Advisories

WDPN32 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (CHOI-WAN) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.9N 144.6E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 128 NM NORTH-NORTHWEST OF TINIAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 26W AS A CONSOLIDATING SYSTEM, WITH IMPROVING VERTICAL
ALIGNMENT REFLECTED IN THE ROTATION PRESENT IN THE CLOUD CANOPY.
ADDITIONALLY, SCATTERED BLOOMS OF OVERSHOOTING DEEP CONVECTION ARE
FORMING WITHIN THE CENTRAL DENSE OVERCAST AND THROUGHOUT THE
CONVECTION EXTENDING TO THE SOUTHWEST. THE 020636Z SSMIS MICROWAVE
DATA REVEALS SYMMETRIC LOWER-LEVEL CLOUD BANDING AND A NASCENT
UPPER-LEVEL MICROWAVE EYE FEATURE WITH AN OPEN NORTHWEST SECTOR.
ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT,
CHARACTERIZED BY WARM (29-30 C) SEA SURFACE TEMPERATURES, HIGH
(125-150 KJ PER CM SQUARED) OCEAN HEAT CONTENT (OHC), STRONG
EQUATORWARD OUTFLOW, AND LOW TO MODERATE (15-20 KTS) VERTICAL WIND
SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE PREVIOUSLY MENTIONED 020636Z SSMIS DATA. THE INITIAL
INTENSITY OF 60 KTS IS ASSESSED WITH LOW CONFIDENCE BASED ON THE
EARLIER 020028Z ASCAT DATA, SUPPLEMENTED BY THE AGENCY DVORAK FIXES
AND THE CIMSS AUTOMATED INTENSITY ESTIMATES LISTED BELOW. THE CIMSS
INTENSITY ESTIMATES ARE ASSESSED TO BE UNDERESTIMATING THE ACTUAL
INTENSITY OF THE STORM.

INITIAL WIND RADII BASIS: PERSISTENCE FROM THE 020028Z ASCAT DATA

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.5 - 55 KTS
   PHFO: T3.5 - 55 KTS
   CIMSS SATCON: 50 KTS AT 020610Z
   CIMSS ADT: 47 KTS AT 020710Z
   CIMSS AIDT: 43 KTS AT 020710Z
   CIMSS D-MINT: 46 KTS AT 020636Z
   CIMSS D-PRINT: 60 KTS AT 020710Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 26W (CHOI-WAN) IS VERY SLOWLY TURNING 
POLEWARD AS THE STR TO ITS NORTHEAST IS ERODED BY A PASSING SHORTWAVE 
TROUGH TO THE NORTH. THE TROUGH WILL CONTINUE TO ERODE THE WESTERN 
FLANK OF THE STR THROUGH TAU 48, INDUCING A NORTHEASTWARD TRACK FOR 
CHOI-WAN. BY TAU 48-60, THE TROUGH IS EXPECTED TO HAVE PASSED AND THE 
STR IS EXPECTED TO RE-ORIENT AND BUILD WESTWARD. THIS IS EXPECTED TO 
CAUSE 26W TO CURVE NORTHWESTWARD FROM TAU 48-60 UNTIL TAU 72-96. JUST 
BEFORE TAU 96, 26W IS ANTICIPATED TO BEGIN ROUNDING THE STR AND 
SKIRTING THE EDGE OF THE UPPER-LEVEL WESTERLIES. 26W IS FORECAST TO 
MAINTAIN A NORTHEASTWARD TRACK FROM TAU 96-120. REGARDING INTENSITY, 
26W IS FORECAST TO STEADILY INTENSIFY THROUGH TAU 48. AT AROUND TAU 
12, THE ENVIRONMENT WILL BECOME MORE FAVORABLE, INCLUDING REDUCED VWS 
OF 10-15 KTS, AN ENHANCED POLEWARD OUTFLOW CHANNEL PROVIDED BY THE 
RETREATING STR, AND A PATCH OF HIGHER (150+ KJ PER CM SQUARED) OCEAN 
HEAT CONTENT (OHC). DUE TO THE IMPROVED ENVIRONMENT BETWEEN TAU 24-48, 
AN INCREASED RATE OF INTENSIFICATION MAY BE OBSERVED, INCLUDING THE
POTENTIAL FOR RAPID INTENSIFICATION AND A PEAK INTENSITY HIGHER THAN 
105 KTS. BY TAU 48-60, 26W IS FORECAST TO ENTER INTO A REGION OF LOWER 
OHC (50-75 KJ PER CM SQUARED), WHICH IS EXPECTED TO INDUCE A WEAKENING 
TREND FROM TAU 60-120. ADDITIONALLY, THE ENVIRONMENT WILL CONTINUE TO
DETERIORATE AS 26W TRACKS FURTHER POLEWARD. CHOI-WAN IS EXPECTED TO
CROSS THE 26C ISOTHERM BETWEEN TAU 96-120 AND SIMULTANEOUSLY CONTEND 
WITH INCREASING VWS DUE TO CLOSING PROXIMITY TO THE WESTERLIES, WHICH 
WILL ALSO FORCE HIGH AMOUNTS OF DRY AIR INTO THE CORE. CHOI-WAN IS 
EXPECTED TO MAINTAIN AN EXPANSIVE WIND FIELD THROUGH THE DURATION OF 
THE FORECAST.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN MODERATE 
AGREEMENT IN TERMS OF TRACK LOCATION, BUT POOR AGREEMENT REGARDING 
TRACK SPEED. THERE REMAINS A DISTINCT SPEED BIFURCATION BETWEEN THE 
PHYSICS-BASED MODELS AND EXPERIMENTAL AI-BASED MODELS. HOWEVER, 
SEVERAL PHYSICS-BASED SOLUTIONS ARE NOW IN AGREEMENT WITH THE AI-
MODELS, INCLUDING ECMWF, UKMET, NAVGEM, AND GALWEM. THE PRIMARY 
OUTLIERS ARE GFS AND GEFS, BOTH OF WHICH DEPICT SIGNIFICANTLY SLOWER 
TRACK SPEEDS THAN ANY OTHER MODEL SOLUTION. THE SIGNIFICANT 
DIFFERENCES IN TRACK SPEED AS 26W TRACKS POLEWARD COMPOUNDS TO A 600 
NM ALONG-TRACK SPREAD MEASURED AT TAU 120. THE JTWC TRACK FORECAST IS 
PLACED NEAR THE PHYSICS-BASED AND AI-BASED MULTI-MODEL CONSENSUSES 
WITH MEDIUM CONFIDENCE FROM TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-
120 AS A RESULT OF THE UNCERTAINTY REGARDING THE MODEL SPREAD AFTER 
TAU 72. RELIABLE INTENSITY AIDS ARE IN MODERATE AGREEMENT IN 
INTENSIFICATION AND WEAKENING TRENDS, BUT DISAGREE ON THE PEAK 
INTENSITY. THE RAPID INTENSIFICATION DETERMINISTIC ENSEMBLE (RIDE) HAS 
BEEN CONSISTENT IN INDICATING THE POSSIBILITY OF RAPID INTENSIFICATION 
WITHIN THE NEXT 48 HOURS. THIS SCENARIO IS DEEMED UNLIKELY BETWEEN TAU 
0-12, BUT IT IS A POSSIBILITY BETWEEN TAU 12-48 AFTER 26W FURTHER 
CONSOLIDATES AND THE ENVIRONMENT IMPROVES. INTENSITY GUIDANCE 
INDICATES A PEAK INTENSITY BETWEEN 75 KTS (COAMPS-TC) AND 140 KTS 
(HAFS-A). THE JTWC INTENSITY FORECAST IS IN ALIGNMENT WITH PREVIOUS 
FORECASTS, THE MULTI-MODEL CONSENSUS, HWRF SOLUTION, AND THE 
EXPERIMENTAL GOOGLE DEEPMIND. THE JTWC INTENSITY FORECAST IS ASSESSED 
WITH OVERALL MEDIUM CONFIDENCE.

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