WDPN33 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (ATSANI) WARNING 
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.3N 138.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 424 NM SOUTH-SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION (TD) 19W (ATSANI) AS A HIGHLY SHEARED AND HIGHLY
ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC). 19W HAS BEGUN TO
ACCELERATE TO THE NORTH AS IT DECOUPLED FROM THE VERY SHORT-LIVED
CENTRAL DEEP CONVECTION AND IS MORE SUSCEPTIBLE TO STEERING
INFLUENCE FROM THE LOWER LEVELS, WHICH ARE CURRENTLY DOMINATED BY
THE STRONG SOUTHEASTERLIES FEEDING INTO TYPHOON 17W (SAUDEL).
ENVIRONMENTAL ANALYSIS REVEALS AN UNFAVORABLE ENVIRONMENT,
CHARACTERIZED BY MODERATE TO HIGH (20-25 KTS) VERTICAL WIND SHEAR,
SUBSTANTIAL DEEP-LAYER DRY AIR ENTRAINMENT, AND NO UPPER-LEVEL
SUPPORT, INSIGNIFICANTLY OFFSET BY THE WARM (29-30 C) SEA SURFACE
TEMPERATURES (SST). THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE FULLY EXPOSED LLCC IN ANIMATED EIR. THE
INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGREEMENT BETWEEN THE CIMSS AUTOMATED INTENSITY
ESTIMATES AND THE AGENCY DVORAK FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: STRONG LOW-LEVEL SOUTHEASTERLIES AND
THE SOUTHEASTWARD EXTENSION OF A SUBTROPICAL RIDGE CENTERED OVER
JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 39 KTS AT 241840Z
   CIMSS ADT: 34 KTS AT 241940Z
   CIMSS AIDT: 34 KTS AT 241940Z
   CIMSS D-PRINT: 25 KTS AT 241910Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: PERSISTENT DEEP-LAYER DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 19W IS FORECAST TO CONTINUE TRACKING
GENERALLY NORTHWARD, WITH A SLIGHT NORTH-NORTHWESTWARD TURN
EXPECTED WITHIN THE NEXT 12 HOURS. 19W WILL TRACK NORTHEASTWARD IN
THE WAKE OF TYPHOON 17W THROUGH TAU 36, AT WHICH POINT, IT IS
EXPECTED TO GET OVERWHELMED BY THE INCREASINGLY HOSTILE ENVIRONMENT
AND DISSIPATE. VWS IS EXPECTED TO REMAIN BETWEEN 25-35 KTS WITH
PERSISTENT DRY AIR ENTRAINMENT FOR THE DURATION OF THE FORECAST
PERIOD, QUICKLY WEAKENING THE SYSTEM. WITHIN THE PAST FEW HOURS,
19W HAS BECOME INCREDIBLY ELONGATED ALONG THE NORTHWEST-SOUTHEAST
AXIS, INDICATING THAT DISSIPATION MAY OCCUR QUICKER THAN EXPECTED. 

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH TAU 36, THOUGH MANY MODELS DROP THE VORTEX AFTER
TAU 12. AS A RESULT, THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. RELIABLE INTENSITY AIDS
ARE ALSO IN STRONG AGREEMENT THAT 19W WILL STEADILY WEAKEN UNTIL
DISSIPATION NO LATER THAN TAU 36, LENDING HIGH CONFIDENCE TO THE
JTWC INTENSITY FORECAST. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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