![Image](http://i.imgur.com/uTZdD1L.jpg)
WDPN31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (NORU) WARNING NR 19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 07W (NORU), LOCATED APPROXIMATELY 231 NM EAST-
NORTHEAST OF MINAMI TORI SHIMA, HAS TRACKED EAST-NORTHEASTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS SPIRAL BANDING WRAPPING INTO A 17 NM RAGGED EYE,
HOWEVER, THE CONVECTIVE CORE HAS SIGNIFICANTLY SHALLOWED OVER THE
PAST FEW HOURS. ANIMATED WATER VAPOR IMAGERY REVEALS THAT AS TS 09W
(KULAP) PASSED APPROXIMATELY 400 NM DIRECTLY NORTH OF TY 07W, THE
ALIGNMENT OF NORTHERLY FLOW ALONG THE WESTERN FLANK OF BOTH SYSTEMS
ALLOWED COOL DRY AIR TO INTRUDE ALONG THE WESTERN AND SOUTHERN
PERIPHERY OF NORU. A 250717Z CORIOLIS 37 GHZ MICROWAVE PASS REVEALS
A WELL DEFINED MICROWAVE EYE AND ASYMMETRIC DEEP CONVECTION LARGELY
TO THE WEST OF THE EYE. AT THE INTERMEDIATE FIX TIME, DVORAK
ESTIMATES WERE BACK UP TO T5.0 (90 KNOTS), SO THE INITIAL INTENSITY
IS ASSESSED AT 85 KNOTS GIVEN THE RECENT DEGRADATION OF CONVECTION.
TY 07W IS CURRENTLY LOCATED APPOXIMATELY 400 NM SOUTH OF TS 09W AND
THE TWO SYSTEMS ARE UNDERGOING BINARY INTERACTION. TY 07W IS UNDER
THE PRIMARY STEERING INFLUENCE OF A NEAR EQUATORIAL RIDGE (NER) TO
THE SOUTH BUT HAS STARTED TO MAKE THE TURN TO THE NORTHEAST AS
RIDGING BUILDS IN TO THE EAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE, HOWEVER, FORECAST INTENSITIES HAVE
BEEN LOWERED DUE TO THE CURRENTLY ANALYZED DEGRADED ENVIRONMENTAL
CONDITIONS.
B. OVER THE NEXT 12-24 HOURS, TY 07W WILL TURN TO THE NORTH AND
THEN NORTHWESTWARD TO WESTWARD AS A RIDGE TO THE NORTH TAKES
OVER AS THE PRIMARY STEERING MECHANISM. DYNAMICAL MODEL GUIDANCE
REMAINS IN GOOD AGREEMENT THROUGH TAU 72, WITH SOME MINOR
DIFFERENCES IN THE TIMING AND SPEED OF THE TURN BACK TO THE WEST-
NORTHWEST. THE FORECAST TRACK IS CONSISTENT WITH THE PREVIOUS JTWC
FORECAST. THE INTENSITY HAS LIKELY PEAKED, AND A WEAKENING TREND IS
EXPECTED DUE TO THE COMBINED EFFECTS OF THE COOL-DRY AIR
ENTRAINMENT, MODERATE (20 KNOTS) VERTICAL WIND SHEAR (VWS) AND
WANING SEA SURFACE TEMPERATURES (SSTS) AS TY 07W LOOPS OVER ITS
PREVIOUS TRACK WITH COOLER UPWELLED WATERS.
C. IN THE EXTENDED FORECAST PERIOD, TY 07W IS FORECAST TO
CONTINUE TRACKING IN A CYCLONIC LOOP, AS A SUBTROPICAL RIDGE BECOMES
FIRMLY ENTRENCHED OVER SOUTHERN JAPAN, RESULTING IN ANOTHER TURN
TOWARDS THE SOUTHWEST. AS TY 07W BEGINS TO TRACK SOUTHWESTWARD, IT
SHOULD GRADUALLY RETURN TO A MORE FAVORABLE ENVIRONMENT WITH WARMER
SSTS AND IMPROVING MID-LEVEL RELATIVE HUMIDITY, ALLOWING FOR
POTENTIAL RE-INTENSIFICATION TO BEGIN. DUE TO THE COMPLEX STEERING
ENVIRONMENT AND BINARY INTERACTION WITH TS 09W, THERE IS LOW
CONFIDENCE IN THE JTWC FORECAST.//
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