WDPN31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (NORU) WARNING NR
51//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON 07W (NORU), LOCATED APPROXIMATELY 300 NM WEST-NORTHWEST
OF IWO TO, HAS TRACKED NORTHWESTWARD AT 06 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A
SYMMETRIC BAND OF CONVECTION THAT COMPLETELY SURROUNDS A WELL
DEFINED EYE FEATURE. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE EYE FEATURE. A 020626Z SSMIS 91 GHZ
MICROWAVE IMAGE SUPPORTS THE INITIAL POSITION AND SHOWS THAT THE
BAND OF CONVECTION IS STRONGEST IN THE SOUTHERN SEMI-CIRCLE. THE
INITIAL INTENSITY OF 100 KNOTS IS HEDGED ABOVE MULTIAGENCY DVORAK
ESTIMATES RANGING FROM T4.5 TO T5.0 (77 TO 90 KNOTS) FROM PGTW AND
RJTD RESPECTIVELY. ENVIRONMENTAL ANALYSIS SHOWS THAT THE SYSTEM IS
LOCATED IN AN AREA OF LOW (5 TO 10 KNOTS) VERTICAL WIND SHEAR (VWS)
AND HIGH SEA SURFACE TEMPERATURES (SSTS) (30 CELSIUS). RADIAL
OUTFLOW CONTINUES, THE RESULT OF A STRONG POINT SOURCE LOCATED OVER
THE SYSTEM. TYPHOON NORU IS TRACKING NORTHWESTWARD ALONG THE
NORTHWESTERN BOUNDARY OF A NEAR-EQUATORIAL RIDGE (NER) TO THE
SOUTHEAST AND TOWARDS A WEAK AREA IN THE SUBTROPICAL RIDGE (STR) TO
THE NORTHWEST, THE RESULT OF A PASSING MID-LATITUDE TROUGH.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST TRACK PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 07W IS FORECAST TO TRACK NORTHWESTWARD TOWARDS THE WEAKNESS
IN THE STR TO THE NORTHWEST AS THE NER BUILDS TO THE SOUTHEAST. THE
TRACK IS FORECAST TO BECOME MORE WESTWARD AFTER TAU 24 AS THE
SUBTROPICAL RIDGE LOCATED TO THE NORTHWEST TRANSITS TO THE NORTH OF
THE SYSTEM. FROM TAU 24 TO TAU 72 TYPHOON NORU WILL TRACK WEST-
NORTHWEST ALONG THE SOUTHERN PERIPHERY OF THE STR. TY 07W IS
FORECAST TO GRADUALLY AND SLIGHTLY WEAKEN THROUGH THE NEXT 36 HOURS
AS THE SYSTEM SLOWLY TRACKS THROUGH AN AREA OF LOW OCEAN HEAT
CONTENT. AFTER TAU 36, THE SYSTEM WILL BEGIN A GRADUAL
INTENSIFICATION AS IT TRACKS OVER THE VERY WARM WATERS AROUND
COASTAL JAPAN. DYNAMIC MODEL GUIDANCE IS IN STRONG AGREEMENT ON
SYSTEM TRACK THROUGH TAU 72 LENDING HIGH CONFIDENCE IN THIS PORTION
OF THE JTWC TRACK FORECAST.
C. AFTER TAU 72, THE RIDGE LOCATED TO THE NORTH OF TYPHOON NORU
BEGINS TO MOVE TO THE EAST AND A MID-LATITUDE TROUGH MOVES IN FROM
THE NORTHWEST. THE SYSTEM WILL SLIGHTLY INTENSIFY AROUND TAU 72, THE
RESULT OF A GENERALLY FAVORABLE ENVIRONMENT AND TRACKING INTO THE
WARM WATERS (31 CELSIUS) AROUND COASTAL JAPAN. AFTER TAU 72 THE
SYSTEM WILL AGAIN BEGIN TO WEAKEN AS IT INTERACTS WITH TERRAIN.
DYNAMIC MODEL GUIDANCE GENERALLY AGREES ON THE TRACK DIRECTION WITH
THE EXCEPTION OF NAVGEM WHICH TURNS THE SYSTEM BACK TO THE EAST
AFTER TAU 72. THE REMAINING MODELS ALL TURN THE SYSTEM TO THE NORTH
AFTER TAU 72 WITH SOME VARIATION IN THE TIMING AND SHARPNESS OF THE
TURN. THE SPREAD IN DYNAMIC MODEL GUIDANCE AROUND THE TURN TO THE
NORTH LENDS LOW CONFIDENCE IN THIS PORTION OF THE JTWC TRACK
FORECAST.//
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