WDPN31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (AERE) WARNING
NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.2N 130.5E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 41 NM EAST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: XX FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A SMALL AREA
OF FLARING CONVECTIVE ACTIVITY, INDUCED BY LOW LEVEL FRICTION
INDUCED CONVERGENCE AND UPSLOPE FLOW COMBINED WITH STRONGLY
DIVERGENT UPPER-LEVEL WIND FLOW, DISPLACED TO THE SOUTHEAST OF A
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON SPIRAL BAND
ANALYSIS, A DENSE CONSTELLATION OF SURFACE WIND OBSERVATIONS AND
ANIMATED RADAR DATA FROM JMA. THE INITIAL INTENSITY OF 25 KNOTS IS
ASSESSED WITH HIGH CONFIDENCE BASED PRIMARILY ON SURFACE PRESSURE
AND WIND READINGS ON THE PERIPHERY OF THE SYSTEM OF 1002MB AND
15-20 KNOT (10-MINUTE) RESPECTIVELY SUPPORTED BY THE RJTD INTENSITY
ASSESSMENT. TD 05W MADE LANDFALL JUST SOUTH OF SASEBO AT ROUGHLY
042000Z AND THEN HAS MOVED NORTHEASTWARD AT ABOUT 10 KNOTS AND LIES
JUST SOUTH OF KURUME. THE FLARING CONVECTION IS BEING SHEARED TO
THE EAST UNDER THE PERSISTENT 20-25 KNOTS OF NORTHWESTWARD VWS,
OFFSETTING THE DIVERGENT FLOW OVER AND DOWNSTREAM OF THE LLCC.

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-SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: NO CURRENT ESTIMATE
   RJTD: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE EQUATORWARD

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: HAVING MADE LANDFALL, TD 05W IS ANTICIPATED TO
RAPIDLY TRANSITION NORTHEASTWARD UNDER THE STEERING INFLUENCE OF
THE STR CENTERED TO THE SOUTH. PASSAGE OVER THE RUGGED TERRAIN OF
NORTHEASTERN KYUSHU WILL TEAR APART THE LLCC A BIT, BUT THE LOW
LEVEL VORTICITY IS FORECAST TO CONTINUE TRACKING ACROSS THE INLAND
SEA AND EMERGE BACK OVER WATER SOUTH OF HAMAMATSU AROUND TAU 24.
ONCE BACK OVER OPEN WATERS, THE VORTICITY WILL BUILD BACK DOWN
TO THE SURFACE AND THE ENERGY WILL MERGE WITH A DEVELOPING LOW
PRESSURE AREA SOUTHEAST OF TOKYO BY TAU 36. AS THE SYSTEM MOVES
OFFSHORE IT WILL BEGIN TO INTERACT WITH A 500MB SHORTWAVE TROUGH,
INDUCING SOME BAROCLINIC FORCING, WHICH WILL ALLOW FOR THE SYSTEM
TO BEGIN TO INTENSIFY FAIRLY QUICKLY. MAXIMUM BAROCLINIC FORCING
WILL OCCUR AROUND TAU 36, BEFORE THE TROUGH ALOFT CUTS OFF FROM THE
MAIN WESTERLIES, TO THE SOUTH OF A 500MB ANTICYCLONE OVER SAKHALIN
ISLAND, PART OF A DEVELOPING REX BLOCK. AT THIS POINT, THE SYSTEM
WILL SLOW DOWN CONSIDERABLY, BECOMING QUASI-STATIONARY BETWEEN TAU
48-72 UNDER VERY WEAK STEERING ASSOCIATED WITH THE REX BLOCK. TD
05W WILL EJECT NORTHWARD AFTER TAU 96 AS THE REX BLOCK BREAKS DOWN
AND THE STR TO THE EAST BUILDS AND REORIENTS TO A NORTH-SOUTH AXIS.
THE SYSTEM WILL BEGIN TRANSITIONING TO A SUBTROPICAL LOW BY TAU 48
AS IT BECOMES VERTICALLY STACKED UNDER A WARM CORE 500MB LOW,
COMPLETING TRANSITION NO LATER THAN TAU 96. THE SYSTEM WILL PEAK AT
40 KNOTS AROUND TAU 36 AS IT EXPERIENCES THE MAXIMUM BAROCLINIC
FORCING AND LIES UNDER STRONGLY DIVERGENT 200MB FLOW. THE SYSTEM
WILL SLOWLY WEAKEN THEREAFTER AS IT MOVES OVER COOLER WATERS, AND
BECOMES SMOTHERED BY DRY AIR.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE MODEL GUIDANCE REMAINS
IN GOOD AGREEMENT THROUGH THE FIRST 48 TO 72 HOURS, CONFINED TO A
NARROW ENVELOPE OF 60-85NM ALONG THE SOUTHERN COAST OF THE JAPANESE
MAIN ISLANDS. ONCE THE SYSTEM BEGINS SUBTROPICAL TRANSITION AND
MOVES INTO THE WEAK STEERING ENVIRONMENT, MODELS STRUGGLE TO TRACK
THE VORTEX AND THE GUIDANCE SHOWS A WIDE RANGE OF POSSIBLE
SOLUTIONS DURING THIS TIMEFRAME. JGMS AND GFS MARK THE SOUTHERN
SIDE OF THE ENVELOPE AND SHOW A SLOW TURN EQUATORWARD BEFORE THE
POLEWARD TURN AROUND TAU 96. THE NAVGEM, ECMWF AND THE BULK OF THE
ENSEMBLE GUIDANCE SUGGESTS A QUASI-STATIONARY PERIOD THROUGH TAU 72
FOLLOWED BY A SHARP POLEWARD TURN. AFTER TAU 96, THE GUIDANCE SHOWS
CONSIDERABLE SPREAD, BOTH ALONG AND CROSS-TRACK, DUE TO
UNCERTAINTIES IN THE TIMING AND RAPIDITY OF THE EJECTION OF THE
VORTEX POLEWARD. IN LIGHT OF THE UNCERTAINTIES, CONFIDENCE IS
MEDIUM IN THE SHORT-TERM AND LOW IN THE EXTENDED RANGE FORECAST.
INTENSITY GUIDANCE SHOWS INCREASED UNCERTAINTY WITH THIS RUN, WITH
SOME RAPID INTENSIFICATION GUIDANCE SUGGESTING A PEAK OF NEAR 55
KNOTS BY TAU 24. THIS IS CONSIDERED HIGHLY UNLIKELY, AND THE
REMAINDER OF THE GUIDANCE LIES IN AN ENVELOPE BETWEEN 35-50 KNOTS,
WITH SHIPS ON THE LOW END AND COAMPS-TC ON THE HIGH SIDE. THE JTWC
FORECAST PEAK IS BUMPED UP 5 KNOTS FROM THE PREVIOUS FORECAST, AND
LIES VERY NEAR THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE.

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