Subject: Pacific-NW: 1. Tropical Depression 17w (seventeen) Warning Nr 001

From: SIU Weather Processor <[email-masked]>
Date: Thu, 21 Oct 2010 16:16:07 -0500

WTPN33 PGTW 212100
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL DEPRESSION 17W (SEVENTEEN) WARNING NR 001
   03 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   211800Z --- NEAR 20.8N 156.0E
     MOVEMENT PAST SIX HOURS - 295 DEGREES AT 09 KTS
     POSITION ACCURATE TO WITHIN 030 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: 20.8N 156.0E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   220600Z --- 21.6N 154.7E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 24 HR POSIT: 320 DEG/ 06 KTS
    ---
   24 HRS, VALID AT:
   221800Z --- 22.5N 153.9E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   VECTOR TO 36 HR POSIT: 355 DEG/ 04 KTS
    ---
   36 HRS, VALID AT:
   230600Z --- 23.3N 153.8E
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
   VECTOR TO 48 HR POSIT: 035 DEG/ 04 KTS
    ---
   EXTENDED OUTLOOK:
   48 HRS, VALID AT:
   231800Z --- 23.9N 154.3E
   MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
212100Z POSITION NEAR 21.0N 155.7E.
TROPICAL DEPRESSION (TD) 17W (SEVENTEEN), LOCATED APPROXIMATELY 780
NM NORTHEAST OF HAGATNA, GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 09
KNOTS OVER THE PAST SIX HOURS. LOW LEVEL STRUCTURE EVIDENT IN RECENT
MICROWAVE SATELLITE IMAGERY, INCLUDING A 211503Z AMSR-E PASS, AND A
212430Z KNES DVORAK INTENSITY ESTIMATE OF 30 KNOTS INDICATE THAT TD
17W HAS FORMED JUST POLEWARD OF A TROPICAL UPPER TROPOSPHERIC (TUTT)
CELL. TD 17W IS TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHERN
PERIPHERY OF A DEEP SUBTROPICAL RIDGE TO THE NORTH. THIS GENERAL
MOTION IS EXPECTED TO CONTINUE THROUGH THE NEXT 24 HOURS.
THEREAFTER, A DEVELOPING MIDLATITUDE TROUGH TO THE NORTH IS EXPECTED
TO WEAKEN THE STEERING RIDGE AND INDUCE A POLEWARD TURN INTO A WEAK
STEERING ENVIRONMENT. THE AVAILABLE NUMERICAL GUIDANCE IS IN GOOD
GENERAL AGREEMENT WITH THIS SCENARIO, ALTHOUGH THERE IS SOME
UNCERTAINTY IN THE EXACT TRACK GIVEN THE EXPECTATION OF A WEAK
STEERING SETUP. UNFAVORABLE ENVIRONMENTAL FACTORS, INCLUDING
PERSISTENT UPPER LEVEL CONVERGENCE, EASTERLY VERTICAL WIND SHEAR,
AND THE INTRODUCTION OF DRIER AIR TOWARD THE CENTER OF TD 17W FROM
THE SOUTHEAST, SHOULD PREVENT THE SYSTEM FROM INTENSIFYING
SIGNIFICANTLY AND EVENTUALLY RESULT IN DISSIPATION BELOW THE 25 KNOT
WARNING THRESHOLD INTENSITY AROUND TAU 48. THIS WARNING SUPERSEDES
AND CANCELS REF A, NAVMARFCSTCEN 210251Z OCT 10 TROPICAL CYCLONE
FORMATION ALERT (WTPN22 PGTW 210300). MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 211800Z IS 10 FEET. NEXT WARNINGS AT 220300Z, 220900Z,
221500Z AND 222100Z. REFER TO TYPHOON 15W (MEGI) WARNINGS (WTPN31
PGTW) FOR SIX-HOURLY UPDATES. REFER TO TROPICAL DEPRESSION 16W
(SIXTEEN) WARNINGS (WTPN32 PGTW) FOR SIX-HOURLY UPDATES.//

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