Advisories

WDPN31 PGTW 310300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 031//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.5N 142.8E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 215 NM SOUTH-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 55 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
30W (IN-FA) MAINTAINING AN IMPRESSIVE 40 NM DIAMETER EYE CONTAINING 
SEVERAL MESOVORTICES. A 302211Z SSMIS PASS SHOWS 30W BEGINNING TO 
DEVELOP SMALL CONVECTIVE BANDING FEATURES ON THE NORTHERN AND SOUTHERN
FLANKS. THE EYE TEMPERATURE HAS REMAINED CONSTANT AT 19 C WHILE THE 
SURROUNDING COLDEST CLOUD TOPS HAVE OSCILLATED BETWEEN -65 AND -75 C. 
ENVIRONMENTAL CONDITIONS ARE ASSESSED AS FAVORABLE WITH LOW (5-10 KTS) 
VERTICAL WIND SHEAR (VWS), WARM (28-29 C) SEA SURFACE TEMPERATURES 
(SSTS), AND STRONG RADIAL OUTFLOW ALOFT, ALTHOUGH 30W CONTINUES TO 
TRACK INTO AN AREA OF LOWER (LESS THAN 75 KJ PER CM SQUARED) OCEAN 
HEAT CONTENT (OHC). THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE WELL-DEFINED EYE. THE INITIAL INTENSITY IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON GOOD AGREEMENT FROM AGENCY 
DVORAK FIXES AND CIMSS OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   CIMSS SATCON: 113 KTS AT 302212Z
   CIMSS ADT: 97 KTS AT 302330Z
   CIMSS AIDT: 116 KTS AT 302330Z
   CIMSS D-MINT: 115 KTS AT 302212Z
   CIMSS D-PRINT: 114 KTS AT 302330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON 30W HAS COMMENCED ITS POLEWARD TURN AND 
IS FORECAST TO CONTINUE NORTH TO NORTHEASTWARD OVER THE NEXT 12 HOURS, 
FOLLOWED BY A SMALL CLOCKWISE LOOP AND A SLOW IN TRACK SPEED AS THE 
PASSAGE OF A LONGWAVE TROUGH TO THE NORTH INDUCES A WEAKNESS IN THE 
STEERING INFLUENCE OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE 
NORTHEAST. FOLLOWING TAU 36, THE NORTHEASTERN EXTENSION OF A SEPARATE 
STR CENTERED TO THE WEST WILL BUILD, DRIVING 30W WEST-NORTHWESTWARD 
UNTIL TAU 60. AFTER THIS POINT A SECOND, WEAKER MID-LATITUDE TROUGH 
WILL PROPAGATE EASTWARD, WEAKENING THE WESTERN STR AND ALLOWING THE 
ORIGINAL EASTERN STR TO REGAIN STEERING INFLUENCE FOR THE REMAINDER OF 
THE FORECAST PERIOD, CAUSING A NORTHEASTWARD TURN NO LATER THAN TAU 
72. REGARDING INTENSITY, 30W IS EXPECTED TO CONTINUE A GRADUAL 
WEAKENING TREND FOR THE REMAINDER OF THE FORECAST PERIOD. BETWEEN TAUS 
24 AND 36 A STEEPER TREND IS FORECAST AS THE LOWERING OHC AND SLOW IN 
TRACK SPEED WILL CAUSE 30W TO UPWELL COOLER SSTS. AFTER THIS POINT,
WEAKENING SLOWS SLIGHTLY AS TRACK SPEED INCREASES, ALLOWING 30W TO
OUTPACE ITS COOL WAKE, BUT BY TAU 96 VWS IS EXPECTED TO SHARPLY 
INCREASE AS IT APPROACHES THE STRONG UPPER-LEVEL WESTERLIES AND 
FURTHER WEAKEN THE SYSTEM.

MODEL DISCUSSION: TRACK MODEL GUIDANCE HAS CONTINUED TO COME INTO
BETTER AGREEMENT WITH THE EXCEPTION OF UKMET AND UKMET ENSEMBLE
WHICH LIE FAR EQUATORWARD. THE SPEED AT WHICH THE FIRST LONGWAVE
TROUGH WILL PROPAGATE AND SUBSEQUENTLY ALLOW FOR THE REBUILDING OF
THE ORIGINAL STEERING STR IS THE MAIN SOURCE OF CONTINUED DISAGREEMENT
ACROSS MODELS. THE MAJORITY OF AI-BASED MODELS CONTINUE TO MAKE UP
THE EASTERNMOST SOLUTIONS WITH THE ADDITION OF ECMWF AND ECMWF
ENSEMBLE MEAN, ALTHOUGH THE AI GFS AND EXPERIMENTAL WEATHERMESH
MODELS LIE WEST OF THE PHYSICS BASED MULTI-MODEL CONSENSUS. 
DISREGARDING THE UKMET OUTLIERS, CROSS-TRACK SPREAD HAS IMPROVED TO 
290 NM AT TAU 120 AND ALONG-TRACK SPREAD IS 120 NM. THE OFFICIAL JTWC 
FORECAST TRACK IS ASSESSED WITH LOW CONFIDENCE THROUGHOUT THE FORECAST
PERIOD, IN BETWEEN THE MULTI-MODEL AND AI CONSENSUS BUT HEDGED CLOSER 
TO THE AICN THROUGHOUT. REGARDING INTENSITY, MODELS ARE IN GOOD 
AGREEMENT ON A STEADY WEAKENING TREND OUT TO TAU 36, FOLLOWED BY A 
MORE GRADUAL WEAKENING OR PLATEAU UNTIL TAU 96 AND THEN A STEEPER DROP 
OFF THEREAFTER. MESOSCALE MODELS DEPICT RE-INTENSIFICATION AROUND TAU 
48 AS THEIR TRACKS LIE MORE EQUATORWARD AND TRACK 30W BACK THROUGH 
AN AREA OF HIGHER. THE OFFICIAL JTWC FORECAST INTENSITY IS ASSESSED 
WITH LOW CONFIDENCE THROUGHOUT, BASED ON THE SPREAD OF GUIDANCE BUT IN 
GOOD AGREEMENT WITH BOTH GOOGLE DEEPMIND MODELS AND GFS-BASED COAMPS-
TC WHOSE ASSOCIATED TRACKS ALIGN WITH THE JTWC FORECAST TRACK.

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