WDPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.3N 118.6E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 172 NM NORTHWEST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 26W (NALGAE) HAS MOVED BACK OVER OPEN WATERS, HAVING
EMERGED OFF WESTERN LUZON SHORTLY AFTER THE 1800Z HOUR. THE LONG
TRANSIT OVER ROUGH TERRAIN TOOK ITS TOLL ON THE SYSTEM HOWEVER, AND
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) CURRENTLY DEPICTS A
RAGGED AND SOMEWHAT DISORGANIZED SYSTEM. DEEP CONVECTION IS LIMITED
IN AREAL EXTENT AND IS CONFINED TO A SMALL REGION NEAR AND WEST OF
THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC). THE LLCC ITSELF
REMAINS OBSCURED UNDER CONVECTIVE CIRRUS BLOWOFF BUT THE GENERAL
ROTATION OF THE LARGER CIRCULATION IS CLEARLY EVIDENT. A PARTIAL
292313Z SSMIS 91GHZ MICROWAVE PASS SHOWED THE WESTERN HALF OF THE
CIRCULATION BUT THE RAGGED NATURE OF THE LLC PRECLUDED DEFINITIVE
ASSESSMENT OF THE CENTER. FORTUNATELY, THE FIXING AGENCIES ALL
CONCUR ON THE PLACEMENT, WITH ALL THREE AGENCIES FIXING WITHIN A
TIGHT 20NM CIRCLE, THUS THE INITIAL POSITION IS ASSESSED WITH
MEDIUM CONFIDENCE. THE INITIAL INTENSITY OF 45 KNOTS IS ASSESSED
WITH MEDIUM CONFIDENCE AS WELL, BASED ON THE KNES AND RJTD CURRENT
INTENSITY ESTIMATES AND THE AIDT, WHICH IS DOWN TO ABOUT 48 KNOTS.
THE ENVIRONMENT IS GENERALLY FAVORABLE, CHARACTERIZED BY LOW (10-15
KNOTS) VWS, WARM (28-29C) SSTS AND GOOD POLEWARD AND EQUATORWARD
OUTFLOW. THE SYSTEM IS NOW MOVING WEST-NORTHWEST ALONG THE
SOUTHWEST SIDE OF A DEEP SUBTROPICAL RIDGE (STR) TO THE EAST.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER STR CENTERED TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 57 KTS AT 292340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 26W, HAVING JUST RECENTLY MOVED
BACK OVER WATER, IS STILL SUFFERING FROM THE LINGERING EFFECTS OF
THE DISRUPTION OF THE CORE IT EXPERIENCED WHILE CROSSING OVER
LUZON. THE OVERALL ENVIRONMENT IS FAVORABLE BUT UNTIL THE SYSTEM
CAN REESTABLISH A VERTICALLY STACKED, SYMMETRICAL CORE, IT WILL BE
SLOW TO DEVELOP. THE STR IS NOW THE PRIMARY STEERING MECHANISM AND
THE SYSTEM WILL CONTINUE TO TRACK GENERALLY TOWARDS THE WEST
THROUGH TAU 12. THE PASSAGE OF A MID-LATITUDE TROUGH TO THE NORTH
IS EXPECTED TO WEAKEN THE RIDGE ENOUGH TO ENTICE TS 26W NORTHWARD
TOWARDS THE WEAKNESS AFTER TAU 12, CONTINUING THROUGH TAU 48,
THOUGH OVERALL TRACK SPEEDS ARE EXPECTED TO BE RATHER SLOW AS THE
STEERING GRADIENTS ARE NOT OVERLY STRONG. THE SYSTEM IS EXPECTED TO
SLOWLY INTENSIFY FOR THE NEXT 24 HOURS AS IT CONTINUES TO
RECONSOLIDATE UNDER SOME MODEST EASTERLY SHEAR. GLOBAL MODELS
SUGGEST DEVELOPMENT OF AN UPPER-LEVEL POINT SOURCE OR MESOSCALE
ANTICYCLONE OVER TOP OF THE SYSTEM BY TAU 24, WHICH WOULD INDUCE
REDUCED SHEAR AND IMPROVED OUTFLOW, WITH THE POSSIBILITY OF A WEAK
TAP INTO SOME STRONG POLEWARD OUTFLOW AROUND TAU 36. THUS, ASSUMING
THE SYSTEM DOES A GOOD JOB OF SYMMETRIZING IN THE NEAR-TERM,
IT SHOULD INTENSIFY FAIRLY QUICKLY, TO A PEAK OF 65 TO 70 KNOTS BY
TAU 48. AFTER THIS POINT IT WILL BEGIN TO EXPERIENCE INCREASING
SOUTHERLY SHEAR, DECREASING SSTS AND ENTRAINMENT OF COOLER, DRIER
AIR IN THE LOW TO MID-LEVELS, MARKING THE BEGINNING OF A WEAKENING
TREND BY TAU 72. THE SYSTEM IS EXPECTED TO RAPIDLY WEAKEN BETWEEN
TAU 72 AND TAU 120, GRADUALLY TURNING TO THE WEST AND THEN
WEST-SOUTHWEST AS IT COMES UNDER THE STEERING INFLUENCE OF
LOWER-LEVEL FLOW OUT OF THE NORTH-NORTHEAST. THE SYSTEM IS EXPECTED
TO BE A WEAK TROPICAL DEPRESSION SOUTHWEST OF HONG KONG BY TAU 120.
 

MODEL DISCUSSION: THERE HAS BEEN NO MAJOR CHANGE IN THE GUIDANCE
PACKAGE SINCE THE PREVIOUS RUN, WITH THE GALWEM REMAINING THE BLACK
SHEEP OF THE FLOCK, ANOMALOUSLY MOVING THE SYSTEM NORTHEAST INTO
THE RIDGE. THE REMAINDER OF THE TRACKERS ARE TIGHTLY GROUPED IN AN
ENVELOPE WHICH GRADUALLY EXPANDS TO 130NM AT TAU 72. THEREAFTER, AS
THE MODELS STRUGGLE TO TRACK THE QUICKLY DISSIPATING VORTEX, THE
GUIDANCE DIVERGES SIGNIFICANTLY, WITH THE ECMWF IN PARTICULAR
RACING AHEAD OF ALL THE OTHERS AND PLACING THE CENTER IN THE GULF
OF TONKIN BY TAU 120 WHILE THE NAVGEM RUNS ASHORE TO THE EAST OF
HONG KONG. THE REMAINDER OF THE GUIDANCE IS CLUSTERED MORE
REASONABLY IN A SMALL WINDOW SOUTHWEST OF HONG KONG AT TAU 120. THE
JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST, AND
LIES JUST WEST AND SOUTH OF THE MULTI-MODEL CONSENSUS MEAN THROUGH
THE FORECAST PERIOD WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS
IN FAIR AGREEMENT, WITH THE GFS AND HWRF ON THE HIGH END OF THE
SPECTRUM WITH A PEAK OF 70-75 KNOTS, WHILE THE DECAY SHIPS (GFS) IS
EXTREMELY BEARISH, DISSIPATING THE SYSTEM AT TAU 48. THE JTWC
FORECAST REMAINS ON THE HIGHER END OF THE ENVELOPE, FOLLOWING THE
AHNI TRACKER BUT PEAKING SLIGHTLY LOWER THAN THE AHNI AND HWRF WITH
MEDIUM CONFIDENCE. 

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