WDPN31 PGTW 310900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.3N 116.8E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 291 NM NORTHWEST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A LARGE
CLUSTER OF PERSISTENT DEEP CONVECTION OVER THE WESTERN AND SOUTHERN
SEMICIRCLE OF A BROAD LOW-LEVEL CIRCULATION CENTER (LLCC). ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES INTENSE
CONVECTIVE BURSTS, AND VORTICAL HOT TOWERS, NOW BEGINNING TO FULLY
WRAP UPSHEAR AROUND THE OUTER PERIPHERY OF THE LLCC, INDICATING THE
SYSTEM IS STRENGTHENING.  ANIMATED WATER VAPOR IMAGERY DEPICTS
MODERATE POLEWARD OUTFLOW STREAMING AWAY FROM THE SYSTEM, OUTWARD
TOWARD THE NORTHEAST. AN EARLIER 302300Z SSMIS 37GHZ MICROWAVE
IMAGE DEPICTED A LARGE 65-NM WIDE EYE FEATURE. THE INITIAL POSITION
IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE EYE FEATURE
AND AGREEMENT WITH AGENCY FIX POSITIONS. THE INITIAL INTENSITY OF
60 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW, RJTD
DVORAK INTENSITY ESTIMATES ALONG WITH A COMBINATION OF OBJECTIVE 
DVORAK INTENSITY ESTIMATES. ENVIRONMENTAL CONDITIONS ARE GENERALLY
FAVORABLE, CHARACTERIZED BY LOW (10-15 KNOTS), WARM (28-29C) SEA
SURFACE TEMPERATURES (SSTS) AND MODERATE RADIAL OUTFLOW AND A
DEVELOPING FAVORABLE POLEWARD OUTFLOW CHANNEL.

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: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   CIMSS ADT: 55 KTS AT 310600Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 WILL CONTINUE TO TRACK
NORTHWARD OVER THE NEXT 48 HOURS ALONG THE WESTERN SIDE OF THE
STEERING RIDGE TO THE EAST, WHICH IS ORIENTED ALMOST DUE
NORTH-SOUTH. ADDITIONALLY, THE SYSTEM IS EXPECTED TO INTENSIFY, AS
AN UPPER-LEVEL POINT SOURCE ALOFT IS ANTICIPATED TO DEVELOP ALOFT
ALONG WITH INCREASED POLEWARD OUTFLOW. THESE IMPROVED ENVIRONMENTAL
FACTORS WILL ALLOW FOR STEADY INTENSIFICATION TO A PEAK OF 75 KNOTS 
BY TAU 24. HOWEVER, AFTER TAU 36, THE SYSTEM WILL BE IMPACTED BY 
COOLING SSTS, DRY AIR ENTRAINMENT, AND REDUCED OUTFLOW WHICH WILL 
LEAD TO A STEADY WEAKENING TREND THROUGH TAU 120. FURTHERMORE, THE 
STEERING PATTERN EVOLVES, AS THE STR TO THE EAST BUILDS WESTWARD, 
ALONG WITH LOWER-LEVEL FLOW OUT OF THE NORTH-NORTHEAST. THESE 
STEERING FACTORS WILL GRADUALLY TURN TS 26W TO THE WEST AND THEN 
SOUTHWEST.THE SYSTEM IS EXPECTED TO DISSIPATE OVER HAINAN ISLAND BY 
TAU 120.  

MODEL DISCUSSION: THE JTWC TRACK FORECAST REMAINS CONSISTENT WITH
THE PREVIOUS FORECAST, AND LIES CLOSE TO THE MULTI-MODEL CONSENSUS
MEAN THROUGH THE FORECAST PERIOD WITH MEDIUM CONFIDENCE. NUMERICAL
MODEL TRACK GUIDANCE REMAINS IN FAIR AGREEMENT, WITH THE PRIMARY
OUTLIERS BEING THE GALWEM AND THE UKMO TRACKERS ON THE EASTERN EDGE
OF THE GUIDANCE ENVELOPE. THE REMAINDER OF THE TRACKERS ARE TIGHTLY
GROUPED IN AN ENVELOPE WHICH GRADUALLY EXPANDS TO 150NM AT TAU 120.


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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