Tropical Storm PHANFONE Advisory Thu Oct 02

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (PHANFONE) WARNING NR 14//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 18W (PHANFONE), LOCATED APPROXIMATELY 343 NM SOUTH-
SOUTHWEST OF IWO TO, HAS TRACKED WEST-NORTHWESTWARD AT 14 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL (MSI) AND ENHANCED
INFRARED (EIR) SATELLITE IMAGERY REVEALS TY 19W HAS STARTED TO
RAPIDLY INTENSIFY AS A SMALL EYE FEATURE HAS DEVELOPED WHILE
CONVECTIVE BANDING HAS INCREASED IN ALL QUADRANTS. A 012218Z SSMIS
MICROWAVE IMAGE ADDITIONALLY DEPICTS A SMALL (APPROXIMATELY 25 NM)
EYEWALL FEATURE WITH MULTIPLE BROKEN CONVECTIVE BANDS IN THE OUTER
PERIPHERIES. THE INITIAL POSITION IS BASED ON THE SMALL EYE FEATURE
OBSERVED IN THE MSI AND EIR ANIMATION WITH HIGH CONFIDENCE. THE
INITIAL INTENSITY HAS BEEN GREATLY INCREASED TO 105 KNOTS WHICH IS
BASED ON SUBJECTIVE DVORAK INTENSITY ESTIMATES THAT HAVE RAPIDLY
INCREASED TO 115 KNOTS OVER THE PAST SIX HOURS WHILE THE OBJECTIVE
INTENSITY ESTIMATES RANGE FROM 65 TO 80 KNOTS. UPPER-LEVEL ANALYSIS
INDICATES THE SYSTEM IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW
VERTICAL WIND SHEAR (VWS) AND GOOD DUAL CHANNEL OUTFLOW WHICH IS
BEING ENHANCED BY THE MID-LATITUDE WESTERLIES TO THE NORTH. TY 18W
IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING BULLETIN ALTHOUGH THE INTENSITY
FORECAST HAS BEEN INCREASED DUE TO ONSET OF RECENT RAPID
INTENSIFICATION EVENT.
   B. TY 18W WILL CONTINUE TO TRACK TO THE NORTHWEST OVER THE NEXT
48 HOURS AS THE SYSTEM PROCEEDS ALONG THE SOUTHWESTERN PERIPHERY OF
THE STR. AN UPPER LEVEL TROUGH, WHICH IS CURRENTLY ANALYZED OVER
EASTERN CHINA, IS EXPECTED TO PROPAGATE TO THE EAST WHICH WILL
MODIFY AND BREAK THE RIDGE AXIS ALLOWING THE SYSTEM TO TRACK MORE
POLEWARD BETWEEN TAU 48 TO 72. THE SYSTEM IS EXPECTED TO REACH A
MAXIMUM INTENSITY OF 130 KNOTS BY TAU 36 AS THE FAVORABLE UPPER
LEVEL ENVIRONMENT AND OCEAN HEAT CONTENT REACH A PEAK NEAR THIS TIME
FRAME. OVERALL, NUMERIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT
THROUGH TAU 72 HAVING ONLY A 140 NM SPREAD WITH THE EXCEPTION OF
ECMWF, WHICH REMAINS THE FAR WESTERN MOST OUTLIER.
   C. IN THE EXTENDED FORECAST, THE SYSTEM IS EXPECTED TO ROUND THE
RIDGE AXIS AND ACCELERATE NORTHEASTWARD, WEAKENING AS THE SYSTEM
ENCOUNTERS THE MID-LATITUDE WESTERLIES AND BEGINS EXTRATROPICAL
TRANSITION (ETT) AFTER TAU 96. MODELS CONTINUE TO DEPICT A RECURVE
SCENARIO SOUTH OF THE HONSHU, WITH THE SYSTEM COMPLETING ETT BY TAU
120 AS IT BECOMES EMBEDDED IN THE BAROCLINIC ZONE AND BECOMES A
STORM-FORCE LOW. LOW CONFIDENCE REMAINS IN THE FORECAST TRACK, WHICH
IS CLOSE TO THE MULTI-MODEL CONSENSUS AS MODELS CONTINUE DISAGREE ON
THE EXTENT OF RECURVATURE AND HOW THE STR MODIFIES IN RESPONSE TO
THE AFOREMENTIONED TROUGH.//
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