Tropical Storm FITOW Advisory Tue Oct 01

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (FITOW)
WARNING NR 04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 22W (FITOW), LOCATED APPROXIMATELY 627 NM EAST OF
MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 05 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
CONFIRMS THE CONVECTION IS CONSOLIDATING AND DEEPENING AROUND THE
LOW-LEVEL CIRCULATION CENTER (LLCC), ESPECIALLY ALONG THE WESTERN
SEMICIRCLE. VIGOROUS CONVECTION NOW EXISTS IN ALL QUADRANTS, WITH
THE EXCEPTION OF A DWINDLING BREAK OVER THE NORTHEASTERN QUADRANT.
HOWEVER, THE LLCC IS ALMOST FULLY EXPOSED AS THE INNER BANDING HAS
YET TO CONSOLIDATE OVER THE CORE. THE LATEST AMSU RADIAL CROSS
SECTION DOES CONFIRM THE PRESENCE OF A POSITIVE TWO-CELSIUS WARM
ANOMALY. RECENT ANIMATED WATER VAPOR IMAGERY INDICATES THAT THE
STORM IS STILL STRUGGLING AGAINST A SUBSIDENT ENVIRONMENT ON THE
POLEWARD FLANK. EQUATORWARD OUTFLOW REMAINS WELL ESTABLISHED AND
THE EAST-NORTHEASTWARD VENTING HAS IMPROVED DURING THE PAST SIX
HOURS. THE CURRENT INTENSITY IS BASED ON AN AVERAGE OF DVORAK
ASSESSMENTS BETWEEN PGTW AND RJTD. EXPECTED NORTHWARD MOVEMENT HAS
YET TO MANIFEST, PRESUMABLY DUE TO STRONGER-THAN-EXPECTED STRENGTH
OF THE NEAR-EQUATORIAL RIDGE (NER). BUT THE LAST TWO FIXES HAVE
SHOWN THE NORTHWESTWARD TRAJECTORY SLOWING. THE SOUTHWESTERN
EXTENSION OF THE NER IS THE STEERING FORCE ON THE STORM. THE
SUBTROPICAL RIDGE, WHICH IS ANCHORED IN AN ANTICYCLONE JUST TO THE
SOUTHWEST OF TAIWAN, IS PRODUCING SOME SHEAR TO THE NORTHWEST OF THE
STORM BUT IS NOT ACTING AS A STEERING INFLUENCE YET.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 22W WILL GRADUALLY TURN MORE POLEWARD DURING THE NEXT 72
HOURS DUE TO A PUSH FROM THE NER. BIFURCATED TRACK GUIDANCE IS
STRADDLING OKINAWA. NAVGEM, GFDN, AND THE JAPANESE ENSEMBLE SHOW A
TRACK SOUTH OF OKINAWA. CONSENSUS INDICATES A TRACK BETWEEN OKINAWA
AND ANAMI SHIMA, WHILE ECMWF AND COAMPS-TC SHOW A TRACK TOWARDS THE
KYUSHU AND SHIKOKU AREA. THERE EXISTS A WIDE WEAKNESS IN THE STR
BETWEEN THE 130TH AND 135TH MERIDIANS THAT WILL COUPLE WITH A GENTLE
PUSH FROM THE NER AND THE BETA FORCE TO NUDGE THE STORM POLEWARD
OVER THE NEAR TERM. THE POLEWARD TRACK WILL TAKE THE STORM THROUGH
AN AREA OF LOW VERTICAL WIND SHEAR (VWS) AND IMPROVING POLEWARD
OUTFLOW, THUS THE INTENSITY FORECAST LOOKS FOR DEVELOPMENT ON THE
HIGH-SIDE OF THE CLIMATOLOGICAL RATE. OCEAN HEAT CONTENT PROFILES DO
SHOW SOME LIMITATIONS, AND ALTHOUGH THE UPPER-LEVEL SUBSIDENCE
POLEWARD OF THE STORM IS EASING, IT IS STILL SIGNIFICANT ENOUGH THAT
A RAPID INTENSIFICATION SCENARIO IS LOOKING INCREASINGLY UNLIKELY.
   C. AFTER TAU 72 AND NEAR THE 23RD LATITUDE, THE STEERING FORCE
WILL SHIFT FROM THE NER TO THE STR. MODEL GUIDANCE, INCLUDING
ENSEMBLES AND MULTI-MODEL CONSENSUS ARE IN POOR AGREEMENT AS TO
EXACTLY WHEN AND WHERE THE STEERING INFLUENCE SWITCHES, AS WELL AS
TO HOW FIRM THE WESTWARD PUSH WILL BE ONCE THE HAND-OFF DOES OCCUR.
THE INTENSITY FORECAST STAYS ON THE HIGH SIDE OF GUIDANCE BASED ON
THE LOW VWS ENVIRONMENT ALONG THE TRACK, BUT AS THE STORM MOVES
NORTH OF THE 30TH LATITUDE, RISING VWS AND FALLING SEA SURFACE
TEMPERATURES WILL COMBINE TO INITIATE A WEAKENING TREND. CONSENSUS
HAS STABILIZED OVER THE PAST TWO MODEL RUNS BUT TRACK GUIDANCE
REMAINS BIFURCATED. THE JTWC TRACK FORECAST STAYS EAST OF CONSENSUS
DUE TO THE UNDUE WESTWARD INFLUENCE PROVIDED BY EGRR, NAVGEM, GFDN,
AND THE JAPANESE ENSEMBLE, AND FAVORS THE ECMWF, GFS, AND COAMPS
SOLUTIONS. THERE IS HIGH CONFIDENCE IN THE TRACK FORECAST THROUGH
TAU 72 AND LOW CONFIDENCE THEREAFTER. TRACK CONFIDENCE WILL NOT
LIKELY IMPROVE GREATLY UNTIL THE HAND-OFF BETWEEN THE STEERING
MECHANISM PLAYS OUT.//
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