 NM NORTHWEST
OF UJELANG, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS OVER THE PAST
SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT ENHANCED IR (EIR)
IMAGERY SHOWING A 25 NM EYE WITH GOOD CONFIDENCE. THE INTENSITY HAS
BEEN RAISED TO 80 KNOTS AS THE DVORAK INTENSITY ESTIMATES FROM ALL
AGENCIES HAVE RISEN WITH PGTW AND RJTD AT 4.5 AND KNES AT 5.0. WHILE
THE EIR LOOP AND A 061043Z AMSU-B MICROWAVE IMAGE SHOW SOME
WEAKENING ON THE WESTERN SIDE OF THE LLCC, UPPER-LEVEL ANALYSIS
SHOWS ALMOST RADIAL OUTFLOW AND LOW TO MODERATE VWS. IT SHOULD BE
NOTED THAT THE VWS IS NORTHWESTERLY, WHICH COULD BE CAUSING THE
PRESSURE ON THE WESTERN SIDE OF THE SYSTEM. TY 11W IS CURRENTLY
TRACKING ON 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 EXTENSION THROUGH TAU 72. THE UPPER LEVEL
ENVIRONMENT WILL REMAIN FAVORABLE OVER THE NEXT 48 HOURS, WITH TY
NANGKA PEAKING AT 110 KNOTS BY TAU 48. BEYOND THAT, EXPECT THE
SYSTEM TO MAINTAIN ITS PEAK INTENSITY AS LOWER OHC AND SOME INCREASE
IN VWS OFFSETS VERY GOOD OUTFLOW DUE TO THE PRESENCE OF A MID-
LATITUDE TROUGH APPROACHING FROM THE WEST.
   C. BEYOND TAU 72, TY 11W WILL SLOW AS THE AFOREMENTIONED MID-
LATITUDE TROUGH WEAKENS THE STR EXTENSION, CREATING A WEAKER
STEERING ENVIRONMENT. INTENSIFICATION WILL BE MARGINAL, IF ANY, AS
THE SSTS AND OHC VALUES DECREASE POLEWARD OF 19 NORTH AND THERE IS
SOME INCREASE IN VWS. THESE WILL BE OFFSET BY GOOD POLEWARD OUTFLOW.
NUMERICAL MODEL GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH TAU 72
WITH THE CURRENT TRACK FORECAST LAID CLOSE TO THE MULTI-MODEL
CONSENSUS. AS SUCH, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST
TRACK.//
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