Tropical Storm LINGLING Advisory 9月7日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (LINGLING) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 15W (LINGLING), LOCATED APPROXIMATELY 156 NM SOUTH-
SOUTHWEST OF KUNSAN AB, HAS TRACKED NORTHWARD AT 25 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY DEPICTS A RAPIDLY DECAYING SYSTEM WITH AN INCREASINGLY
RAGGED EYE FEATURE. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE RAGGED EYE FEATURE EVIDENT IN THE EIR,
SUPPORTED BY AN EXTRAPOLATION OF A 061311Z AMSU-B 89 GHZ MICROWAVE
IMAGE AND ANALYSIS OF THE ACCOMPANYING ASCAT-B SCATTEROMETER DATA.
THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON
MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T5.0 (90 KNOTS)
FROM PGTW, AND T4.5 (77 KNOTS) FROM PGTW AND RJTD, HEDGED SLIGHTLY
HIGHER TO REFLECT AN ADVANCED DVORAK TECHNIQUE ESTIMATE OF T4.9 (89
KNOTS) FROM CIMSS. ENVIRONMENTAL ANALYSIS REVEALS THAT THE SYSTEM
LIES IN AN OVERALL UNFAVORABLE ENVIRONMENT, WITH MODERATE TO STRONG
(20-25 KT), LOW SSTS (25-26 CELSIUS), OFFSETTING FAVORABLE POLEWARD
OUTFLOW. HOWEVER, DUE TO THE RAPID NORTHWARD MOTION OF THE STORM AND
THE SOUTHERLY SHEAR VECTOR, THE ACTUAL RELATIVE SHEAR IMPACTING THE
SYSTEM IS LOW, WHICH IS SUPPORTED BY THE FACT THAT THE LOWER LEVELS
HAVE NOT YET DECOUPLED FROM THE UPPER LEVELS, AS WOULD BE EXPECTED
WITH SUCH A HIGH ENVIRONMENTAL SHEAR VALUE. THE NET EFFECT IS THAT
WHILE THE OVERALL ENVIRONMENT IS UNFAVORABLE, THE SYSTEM IS ONLY
SLOWLY WEAKENING. TY 15W IS TRACKING RAPIDLY NORTHWARD ALONG THE
WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 15W IS FORECAST TO CONTINUE TRACKING RAPIDLY NORTHWARD OVER
THE NEX 12 HOURS, MAKING LANDFALL ALONG THE SOUTHWEST COAST OF NORTH
KOREA BY TAU 12, THEN SHIFT NORTH-NORTHEASTWARD THROUGH THE
REMAINDER OF THE FORECAST PERIOD, AS THE SYSTEM ACCELERATES INTO THE
MIDLATITUDE WESTERLIES. THE SYSTEM WILL RAPIDLY WEAKEN DUE TO
INTERACTION WITH THE RUGGED TERRAIN OF THE NORTHERN KOREAN PENINSULA
AS IT SIMULTANEOUSLY UNDERGOES EXTRATROPICAL TRANSITION (ETT) BY
AROUND TAU 12. ETT IS FORECAST TO BE COMPLETE BY TAU 24 AS THE
SYSTEM TRANSITS OVER NORTHEASTERN MANCHURIA. NUMERICAL MODELS ARE IN
TIGHT AGREEMENT THROUGHOUT THE FORECAST, LENDING HIGH CONFIDENCE TO
THE JTWC TRACK FORECAST.//
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