WDXS31 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (EMNATI) WARNING NR 
016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.7S 43.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 236 NM SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND A 221533Z
SSMIS 91 COLOR DEPICTS SEPARATION OF THE MID AND UPPER LEVEL CLOUD
SHIELD FROM THE LOW LEVEL CIRCULATION CENTER (LLCC). THE CURRENT
POSITION IS ASSESSED FROM A COMBINATION OF THE PGTW FIX ON THE LLCC
VIA ANIMATED EIR AND A FIX ON THE MICROWAVE IMAGERY. TC 13S IS NOW
REGROUPING IN THE MOZAMBIQUE CHANNEL IN A MODERATELY FAVORABLE
ENVIRONMENT. THE SYSTEM SURVIVED THE OVERLAND TREK BUT THERE WAS
SIGNIFICANT WARMING AND COLLAPSE OF THE CLOUD TOPS DURING THE LAST
SIX HOURS. ANIMATED WATER VAPOR IMAGERY SHOWS DISTINCT EDGES TO THE
WEST AND SOUTH ALONG THE 35TH LATITUDE, BUT THUS FAR THE SYSTEM
SEEMS TO BE COCOONED FROM BOTH DRY AIR ENTRAINMENT AND STRONG
VERTICAL WINDSHEAR. A STRONG ANTICYCLONE OVER THE SOUTHERN OCEAN
CENTERED NEAR 25N 64E ON THE 21200Z JTWC STREAMLINE ANALYSIS IS
PROVIDING THE SYSTEM WITH EXCELLENT OUTFLOW. NONETHELESS, WITH SEA
SURFACE TEMPERATURES BARELY SUBSTANTIVE AND VIRTUALLY NO OCEAN HEAT 
CONTENT, EMNATI HAS SEEN ITS BEST DAYS. THE CURRENT INTENSITY 
ASSESSMENT IS BASED ON A RAW ADJ ADT OUTPUT OF T3.5 AND IN EXCESS OF 
THE JTWC DVORAK ASSESSMENT USING THE SHEAR TECHNIQUE. 45 KTS IS ALSO 
COHERENT WITH THE EXPECTED AMOUNT OF DECAY DURING AN OVERLAND TRAVERSE 
ALONG THE TRACK OF TC 13S. 

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: THE WESTERN FLANK OF A DEEP ANTICYCLONE
CENTERED NEAR 25N 64E.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   CIMSS ADT: 47 KTS AT 231715Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: LOW OCEAN HEAT CONTENT AND DRY AIR OVER THE
MAJORITY OF THE MOZAMBIQUE CHANNEL.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: THE BOOOST IN OUTFLOW WILL HELP SUSTAIN THE
SYSTEM THROUGH THE NEXT 36 HOURS DESPITE SEA SURFACE TEMPERATURES
THAT ARE NOTHING SPECIAL AND AN LLCC THAT IS UNDERGOING INCREASING
SEPARATION FROM THE UPPER LEVEL ENGERY. BY THE TIME THE SYSTEM
MOVES POLEWARD OF THE 26TH LATITUDE, WATERS WILL BE TOO COOL TO
DEEPEN THE SYSTEM AND DRY AIR WILL WRAP AROUND THE SYSTEM AND ISOLATE 
IT FROM THE EXTERNAL ENVIRONMENT AND BEGIN WEAKENING THE CORE. AS THE 
SYSTEM APPROACHES THE 30TH LATITUDE IT WILL ENCOUNTER THE INFLUENCE OF 
VIGOROUS UPPER LEVEL WESTERLIES AND THE VERTICAL WINDSHEAR WILL 
DECOUPLE THE LLCC AND ISOLATE THE CORE. NONETHELESS, A SHALLOW ARM 
CORE WILL PERSIST AND THE SYSTEM WILL REMAIN AT OR NEAR GALE FORCE 
UNTIL IT BECOMES COMPLETELY ABSORBED INTO THE WESTERLIES. 

MODEL DISCUSSION: TRACK GUIDANCE IS TIGHT AND THE JTWC FORECAST
RIDES THE MULTI-MODEL CONSENSUS. INTENSITY GUIDANCE IS ALSO IN
RELATIVELY GOOD AGREEMENT WITH NO SIGNIFICANT OUTLIERS. DYNAMIC
INTENSITY GUIDANCE IS HIGHER THAN THE STATISTICAL-DYNAMICAL
GUIDANCE. THE JTWC FORECAST STAYS JUST ABOVE THE MEAN OF THE
CONSENSUS. FORECASTED WIND RADII ARE GENERATED USING THE RVCN
PROGAM DEVELOPED AT THE NAVAL RESEARCH LAB. 

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