Advisories

WDPN32 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (CHOI-WAN) WARNING NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.3N 146.2E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 307 NM NORTH OF SAIPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
26W (CHOI-WAN) WITH A COMPACT INNER-CORE AND AN INTERMITTENT EYE
THAT HAS BEEN CYCLING OVER THE PAST 6 HOURS. CLOUD TOPS HAVE
NOTICEABLY COOLED FOLLOWING 031200Z, INDICATIVE OF CONTINUING
INTENSIFICATION. A 030909Z F16 SSMIS 37 GHZ MICROWAVE IMAGE
REVEALED A DEFINED LOW EMISSIVITY REGION, WHICH LINED UP WITH THE
UPPER-LEVEL CENTER IN THE 91 GHZ IMAGE. THIS ALIGNMENT SUGGESTS
THAT THE SYSTEM HAS MINIMAL VORTEX TILT WITH HEIGHT. A PARTIAL
031117Z METOP-C ASCAT PASS REVEALED THE COMPACT INNER-CORE,
HOWEVER, IT ALSO SHOWED THAT 26W HAS EXPANSIVE 34-KNOT WIND RADII.
THIS IS ESPECIALLY TRUE FOR THE SOUTHEASTERN QUADRANT OF THE
SYSTEM. WHICH IS MEASURED TO BE ABOUT 300 NM. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE ASCAT PASS AND ANIMATED
EIR IMAGERY. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 031117Z METOP-C ASCAT SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: THE WESTERN EXTENSION OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   CIMSS SATCON: 85 KTS AT 031040Z
   CIMSS ADT: 65 KTS AT 031140Z
   CIMSS AIDT: 68 KTS AT 031140Z
   CIMSS D-MINT: 100 KTS AT 030908Z
   CIMSS D-PRINT: 92 KTS AT 031140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG DUAL-CHANNEL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 26W IS FORECAST TO TRACK GENERALLY
NORTHWARD THROUGH TAU 60 AS IT TRAVERSES THE WESTERN PERIPHERY OF
THE STR TO THE NORTHEAST. AFTER TAU 60, THE SYSTEM WILL ACCELERATE
NORTHEASTWARD AS IT ROUNDS THE RIDGE AXIS AND BEGINS TO INTERACT
WITH THE STRONG UPPER-LEVEL FLOW. EXTRATROPICAL TRANSITION IS
EXPECTED TO BE COMPLETE NO LATER THAN TAU 96, ONCE THE SYSTEM
BECOMES EMBEDDED UNDERNEATH THE JET SOUTH OF THE KAMCHATKA
PENINSULA. IN TERMS OF INTENSITY, 26W IS FORECAST TO INTENSIFY OVER
THE NEXT 24 HOURS TO A PEAK INTENSITY OF AROUND 110 KTS AS THE
ENVIRONMENT REMAINS FAVORABLE WITH LOW SHEAR, VERY WARM SST, AND
ROBUST OUTFLOW. THE PEAK INTENSITY COULD POTENTIALLY BE EVEN HIGHER
IF 26W IS ABLE TO MAINTAIN ITS COMPACT CORE AND STAVE OFF THE DRY
AIR TO THE WEST. AFTER TAU 24, OCEAN HEAT CONTENT WILL START TO
DROP AND EQUATORWARD OUTFLOW WILL BECOME RESTRICTED, CAUSING 26W TO
GRADUALLY WEAKEN THROUGH TAU 72. FOLLOWING TAU 72, THE SYSTEM WILL
TAP INTO AN EXTREME POLEWARD OUTFLOW CHANNEL, SUPPORTED BY A STRONG 
JET MAX TO THE NORTH. THIS WILL SOMEWHAT OFFSET THE COOL SST AND VERY
HIGH SOUTHWESTERLY VERTICAL WIND SHEAR, ALLOWING FOR 26W TO MAINTAIN 
AN INTENSITY NEAR TYPHOON-STRENGTH THROUGH THE INITIAL STAGES OF
FRONTOGENESIS.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT
THROUGH TAU 72 WITH MOST OF THE UNCERTAINTY REVOLVING AROUND THE
SPEED OF ADVANCE AROUND THE RIDGE. WHILE CROSS-TRACK SPREAD IS ONLY
ABOUT 100 NM AT TAU 72, ALONG-TRACK SPREAD IS NEAR 300 NM. GFS AND
NAVGEM CONTINUE TO BE THE SLOWEST TRACKERS WHILE EC-AIFS AND THE
GOOGLE DEEPMIND ARE THE FASTEST. AT TAU 96, THE ALONG-TRACK SPREAD
SIGNIFICANTLY INCREASES TO OVER 700 NM. THE JTWC TRACK FORECAST IS
PLACED SLIGHTLY FASTER THAN THE CONSENSUS THROUGH TAU 72 WITH
MEDIUM CONFIDENCE, AND THEN HEDGES CLOSER TO THE GOOGLE DEEPMIND
ENSEMBLE MEAN THROUGH TAU 96 WITH LOW CONFIDENCE. INTENSITY
GUIDANCE IS IN SLIGHTLY WORSE AGREEMENT THIS RUN WITH HAFS-A NOW
SUGGESTING A PEAK INTENSITY CLOSER TO 125 KTS. THIS MIGHT NOT BE
OUT OF THE QUESTION BASED ON THE RECENT STRUCTURAL IMPROVEMENT.
RAPID INTENSIFICATION (RI) AIDS CONTINUE TO SHOW A PEAK THAT IS
MARKEDLY HIGHER THAN THE REMAINDER OF GUIDANCE (WITH THE EXCEPTION
OF HAFS-A). MULTIPLE MODELS ARE NOW ACTUALLY SHOWING LITTLE TO NO
FURTHER INTENSIFICATION, SUCH AS COAMPS-TC AND HWRF. THE JTWC
INTENSITY FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS 
THROUGHOUT THE FORECAST PERIOD WITH LOW CONFIDENCE.

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