WDPN31 PGTW 302100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 
016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.3N 117.3E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 237 NM WEST-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TS 26W (NALGAE) HAS TRACKED ERRATICALLY OVER THE PREVIOUS 12 HOURS,
HAVING SPENT THE NIGHT LOOPING BACK ON ITSELF WHILE IT SLOWLY
CONSOLIDATED, BUT HAS EJECTED OUT TO THE NORTH OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
LOPSIDED SYSTEM, WITH DEEP CONVECTION PERSISTING OVER THE WESTERN
AND SOUTHERN QUADRANTS, AND FLARING UP, BUT REMAINING RELATIVELY
DISORGANIZED, IN THE EASTERN PORTIONS OF THE CIRCULATION. A 301729Z
AMSR-2 89GHZ MICROWAVE IMAGE SHOWED CYCLONICALLY CURVED BANDS OF
DEEP CONVECTION TO THE WEST AND SOUTH, AND FRAGMENTED AND SHALLOW
BANDS TO THE EAST. NO LOW LEVEL CIRCULATION CENTER (LLCC) WAS
EVIDENT IN THE 89GHZ IMAGE, BUT A LOW EMISSIVITY REGION AND SHALLOW
BANDING FEATURES WERE CLEAR IN THE 36GHZ BAND, WHICH LENT SOME
INCREASED CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY
IS ASSESSED TO HAVE REMAINED STEADY AT 45 KNOTS, IN LINE WITH THE
ADT VALUES, RIGHT IN THE MID-RANGE OF THE AGENCY DVORAK CURRENT
INTENSITY ESTIMATES. THE ENVIRONMENT IS GENERALLY FAVORABLE, WITH
WARM SSTS AND LOW VWS. UPPER-LEVEL OUTFLOW HAS IMPROVED, WHICH IS
ALLOWING FOR THE SYSTEM TO CONTINUE TO CONSOLIDATE, THOUGH EARLIER
SCATTEROMETER DATA SHOWS THE RADIUS OF MAXIMUM WINDS IS STILL
FAIRLY LARGE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 50 KTS AT 301725Z
   CIMSS ADT: 43 KTS AT 301740Z

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: HIGH
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: HAVING SPENT THE LAST 12 HOURS OR SO JUST
MEANDERING IN A WEAK STEERING ENVIRONMENT, TS 26W HAS BEEN EJECTED
OUT TO THE NORTH AS THE DEEP-LAYER STEERING GRADIENT HAS
STRENGTHENED ON THE WESTERN SIDE OF THE STR. THE STRUCTURE OF THE
SYSTEM HAS STEADILY IMPROVED, THOUGH OVERNIGHT SCATTEROMETER DATA
INDICATED THE RMW REMAINS AROUND 60NM. THE LATEST IMAGERY SHOWS A
CLEAR AREA, THAT LOOKS LIKE A DEVELOPING EYE, BUT THE ACTUAL CENTER
IS FURTHER NORTH, UNDER SOME VERY COLD CLOUD TOPS AND BURSTS OF
LIGHTNING. HOWEVER, THERE ARE SOME INDICATIONS THE ACTUAL CENTER
MAY BE ROTATING AROUND A CENTROID AS IT CONSOLIDATES DOWN. IF THE
SYSTEM CAN CONTINUE THIS CONSOLIDATION PHASE, IT SHOULD THEN
COMMENCE AN INTENSIFICATION PHASE, WITH ALL OTHER ENVIRONMENTAL
PARAMETERS BEING FAVORABLE. THE SYSTEM IS EXPECTED TO REACH A PEAK
OF 65 KNOTS BY TAU 36. AT THIS POINT, THE SYSTEM WILL START TO FEEL
THE EFFECTS OF DECREASING SSTS, INCREASING SHEAR AND DECREASED
OUTFLOW ALOFT AND WILL STEADILY WEAKEN THROUGH THE REMAINDER OF THE
FORECAST. AS IT WEAKENS, IT WILL BE STEERED BY PROGRESSIVELY LOWER
LEVEL FLOWS, AND WILL BEGIN A GRADUAL TURN TO THE WEST BY TAU 48,
ALONG THE SOUTHERN SIDE OF A SHALLOW ANTICYCLONE OVER CENTRAL
CHINA. THE SYSTEM IS EXPECTED TO REMAIN OFFSHORE OF SOUTHERN CHINA
AND MAKE LANDFALL ALONG THE NORTHEAST COAST OF HAINAN ISLAND AROUND
TAU 120 AS A WEAK TROPICAL DEPRESSION AT BEST. IT IS POSSIBLE THE
SYSTEM COULD DISSIPATE AS A TROPICAL CYCLONE PRIOR TO TAU 120, TO
THE SOUTHWEST OF HONG KONG. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
GOOD AGREEMENT, WITH THE EXCEPTION OF THE GALWEM AND UKMET
TRACKERS, WHICH STUBBORNLY CONTINUE TO TRACK THE SYSTEM DUE NORTH
INTO THE TAIWAN STRAIT. THE REMAINDER OF THE GUIDANCE IS CONFINED
TO AN ENVELOPE THAT GRADUALLY EXPANDS TO 85NM BY TAU 72. AFTER TAU
72, AS THE SYSTEM WEAKENS DRAMATICALLY AND THE MODELS BEGIN TO LOSE
TRACK OF THE VORTEX, MODEL GUIDANCE SPREADS OUT TO A 200NM
CROSS-TRACK ENVELOPE, WHILE ALONG-TRACK SPREAD ALSO INCREASES,
PARTICULARLY AFTER TAU 96 AS THE SYSTEM DISSIPATES. THE JTWC
FORECAST LIES SOUTH OF THE MULTI-MODEL CONSENSUS WHICH IS BEING
PULLED TOO FAR NORTH BY THE GALWEM AND UKMET, AND MOST CLOSELY
TRACKS THE ECMWF TRACKER WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE
IS MIXED, WITH THE DECAY-SHIPS DISSIPATING THE SYSTEM WITHIN 36
HOURS, WHILE THE HWRF AND GFS INTENSIFY IT UP TO 65 KNOTS. THE JTWC
FORECAST TRACKS THE GFS SOLUTION THROUGH THE FORECAST PERIOD 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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