Tropical Storm FRANCISCO Advisory 19.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 26W (FRANCISCO) WARNING
NR 13//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON 26W (FRANCISCO), LOCATED APPROXIMATELY 936 NM
SOUTHEAST OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 07
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS A HIGHLY SYMMETRICAL EYE FEATURE SURROUNDED BY
AN EXTENSIVE DEEP CONVECTIVE EYEWALL AND A STRONG FEEDER BAND
TIGHTLY WRAPPING ACROSS THE WESTERN PERIPHERY OF THE SYSTEM AND INTO
THE STORM CENTER. AN 182238Z SSMIS MICROWAVE IMAGE REVEALS THE
SYSTEM HAS MAINTAINED EXTENSIVE DEEP CONVECTION WITHIN THE EYEWALL
AND THE MAIN FEEDER BAND. HOWEVER, THE IMAGE DOES INDICATE THE
SOUTHEAST QUADRANT OF THE EYEWALL APPEARS TO HAVE SLIGHTLY WEAKENED
AND MAY BE A PRELUDE TO THE BEGINNING OF AN EYEWALL REPLACEMENT
CYCLE (ERC). THE CURRENT POSITION IS BASED ON THE MSI AND THE
AFOREMENTIONED MICROWAVE IMAGE WITH HIGH CONFIDENCE. THE CURRENT
INTENSITY HAS BEEN MAINTAINED AT 135 KNOTS BASED ON CONGRUENT DVORAK
ESTIMATES FROM PGTW AND KNES AS WELL AS A 134 KNOT CIMSS SATCON
ESTIMATE. UPPER-LEVEL ANALYSIS INDICATES A POINT SOURCE ANTICYCLONE
REMAINS OVER THE SYSTEM, PROVIDING AMPLE RADIAL OUTFLOW AND LOW (05-
10 KNOTS) VERTICAL WIND SHEAR (VWS). THE 14 NM EYE REMAINS CLOUD-
FREE AND HAS MAINTAINED A FAIRLY SYMMETRIC ORIENTATION AS THE SYSTEM
TRACKS GENERALLY TO THE NORTHWEST UNDER THE INFLUENCE OF THE
SUBTROPICAL RIDGE (STR) EXTENSION.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING.
   B. THROUGH TAU 72, STY 26W IS EXPECTED TO SLOWLY TRACK
NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR LOCATED WELL
TO THE NORTH OF GUAM. FAVORABLE ENVIRONMENTAL CONDITIONS OF LOW VWS,
WARM SEA SURFACE TEMPERATURES (SSTS), AND AMPLE OUTFLOW WILL ALLOW
STY 26W TO INTENSIFY TO A MAXIMUM OF 140 KNOTS BY TAU 12. ALONG THE
FORECAST TRACK, ERCS HAVE THE POTENTIAL TO BRIEFLY WEAKEN THE SYSTEM
AS AN EXPANDED EYEWALL REPLACES THE SMALLER INNER EYEWALL. THIS IS
USUALLY FOLLOWED BY A SLIGHT RE-INTENSIFICATION AS THE NEW OUTER
EYEWALL CONSOLIDATES. AFTER TAU 24, THE SYSTEM WILL START TO MOVE
INTO LESS FAVORABLE SSTS, WHICH WILL IMPACT THE LOW LEVEL INFLOW,
CAUSING A SLOW WEAKENING TREND TO BEGIN AND PERSIST THROUGH TAU 72.
HOWEVER, AS THE SYSTEM CONTINUES FURTHER TO THE NORTH, A STRONG
POLEWARD OUTFLOW CHANNEL MAY DEVELOP WHICH COULD HELP TO OFFSET THE
COOLER SSTS AND MAINTAIN HIGHER INTENSITIES.
   C. AFTER TAU 72, STY 26W WILL BEGIN TO ROUND THE WESTERN
PERIPHERY OF THE STR, ALLOWING FOR A MORE NORTH-NORTHWESTWARD TRACK.
A DECREASE IN SSTS AND AN INCREASE IN VWS WILL AMPLIFY THE WEAKENING
TREND THROUGH TAU 120 WHEN THE SYSTEM IS EXPECTED TO BEGIN EXTRA-
TROPICAL TRANSITION. NUMERIC MODEL GUIDANCE REMAINS WIDELY DIVERGENT
IN THE EXTENDED TAUS, DUE TO VARYING SOLUTIONS TO THE ORIENTATION OF
THE STR AS A SERIES OF MID-LATITUDE TROUGHS PROGRESS TO THE NORTH.
ALL OBJECTIVE AIDS, WITH THE EXCEPTION OF GFDN, ARE BEGINNING TO
INDICATE A RECURVE SCENARIO, BUT WIDELY VARY IN POSITION AND TRACK
SPEED OF THE SYSTEM. MODEL ENSEMBLES ALSO CONTINUE TO INDICATE A
WIDE RANGE OF SOLUTIONS IN ENSEMBLE MEMBERS, LEAVING CONSIDERABLE
UNCERTAINTY IN THE FORECAST TRACK AFTER TAU 72. THE CURRENT FORECAST
REMAINS CLOSE TO THE MULTI-MODEL CONSENSUS AND IS HEDGED TOWARD THE
ECMWF SOLUTION. DUE TO THE WEAKLY DEFINED STR EXTENSION, AND THE
HIGH UNCERTAINTY IN THE EXTENDED TAUS, THE CONFIDENCE IN THE
FORECAST REMAINS LOW.//
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