Tuesday, September 6, 2011

JTWC - Prognostic Reasoning for Tropical Cyclone Advisory 12 - Tropical Storm Noru

WDPN31 PGTW 060300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (NORU) WARNING NR
12//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. TROPICAL STORM 16W (NORU), LOCATED APPROXIMATELY 415 NM EAST-
SOUTHEAST OF MISAWA, JAPAN, HAS TRACKED NORTHEASTWARD AT 13 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS A FULLY-EXPOSED, WELL-DEFINED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH NO DEEP CONVECTION PRESENT OVER THE LLCC DURING
THE PAST 12 HOURS. A 052202Z TRMM IMAGE SHOWS AN AREA OF DEEP
CONVECTION, NOT ASSOCIATED WITH THE LLCC, DISPLACED ABOUT 120 NM
SOUTHEAST OF THE CENTER. THE TRMM WIND PRODUCT INDICATES THAT THERE
IS A BELT OF NEAR GALE FORCE WINDS ASSOCIATED WITH THIS DEEP
CONVECTION. THE CURRENT POSITION AND RECENT ERRATIC MOTION ARE BASED
ON THE MSI WITH HIGH CONFIDENCE. THE CURRENT INTENSITY IS ASSESSED
AT 35 KNOTS BASED ON RECENT ASCAT DATA AND A SHIP REPORT SHOWING 30-
35 KNOT WINDS NEAR THE CENTER.
B. TS 16W APPEARS TO BE A HYBRID SYSTEM WITH, PRIMARILY,
SUBTROPICAL CHARACTERISTICS. DESPITE RETAINING A COCOON OF DEEP
MOISTURE TYPICAL OF A TROPICAL SYSTEM, TS 16W IS EMBEDDED WITHIN
A 500 MB UPPER-LEVEL TROUGH WHICH IS SUPPRESSING THE FORMATION OF
DEEP CONVECTION OVER THE LLCC. TS 16W HAS CONTINUED TO TRANSITION
INTO A SUBTROPICAL SYSTEM AS EVIDENCED BY THE ASCAT IMAGE WHICH
DEPICTS A BROADENING WIND FIELD WITH A RELATIVELY WEAK CORE OF
WINDS (15-20 KNOTS) SURROUNDED BY NEAR GALE FORCE WINDS, AND BY
THE 05/16Z AND 05/19Z AMSU CROSS-SECTIONS THAT NO LONGER SHOW
A MID-LEVEL WARM TEMPERATURE ANOMALY BUT RATHER A COLD ANOMALY
IN THE MID- TO UPPER-LEVELS.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY.
B. BASED ON RECENT MSI, THIS SYSTEM HAS BEGUN TO INTERACT WITH
A FRONTAL ZONE CURRENTLY MOVING THROUGH CENTRAL JAPAN. THIS EXTRA-
TROPICAL TRANSITION (ETT) IS EXPECTED TO CONTINUE AND TS 16W WILL
COMPLETE ETT BY TAU 24 AS IT GETS ABSORBED INTO THE FRONTAL ZONE.
DYNAMIC MODEL GUIDANCE IS EVENLY SPLIT ON WHETHER THE SYSTEM
DISSIPATES AS IT TRACKS NORTHWARD OR GETS ABSORBED INTO THE LOW
ASSOCIATED WITH THE FRONTAL ZONE. HOWEVER, THE MODELS ARE CONSISTENT
IN THE TIMING OF TS 16W'S DEMISE OCCURRING WITHIN THE NEXT 24 TO 36
HOURS.//

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