WDPN31 PGTW 312100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (NALGAE) 
WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.6N 116.3E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 251 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
IMPROVING SYSTEM WITH TOWERING DEEP CONVECTION OVER THE
SOUTHWESTERN QUADRANT WITH CLOUD TOP TEMPERATURES OF -84 C. A
PARTIAL 311348Z ASCAT-C PASS REVEALS WHAT APPEARS TO BE A
RELATIVELY TIGHT LOW LEVEL CIRCULATION CENTER (LLCC) WITH A DEFINED
AREA OF 35-40 KNOT WINDS IN THE EASTERN SEMI-CIRCLE. EXTRAPOLATION
FROM THIS ASCAT PASS AND MULTI-AGENCY FIXES LENDS MEDIUM CONFIDENCE
TO THE INITIAL POSITION. THE HIGHER WINDS OF 65-70 KNOTS ARE IN THE
WESTERN SEMI-CIRCLE WHICH WERE INDICATED ON PREVIOUS SMAP DATA. THE
OVERALL IMPROVING STRUCTURE OF THE SYSTEM ALONG WITH AIDT OF 66
KNOTS, SATCON OF 69 KNOTS, AND THE PGTW DVORAK ESTIMATE OF 4.0
LENDS HIGH CONFIDENCE IN THE INITIAL INTENSITY OF 70 KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN AXIS OF THE SUBTROPICAL RIDGE
(STR) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 69 KTS AT 311441Z
   CIMSS ADT: 61 KTS AT 311740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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: TY NALGAE HAS REACHED ITS PEAK INTENSITY OF 70
KNOTS AND WILL NOW BEGIN TO SHOW SIGNS OF WEAKENING THROUGHOUT THE
REMAINDER OF THE FORECAST PERIOD. THE SYSTEM WILL CONTINUE TO TRACK
NORTH-NORTHWESTWARD OVER THE NEXT 24 HOURS AS IT RIDES THE WESTERN
PERIPHERY OF THE STR. AS IT TRANSITS TO THE NORTHERN PORTION OF THE
SOUTH CHINA SEA IT WILL ENCOUNTER RELATIVELY COOLER SEA SURFACE
TEMPERATURES OF 25-26C THAT ARE BEING INTRODUCED INTO THE REGION
DUE TO THE INTENSE NORTHEASTERLY WIND FLOW THROUGH THE TAIWAN
STRAIT. AFTER TAU 36, THOSE INTENSE WINDS FROM THE NORTHEAST WILL
BE THE STEERING MECHANISM OF THE SYSTEM AS IT MAKES A DRAMATIC TURN
WESTWARD AND BEGIN TO FURTHER DECREASE IN INTENSITY DUE TO LAND
INTERACTION WITH SOUTHEAST CHINA. IN ADDITION TO LAND INTERACTION,
DRY AIR FOR THE NORTH AND WEST WILL BE ENTRAINED INTO THE SYSTEM,
FURTHER HAMPERING ANY FURTHER DEVELOPMENT. BY TAU 96, TY NALGAE
WILL FULLY DISSIPATE OVER THE ISLAND OF HAINAN.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT WITH THE CONSENSUS ENVELOPE LYING SLIGHTLY MORE POLEWARD
THAN PREVIOUS RUNS. UEMI AND AFUI ARE THE OUTLIERS SHOWING A MORE
NORTHERLY PROGRESSION OVER THE 48 HOURS, FOLLOWED BY A SHARP TURN
TO THE SOUTH-SOUTHWEST. DUE TO THESE OUTLIERS, THE JTWC TRACK WAS
PLACED WITH MEDIUM CONFIDENCE SLIGHTLY TO THE LEFT OF THE CONSENSUS
TRACK AND SLIGHTLY MORE POLEWARD THAN THE PREVIOUS JTWC FORECAST
TRACK THROUGH TAU 72. INTENSITY CONSENSUS IS IN REALLY GOOD
AGREEMENT THROUGH TAU 60, THEN DISAGREE WITH A 15 KNOT SPREAD
THROUGH TAU 96. THIS IS MORE THAN LIKELY DUE TO VARIOUS SOLUTIONS
TAKING THE SYSTEM OVER LAND SOONER RATHER THAN LATER. THE JTWC
INTENSITY FORECAST IS SET WITH HIGH CONFIDENCE THROUGH TAU 72 AND
MEDIUM CONFIDENCE THROUGH TAU 96.

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