WDPN31 PGTW 310300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.6N 117.0E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 260 NM WEST-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 26W (NALGAE) IS QUICKLY ORGANIZING AND INTENSIFYING
UNDER FAVORABLE ENVIRONMENTAL CONDITIONS IN THE SOUTH CHINA SEA.
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS DEEP
CONVECTIVE TOWERS DEVELOPING TO THE NORTHWEST AND SOUTH OF, AND
WRAPPING INTO, THE CONSOLIDATING LOW LEVEL CIRCULATION CENTER
(LLCC), AND DEVELOPING A BANDING EYE FEATURE. A 302300Z SSMIS 37GHZ
MICROWAVE IMAGE SHOWED A LARGE MICROWAVE EYE FEATURE, WITH A BROAD
BAND OF DEEP CONVECTION TO THE WEST AND A NARROWER BAND OF WEAKER
CONVECTION BEGINNING TO WRAP UP THE EAST SIDE. MSI AT THE 0100Z
HOUR DEPICTS VORTICAL HOT TOWERS WITH STRONG LIGHTNING BURSTS NOW
ROTATING UPSHEAR TO THE EAST OF THE CENTER. IF THIS PERSISTS WE
WILL LIKELY SEE AN EYE FORMING OVER THE NEXT FEW HOURS. THE INITIAL
POSITION IS ASSESSED WITH MEDIUM CONFIDENCE USING THE BROAD
MICROWAVE EYE IN THE RECENT MICROWAVE DATA. THE INITIAL INTENSITY
IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PREPONDERANCE OF THE
AGENCY FIX INTENSITIES, AND THE ADT. OF NOTE, THE CIMSS OPEN-AIIR
TECHNIQUE IS SHOWING A SHARP UPTICK IN INTENSITY, NOW ESTIMATED TO
BE NEAR 65 KNOTS, UP FROM JUST 50 KNOTS SIX HOURS AGO, AND IS
POTENTIALLY A GOOD LEADING INDICATOR OF THINGS TO COME. THE OVERALL
ENVIRONMENT IS FAVORABLE FOR DEVELOPMENT WITH WARM SSTS, LOW VWS
AND AN IMPROVING UPPER-LEVEL FLOW PATTERN CHARACTERIZED BY
DIVERGENT EASTERLY FLOW AND A DEVELOPING POLEWARD OUTFLOW CHANNEL.
THE SYSTEM IS MOVING NORTHWARD ALONG THE WESTERN SIDE OF A
DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE EAST.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 53 KTS AT 310010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: DEVELOPING POLEWARD OUTFLOW CHANNEL; MODERATE
EQUATORWARD OUTFLOW. 

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: TROPICAL STORM 26W IS STILL MOVING NORTHWARD,
THOUGH TRACK SPEEDS HAVE SLOWED A BIT SINCE THE PREVIOUS BEST
TRACK, DOWN TO ABOUT SIX KNOTS. WITH THE WESTERN SIDE OF THE
STEERING RIDGE ORIENTED ALMOST DUE NORTH-SOUTH AND A WEAKNESS TO
THE NORTH INDUCED BY A PASSING TROUGH, THE SYSTEM IS EXPECTED TO
CONTINUE TRACKING NORTHWARD THROUGH TAU 48. OVER THE NEXT 24 HOURS,
THE UPPER-LEVEL ENVIRONMENT WILL CONTINUE TO IMPROVE, WITH
DEVELOPMENT OF A MESOSCALE ANTICYCLONE OVER TOP OF THE SYSTEM AND
AN IMPROVED POLEWARD OUTFLOW CHANNEL. THIS WILL ALLOW FOR A FAIRLY
RAPID UPTICK IN INTENSITY, TO A PEAK OF 75 KNOTS BY TAU 24. THIS
BURST OF INTENSIFICATION WILL BE SHORT-LIVED, AS THE SYSTEM FIRST
GETS SLAMMED BY A SHARP INCREASE IN SOUTHERLY SHEAR, THEN SEES A
DRASTIC REDUCTION IN OUTFLOW ACCOMPANIED BY AN INFLUX OF DRIER
MID-LEVEL AIR, AND THEN BEGINS TO TRACK OVER RELATIVELY COOLER
WATERS TO THE SOUTHEAST OF CHINA. THE COMBINED EFFECTS OF THE ABOVE
WILL SEE THE SYSTEM STEADILY WEAKENING AFTER IT REACHES ITS PEAK.
AS IT WEAKENS, TS 27W WILL GRADUALLY TURN TO THE WEST AND THEN
SOUTHWEST AS IT COMES UNDER THE STEERING INFLUENCE OF PROGRESSIVELY
LOWER LEVELS OF THE ATMOSPHERE. THE SYSTEM IS EXPECTED TO DISSIPATE
OVER HAINAN ISLAND BY TAU 120.  

MODEL DISCUSSION: TRACK GUIDANCE IS IN FAIR AGREEMENT WITH A COUPLE
OF DISTINCT GROUPINGS. THE GALWEM, UKMET AND UKMET ENSEMBLE CARRY
THE SYSTEM TO THE NORTHEAST TOWARDS THE SOUTHERN TAIWAN STRAIT
BEFORE TURNING SHARPLY BACK TO THE SOUTHWEST AFTER TAU 72. THE
REMAINDER OF THE CONSENSUS MEMBERS ARE CONSTRAINED TO A FAIRLY
TIGHT ENVELOPE WITH A 110NM SPREAD AT TAU 72. CONSISTENT WITH
PREVIOUS MODEL RUNS, THE GUIDANCE GETS SQUIRRELLY AFTER TAU 72, AS
THE SYSTEM WEAKENS. CROSS-TRACK SPREAD INCREASES TO OVER 300NM BY
TAU 120, WITH A MODEST INCREASE IN ALONG-TRACK SPREAD AS WELL. THE
JTWC FORECAST LIES ON THE SOUTH SIDE OF THE CONSENSUS MEAN TO
OFFSET THE UNREALISTIC MODELS NOTED ABOVE, BUT CONFIDENCE REMAINS
MEDIUM. THE JTWC INTENSITY FORECAST LIES ABOUT 10 KNOTS ABOVE ALL
OF THE AVAILABLE GUIDANCE, HEDGED HIGHER BASED ON THE RAPID
DEVELOPMENT OF THE SYSTEM OVER THE PAST SIX HOURS AND IN
ANTICIPATION OF DEVELOPMENT OF AN EYE. THE BULK OF THE INTENSITY
GUIDANCE HOVERS AROUND 55 KNOTS THROUGH TAU 24, THOUGH THE GFS DOES
JUMP UP TO 65 KNOTS. TAU 24 LOOKS TO BE THE TIMING OF THE PEAK
REGARDLESS OF THE VALUE, WITH ALL OF THE GUIDANCE INDICATING RAPID
WEAKENING AFTER THIS POINT. 

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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