WDPN33 PGTW 201500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (FRANCISCO) WARNING 
NR 19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 26W (FRANCISCO), LOCATED APPROXIMATELY 687 NM
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWESTWARD AT
05 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS THE EYE HAS BECOME CLOUD-FILLED AND THE DEEP
CONVECTIVE FEEDER BANDS HAVE LOOSENED SLIGHTLY. IN EFFECT, TY 26W HAS
BECOME MORE EXPANSIVE. ADDITIONALLY, THERE IS A SLIGHT ELONGATION
OCCURRING ALONG THE NORTHEAST PERIPHERY AS THE SYSTEM APPROACHES THE
STRONG MID-LATITUDE WESTERLIES. THE INITIAL POSITION IS EXTRAPOLATED
FROM A MICROWAVE EYE FEATURE ON A 200947Z TRMM PASS WITH FAIR
CONFIDENCE. THE INITIAL INTENSITY OF 125 KNOTS IS AVERAGED FROM
DVORAK ESTIMATES FROM PGTW, RJTD, AND KNES RANGING FROM 120 TO 127
KNOTS. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS 05 DEGREES SOUTH
OF THE RIDGE AXIS AND HAS MOVED INTO AN AREA OF MODERATE (20 KNOT)
VERTICAL WIND SHEAR (VWS). HOWEVER, A POLEWARD OUTFLOW CHANNEL HAS
BECOME APPARENT ON ANIMATED WATER VAPOR IMAGERY. THE CYCLONE IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE
DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING.
   B. THROUGH TAU 36, TY 26W IS EXPECTED TO CONTINUE ALONG ITS 
CURRENT TRACK UNDER THE STEERING INFLUENCE OF THE STR. AFTERWARDS, AN
EXTENSION OF THE STR IS EXPECTED TO BUILD WESTWARD AND PUSH THE TRACK
SLIGHTLY FURTHER WEST AS TY 26W BEGINS TO ROUND THE STR AXIS. THE
SYSTEM HAS BEGUN TO SLOWLY WEAKEN DUE TO COOLING SEA SURFACE
TEMPERATURES (SSTS) AND INCREASING VWS ASSOCIATED WITH THE
MID-LATITUDE WESTERLIES. HOWEVER, THE INCREASED POLEWARD OUTFLOW WILL
PARTIALLY OFFSET THE VWS AND HELP SUSTAIN THE CONVECTION, THEREBY
TEMPERING THE WEAKENING TREND.
   C. AFTER TAU 72, TY FRANCISCO WILL CREST THE STR AXIS, ALLOWING
FOR A MORE POLEWARD TRACK AND SETTING INTO A NORTHEASTWARD
RECURVATURE TOWARD EASTERN JAPAN. COOLING SSTS AND FURTHER INCREASE
IN VWS WILL AMPLIFY THE WEAKENING TREND. BY TAU 96 THROUGH TAU 120,
THE SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION. NUMERIC MODEL
GUIDANCE REMAINS WIDELY SPREAD IN THE EXTENDED TAUS DUE TO VARYING
SOLUTIONS TO THE ORIENTATION AND STRENGTH OF THE STR. ALL OBJECTIVE
AIDS INDICATE SOME DEGREE OF A RECURVE SCENARIO, BUT WIDELY VARY IN
THE TIGHTNESS OF THE TURN AS WELL AS TRACK SPEED. THE CURRENT
FORECAST REMAINS CLOSE TO THE MULTI-MODEL CONSENSUS AND IS BIASED
TOWARDS THE ECMWF SOLUTION. DUE TO THE HIGH UNCERTAINTY IN THE
STEERING MECHANISM AT THE EXTENDED TAUS, THE CONFIDENCE IN THE
FORECAST REMAINS LOW.  //
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