WDXS31 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07S (SEVEN) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.2S 98.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 267 NM NORTH-NORTHEAST OF THE COCOS
ISLANDS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION, AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 07S BECOMING BETTER DEFINED WITH INCREASED CONVECTIVE
ACTIVITY ESPECIALLY THROUGHOUT THE SOUTHWESTERN QUADRANT AND
COOLING CLOUD TOP TEMPERATURES NEAR THE CENTER OF THE CIRCULATION.
ENVIRONMENTAL ANALYSIS DEPICTS A FAVORABLE ENVIRONMENT FOR
DEVELOPMENT WITH SEA SURFACE TEMPERATURES BETWEEN 28 C AND 29 C,
LOW VERTICAL WIND SHEAR (10-15 KTS), AND GOOD OUTFLOW. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANIMATED EIR
IMAGERY AND PGTW DVORAK FIX. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON AN EARLIER (110223Z) METOP-C
ASCAT PASS SHOWING A BAND OF 30 KT WINDS TO THE NORTH OF THE
LOW-LEVEL CIRCULATION CENTER (LLCC), PERSISTENT CONVECTIVE
DEVELOPMENT AND SUBJECTIVE DVORAK ESTIMATE FROM PGTW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS D-PRINT: 25 KTS AT 111800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: INITIALLY TC 07S WILL TRACK SOUTHWESTWARD
ALONG THE NORTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE CENTERED
TO THE SOUTHEAST, WHILE CONTINUING TO STRENGTHEN AND CONSOLIDATE.
AFTER TAU 60 THE SYSTEM IS FORECASTED TO ENTER A REGION OF THE
SOUTHERN INDIAN OCEAN ENCOUNTERING A CHANGING STEERING
ENVIRONMENT. THE TRACK WILL BE DETERMINED PRIMARILY BY RIDGING TO
THE EAST AND NORTH, AFFECTED BY A PASSING LONGWAVE TROUGH TO THE
SOUTH. BETWEEN TAUS 96 AND 120, ANOTHER STR CENTERED TO THE
SOUTHWEST WILL BUILD AND BEGIN INFLUENCING THE TRACK OF TC 07S
TOWARD A MORE WESTWARD TRAJECTORY. IN THE MEANTIME, THIS COMPETING
STEERING PATTERN WILL CREATE A BOXING SCENARIO WITH THE SYSTEM
ALLOWED ONLY SLOW AND ERRATIC MOVEMENT. IN ADDITION INVEST 92S
WILL COME WITHIN 250-300 NM OF THE FORECAST TRACK FOR TC 07.
THIS WILL FURTHER COMPLICATE THE PREDICTED TRACK. IN
TERMS OF INTENSITY DURING THE SECOND PART OF THE FORECAST, THE
SYSTEM IS EXPECTED TO BEGIN WEAKENING AFTER TAU 48, PRIMARILY DUE TO
INCREASING VWS, SLOWER TRANSLATIONAL SPEED RESULTING IN POTENTIAL
COOLER WATER UPWELLING, AND DIRECT CYCLONE INTERACTION WITH
INVEST 97S.

MODEL DISCUSSION: CROSS TRACK MODEL GUIDANCE IS SPREAD UP TO 150 NM
BY TAU 60 WITH THE MODELS STRUGGLING TO RESOLVE HOW LONG TC 07 WILL
STALL IN THE SOUTHERN INDIAN OCEAN UNDER THE EFFECTS OF COMPETING
STEERING MECHANISMS AND POTENTIAL INTERACTION WITH ANOTHER TROPICAL
SYSTEM (INVEST 91S). THE JTWC FORECASTED TRACK IS PLACED CLOSE TO
THE MULTI MODEL CONSENSUS WITH LOW CONFIDENCE AND SLOWER
PROGRESSION AFTER TAU 72. INTENSITY GUIDANCE IS SPREAD UP TO 45 KTS
WITHIN THE FIRST 48 HOURS OF THE FORECAST. AFTER TAU 48 THE MODELS
COME INTO BETTER AGREEMENT ON THE DOWNWARD TREND OF THE SYSTEM AS IT
MOVES FURTHER WEST INTO THE SOUTHERN INDIAN OCEAN. ALTHOUGH THE
JTWC FORECASTED INTENSITY REFLECTS CLOSELY THE VALUES OF THE
MULTI-MODEL CONSENSUS THERE IS LOW CONFIDENCE IN THIS OUTCOME
ACCOUNTING FOR UNCERTAINTY IN THE DEVELOPMENT OF ANOTHER TROPICAL
SYSTEM (91S) AND THE STRENGTH OF STEERING MECHANISMS.   

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