WDPN32 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10E (HECTOR)
WARNING NR 56//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 10E (HECTOR), LOCATED APPROXIMATELY 992 NM
NORTHWEST OF JOHNSTON ISLAND, HAS TRACKED WEST-NORTHWESTWARD AT
10 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON A
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER EVIDENT IN VISIBLE
SATELLITE IMAGERY AND 140540Z CORIOLIS 37 GHZ IMAGERY. THE INTENSITY
OF 35 KNOTS IS BASED ON A DVORAK CURRENT INTENSITY ESTIMATE OF T2.5
FROM PGTW AND LOW-LEVEL STRUCTURE EVIDENT IN THE CORIOLIS IMAGERY.
TS 10E IS TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN
PERIPHERY OF A SUBTROPICAL STEERING RIDGE SITUATED TO THE NORTHEAST.
DEEP CONVECTION OVER THE CIRCULATION HAS WANED A BIT DURING THE PAST
SIX HOURS UNDER THE INFLUENCE OF LOW TO MODERATE, BUT PERSISTENT,
SOUTHEASTERLY VERTICAL WIND SHEAR. SEA SURFACE TEMPERATURES REMAIN
FAVORABLE FOR SUSTAINMENT AT APPROXIMATELY 27 DEGREES CELSIUS.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 10E WILL CONTINUE TO TRACK WEST-NORTHWESTWARD IN THE
NEAR-TERM UNDER THE CONTINUED STEERING INFLUENCE OF THE SUBTROPICAL
RIDGE LOCATED TO THE NORTHEAST. SLOW WEAKENING IS ANTICIPATED AS THE
FAVORABLE INFLUENCE OF ENHANCED UPPER-LEVEL OUTFLOW TOWARD A TROPICAL
UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO THE NORTHWEST VIES WITH
VERTICAL WIND SHEAR AND DECREASING ALONG-TRACK SEA SURFACE
TEMPERATURES TO INFLUENCE INTENSITY. THE SYSTEM IS EXPECTED TO TURN
POLEWARD AROUND THE STEERING RIDGE AXIS AFTER TAU 48 AND BEGIN
EXTRATROPICAL TRANSITION AS IT ENCOUNTERS AN APPROACHING MID-LATITUDE
TROUGH. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT, LENDING
HIGH CONFIDENCE IN THE JTWC FORECAST TRACK THROUGH TAU 72.
C. IN THE EXTENDED PERIOD, TS 10E IS EXPECTED TO CONTINUE TRACKING
AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL STEERING RIDGE,
WEAKEN AND COMPLETE EXTRATROPICAL TRANSITION AS IT MERGES WITH THE
FLOW AHEAD OF THE AFOREMENTIONED MID-LATITUDE TROUGH. DYNAMIC MODEL
GUIDANCE SUPPORTS THIS SCENARIO, ALTHOUGH THERE IS SOME DISAGREEMENT
REGARDING THE SPEED AND ORIENTATION OF THE TRACK AS TS 10E ROUNDS THE
STEERING RIDGE AXIS DURING THIS PERIOD. DESPITE THESE MINOR
DISCREPANCIES, THERE IS OVERALL HIGH CONFIDENCE IN THIS PORTION OF
THE JTWC FORECAST TRACK.//
NNNN
