WDXS31 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07S (DIKELEDI) WARNING 
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.9S 49.0E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 370 NM NORTH-NORTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 29 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION REDEVELOPING OVER THE WESTERN PORTION OF THE CIRCULATION
IN THE MOZAMBIQUE CHANNEL FOLLOWING A SHORT DISRUPTION DUE TO
PASSAGE OVER THE NORTHERN TIP OF MADAGASCAR. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED ON GEOSTATIONARY SATELLITE
POSITION ESTIMATES FROM PGTW AND DEMS. THE INITIAL INTENSITY OF 75
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A CONSENSUS OF
AVAILABLE SUBJECTIVE DVORAK AND AUTOMATED INTENSITY ESTIMATES
LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   DEMS: T4.5 - 77 KTS
   FMEE: T5.0 - 90 KTS
   CIMSS D-MINT: 59 KTS AT 111528Z
   CIMSS D-PRINT: 73 KTS AT 111800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG WESTWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECAST INTENSITIES HAVE INCREASED
FROM THE PREVIOUS WARNING FOR EACH TAU DUE TO ANTICIPATED FAVORABLE
ENVIRONMENTAL SUPPORT IN THE MOZAMBIQUE CHANNEL. THE PEAK INTENSITY
HAS INCREASED FROM 80 KNOTS IN THE PREVIOUS WARNING TO 105 KNOTS IN
THE CURRENT WARNING.

FORECAST DISCUSSION: TC 07S IS EXPECTED TO FOLLOW THE PERIPHERAL
FLOW ASSOCIATED WITH THE CURRENT STEERING RIDGE THROUGHOUT THE
FORECAST PERIOD. OVER THE NEXT SEVERAL DAYS, A MID-LATITUDE TROUGH
WILL AMPLIFY OVER THE SOUTHERN PORTION OF THE AFRICAN CONTINENT,
GRADUALLY ERODE THE STEERING RIDGE, AND INDUCE A BREAK OVER THE
MOZAMBIQUE CHANNEL. TC 07S WILL TURN POLEWARD TOWARD THE BREAK IN
THE RIDGE BY TAU 36 AND CONTINUE TO ROUND THE RIDGE AXIS
THEREAFTER. AFTER TAU 96, THE SYSTEM WILL ACCELERATE AND BEGIN TO
INTERACT WITH THE MID-LATITUDE TROUGH TO THE WEST, INDUCING THE
FIRST STAGE OF A LIKELY PROLONGED EXTRATROPICAL TRANSITION. SLOW
INTENSIFICATION IS PROBABLE IN THE NEAR TERM DESPITE HIGH SEA
SURFACE TEMPERATURES AND FAVORABLE OUTFLOW ALOFT AS THE SYSTEM IS
POSITIONED TO THE NORTH OF AN UPPER-LEVEL RIDGE AXIS IN AN AREA OF
PERSISTENT, MODERATE EASTERLY VERTICAL WIND SHEAR. AFTER TAU 24,
STEADY TO RAPID INTENSIFICATION IS ANTICIPATED AS THE SYSTEM MOVES
UNDER THE UPPER-RIDGE AXIS AND BENEFITS FROM LOW VERTICAL WIND
SHEAR, FAVORABLE OUTFLOW ALOFT, AND PASSAGE OVER VERY WARM WATER.
WESTERLY VERTICAL WIND SHEAR INDUCED BY THE UPPER-LEVEL FLOW AHEAD
OF THE AFOREMENTIONED MID-LATITUDE TROUGH WILL INDUCE WEAKENING IN
THE LATER TAUS.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY GOOD
AGREEMENT REGARDING THE OVERALL FORECAST SCENARIO, INCLUDING A
POLEWARD TURN AROUND THE STEERING RIDGE AXIS AND PASSAGE OVER THE
MOZAMBIQUE CHANNEL. THE GUIDANCE PACKAGE IS BRACKETED ON THE WEST
BY THE ECMWF DETERMINISTIC AND ENSEMBLE MEAN SOLUTIONS AND ON THE
RIGHT BY THE GALWEM SOLUTION. THE DISTRIBUTION OF CONSENSUS MODEL
AND ENSEMBLE MEMBER TRACKS IS FAIRLY EVEN, REFLECTING SLIGHT
DIFFERENCES IN THE SPEED AND ORIENTATION OF THE EXPECTED POLEWARD
TURN BUT A CONSISTENT OVERALL PICTURE. THE CURRENT JTWC TRACK
FORECAST IS CONSISTENT WITH THE PRIMARY MODEL GROUPING AND LIES
JUST SLIGHTLY TO THE EAST OF THE PREVIOUS FORECAST. MORE SPREAD IS
EVIDENT IN THE INTENSITY GUIDANCE, WITH A RANGE OF SOLUTIONS FROM
SLOW INTENSIFICATION IN THE GFS AND SHIPS FORECASTS TO STEADY TO
RAPID INTENSIFICATION IN THE LATEST HAFS AND HWRF RUNS. THE CURRENT
FORECAST ALIGNS ABOVE THE INTENSITY CONSENSUS GIVEN ANTICIPATED
FAVORABLE ENVIRONMENTAL CONDITIONS AND SUPPORT FROM THE AVAILABLE
MESOSCALE MODELS. THE SYSTEM COULD EASILY PEAK ABOVE 105 KNOTS IN
THE CENTRAL MOZAMBIQUE CHANNEL IF CONDITIONS REMAIN FAVORABLE,
WARRANTING FURTHER UPWARD ADJUSTMENTS TO THE INTENSITY IN
SUBSEQUENT FORECASTS. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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