18th tropical cyclone of the year but will only be short lived...
WTPN31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/172021Z SEP 13//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. TROPICAL DEPRESSION 18W (EIGHTEEN) WARNING NR 001
02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
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WARNING POSITION:
180600Z --- NEAR 16.5N 110.4E
MOVEMENT PAST SIX HOURS - 285 DEGREES AT 07 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
WIND RADII VALID OVER OPEN WATER ONLY
REPEAT POSIT: 16.5N 110.4E
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FORECASTS:
12 HRS, VALID AT:
181800Z --- 16.4N 108.6E
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 24 HR POSIT: 260 DEG/ 10 KTS
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24 HRS, VALID AT:
190600Z --- 16.1N 106.6E
MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
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REMARKS:
180900Z POSITION NEAR 16.5N 109.9E.
TROPICAL DEPRESSION 18W (EIGHTEEN), LOCATED APPROXIMATELY 125 NM
EAST-NORTHEAST OF DA NANG, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD
AT 07 KNOTS OVER THE PAST SIX HOURS. MAXIMUM SIGNIFICANT WAVE HEIGHT
AT 180600Z IS 7 FEET. NEXT WARNINGS AT 181500Z, 182100Z AND 190300Z.
THIS WARNING SUPERSEDES AND CANCELS REF A, JOINT TYPHOON WRNCEN
PEARL HARBOR HI 172021Z SEP 13 TROPICAL CYCLONE FORMATION ALERT
(WTPN21 PGTW 172030). REFER TO TROPICAL STORM 17W (USAGI) WARNINGS
(WTPN32 PGTW)FOR SIX-HOURLY UPDATES.//
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WDPN31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (EIGHTEEN)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 18W (EIGHTEEN), LOCATED APPROXIMATELY 125 NM
EAST-NORTHEAST OF DA NANG, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD
AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY INDICATES A BROAD BUT CONSOLIDATING CIRCULATION
WITH DISORGANIZED CONVECTION ALONG THE NORTHERN AND WESTERN
PERIPHERIES. AN 180231Z ASCAT PASS ALONG WITH AN 180450Z OSCAT PASS
SHOWS THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS STARTED TO
CONSOLIDATE, EVEN AS CONVECTIVE ORGANIZATION OF THE SYSTEM REMAINS
POOR. THE CURRENT POSITION HAS BEEN POSITIONED ON THE CENTER OF THE
BROAD CIRCULATION WHICH IS CLOSE TO POSITION FIXES FROM RJTD AND
PGTW. THE INITIAL INTENSITY HAS BEEN ASSESSED AT 25 KNOTS BASED ON
THE AFOREMENTIONED SCATTEROMETER DATA AS DVORAK INTENSITY ESTIMATES
ARE NOT HANDLING THIS SYSTEM WELL DUE TO THE DISORGANIZED AND
FLARING NATURE OF THE CONVECTION. UPPER LEVEL ANALYSIS REVEALS THE
SYSTEM IS LOCATED JUST EQUATORWARD OF THE SUBTROPICAL RIDGE AXIS IN
A REGION OF MODERATE VERTICAL WIND SHEAR (VWS) (15 TO 20 KNOTS) AND
EASTERLY DIFFLUENT OUTFLOW. TD 18W IS CURRENTLY TRACKING WEST ALONG
THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE NORTH OF THE SYSTEM.
3. FORECAST REASONING.
A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
B. TD 18W WILL CONTINUE TO TRACK GENERALLY TO THE WEST UNDER THE
STEERING INFLUENCE OF THE LOW TO MID-LEVEL SUBTROPICAL RIDGE THAT IS
WELL ESTABLISHED ACROSS CENTRAL CHINA. TD 18W WILL STRUGGLE TO
MAINTAIN TROPICAL DEPRESSION STATUS AS IT PROCEEDS WEST INTO THE
VIETNAMESE COAST WITH DISSIPATION FORECASTED BY TAU 24 DUE TO THE
FRICTIONAL EFFECTS OF LANDFALL. NUMERIC MODEL GUIDANCE IS IN GOOD
AGREEMENT WITH THE FORECAST TRACK ALTHOUGH SOME OF THE MODELS ARE
LOSING THE VORTEX WITHIN THE NEXT TWELVE HOURS DUE TO ITS WEAKENED
STATE. THE FORECAST TRACK IS LAID CLOSE TO MULTI-MODEL CONSENSUS
WITH HIGH CONFIDENCE.//
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