Tropical Storm PRAPIROON Advisory Wed Oct 17

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (PRAPIROON)
WARNING NR 39//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 22W (PRAPIROON), LOCATED APPROXIMATELY 185
NM SOUTH-SOUTHEAST OF KADENA AIR BASE, OKINAWA, JAPAN, HAS TRACKED
NORTH-NORTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS WEAK CENTRAL
CONVECTION BUT EXTENSIVE CONVECTIVE BANDING AROUND A LARGE TIGHTLY-
WRAPPED AND WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC). THE
INITIAL INTENSITY WAS ASSESSED AT 50 KNOTS, WHICH IS SLIGHTLY
HIGHER THAN DVORAK CURRENT INTENSITY ESTIMATES FROM RJTD AND PGTW,
DUE TO THE MICROWAVE EYE FEATURE SEEN IN A PARTIAL 162206Z CORIOLIS
37 GHZ MICROWAVE IMAGE. UPPER LEVEL ANALYSIS AND ANIMATED WATER
VAPOR IMAGERY REVEAL POLEWARD OUTFLOW HAS DECREASED AND AN UPPER
LEVEL LOW IS BEGINNING TO FORM OVER THE SYSTEM. TS 22W REMAINS IN
AREA OF LOW (05-10 KNOT) VERTICAL WIND SHEAR. THERE IS GOOD
CONFIDENCE IN THE INITIAL POSITION AND CURRENT MOTION BASED UPON
THE MSI LOOP AND THE MICROWAVE IMAGE. TS 22W HAS CONTINUES TO TRACK
IN A NORTHWESTWARD MOTION BETWEEN A MID-LATITUDE TROUGH DIGGING IN
FROM EASTERN CHINA AND THE SUBTROPICAL RIDGE TO THE WEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. TS 22W WILL ACCELERATE ON A MORE NORTHEASTWARD TRACK IN THE
NEXT 24 HOURS AS THE TROUGH THAT IS CURRENTLY OVER EASTERN CHINA
DIGS IN AND STEERS TS 22W ALONG THE SUBTROPICAL RIDGE. DYNAMIC
MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGH TAU 72 WITH ONLY
NOGAPS OUTSIDE OF THE GROUPING, DUE TO IT ERRONEOUSLY UNDER
ESTIMATING TS 22W INTENSITY. THE JTWC FORECAST IS SLIGHTLY AHEAD OF
THE MULTI-MODEL CONSENSUS, TO OFFSET NOGAPS, AND IS CONSISTENT WITH
THE PREVIOUS FORECAST. TS 22W IS FORECAST TO SLIGHTLY INTENSIFY IN
THE NEXT 24 HOURS AS IT FAVORABLE POLEWARD IS FORECASTED WITH THE
TROUGH PASSAGE. NEAR TAU 48, TS 22W IS FORECAST TO BEGIN EXTRA-
TROPICAL TRANSITION (ETT) AS IT BEGINS TO INTERACT WITH THE
BAROCLINIC ZONE.
   C. IN THE EXTENDED TAUS, TS 22W IS EXPECTED TO COMPLETE ETT BY
TAU 72 AND ACCELERATE NORTHEASTWARD AS IT BECOMES EMBEDDED WITHIN
THE STRONG MIDLATITUDE WESTERLY FLOW. DYNAMIC MODEL GUIDANCE
REMAINS IN GOOD AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN
THE ENTIRE JTWC FORECAST TRACK.//
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