#110 Postby Chacor » Tue Jul 20, 2010 10:02 pm
485
WDPN31 PGTW 210300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (CHANTHU)
WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. TROPICAL STORM (TS) 04W (CHANTHU), LOCATED APPROXIMATELY 250
NM SOUTH-SOUTHWEST OF HONG KONG, HAS TRACKED WESTWARD AT 06 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL IMAGERY SHOWS
IMPROVED DEEP CONVECTIVE BANDING WRAPPING TIGHTLY AROUND A LOW LEVEL
CIRCULATION CENTER (LLCC) AND A 202126Z TRMM IMAGE DEPICTS A
FORMATIVE LOW LEVEL MICROWAVE EYE. INTENSITY HAS INCREASED BY 10
KNOTS IN THE PAST 6 HOURS AND IS BASED ON PGTW, RJTD, AND KNES
DVORAK ESTIMATES OF 55 KNOTS. INITIAL POSITION IS BASED ON ANIMATED
MULTISPECTRAL IMAGERY AND TRMM IMAGE. UPPER LEVEL ANALYSIS SHOWS
IMPROVED OUTFLOW OVERALL, ALTHOUGH POLEWARD OUTFLOW IS STILL
SOMEWHAT HINDERED BY AN UPPER LEVEL TROUGH CAUSING SUBSIDENCE.
3. FORECAST REASONING
A. WHILE NOT REFLECTING A CHANGE IN FORECAST PHILOSOPHY, THE
FORECAST TRACK HAS SHIFTED FARTHER WEST BECAUSE THE SUBTROPICAL
STEERING RIDGE HAS EXTENDED FARTHER WESTWARD THAN PREVIOUSLY
FORECAST. ADDITIONALLY, THE PEAK INTENSITY HAS BEEN INCREASED TO 65
KNOTS BASED ON IMPROVING OUTFLOW AND WEAKENING OF AN UPPER LEVEL
TROUGH TO THE NORTHWEST OF TS 04W THAT HAD BEEN SUPPRESSING
CONVECTION.
B. TS 04W IS CURRENTLY TRACKING ALONG THE SOUTHWESTERN PERIPHERY
OF A SUBTROPICAL RIDGE AND IS EXPECTED TO REACH A WEAKNESS IN THE
RIDGE, ALLOWING IT TO TURN NORTHWESTWARD WITHIN THE NEXT 12 HOURS.
NEARBY UPPER LEVEL OBSERVATIONS SHOW THAT TS 04W IS CURRENTLY
LOCATED IN THE VICINITY OF THIS WEAKNESS IN THE RIDGE. TS CHANTHU
WILL THEN TRACK NORTHWESTWARD TO THE EAST OF HAINAN AND REACH LAND
WEST OF HONG KONG AROUND TAU 36, THEN DISSIPATE OVER LAND BY TAU 72.
TS CHANTHU IS TRACKING OVER WARM WATER (SST > 28) AND IN AN AREA OF
LOW VERTICAL WIND SHEAR FAVORABLE FOR FURTHER INTENSIFICATION.
ADDITIONALLY, A WEAK UPPER-LEVEL LOW THAT HAS DEVELOPED TO THE
NORTHEAST OF TS 04W MAY IMPROVE POLEWARD OUTFLOW. THE CONSENSUS OF
AVAILABLE NUMERICAL TRACKER MODELS HAVE BEEN TRENDING WESTWARD, BUT
ARE IN AGREEMENT. THIS FORECAST IS SLIGHTLY WEST OF CONSENSUS DUE TO
PREVIOUS TRENDS.//
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