WDPN31 PGTW 292100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.8N 120.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 86 NM NORTH-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE TRACK OF TROPICAL STORM 26W (NALGAE) HAS BEEN UPDATED TO
REFLECT PASSAGE TO THE EAST OF MANILA VICE THE WEST, OVER THE PAST
12 HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
DEPICTS A RELATIVELY DISORGANIZED PRESENTATION AT THE MOMENT, WITH
DETERMINATION OF THE CENTER BEING CHALLENGING AT BEST. BASED ON
SURFACE OBSERVATIONS AND ANIMATED PAGASA RADAR IMAGERY, THE LOW
LEVEL CIRCULATION CENTER (LLCC) IS ASSESSED TO HAVE FOLLOWED THE
TERRAIN FEATURES, PASSED EAST OF MANILA AND THEN TRACKED UP THE
EAST SIDE OF THE ZAMBALES MOUNTAINS. THE MOST RECENT OBSERVATIONS
SUGGEST THE LLCC IS POSITIONED JUST SOUTH OF DAGUPAN, ABOUT TO
EMERGE BACK INTO THE SOUTH CHINA SEA (SCS). BUT DUE TO THE LACK OF
A DISTINCT RADAR PRESENTATION AND NO LLCC EVIDENT IN THE EIR, THE
INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE. INTENSITY
ESTIMATES SHOW A WIDE SPREAD, WITH PGTW OVER LAND, BUT KNES AND
RJTD CAME IN WITH A T3.0 CURRENT INTENSITY ESTIMATE, AND THE CIMSS
OPEN-AIIR TECHNIQUE REPORTED A 43 KNOT INTENSITY ESTIMATE AT
1800Z. THE ADT AND SATCON ARE UNREALISTICALLY HIGH, AS THEY ARE
FOLLOWING THE PREVIOUS FORECAST INTERPOLATION, AND ARE POSITIONED
WELL TO THE SOUTHWEST OF THE ACTUAL POSITION. MEAN SEA-LEVEL
PRESSURE READINGS FROM CLARK AIR BASE AND DAGUPAN BOTTOMED OUT
AROUND 991MB WHICH SUPPORTS THE 45 KNOT INITIAL INTENSITY WITH HIGH
CONFIDENCE. THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE, WITH LOW
VWS, AND DECENT POLEWARD AND EQUATORWARD OUTFLOW, BUT THE TIME
OVER LAND HAS ROBBED THE SYSTEM OF ENERGY AND ERODED THE LOW-LEVEL
CORE. ONCE BACK OVER WATER, THE ENVIRONMENT IS EXPECTED TO QUICKLY
IMPROVE HOWEVER. THE SYSTEM IS MOVING ALONG THE LOCALIZED TERRAIN
FEATURES AND IS CURRENTLY DECOUPLED FROM THE DEEP-LAYER STEERING
RIDGE, BUT AGAIN, AS IT MOVES BACK OVER WATER THE SUBTROPICAL RIDGE
(STR) WILL RESUME STEERING.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST, AND LOCALIZED TERRAIN
FEATURES. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 54 KTS AT 291745Z
   CIMSS ADT: 57 KTS AT 291730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: HAVING MOVED UP THE CENTRAL PLAINS OF LUZON,
ALONG THE EAST SIDE OF THE ZAMBALES RANGE, TS 26W IS CURRENTLY
MOVING BACK OVER WATER TO THE WEST OF THE LINGAYAN GULF. THE SYSTEM
IS EXPECTED TO TRACK GENERALLY WESTWARD FOR THE NEXT 12 TO 18 HOURS
AS IT CONTINUES TO RECONSOLIDATE. AS IT CONSOLIDATES AND
INTENSIFIES, THE STEERING LEVEL INCREASES AND THE TRACK IS EXPECTED
TO TURN POLEWARD AFTER TAU 24 AS THE SYSTEM MOVES UP THE WEST SIDE
OF THE DEEP-LAYER STEERING RIDGE TO THE EAST. A RELATIVELY WEAK
MID-LATITUDE TROUGH MOVING QUICKLY TO THE EAST IN ZONAL FLOW WILL
PASS BY TO THE NORTH AROUND TAU 36, INDUCE A WEAKNESS IN THE
STEERING RIDGE, AND ALLOW TS 26W TO TRACK TOWARDS THE WEAKNESS
THROUGH 48. AFTER EMERGING BACK OVER WATER AND MOVING AWAY FROM THE
INFLUENCE OF TERRAIN, IT IS EXPECTED THAT TS 26W WILL FAIRLY
QUICKLY REESTABLISH ITS LOW-LEVEL CORE STRUCTURE AND BEGIN TO
INTENSIFY, THOUGH ONLY SLOWLY AT FIRST. AFTER ABOUT TAU 12,
INTENSIFICATION IS EXPECTED TO PICK UP AS THE UPPER-LEVEL PATTERN
BECOMES MORE FAVORABLE, SHEAR REMAINS LOW, AND SSTS REMAIN WARM. THE
SYSTEM IS EXPECTED TO PEAK AT 70 KNOTS BY 48. AS THE SYSTEM
INTENSIFIES, IT WILL PUMP WARM AIR POLEWARD ON THE EASTERN SIDE,
INTO THE WESTERN SIDE OF THE STEERING RIDGE AND THIS WILL IN TURN
BUILD THE RIDGE TO THE NORTH OF THE SYSTEM. THIS EFFECT IS MOST
CLEARLY SEEN IN THE ECMWF AND TO A LESSER EXTENT IN GFS. AFTER
REACHING THE PEAK INTENSITY AT TAU 48, SSTS BEGIN TO DECREASE,
SHEAR BEGINS TO PICK UP, AND THE SYSTEM BEGINS TO ENTRAIN
RELATIVELY LOW THETA-E AIR, CURRENTLY LURKING ALONG THE COAST OF
CHINA, INTO THE CORE OF THE SYSTEM. THE SYSTEM WILL BEGIN TO
RAPIDLY WEAKEN AFTER TAU 48, AND AS IT DOES SO, WILL TURN TO A
WESTWARD TRAJECTORY AS IT COMES UNDER THE INCREASING INFLUENCE OF
THE LOW-LEVEL FLOW FROM THE NORTH. BY THE END OF THE FORECAST, THE
SYSTEM IS FORECAST TO BE A MINIMAL TROPICAL DEPRESSION SOUTH OF
HONG KONG. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE CONCUR
ON THE OVERALL TRACK SCENARIO, THOUGH THE ENSEMBLES STILL SHOW A
FAIRLY WIDE SPREAD IN POSSIBLE SOLUTIONS. THE DETERMINISTIC
CONSENSUS MEMBERS, WITH THE EXCEPTION OF GALWEM, ARE IN TIGHT
AGREEMENT, WITH THE ENVELOPE GRADUALLY EXPANDING FROM 50NM AT TAU
36 TO 110NM AT TAU 72. THE ENVELOPE EXPANDS SIGNIFICANTLY AFTER TAU
72 HOWEVER, AS THE MODELS WEAKEN THE VORTEX AT DIFFERING TIMES AND
THUS TURN THE SYSTEM WEST AT VARIOUS POINTS AND TIMES. ACROSS-TRACK
SPREAD INCREASES TO A MAXIMUM OF 555NM AT TAU 120 BETWEEN THE ECMWF
AND THE GALWEM OUTLIERS. THE BULK OF THE CONSENSUS MEMBERS HOWEVER
ARE CONTAINED WITHIN A 250NM WINDOW CONCENTRATED TO THE SOUTH OF
HONG KONG. THE JTWC FORECAST LIES WEST AND SOUTH OF THE CONSENSUS
MEAN, MOSTLY CLOSELY TRACKING THE GFS ENSEMBLE MEAN, WITH MEDIUM
CONFIDENCE. INTENSITY GUIDANCE HAS IMPROVED SINCE THE PREVIOUS RUN,
WITH ALL OF THE RELIABLE MEMBERS CONSTRAINED WITHIN A 20 KNOT
ENVELOPE WITH A PEAK BETWEEN 55-75 KNOTS. THE ENSEMBLE INTENSITY
PROBABILITY DATA FOR GEFS AND COAMPS-TC ENSEMBLE SUPPORT A HIGH
PROBABILITY OF MODERATE INTENSIFICATION THROUGH TAU 48 AND A 30
PERCENT CHANCE OF RAPID INTENSIFICATION (RI). THE JTWC FORECAST
LIES ON THE HIGHER END OF ENVELOPE AND ABOUT FIVE KNOTS HIGHER THAN
THE CONSENSUS MEAN, 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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