WOW. Big increase in peak intensity now below category 4!
WDPN32 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (CHAMPI) WARNING NR
05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 25W (CHAMPI), LOCATED APPROXIMATELY 614 NM
EAST OF SAIPAN, HAS TRACKED WEST-NORTHWESTWARD AT 20 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS FLARING CONVECTION SHEARED SOUTHWEST OF AN EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC). ANIMATED INFRARED SATELLITE IMAGERY
REVEALS THAT EVEN THOUGH THE LLCC IS DISPLACED, THE CONVECTION HAS
INTENSIFIED SLIGHTLY OVER THE PAST SIX HOURS. A 140415Z SSMI 85GHZ
MICROWAVE IMAGE SHOWED AN ELONGATED BUT WELL DEFINED LLCC WITH DEEP
CONVECTION ALONG THE WESTERN PERIPHERY. THE INITIAL POSITION IS
BASED ON THE EXPOSED LLCC SEEN IN THE ABOVE IMAGERY WITH HIGH
CONFIDENCE. THE INTENSITY HAS BEEN INCREASED TO 35 KNOTS BASED ON A
132321Z ASCAT PARTIAL PASS SHOWING 35 KNOT WINDS WRAPPING AROUND THE
EASTERN PERIPHERY. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS IN A
MARGINALLY-FAVORABLE ENVIRONMENT WITH 15 TO 20 KNOT EASTERLY
VERTICAL WIND SHEAR (VWS) BEING PARTIALLY OFFSET BY STRONG DIVERGENT
OUTFLOW. TS 25W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF
THE SUB-TROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS CHAMPI WILL TRACK WEST-NORTHWESTWARD UNDER THE INFLUENCE OF
THE STEERING STR THROUGH TAU 72 WHEN IT REACHES THE WESTERN
PERIPHERY OF THE STEERING STR. ENVIRONMENTAL CONDITIONS WILL REMAIN
MARGINALLY-FAVORABLE LEADING TO A SLIGHT INTENSIFICATION THROUGH TAU
48. BEYOND TAU 48, TS 25W WILL ENCOUNTER REDUCED VWS AND AN ENHANCED
POLEWARD OUTFLOW CHANNEL WHICH WILL SUPPORT A PERIOD OF RAPID
INTENSIFICATION.
C. BEYOND TAU 72, TS 25W WILL TURN POLEWARD AND ROUND THE
STEERING STR. THE RATE OF INTENSIFICATION WILL DECREASE AS THE
SYSTEM GAINS LATITUDE AND MOVES OVER COOLER SSTS. HOWEVER, THE
ADDITION OF THE POLEWARD OUTFLOW CHANNEL WILL OFFSET THE NEGATIVE
EFFECTS, ALLOWING SOME INTENSIFICATION BEFORE LEVELING OUT BY THE
END OF FORECAST PERIOD. WITH THE EXCEPTION OF EGRR AND GFDN, ALL
DYNAMIC MODEL GUIDANCE NOW SHOWS A RECURVE SCENARIO AS A LOW- TO MID-
LEVEL TROUGH MOVES OFF THE COAST OF MAINLAND JAPAN, ALLOWING A BREAK
IN THE STEERING STR. ALTHOUGH THE MODEL SOLUTIONS AGREE ON THE
OVERALL STEERING SCENARIO AND ARE IN TIGHT AGREEMENT THROUGH TAU 48,
THE TIMING AND DEGREE OF THE POLEWARD TURN IS WIDESPREAD. THIS
SPREAD BEYOND TAU 48 LEADS TO LOW CONFIDENCE IN THE OVERALL JTWC
FORECAST.//
NNNN
