Tropical Storm FRANCISCO Advisory jue, 17-10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (FRANCISCO ) WARNING NR
05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 26W (FRANCISCO), LOCATED APPROXIMATELY 203 NM
SOUTHWEST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-SOUTHWESTWARD AT
02 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS A INCREASINGLY CONSOLIDATED SYSTEM WITH DEEP
CONVECTIVE BANDING WRAPPING AROUND A RAGGED EYE FEATURE. A 170004Z
AMSU-B MICROWAVE IMAGE SHOWS A CONTINUED IMPROVEMENT IN STRUCTURE AS
A MICROWAVE EYE FEATURE CONTINUES TO PERSIST AND DEEP CONVECTIVE
BANDING HAS IMPROVED. THE INITIAL POSITION IS BASED ON THE MSI LOOP
AND THE AFOREMENTIONED MICROWAVE IMAGE WITH GOOD CONFIDENCE. THE
INITIAL INTENSITY HAS BEEN INCREASED TO 70 KNOTS WHICH IS SLIGHTLY
HIGHER THAN A SUBJECTIVE DVORAK INTENSITY ESTIMATE FROM PGTW OF 65
KNOTS TO SHOW THE CONTINUED INCREASE IN STRUCTURE SEEN IN THE
SATELLITE IMAGERY AND IS FURTHER SUPPORTED BY OBJECTIVE INTENSITY
ESTIMATES THAT SUGGEST THIS IS A 75 KNOT SYSTEM. UPPER-LEVEL
ANALYSIS INDICATES A POINT SOURCE REMAINS OVER THE SYSTEM WHICH
IS CREATING A FAVORABLE ENVIRONMENT WITH ROBUST RADIAL OUTFLOW AND
LOW (05-10 KNOTS) VERTICAL WIND SHEAR (VWS). TY FRANCISCO IS
CURRENTLY IN A WEAK STEERING ENVIRONMENT AS THE SYSTEM IS DISPLACED
WELL TO THE SOUTH OF THE STR.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 26W IS EXPECTED TO REMAIN IN THIS WEAK STEERING
ENVIRONMENT THROUGH THE NEXT 12 HOURS AS THE SYSTEM CONSOLIDATES
SOUTH OF THE STR. AFTER TAU 12, THE STR IS EXPECTED TO BUILD AND
MODIFY, WHICH WILL FORCE TY 26W TO TURN POLEWARD THROUGH TAU 48.
AFTER TAU 48, THE STR WILL CONTINUE TO BUILD SOUTH OF JAPAN AND
STEER TY 26W TO A MORE NORTHWESTWARD TRACK. EXTREMELY FAVORABLE
ENVIRONMENTAL CONDITIONS OF LOW VWS, WARM SEA SURFACE TEMPERATURES,
AND GOOD OUTFLOW WITH AN EXPECTED FURTHER INCREASE IN POLEWARD
OUTFLOW, WILL ALLOW FOR TY 26W TO REACH OF PEAK INTENSITY OF 125
KNOTS BY TAU 72.
   C. AFTER TAU 72, TY 26W WILL CONTINUE TO TRACK TO THE NORTHWEST
ALONG THE SOUTHWESTERN PERIPHERY OF THE STR. SLOW WEAKENING IS
EXPECTED AS THE SYSTEM BEGINS TO TRACK ALONG COOLER SEA SURFACE
TEMPERATURES TO THE SOUTH OF JAPAN. THE NUMERIC MODEL GUIDANCE IS IN
GOOD AGREEMENT WITH ONLY SLIGHT VARIANCES IN TRACK AND TRANSLATIONAL
SPEED THROUGH TAU 72 ALTHOUGH, THERE HAS BEEN AN INCREASED SPREAD
AFTERWARDS, AS SOLUTIONS HAVE DIVERGED IN THE EXTENT ON THE
NORTHWEST TRACK TOWARDS JAPAN. THE JTWC TRACK FORECAST IS LAID CLOSE
TO THE MULTI-MODEL CONSENSUS WITH LOW CONFIDENCE DUE TO THE CURRENT
WEAK STEERING ENVIRONMENT AND THE SPREAD IN SOLUTIONS IN THE
EXTENDED TAUS.//
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