
North of Miyako and a potential recurving typhoon for Shanghai?

WDPN31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (CHAN-HOM) WARNING NR 36//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 09W (CHAN-HOM), LOCATED APPROXIMATELY 197 NM SOUTH-
SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 13 KNOTS OVER
THE PAST SIX HOURS. AS DEPICTED IN IR SATELLITE IMAGERY AND
MICROWAVE IMAGERY,
TY 09W REMAINS A LARGE SYSTEM WITH A RADIUS OF
APPROXIMATELY 240 NM, THEREFORE, GALE-FORCE WINDS ASSOCIATED WITH
THE SYSTEM'S TIGHT OUTER GRADIENT CURRENTLY EXTEND OVER OKINAWA WITH
STORM-FORCE WINDS EXTENDING ABOUT 120 NM FROM THE CENTER. A 090758Z
SSMIS IMAGE SHOWS CONVECTIVE BANDING ALONG 26N WITH MORE INTENSE
CONVECTIVE BANDING ALONG 25N WRAPPING TIGHTLY INTO THE EYEWALL.
ANIMATED IR IMAGERY REVEALS A RAGGED 38-NM EYE, THEREFORE, THERE IS
GOOD CONFIDENCE IN THE CURRENT POSITION. IR IMAGERY INDICATES A
SLIGHT WOBBLE, HOWEVER, THE SYSTEM HAS MAINTAINED A STEADY
NORTHWESTWARD TRACK. THE CURRENT INTENSITY IS ASSESSED AT 90 KNOTS
BASED ON CURRENT INTENSITY ESTIMATES OF T5.0 (90 KNOTS) FROM BOTH
PGTW AND RJTD. UPPER-LEVEL ANALYSIS INDICATES LOW TO MODERATE (10 TO
20) VWS BEING OFFSET BY NEAR-RADIAL OUTFLOW. TY 09W IS TRACKING
ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP-LAYERED STR TO THE
NORTH.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE. HOWEVER, THE 34-KNOT AND 50-KNOT WIND
RADII HAVE BEEN EXPANDED SIGNIFICANTLY BASED ON SURFACE OBSERVATIONS
AND RECENT SCATTEROMETER DATA.
B. TY 09W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD UNDER
THE STEERING INFLUENCE OF THE STR THROUGH TAU 36. WITH THE EXCEPTION
OF GFDN, DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT. TY CHAN-HOM WILL
STEADILY INTENSIFY THROUGH TAU 36 WITH A PEAK INTENSITY OF 115
KNOTS. AFTER TAU 36, TY CHAN-HOM SHOULD BEGIN TO TRACK POLEWARD
ALONG THE WESTERN PERIPHERY OF A POLEWARD-ORIENTED STR, WHICH WILL
RE-ORIENT IN RESPONSE TO AN APPROACHING SUBTROPICAL TROUGH. TY 09W
WILL WEAKEN SIGNIFICANTLY AS IT TRACKS OVER EASTERN CHINA. DYNAMIC
GUIDANCE DIVERGES WITH NAVGEM, COAMPS-TC AND GFDN TRACKING THE
SYSTEM WESTWARD. THE REMAINDER OF THE GUIDANCE IS IN GOOD AGREEMENT
WITH A NORTHWARD TO NORTHEASTWARD TRACK INTO THE WEST SEA.
C. IN THE EXTENDED TAUS, THE APPROACHING MID-LATITUDE TROUGH WILL
PASS TO THE NORTHEAST, CAUSING A BREAK IN THE STR AND ALLOWING TY
09W TO TURN NORTHEASTWARD AS THE STR RE-ORIENTS. TY 09W IS FORECAST
TO CONTINUE TO DECAY AS IT INTERACTS WITH THE SUBTROPICAL TROUGH. AT
THIS TIME, THERE IS NO EVIDENCE OF EXTRA-TROPICAL TRANSITION DUE TO
THE LACK OF A DYNAMIC TROUGH AND BAROCLINIC ZONE. DUE TO THE SPREAD
IN DYNAMIC GUIDANCE, THERE IS LOW OVERALL CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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