WDPN32 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (HIGOS) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7N 145.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 18 NM SOUTH OF TINIAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC) PASSING JUST
SOUTH OF TINIAN. THE CONVECTION CONTINUES TO FLARE OVER THE
NORTHERN PERIPHERY OF THE LLCC. THE SOUTHERN SEMICIRCLE OF THE
CIRCULATION IS PARTIALLY EXPOSED, AND THE MID-LEVEL CENTER IS
OFFSET FROM THE LLCC DUE TO MODERATE SOUTHEASTERLY SHEAR ALOFT.
ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR INTENSIFICATION,
CHARACTERIZED BY VERY WARM SEA SURFACE TEMPERATURE (SST) AND HIGH
OCEAN HEAT CONTENT (OHC) OFFSET BY MODERATE VERTICAL WIND SHEAR
(VWS). THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE PARTIALLY EXPOSED LLCC ON MSI AND A 222352Z ASCAT-B
PASS DEPICTING A CLOSE LOW LEVEL CIRCULATION. A 222351Z OBSERVATION
AT SAIPAN INTERNATIONAL AIRPORT REPORTED A SUSTAINED WIND OF 33 KTS
AND A GUST OF 45 KTS, THOUGH THIS LIKELY REPRESENTS THE PEAK WINDS
FOR TINIAN AND SAIPAN. TROPICAL STORM 08W IS NOW MOVING DOWNSTREAM
OF THE NORTHERN MARIANA ISLANDS, SO THE ASSOCIATED IMPACTS WILL
SUBSIDE SHORTLY. THE SAIPAN OBSERVATION, IN CONJUNCTION WITH THE
IMPROVED STRUCTURE IN THE MSI AND THE AFOREMENTIONED SCATTEROMETER
PASS, WAS USED TO JUSTIFY RAISING THE INITIAL INTENSITY TO 35 KTS
WITH HIGH CONFIDENCE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A LOW- TO
MID-LEVEL SUBTROPICAL RIDGE (STR) CENTERED OVER THE CENTRAL NORTH
PACIFIC

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 34 KTS AT 221810Z
   CIMSS ADT: 35 KTS AT 230130Z
   CIMSS AIDT: 36 KTS AT 230130Z
   CIMSS D-MINT: 30 KTS AT 221608Z
   CIMSS D-PRINT: 25 KTS AT 230130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD

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: TROPICAL STORM 07W IS BEING STEERED TO THE
WEST-NORTHWEST BY A LOWER LEVEL STR, WHICH WILL CONTINUE THROUGH
TAU 36. THE SYSTEM WILL APPROACH A WEAKNESS IN THE STR AND ROUND
THE RIDGE AXIS AFTER TAU 60. THE MID-LATITUDE WESTERLIES WILL PULL
THE SYSTEM NORTHEASTWARD, AND EXTRATROPICAL TRANSITION (ETT) WILL
RAPIDLY OCCUR. WHILE THE FORECAST SHOWS A TAU 120 POINT TO SHOW
COMPLETION OF ETT, 08W WILL MORE THAN LIKELY BE ABSORBED BY A
FRONTAL SYSTEM NEAR THE KURIL ISLANDS BY THAT TIME. THE ASCAT-B
INDICATED THAT 30-35 KT WINDS HAVE NOW WRAPPED AROUND 50 PERCENT OF
THE LLCC, A NOTABLE IMPROVEMENT IN THE SYMMETRY OF THE WIND FIELD.
THE FORECAST STILL CALLS FOR SLOW INTENSIFICATION DUE TO REMAINING
ASYMMETRIES IN THE STRUCTURE AND PERSISTENT SOUTHEASTERLY SHEAR
THROUGH TAU 24. HOWEVER, FROM TAU 24 TO TAU 48, CONDITIONS WILL
BECOME MORE FAVORABLE FOR DEVELOPMENT. THE VWS WILL EASE, WHILE THE
SST WILL HOVER NEAR 30 DEGREES CELSIUS. THESE FACTORS WILL PROMOTE
STEADIER INTENSIFICATION BEFORE THE LARGER, MORE POTENT CIRCULATION
OF 07W INTERACTS WITH 08W AND CAPS FURTHER DEVELOPMENT. AFTER TAU
72, INCREASING VWS AND COOLER SST WILL INDUCE WEAKENING. SEVERAL
SCENARIOS REMAIN POSSIBLE: 07W COULD STILL ABSORB 08W LEADING TO
DISSIPATION OF THE TROPICAL STORM AROUND TAU 72, ALTHOUGH THIS IS
BECOMING LESS LIKELY. THERE IS ALSO A POSSIBILITY THAT 08W TAPS
INTO A JET STREAM OVER NORTHERN HONSHU, WHICH WOULD LESSEN THE RATE
OF WEAKENING.

MODEL DISCUSSION: THE AVAILABLE GUIDANCE GENERALLY AGREES ON A
RECURVATURE SCENARIO FOR TROPICAL STORM HIGOS, AND THE JTWC
FORECAST TRACK IS LAID WITHIN THE TIGHTEST CLUSTER OF MODELS
THROUGH TAU 72 WITH MEDIUM CONFIDENCE. UNCERTAINTY REGARDING THE
EXTENT OF INTERACTION WITH 07W LENDS LOW CONFIDENCE AFTER TAU 72.
NAVGEM AND A FLURRY OF AI MODELS RESIDE ON THE EASTERN SIDE OF THE
GUIDANCE ENVELOPE, WHICH ARE MOST SUSCEPTIBLE TO SIGNIFICANT
INTERACTION WITH 07W. AFTER TAU 72, THE TRACK FORECAST FOLLOWS THE
MEAN OF THE GFS AND ECMWF GLOBAL MODELS, WHICH TEND TO HAVE HIGHER
SKILL DEALING WITH BAROCLINIC SYSTEMS. THE RELIABLE INTENSITY AIDS
SHOW MODEST INTENSIFICATION FOR THE NEXT 2-3 DAYS. THE EXPERIMENTAL
GOOGLE DEEPMIND AND COAMPS-TC ARE THE MOST AGGRESSIVE AND SHOW A
PEAK OF 55 KTS. HAFS-A IS LOWER AT 50 KTS, WHILE GFS SITS AT 45
KTS. THE INTENSITY FORECAST IS SET ON THE HIGHER END OF THE
GUIDANCE WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW CONFIDENCE
THEREAFTER.

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