Advisories

WDPN32 PGTW 301500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (TWENTYSIX) WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0N 151.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 304 NM EAST OF SAIPAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 26W AS A BROAD, BUT CONSOLIDATING, SYSTEM WITH TWO
RECENTLY FORMED PLUMES OF DEEP CONVECTION IN THE SOUTHWESTERN
QUADRANT. THE 301015Z ASCAT PASS REVEALS 26W HAS A VAST WIND FIELD
OF 20-25 KT WINDS WITH A SMALL POCKET OF 35 KTS IN THE NORTHWESTERN
QUADRANT. THE ASCAT ALSO REVEALS THE CENTER REMAINS ASYMMETRIC AND
ELONGATED IN THE EAST-WEST DIRECTION. ENVIRONMENTAL ANALYSIS
REVEALS A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW TO
MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS), WARM (29-30 C) SEA
SURFACE TEMPERATURES (SST), AND MODERATE RADIAL OUTFLOW. THE MAIN
INHIBITOR TO INTENSIFICATION REMAIN THE STORM'S POOR ORGANIZATION
AND DRY AIR INTRODUCED BY MID-LEVEL WIND SHEAR. THE INITIAL POSITION
AND INTENSITY ARE PLACED WITH HIGH CONFIDENCE BASED ON THE 301015Z
ASCAT.

INITIAL WIND RADII BASIS: WIND RADII BASED ON THE 301015Z ASCAT
DATA

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE CENTERED FAR TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 301140Z
   CIMSS AIDT: 35 KTS AT 301240Z
   CIMSS D-PRINT: 36 KTS AT 301210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 26W IS FORECAST TO CONTINUE TRACKING
WESTWARD WHILE IT REMAINS ON THE SOUTHWESTERN PERIPHERY OF THE
STEERING RIDGE. AT AROUND TAU 24-36, A SHORTWAVE TROUGH TO THE
NORTHWEST WILL WEAKEN THE WESTERN EXTENT OF THE RIDGE, CAUSING 26W
TO TURN NORTHWARD. 26W WILL TRACK GENERALLY NORTHWARD FROM TAU 36
THROUGH THE END OF THE FORECAST PERIOD. 26W IS EXPECTED TO CURVE
SLIGHTLY TO THE NORTHEAST BETWEEN TAU 60-96 AS THE STEERING RIDGE
REBUILDS TO THE WEST FOLLOWING THE PASSING OF THE TROUGH. REGARDING
INTENSITY, 26W IS FORECAST TO GRADUALLY INTENSIFY UNTIL TAU 48.
FOLLOWING TAU 48, 26W IS EXPECTED TO STEADILY INTENSIFY AT AN
INCREASED RATE UNTIL PEAKING AT TAU 96-120. THE ENVIRONMENT IS
EXPECTED TO IMPROVE AFTER TAU 48, NOTABLY LOWER VWS, IMPROVED
POLEWARD OUTFLOW AFTER THE TROUGH PASSES, AND IMPROVED
CONSOLIDATION OF THE STORM STRUCTURE, WHICH WILL ALLOW 26W TO
STRENGTHEN.

MODEL DISCUSSION: DETERMINISTIC PHYSICS-BASED MODEL TRACK GUIDANCE
REMAINS IN POOR AGREEMENT THROUGHOUT THE FORECAST DURATION. THE
MODELS STRUGGLE TO INITIALIZE THE RECURVE TIMING, BOOKENDED BY
NAVGEM AND ECMWF DEPICTING A SHARP RECURVE BEGINNING AT TAU 24, AND
GFS AND GEFS DEPICTING A CHECKMARK TO THE NORTHEAST AT TAU 36. IN
CONTRAST, EXPERIMENTAL AI-BASED MODELS ARE IN STRONG AGREEMENT WITH
MINIMAL CROSS-TRACK OR ALONG-TRACK SPREAD. THE JTWC TRACK FORECAST
IS PLACED IN CONCURRENCE E WITH THE AI MODELS, BASED ON HISTORICAL
HIGH-PERFORMANCE. AS A RESULT OF THE SIGNIFICANT MODEL SPREAD
AMONGST PHYSICS-BASED MODEL SOLUTIONS AND THEIR DISTINCT DIFFERENCE
FROM THE AI MODELS, THE JTWC TRACK FORECAST IS PLACED WITH OVERALL
LOW CONFIDENCE. RELIABLE INTENSITY AIDS ARE ALSO IN POOR AGREEMENT,
THOUGH THE INTENSITY SPREAD IS IMPROVED FROM PREVIOUS CYCLES. MOST
MODELS ARE IN AGREEMENT IN A GRADUAL INTENSIFICATION UNTIL TAU
48-60, FOLLOWED BY A QUICKER RATE OF INTENSIFICATION THROUGH TAU
96. THE JTWC INTENSITY FORECAST LIES CLOSE TO THE MULTI-MODEL
CONSENSUS, GFS, AND HAFS-A THROUGH TAU 36-48. AFTER THAT POINT,
THE JTWC FORECAST IS HEDGED SLIGHTLY HIGHER IN RESPONSE TO THE
IMPROVING ENVIRONMENT DURING THAT TIME. SEVERAL JTWC RAPID
INTENSIFICATION AIDS HAVE REACHED CRITERIA, INDICATING THE
POSSIBILITY OF RAPID INTENSIFICATION IN THE NEXT 24 HOURS. THIS IS
DEEMED UNLIKELY DUE TO THE CURRENT STORM STRUCTURE, BUT NOT
IMPOSSIBLE. DUE TO THE UNCERTAINTY THROUGHOUT THE FORECAST, THE
JTWC INTENSITY FORECAST IS ASSESSED WITH OVERALL MEDIUM CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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