WDPN31 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SIXTEEN) WARNING
NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 12.8N 167.0E
INITIAL INTENSITY: 35 KTS
GEOGRAPHIC REFERENCE: 250 NM NORTH OF KWAJALEIN ATOLL, MARSHALL
ISLANDS
MOVEMENT PAST 6 HOURS: WESTWARD AT 16 KTS
SIGNIFICANT WAVE HEIGHT: 12 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A MIDGET
SYSTEM WITH FLARING CENTRAL CONVECTION THAT IS OFFSET NORTHWARD
FROM AN OBSCURED LOW LEVEL CIRCULATION (LLC). THE CONVECTIVE
PATTERN HAS NOT CHANGED MUCH OVER THE PAST SIX HOURS; FORMATIVE
BANDS REMAIN SHORT AND FRAGMENTED AND THE DEGREE OF WRAP IS STILL THE
SAME. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
A RAGGED BUT DEFINED LLC IN THE 130454Z 91GHZ SSMIS IMAGE. THE
INITIAL INTENSITY IS BASED ON AN OVERALL ASSESSMENT OF AGENCY AND
AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SUSTAINED 6-HR
CONVECTIVE PATTERN. THE SYSTEM IS IN A MARGINAL ENVIRONMENT
CHARACTERIZED BY STRONG POLEWARD OUTFLOW AND VERY WARM SSTS OFFSET
BY MEDIUM TO STRONG VWS. THE CYCLONE IS TRACKING ALONG THE SOUTHERN
PERIPHERY OF A DEEP LAYERED SUBTROPICAL RIDGE TO THE NORTH.
INITIAL WIND RADII BASIS: PERSISTENCE.
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTH.
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
VWS: 15-20 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: HIGH
INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 16W WILL REMAIN ON A WESTWARD TRACK UNDER
THE STR UP TO TAU 96; AFTERWARD, IT WILL TURN MORE
WEST-NORTHWESTWARD AS IT BEGINS TO ROUND THE WESTERN EDGE OF THE
STR. THE MARGINAL CONDITIONS, EXACERBATED BY INCREASING VWS AND THE
SUBSIDING EFFECT AS THE SYSTEM CLOSES IN ON A TUTT CELL TO THE
NORTHWEST, WILL TEMPER ANY MEANINGFUL OR SUSTAINED INTENSIFICATION
UP TO TAU 72. AFTERWARD, DECREASING VWS WILL ALLOW FOR GRADUAL
INTENSIFICATION TO 45KTS AT TAU 96 AFTER IT PASSES JUST TO THE
SOUTH OF GUAM, THEN RAPIDLY TO 60 KTS BY TAU 120 AS IT ENTERS THE
PERENNIALLY WARM AND DEEP OHC WATERS OF THE PHILIPPINE SEA.
MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH A
GRADUAL AND EVEN SPREAD TO MERE 193NM AT TAU 120, LENDING HIGH
CONFIDENCE TO THE JTWC TRACK AND INTENSITY FORECASTS UP TO TAU 72.
THE CONFIDENCE IS MEDIUM FOR BOTH TRACK AND INTENSITY AFTER TAU 72,
DUE TO THE UNCERTAINTY IN THE CONVECTIVE STRUCTURE OF THE CYCLONE
IN THE INTERIM.
FORECAST CONFIDENCE:
TRACK 0 - 72 HR: HIGH
TRACK 72-120 HR: MEDIUM
INTENSITY 0 - 72 HR: HIGH
INTENSITY 72-120 HR: MEDIUM//
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