WDXS31 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (TWENTYNINE) 
WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.6S 128.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 200 NM NORTHWEST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) OVER THE PAST SIX
HOURS SHOWS TC 29S FIGHTING BACK ON THE UPSHEAR SIDE AGAINST
VIGOROUS EASTERLY SHEAR. COOLING TOPS ARE ORGANIZING AROUND A
CENTRAL DENSE OVERCAST AND BD CURVES SHOW AN ESTABLISHED RING OF
COLD DARK GREY SURROUNDING THE PROBABLE LOW LEVEL CIRCULATION
CENTER (LLCC).  AN 111313Z 25KM ASCAT PASS VERIFIES THE SURGE IN
DEEP CONVECTION, SHOWING A FEW HITS OF GALE FORCE WINDS UNDER THE
DEEPEST CONVECTION. THE STRONGEST CONVECTION WITHIN THE
IMMATURE AND LOPSIDED SYSTEM EXISTS JUST TO THE SOUTHWEST OF THE
SUPPOSED LLCC. 29S IS NOT YET VERTICALLY ALIGNED. THE WESTERLIES IN
THE LOWER LEVELS OF THE STORM ARE BEING SUSTAINED BY A BOOST FROM
A WEAK MJO TAKING A LEISURELY TRACK THROUGH THE MARITIME CONTINENT, 
WHILE GRADIENT LEVEL SOUTHEASTERLIES STREAMING OVER THE TOP END OF 
THE CONTINENT ARE PROVIDING PLENTY OF SPIN TO THE POLEWARD SIDE. THE
SOUTHWESTERLY BEARING IS TAKING THE SYSTEM AWAY FROM THE WORST OF
THE SHEAR AND ALONG A TRACK OF GRADUALLY DECREASING SHEER. THE JTWC
12Z UPPER LEVEL STREAMLINE ANALYSIS REVEALS THAT THE SUBTROPICAL 
RIDGE EXTENDS FROM AN ANTICYCLONE OVER THE EASTERN SIDE OF THE GULF OF
CARPENTARIA ALONG THE 15TH LATITUDE. CURRENT DEEP LAYER SHEAR IS
DOWN TO 15 TO 20KTS BUT A HAFS-A VORTEX AVERAGED SKEW T REVEALS
OVER 25KTS OF MID-LEVEL SHEAR.  ANIMATED WATER VAPOR SHOWS GOOD 
VENTING BUT NO WELL-DEVELOPED OUTFLOW CHANNELS ON ALL SIDES OTHER THAN 
THE NORTHEAST QUADRANT. TOTAL PRECIPTIABLE WATER LOOPS SHOW AN 
ABUNDANCE OF DEEP MOISTURE AND 30-31 DEGREE SEA SURFACE TEMPERATURES 
WITH EXTREMELY HIGH OCEAN HEAT CONTENT VALUES SO THE ONLY THING 
HOLDING THIS STORM BACK IS VWS.

INITIAL WIND RADII BASIS: 111311Z ASCAT 25KM. 

CURRENT STEERING MECHANISM: STEERING IS CONFINED TO A RELATIVELY
NARROW CHANNEL BETWEEN AN UPPER LEVEL RIDGE EXTENDING FROM THE TOP
OF THE YORK PENINSULA TOWARDS THE MOLUCCAS AND A WARM RIDGE
EXTENDING FROM THE GIBSON DESERT OVER EXMOUTH AND FURTHER SEAWARD
FROM THERE.  

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   APRF: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: OUTFLOW IS RADIAL BUT WITH SIGNIFICANT
IMPINGEMENT ON THE NORTHEAST QUADRANT. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 29S IS EXPECTED TO STEADILY INTENSIFY ALONG
A SOUTHWESTWARD TRACK FOR THE NEXT 48 HOURS BEFORE LEAVING THE
INFLUENCE OF THE UPSTREAM RIDGE AND BEING DRIVEN WESTWARD BY THE
RIDGE EXTENDING FROM THE GIBSON DESERT. THE ISSUES OF RAPID
INTENSIFICATION AND PEAK INTENSITY ARE THE MOST DIFFICULT ASPECTS
OF THE FORECAST. THE DECLINE IN SHEAR WILL BE STEADY RATHER THAN
SUDDEN BUT BY THE TIME THE SYSTEM RESUMES A WESTWARD TRACK, VWS
SHOULD NOT BE AN IMPEDIMENT. NONETHELESS, RAPID INTENSIFICATION
AIDS HAVE NOT TRIGGERED THE PAST TWO CYCLES AND NO DYNAMIC OR
STATISTICAL GUIDANCE ARE INDICATING INTENSITIES ABOVE 75KTS. 200MB
CHI ANOMALIES DO INDICATE AN EASTWARD SHIFT IN DIVERGENCE ALOFT
AWAY FROM THE STORM, PROBABLY ASSOCIATED WITH THE MJO PROGRESSION,
AND TOTAL PRECIPITABLE WATER LOOPS DO SHOW RELATIVE DRYNESS
OFF-SHORE OF THE KIMBERLY AND PILBARRA COASTS, SO IT IS PLAUSIBLE
THAT THIS STORM WILL HAVE A CEILING AT LOW HURRICANE STRENGTH. IT
IS WORTH NOTING THAT DIANNE REMAINED FAIRLY WEAK WHILE IN THE TIMOR
SEA AND DID NOT REALLY RAMP UP UNTIL JUST OFF-SHORE.  


MODEL DISCUSSION: TRACK GUIDANCE IS EMPHATIC IN SHOWING THAT THE
SYSTEM WILL REMAIN OFF-SHORE OF THE TOP END. DUE TO THE SMALL SIZE
OF THE SYSTEM THERE IS GREATER THAN AVERAGE ALONG TRACK SPREAD BUT
IT DOESN'T CHANGE THE STORY. THE JTWC TRACK EDGES SLIGHTLY TOWARDS
THE ECMWF AND GFS ENSEMBLES WHILE HUGGING THE MULTI-MODEL
CONSENSUS. INTENSITY GUIDANCE AND THE ASSOCIATED LOWER THAN AVERAGE
CONFIDENCE IN THE INTENSITY FORECAST WAS DISCUSSED IN THE PREVIOUS
FORECAST. 

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