Advisories

WDPN33 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (KOGUMA) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.5N 163.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 300 NM SOUTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT,
ORGANIZING CONVECTIVE STRUCTURE ASSOCIATED WITH TROPICAL STORM (TS)
27W, FEATURING A SPIRAL BAND WRAPPING INTO A COMPACT CENTRAL DENSE
OVERCAST (CDO). MORE RECENT SATELLITE FRAMES SUGGEST THAT THE
VORTEX IS COMING INTO BETTER ALIGNMENT, WITH AN INCREASING PORTION
OF THE LOW-LEVEL CIRCULATION CENTER (LLCC) BECOMING EMBEDDED
BENEATH THE CDO. A 070527Z SSMIS PASS SUPPORTS THIS ASSESSMENT,
DEPICTING A MID- TO UPPER-LEVEL CIRCULATION DISPLACED SLIGHTLY
SOUTHWEST OF A FORMATIVE LOWER-LEVEL INNER CORE. THE ENVIRONMENT IS
GENERALLY FAVORABLE, CHARACTERIZED BY VERY WARM SEA SURFACE
TEMPERATURES (SST) OF 30 DEGREES CELSIUS AND MODERATE UPPER-LEVEL
DIVERGENCE, PARTIALLY OFFSET BY 15-20 KTS OF NORTHEASTERLY VERTICAL
WIND SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE CLEAR CENTER DEPICTED IN THE SSMIS IMAGERY.
BASED ON THE T3.5 DVORAK CLASSIFICATIONS FROM PGTW AND PHFO, THE
INITIAL INTENSITY HAS BEEN RAISED TO 55 KTS WITH MEDIUM CONFIDENCE.
THIS ASSESSMENT FALLS WITHIN THE RANGE OF OBJECTIVE ESTIMATES FROM
CIMSS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF THE SOUTHERN
EXTENSION OF THE SUBTROPICAL RIDGE (STR) POSITIONED FAR TO THE
NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.0 - 45 KTS
   PHFO: T3.5 - 55 KTS
   CIMSS SATCON: 50 KTS AT 070350Z
   CIMSS ADT: 57 KTS AT 070550Z
   CIMSS AIDT: 49 KTS AT 070550Z
   CIMSS D-MINT: 58 KTS AT 070235Z
   CIMSS D-PRINT: 57 KTS AT 070550Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE WESTWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 27W WILL MAINTAIN A WEST-NORTHWESTWARD
TRAJECTORY ALONG THE SOUTHWESTERN PERIPHERY OF THE STR POSITIONED
FAR TO THE NORTH. THE SYSTEM WILL MODESTLY ACCELERATE FROM 8 KTS TO
12-13 KTS BY TAU 48 AS THE RIDGE AMPLIFIES. TOWARD THE END OF THE
FORECAST PERIOD, TS 27W WILL TURN POLEWARD AND SLOW DOWN AS IT
APPROACHES A WEAKNESS IN THE STR ASSOCIATED WITH TYPHOON (TY) 15E,
LOCATED APPROXIMATELY 650 NM TO THE NORTH. THE FORECAST CALLS FOR A
SLOW RATE OF INTENSIFICATION OVER THE NEXT 12 HOURS AS THE SYSTEM
GRADUALLY BECOMES VERTICALLY ALIGNED UNDER MODERATE VWS. BY TAU 24,
THE SHEAR WILL EASE TO BELOW 10 KTS. COUPLED WITH VERY WARM SST AND
VERY HIGH OCEAN HEAT CONTENT EXCEEDING 150 KJ PER CM2, THE
LOW-SHEAR ENVIRONMENT WILL SUPPORT RAPID INTENSIFICATION (RI) TO A
PEAK OF 125 KTS BY TAU 60. AFTER TAU 72, THE SYSTEM WILL ENCOUNTER
LOWER SST AND OHC, AND A WEAKENING TREND WILL COMMENCE. THE VORTEX
IS COMPACT, MAKING IT SUSCEPTIBLE TO SIGNIFICANT SHORT-TERM
INTENSITY FLUCTUATIONS. IT IS POSSIBLE THAT TS 27W WILL INTENSIFY
MORE QUICKLY AND REACH A HIGHER PEAK INTENSITY THAN CURRENTLY
FORECAST.

MODEL DISCUSSION: TRACK GUIDANCE IS COMING INTO BETTER AGREEMENT.
THE TWO PREVIOUS DIVERGENT TRACK SCENARIOS, IN WHICH THE DYNAMICAL
MODELS FAVORED A FASTER POLEWARD MOTION AND AI MODELS FAVORED A
MORE WESTWARD TRACK, ARE CONVERGING TOWARD A SOLUTION NEAR THE
MIDPOINT. THE DYNAMICAL AND AI MODELS ARE FORMING A TIGHTER CORE
CLUSTER. THE JTWC FORECAST TRACK, WHICH HAD BEEN HEDGING BETWEEN
THE MULTI-MODEL CONSENSUS (CONW) AND THE MEAN OF THE AI MODELS, IS
THEREFORE, NEARLY IDENTICAL TO THE LAST CYCLE. RI AIDS CONTINUE TO
TRIGGER CYCLE AFTER CYCLE, AND HAFS-A INSISTS ON IMMEDIATE RI.
GIVEN THE CURRENT SATELLITE PRESENTATION OF THE SYSTEM, IMMEDIATE
RI APPEARS UNLIKELY. GOOGLE DEEPMIND AND GFS DELAY THE ONSET OF RI
UNTIL TAU 24. THE JTWC INTENSITY FORECAST REPRESENTS A BLEND OF THE
TWO SCENARIOS, DEPICTING SLOW INTENSIFICATION THROUGH TAU 12 AND RI
 THEREAFTER. THE FORECAST IS NEAR THE UPPER END OF THE GUIDANCE
ENVELOPE THROUGH TAU 120, THOUGH THE 125-KT FORECAST PEAK IS LOWER
THAN THE 135-KT PEAK PREDICTED BY HAFS-A AND COAMPS-TC.

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