WDPS31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07P (SEVEN) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.0S 156.6E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 442 NM NORTH-NORTHEAST OF BRISBANE,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PERSISTENT
AND SIZABLE CENTRAL DENSE COVER (CDC) MEASURING 200NM ACROSS. THIS
FEATURE IS FULLY OBSCURING THE SOUTHERN EXTENT OF AN ELONGATED
CIRCULATION THAT IS ALSO WELL OVER 100NM IN SIZE. A FORTUITOUS
SUITE OF SSMIS MICROWAVE IMAGERY, SPECIFICALLY A 070604Z SSMIS
91GHZ IMAGE REVEALS THAT THE SOUTHERN EXTENT OF THE CIRCULATION IS
TUCKED UNDER THE LARGE CDC WITH LOW LEVEL CLOUD LINES TRACING THE
LARGE NORTHWESTERN EXTENT OF THE CIRCULATION. IT IS STILL FORECAST
THAT THIS FULLY OBSCURED PORTION OF THE ELONGATION WILL EMERGE AS
THE DOMINATE DOWNSTREAM CIRCULATION. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON MSI AND SSMIS IMAGERY. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A
DISCREPANCY BETWEEN AGENCY DVORAK INTENSITY ESTIMATES AND AUTOMATED
INTENSITY ESTIMATES WHICH INDICATE 35-55KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   ABRF: T2.5 - 35 KTS
   CIMSS ADT: 55 KTS AT 070530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TC 07P (SEVEN) IS FORECAST TO CONTINUE
TRACKING EAST-SOUTHEASTWARD UNDER THE STEERING INFLUENCE OF THE STR
TO THE NORTHEAST. OVER THE NEXT 12 HOURS WHILE STILL IN A FAVORABLE
ENVIRONMENT CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES, STRONG
DUAL CHANNEL OUTFLOW ALOFT AND RELATIVELY LOW VERTICAL WIND SHEAR
(VWS), THE SYSTEM IS FORECAST TO REACH A PEAK INTENSITY OF 45
KNOTS. THROUGH TAU 24, TC 07P WILL EXPERIENCE INCREASING DRY AIR
ENTRAINMENT FROM THE WEST AS WELL AS INCREASING VWS, THESE FACTORS
WILL CONSPIRE TO WEAKEN THE SYSTEM AS IT PASSES SOUTH OF NEW
CALEDONIA. AT THE SAME TIME, NEAR TAU 24 THE SYSTEM WILL CROSS
POLEWARD OF THE 26C ISOTHERM AND MOVE UNDER THE SUBTROPICAL
WESTERLIES ALOFT, THEREBY INITIATING SUBTROPICAL TRANSITION (STT).
BY TAU 36 AND THROUGH TAU 48, TC 07P WILL ENGULF AND MERGE WITH
INVEST 95P AS THE SYSTEM CONTINUES POLEWARD WEAKENING TO 35KTS AND
EVENTUALLY COMPLETING STT. THE FORECASTED WEAKENING SEEN IN THE
LATER TAUS AND BEYOND THE FORECAST PERIOD MAY BE BLUNTED BY STRONG
BAROCLINIC FORCING AS THE SYSTEM TURNS SOUTH AND EVENTUALLY BECOMES
EXTRATROPICAL.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH
THE FORECAST PERIOD WITH ALL MEMBERS INDICATING A
SOUTH-SOUTHEASTERLY COURSE AND ONLY A 130NM SPREAD IN SOLUTIONS AT
TAU 48. FOR THIS REASON THE JTWC TRACK FORECAST IS PLACED WITH HIGH
CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE INDICATES A WIDE
RANGE OF SOLUTIONS. GFS INDICATES AN UNREALISTIC AND UNCORROBORATED
WEAKENING TREND THROUGH THE FORECAST PERIOD, WHILE THE BULK OF THE
GUIDANCE INDICATES INITIAL INTENSIFICATION THROUGH TAU 12. AFTER
WHICH, DECAY-SHIPS (BOTH NAVGEM AND GFS VERSIONS) HOLD THE SYSTEM
UNREALISTICALLY ABOVE 45 KNOTS THROUGH TAU 48, WHILE THE MESOSCALE
MODELS (HWRF AND COAMPS-TC) INDICATE A GRADUAL WEAKENING TREND
THROUGH THE FORECAST PERIOD. FOR THIS REASON THE JTWC FORECAST
INTENSITY GUIDANCE IS PLACED CLOSE TO THE HWRF SOLUTION WITH MEDIUM
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
NNNN