WDPN31 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (AERE) WARNING 
NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.7N 136.5E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 185 NM WEST-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EASTWARD AT 22 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AT PRESENT THERE IS NO SIGN OF VISIBLE LOW LEVEL CIRCULATION BASED
ON THE ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY. THE
INITIAL POSITION IS PLACED WITH VERY LOW CONFIDENCE, ON THE
NORTHERN SIDE OF AN AREA OF ELONGATED CONVECTIVE ACTIVITY SOUTH OF
HONSHU. ANIMATED IMAGERY ALSO SUGGEST A SURFACE LOW DEVELOPING JUST
EAST OF TOKYO WHICH IS MOVING EASTWARD INTO OPEN WATERS. THE
INITIAL INTENSITY OF 25 KNOTS IS ASSESSED WITH LOW CONFIDENCE BASED
ON PERSISTENCE AND A CIMSS ADT OF 27 KNOTS. THE CURRENT
ENVIRONMENTAL ANALYSIS IS UNFAVORABLE FOR TROPICAL CYCLONE
DEVELOPMENT. SEA SURFACE TEMPERATURES ARE ABOVE 26C BUT WIND SHEAR
IS HIGH, YET THE UPPER LEVEL DIVERGENT FLOW AND THE POSITIVE
VORTICITY ASSOCIATED WITH THE 500MB TROUGH ARE PROVIDING JUST ENOUGH
ENERGY FOR THE CIRCULATION TO MAINTAIN ITSELF AT LEAST AT THE 850MB
LEVEL.

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

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF  A DEEP LAYER
SUBTROPICAL RIDGE (STR) TO THE SOUTH 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS SATCON: 36 KTS AT 051714Z
   CIMSS ADT: 27 KTS AT 051740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE EASTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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: AFTER MOVING OVER SHIKOKU AND SOUTHERN HONSHU
LITTLE EVIDENCE REMAINS OF THE LOW LEVEL VORTEX, HOWEVER MODEL
FIELDS AND CMSS ANALYSIS REVEALS A 850MB VORTICITY MAXIMA MOVING
RAPIDLY TO THE NORTHEAST. IT IS ANTICIPATED THAT THIS AREA OF
VORTICITY, THE REMNANTS OF TD 05W, WILL MERGE WITH THE AREA OF LOW
PRESSURE CURRENTLY DEVELOPING EAST OF HONSHU WITHIN THE NEXT 12-24
HRS. AS THE TWO AREAS MERGE THEY WILL BE IN AN AREA OF MAXIMUM
BAROCLINIC FORCING AHEAD OF A 500MB TROUGH AND 200MB DIVERGENCE.
THE SYSTEM IS EXPECTED TO QUICKLY INTENSIFY TO A PEAK OF 40 KTS BY TAU
24. BY TAU 36 THE 500MB TROUGH CUTS OF TO A UPPER LOW AND THE
SYSTEM BECOMES VERTICALLY STACKED, WHILE THE UPPER LOW IS CUT OFF
THE SYSTEM WILL REMAIN WARM CORE IN NATURE. AT THIS POINT SEA
SURFACE TEMPERATURES ARE 24-26C, AND THE SYSTEM WILL BEGIN TO
TRANSITION TO A SUBTROPICAL LOW. THEN BY TAU 48 THE SYSTEM IS
FORECAST TO BECOME QUASI-STATIONARY IN A WEAK STEERING ENVIRONMENT
INDUCED BY THE DEVELOPMENT OF A REX BLOCK TO THE NORTH. DURING THIS
TIME THE SYSTEM IS QUASI-STATIONARY AND VERTICALLY STACKED, THE
SYSTEM WILL SLOWLY WEAKEN AS A RESULT OF A DRY AIR ENTRAINMENT AND
COOLER UPWELLING OF SSTS. BY TAU 48 THE SYSTEM IS EXPECTED TO
COMPLETE SUBTROPICAL TRANSITION. BY TAU 72 THE REX BLOCK IS
FORECAST TO BREAK DOWN AND THE STR REORIENT TO A NORTH SOUTH AXIS
TO THE EAST OF THE SYSTEM, WHICH WILL EJECT TD 05W SHARPLY TO THE
NORTH, WHILE CONTINUING TO WEAKEN.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT IN A TRACK EASTWARD BEFORE BECOMING QUASI-STATIONARY. THE
MODELS SHOW HIGH UNCERTAINTY IN THE EXACT TRACK BETWEEN 36-72 HRS
AS THE SYSTEM MEANDERS IN THE WEAK STEERING ENVIRONMENT, BUT ALL
REMAIN WITHIN A 110 NM CIRCLE. ALL THE GUIDANCE AGREES WITH AN
EJECTION NORTHWARD AROUND TAU 72. THE FORECAST REMAINS CONSISTENT
WITH THE PREVIOUS FORECAST AND LIES ON THE NORTH AND EASTERN SIDE
OF THE GUIDANCE ENVELOPE. CONFIDENCE IS LOW, HOWEVER DUE TO THE
UNCERTAINTIES IN THE INITIAL POSITION AND THE TIMING AND STRENGTH
OF THE POLEWARD TURN. INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH
ALL MODELS CONSTRAINED WITHIN A 5 KNOT ENVELOPE TROUGH THE DURATION
OF THE FORECAST, LENDING HIGH FORECAST IN THE JTWC FORECAST.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: HIGH//
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