IMAGERY OF THE DAY
SEPTEMBER 15, 2009
SUPER TYPHOON (CATEGORY 4) CHOI-WAN/15W
LOCATION: 17.51N, 146.02E (20 KM E MARIANAS ISLANDS)
SEPTEMBER 15, 2009
STRUCTURE OF CHOI-WAN
EYE OF CHOI-WAN NEARS MARIANAS IS
SUPER TYPHOON (CATEGORY 4) CHOI-WAN/15W
LOCATION: 17.51N, 146.02E (20 KM E MARIANAS ISLANDS)
MSLP: 929MB
WINDSPEED: 125-155KT (232-287KPH)
MOVEMENT: NW 6KT/11KPH
RAINRATE: 11MM/HR
EYE TEMP: +4C AT 13.1KM HIGH 50KM RADIUS
CENTER TEMP.: (DVORAK): +14.51C
CONVECTION: LEVEL 6 (-75.06C)
NEXT 12HRS: 140KT/260KPH
DVORAK
MSLP : 907.5MB VMAX: 134KT/248KPH
DIFFERENT AGENCIES:
(JTWC): MSLP : 906.4MB VMAX: 135KT/250KPH
(RSMC): MSLP : 909.6MB VMAX: 132KT/245KPH
(CIMSS): MSLP : 906.4MB VMAX: 135KT/250KPH
(PAGASA): MSLP : 0MB VMAX: 0KT/0KPH
DISCUSSION:
TYPHOON 15W (CHOI-WAN) HAS UNDERGONE RAPID INTENSIFICATION OVER THE LAST 12 HOURS AND HAS CONTINUED TO TRACK TOWARDS THE
NORTHWEST. ANIMATED MULTISPECTRAL IMAGERY SHOWS MULTIPLE SPIRAL BANDS WRAPPING TIGHTLY INTO A WELL-DEFINED EYE. ANIMATED WATER VAPOR IMAGERY SHOWS A WELL DEFINED OUTFLOW CHANNEL INTO A TROPICAL UPPER TROPOSPHERIC TROUGH TO THE NORTHEAST ALONG WITH A BROAD OUTFLOW PATTERN TO THE EAST AND SOUTH. A 141944Z SSMIS PASS SHOWS A VERY WELL DEFINED EYE WITH MULTIPLE DEEP CONVECTIVE BANDS WRAPPING INTO THE CENTER. TY 15W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. RAPID INTENSIFICATION WAS CAUSED BY A COMBINATION OF HIGH SEA SURFACE TEMPERATURES, LOW VERTICAL WINDSHEAR, AND DUAL OUTFLOW MECHANISMS ALOFT. THE CURRENT POSITION IS BASED ON A 142330Z INFRARED IMAGE WITH HIGH CONFIDENCE. THE CURRENT INTENSITY IS BASED ON DVORAK ESTIMATES FROM PGTW, RJTD, AND KNES
THE FORECAST PHILOSOPHY HAS NOT CHANGED SIGNIFICANTLY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE, WITH THE EXCEPTION OF A
RISE IN PEAK INTENSITY FOLLOWING THE RECENT RAPID INTENSIFICATION
TY CHOI-WAN WILL CONTINUE TO TRACK NORTHWESTWARD THROUGH TAU 48 UNDER THE INFLUENCE OF THE STEERING RIDGE DESCRIBED IN PARA 2.A.
THE SYSTEM WILL CONTINUE TO STEADILY INTENSIFY, ALBEIT LESS RAPIDLY, AS IT MOVES THROUGH A FAVORABLE ENVIRONMENT CHARACTERIZED BY EXCELLENT DUAL OUTFLOW AND WARM WATERS. DECREASING SEA SURFACE TEMPERATURES AND OCEAN HEAT CONTENT ALONG THE TRACK OF TY 15W WILL NO LONGER SUPPORT RAPID INTENSIFICATION. AFTER TAU 48, CHOI-WAN WILL START TO GRADUALLY RECURVE TO THE NORTHEAST AROUND THE WESTERN PERIPHERY OF THE STR MENTIONED.
AFTER TAU 72, CHOI-WAN WILL CONTINUE TO RECURVE TO THE NORTHEAST AS A SECONDARY MID-LATITUDE TROUGH CURRENTLY APPROACHING
NORTH KOREA WILL ERODE THE WESTERN SEGMENT OF THE STR. THE SYSTEM WILL THEN START TO ACCELERATE TO THE NORTHEAST AND BEGIN
EXTRATROPICAL TRANSITION AFTER TAU 120. THE NUMERICAL MODELS ARE GENERALLY IN FAIR AGREEMENT UP TO TAU 48, WITH JGSM AS AN OUTLIER TO THE FAR WEST AND THE REMAINDER OF THE AIDS INCONSISTENT ON TRACK SPEED. AFTER TAU 48, THE SPREAD CONTINUES TO GROW AS THE MODELS COUPLE TRACK SPEED INCONSISTENCIES WITH RECURVATURE TIMING DIFFERENCES, ATTRIBUTED TO TIMING DIFFERENCES WITH THE PASSAGE OF THE MID-LATITUDE TROUGH. THIS FORECAST FAVORS THE MODEL CONSENSUS WITH REGARDS TO TRACK, AND IS SLOWER THAN CONSENSUS TO CORRECT FOR KNOWN CONSENSUS TENDENCIES IN THE CURRENT SYNOPTIC PATTERN
TYPHOON 15W (CHOI-WAN) HAS UNDERGONE RAPID INTENSIFICATION OVER THE LAST 12 HOURS AND HAS CONTINUED TO TRACK TOWARDS THE
NORTHWEST. ANIMATED MULTISPECTRAL IMAGERY SHOWS MULTIPLE SPIRAL BANDS WRAPPING TIGHTLY INTO A WELL-DEFINED EYE. ANIMATED WATER VAPOR IMAGERY SHOWS A WELL DEFINED OUTFLOW CHANNEL INTO A TROPICAL UPPER TROPOSPHERIC TROUGH TO THE NORTHEAST ALONG WITH A BROAD OUTFLOW PATTERN TO THE EAST AND SOUTH. A 141944Z SSMIS PASS SHOWS A VERY WELL DEFINED EYE WITH MULTIPLE DEEP CONVECTIVE BANDS WRAPPING INTO THE CENTER. TY 15W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. RAPID INTENSIFICATION WAS CAUSED BY A COMBINATION OF HIGH SEA SURFACE TEMPERATURES, LOW VERTICAL WINDSHEAR, AND DUAL OUTFLOW MECHANISMS ALOFT. THE CURRENT POSITION IS BASED ON A 142330Z INFRARED IMAGE WITH HIGH CONFIDENCE. THE CURRENT INTENSITY IS BASED ON DVORAK ESTIMATES FROM PGTW, RJTD, AND KNES
THE FORECAST PHILOSOPHY HAS NOT CHANGED SIGNIFICANTLY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE, WITH THE EXCEPTION OF A
RISE IN PEAK INTENSITY FOLLOWING THE RECENT RAPID INTENSIFICATION
TY CHOI-WAN WILL CONTINUE TO TRACK NORTHWESTWARD THROUGH TAU 48 UNDER THE INFLUENCE OF THE STEERING RIDGE DESCRIBED IN PARA 2.A.
THE SYSTEM WILL CONTINUE TO STEADILY INTENSIFY, ALBEIT LESS RAPIDLY, AS IT MOVES THROUGH A FAVORABLE ENVIRONMENT CHARACTERIZED BY EXCELLENT DUAL OUTFLOW AND WARM WATERS. DECREASING SEA SURFACE TEMPERATURES AND OCEAN HEAT CONTENT ALONG THE TRACK OF TY 15W WILL NO LONGER SUPPORT RAPID INTENSIFICATION. AFTER TAU 48, CHOI-WAN WILL START TO GRADUALLY RECURVE TO THE NORTHEAST AROUND THE WESTERN PERIPHERY OF THE STR MENTIONED.
AFTER TAU 72, CHOI-WAN WILL CONTINUE TO RECURVE TO THE NORTHEAST AS A SECONDARY MID-LATITUDE TROUGH CURRENTLY APPROACHING
NORTH KOREA WILL ERODE THE WESTERN SEGMENT OF THE STR. THE SYSTEM WILL THEN START TO ACCELERATE TO THE NORTHEAST AND BEGIN
EXTRATROPICAL TRANSITION AFTER TAU 120. THE NUMERICAL MODELS ARE GENERALLY IN FAIR AGREEMENT UP TO TAU 48, WITH JGSM AS AN OUTLIER TO THE FAR WEST AND THE REMAINDER OF THE AIDS INCONSISTENT ON TRACK SPEED. AFTER TAU 48, THE SPREAD CONTINUES TO GROW AS THE MODELS COUPLE TRACK SPEED INCONSISTENCIES WITH RECURVATURE TIMING DIFFERENCES, ATTRIBUTED TO TIMING DIFFERENCES WITH THE PASSAGE OF THE MID-LATITUDE TROUGH. THIS FORECAST FAVORS THE MODEL CONSENSUS WITH REGARDS TO TRACK, AND IS SLOWER THAN CONSENSUS TO CORRECT FOR KNOWN CONSENSUS TENDENCIES IN THE CURRENT SYNOPTIC PATTERN
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