Subject: Pacific-NW: Ampn/tropical Cyclone Formation Alert//

From: SIU Weather Processor <[email-masked]>
Date: Tue, 14 Sep 2010 16:07:07 -0500

WTPN31 PGTW 142100
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/TROPICAL CYCLONE WARNING//
REF/A/NAVMARFCSTCEN PEARL HARBOR HI/140621Z SEP 10//
AMPN/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. TROPICAL DEPRESSION 12W (TWELVE) WARNING NR 001
   01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   141800Z --- NEAR 19.6N 129.1E
     MOVEMENT PAST SIX HOURS - 315 DEGREES AT 11 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   REPEAT POSIT: 19.6N 129.1E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   150600Z --- 20.1N 128.2E
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 24 HR POSIT: 305 DEG/ 03 KTS
    ---
   24 HRS, VALID AT:
   151800Z --- 20.5N 127.6E
   MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 36 HR POSIT: 305 DEG/ 03 KTS
    ---
   36 HRS, VALID AT:
   160600Z --- 20.8N 127.1E
   MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT
                            040 NM SOUTHEAST QUADRANT
                            030 NM SOUTHWEST QUADRANT
                            030 NM NORTHWEST QUADRANT
   VECTOR TO 48 HR POSIT: 315 DEG/ 02 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   161800Z --- 21.1N 126.8E
   MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT
                            050 NM SOUTHEAST QUADRANT
                            040 NM SOUTHWEST QUADRANT
                            040 NM NORTHWEST QUADRANT
   VECTOR TO 72 HR POSIT: 345 DEG/ 01 KTS
    ---
   72 HRS, VALID AT:
   171800Z --- 21.5N 126.7E
   MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   RADIUS OF 050 KT WINDS - 025 NM NORTHEAST QUADRANT
                            025 NM SOUTHEAST QUADRANT
                            025 NM SOUTHWEST QUADRANT
                            025 NM NORTHWEST QUADRANT
   RADIUS OF 034 KT WINDS - 060 NM NORTHEAST QUADRANT
                            060 NM SOUTHEAST QUADRANT
                            050 NM SOUTHWEST QUADRANT
                            050 NM NORTHWEST QUADRANT
   VECTOR TO 96 HR POSIT: 030 DEG/ 03 KTS
    ---
   LONG RANGE OUTLOOK:
   NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 250 NM
   ON DAY 4 AND 350 NM ON DAY 5... AND FOR INTENSITY
   NEAR 20 KT EACH DAY.
    ---
   96 HRS, VALID AT:
   181800Z --- 22.6N 127.4E
   MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 120 HR POSIT: 030 DEG/ 06 KTS
    ---
   120 HRS, VALID AT:
   191800Z --- 24.7N 128.8E
   MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
REMARKS:
142100Z POSITION NEAR 19.7N 128.9E.
TROPICAL DEPRESSION (TD) 12W (TWELVE) LOCATED APPROXIMATELY 415 NM
SOUTH OF OKINAWA, JAPAN HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER
THE PAST 06 HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS
INCREASED CENTRAL CONVECTION OVER A WELL-DEFINED LOW LEVEL
CIRCULATION CENTER (LLCC). A RECENT 141255Z ASCAT PASS DEPICTS THE
TIGHT LLCC WITH THE STRONGEST WINDS (MAXIMUM OF 30 KNOTS) ON THE
SOUTHEASTERN TO NORTHEASTERN PERIPHERY, WHICH IS ALSO ALLOWING FOR
INCREASED CONVECTION IN THESE AREAS. A TROPICAL UPPER TROPOSPHERIC
TROUGH (TUTT) TO THE WEST AND NORTH IS CAUSING SUBSIDENCE AND
LIMITING POLEWARD OUTFLOW. HOWEVER, THERE IS MODERATE EQUATORWARD
OUTFLOW. TD 12W IS LOCATED IN AN AREA OF LOW VERTICAL WIND SHEAR AND
GOOD DIVERGENCE ALOFT FAVORABLE FOR DEVELOPMENT. TD 12W IS CURRENTLY
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A LOW- TO MID-LEVEL
STEERING RIDGE IN A WEAK STEERING ENVIRONMENT. TD 12W IS EXPECTED TO
CONTINUE SLOWLY TRACKING NORTHWESTWARD UNTIL TAU 48 WHEN IT SHOULD
TURN NORTHWARD AS AN UPPER LEVEL, MID-LATITUDE TROUGH WEAKENS THE
STEERING RIDGE TO THE NORTH. TD 12W SHOULD THEN TAKE A SHARP TURN
NORTHEASTWARD, SOUTH OF OKINAWA AROUND TAU 72 AND BEGIN TRACKING
ALONG THE NORTHWESTERN PERIPHERY OF A STEERING RIDGE EXTENSION THAT
BUILDS IN TO THE SOUTH. BECAUSE OF THE LIMITED OUTFLOW, TD 12W IS
FORECAST TO SLOWLY INTENSIFY IN THE FIRST 36 HOURS. AS TD 12W
CONTINUES TO MOVE NORTHWARD, POLEWARD OUTFLOW SHOULD INCREASE INTO
THE MID-LATITUDE UPPER LEVEL TROUGH ALONG WITH THE TUTT CELL TO THE
EAST WILL ALLOW FOR INCREASED INTENSIFICATION. THERE IS UNCERTAINTY
IN THE AVAILABLE NUMERICAL MODELS WHICH SHOW SPREAD IN THE TIMING OF
THE TURN NORTHEASTWARD. THIS FORECAST PHILOSOPHY FOLLOWS THE NOGAPS
AND GFS MODELS, WHICH TURN THE SYSTEM NORTHEASTWARD BETWEEN TAU 24
AND 48. AN ALTERNATE SCENARIO SUGGESTS THE RIDGE TO THE NORTH WILL
BUILD IN AND CAUSE THE SYSTEM TO TURN WESTWARD IN THE LATER TAUS.
THIS WARNING SUPERSEDES AND CANCELS REF A, NAVMARFCSTCEN 140630Z SEP
10 TROPICAL CYCLONE FORMATION ALERT (WTPN21 PGTW 140630) MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 141800Z IS 11 FEET. NEXT WARNINGS AT
150300Z, 150900Z, 151500Z AND 152100Z.//

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