WDPN31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (CIMARON) 
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.1N 131.9E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 239 NM EAST-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH PERSISTENT
FLARING CONVECTION ALONG CONVERGENT LOW-LEVEL FLOW LINES TO THE
NORTHEAST. ANIMATED WATER VAPOR IMAGERY AND HIGH-RESOLUTION MODEL
FIELDS SHOW A SIGNIFICANT AMOUNT DRY MID-LEVEL AIR OVER AND WEST OF
THE LLCC, AND THE LATEST CIMSS UPPER-LEVEL ANALYSIS REVEALS AN AREA
OF CONVERGENT FLOW ALOFT PUSHING SOUTHWARD OVER TOP OF THE SYSTEM
FROM THE NORTH. THE INITIAL POSITION WAS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC. THE INITIAL INTENSITY WAS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE LOW T1.0 FIXES FROM BOTH
PGTW AND KNES AND A CIMSS DPRINT ESTIMATE OF 25 KNOTS. OF NOTE, THE
CIMSS ADT, AIDT AND SATCON ESTIMATES SEEM UNREALISTICALLY HIGH AND
DO NOT ALIGN WITH EARLIER SCATTEROMETER DATA. THE ENVIRONMENT IS
UNFAVORABLE, WITH MODERATE POLEWARD OUTFLOW AND WARM SSTS OFFSET BY
MODERATE TO HIGH (20-25 KTS) VWS, AND COPIOUS AMOUNTS OF DRY
MID-LEVEL AIR. THE SYSTEM HAS TRACKED WESTWARD OVER THE PAST SIX
HOURS, MEANDERING IN A WEAK STEERING PATTERN.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN, WITH RIDGING
OVER NORTHEASTERN CHINA AND EAST OF JAPAN, AND A TROUGH EXTENDING
FROM LUZON TO 18W AND A FRONTAL BOUNDARY EXTENDING FROM 18W TO A
SUBTROPICAL LOW EAST OF NORTHERN JAPAN. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   KNES: T1.0 - 25 KTS
   CIMSS SATCON: 38 KTS AT 261039Z
   CIMSS ADT: 34 KTS AT 261140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TD 18W IS MEANDERING WITHIN THE WEAK STEERING
PATTERN, HAVING TAKEN A BIT OF AN UNEXPECTED JOG TO THE WEST OVER
THE PAST SIX HOURS. THE SYSTEM IS LIKELY TO MAKE IT A LITTLE
FURTHER WEST IN THE NEXT FEW HOURS, BEFORE IT STARTS MOVING NORTH
THEN NORTHEAST AS IT STARTS TO RIDE UP THE ENHANCED GRADIENT ALONG
THE FRONTAL BOUNDARY TO THE NORTHEAST. DUE TO THE COPIOUS DRY AIR
AND CONVERGENT FLOW ALOFT, THERE IS LITTLE TO NO CHANCE FOR
CONVECTIVE ACTIVITY TO REFORM OVER THE CENTER OF TD 18W. WHAT
CONVECTION HAS BEEN ABLE TO DEVELOP OF THE LAST 12 HOURS HAS BEEN
ALONG CONVERGENT FLOW LINES AND IS IMMEDIATELY SHEARED TO THE
NORTHEAST AWAY FROM THE CENTER. AFTER TAU 12, SHEAR IS EXPECTED TO
INCREASE EVEN MORE AS THE SYSTEM BEGINS TO INTERACT WITH THE
SOUTHERN EDGE OF A 200MB JET MAX OVER JAPAN, WHICH WILL LEAD TO THE
RAPID DISSIPATION OF TD 18W BY TAU 24. AS WITH THE PREVIOUS
FORECAST, IT BEARS MENTIONING THAT THE GFS CONTINUES TO SHOW THE
VORTICITY ASSOCIATED WITH THE REMNANTS OF TD 18W MOVING
NORTHEASTWARD ALONG THE FRONTAL BOUNDARY UNTIL ABOUT TAU 60 OR SO.
AT THIS POINT THE GFS SHOWS REDEVELOPMENT ALONG THE LEADING EDGE OF
A NORTHEAST SURGE ALONG THE COAST OF JAPAN, BRIEFLY THE REMNANTS OF
TD 18W BACK TO LIFE AS THEY SLIDE SOUTHWESTWARD IN A BINARY
INTERACTION WITH WHAT IS NOW TD 19W. THE SYSTEM WILL BE CLOSELY
MONITORED FOR SIGNS OF THIS SCENARIO PLAYING OUT. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN FAIR AGREEMENT
ON THE OVERALL TRACK BUT DID NOT, AND IS NOT, CAPTURING THE RECENT
WESTWARD JOG. ADDITIONALLY, THE MODELS REMAIN TOO FAST IN MOVING TD
18W TO THE NORTHEAST. THUS THE JTWC FORECAST DEVIATES FROM THE
MODEL GUIDANCE FROM THE START OF THE FORECAST, TAKING THE SYSTEM
FURTHER WEST THAN THE GUIDANCE PACKAGE AND SIGNIFICANTLY SLOWLY
THAN THE GUIDANCE. CONFIDENCE IS THUS LOW OVERALL. INTENSITY
GUIDANCE IS IN AGREEMENT THAT TD 18W WILL LINGER FOR ABOUT 12 TO 18
HOURS BEFORE FINALLY DISSIPATING, LENDING HIGH CONFIDENCE TO THE
JTWC FORECAST INTENSITY. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   INTENSITY 0 - 72 HR: HIGH//
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