WDXS32 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 16S (SIXTEEN) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.9S 54.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 348 NM NORTH-NORTHWEST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 16S (SIXTEEN) CONTINUES TO RAPIDLY
CONSOLIDATE, THOUGH IT LIKELY REMAINS MORE DISORGANIZED IN THE
LOW-LEVELS THAN IT APPEARS IN THE INFRARED IMAGERY. THE LATEST
ANIMATED ENHANCED INFRARED (EIR) IMAGERY DEPICTS A RAGGED CENTRAL
DENSE OVERCAST (CDO)-LIKE FEATURE DEVELOPING OVER THE PAST SIX
HOURS. THE MOST RECENT FRAMES OF EIR SUGGEST CLOUD TOPS ARE WARMING
ALREADY AND CIRRUS DEBRIS IS SHEARING OFF TO THE EAST. HOWEVER,
ANOTHER HOT TOWER IS FLARING UP JUST WEST OF THE ASSESSED LOW LEVEL
CIRCULATION CENTER (LLCC) POSITION. AN 182120Z AMSR2 MICROWAVE PASS
REVEALED A DISORGANIZED CORE, THOUGH THERE WERE SOME HINTS OF WEAK
CYCLONIC CURVATURE IN THE DEEP CONVECTIVE ACTIVITY. NO DEFINED LLCC
COULD BE DISCERNED FROM THE AMSR2 IMAGERY AND THUS THE INITIAL
POSITION IS ASSESSED WITH LOW CONFIDENCE, PLACED ON THE SOUTHERN
SIDE OF THE CONVECTIVE MASS, IN LINE WITH THE PGTW AND KNES FIX
POSITIONS. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE T2.5 DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND
DEMS, AND STEADILY IMPROVING STRUCTURE SEEN IN THE LAST FEW HOURS.
THE SYSTEM IS CURRENTLY TRACKING EASTWARD ALONG THE SOUTHERN SIDE
OF A STRONG NER ENTRENCHED TO THE NORTH. ANALYSIS REVEALS A
FAVORABLE ENVIRONMENT, CHARACTERIZED BY VERY WARM SSTS, HIGH OHC,
LOW VWS, AND GOOD DUAL-CHANNEL OUTFLOW. THE SYSTEM REMAINS QUITE
SMALL AND THE VORTEX IS LIKELY STILL SOMEWHAT TILTED, WHICH MAKES
IT SUSCEPTIBLE TO THE SLIGHTLY HIGHER MID-LEVEL WESTERLY SHEAR.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER NER
TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T1.5 - 25 KTS
   DEMS: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 16S FORECAST TO TRACK GENERALLY EASTWARD
ALONG THE SOUTHERN SIDE OF THE STRONG NER TO THE NORTH THROUGH THE
FIRST 24 HOURS OF THE FORECAST. AFTER TAU 24, THE NER BEGINS TO
BREAK DOWN TO THE NORTH OF THE SYSTEM, GENERATING A WEAKNESS IN THE
STEERING GRADIENT. BY TAU 36, A MIGRATORY RIDGE PASSING FAR TO THE
SOUTH WILL BUILD TOWARDS THE NORTHEAST, ULTIMATELY MERGING WITH AN
EASTERN LOBE OF THE NER CENTERED NEAR 10S 75E, GENERATING A SOLID
WALL OF RIDGING EXTENDING ALONG A SOUTHWEST-NORTHEAST AXIS FROM 10S
TO 30S. TC 16S WILL NOT HAVE THE JUICE TO PUSH INTO THIS DEEP
RIDGING AND INSTEAD WILL TAKE THE PATH OF LEAST RESISTANCE, AND
TURN SHARPLY SOUTHWARD BETWEEN TAUS 36 AND 48. TC 16S THEN TRACKS
SOUTH-SOUTHWESTWARD THROUGH TAU 96, GENERALLY TOWARDS THE
MASCARENE ISLANDS, ALONG THE WEST SIDE OF A COMPLEX RIDGE PATTERN
THAT DEVELOPS IN THE CENTRAL INDIAN OCEAN. BY THE END OF THE
FORECAST PERIOD, A TROUGH PASSING BY TO THE SOUTH WILL ERODE
THE STEERING RIDGE AND WEAKEN THE GRADIENT, LEADING TO A SLOW-DOWN IN
TRACK SPEED AND A TURN MORE WESTWARD BY TAU 120. IN TERMS OF
INTENSITY, THE SYSTEM WILL TAKE ADVANTAGE OF THE FAVORABLE
ENVIRONMENT, BUT WILL BE RELATIVELY SLOW TO INTENSIFY FOR THE FIRST
24 HOURS AS IT CONTINUES TO CONSOLIDATE THE VORTEX. ONCE THE VORTEX
IS FIRMLY ESTABLISHED, THE FORECAST CALLS FOR A MORE RAPID PACE OF
INTENSIFICATION AS IT PASSES OVER VERY WARM WATERS WITH RELATIVELY
HIGH OHC VALUES, AND UPPER-LEVEL OUTFLOW INCREASES. A PEAK OF 85
KNOTS IS EXPECTED BY TAU 72 BEFORE CONDITIONS BEGIN TO DETERIORATE.
REDUCED OUTFLOW ACCOMPANIED BY INCREASED SHEAR AND DRY AIR
ENTRAINMENT BEGIN TO TAKE THEIR TOLL AFTER TAU 72, AND TC 16S WILL
STEADILY WEAKEN THROUGH THE REMAINDER OF THE FORECAST. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE SHOWS A WIDE SPREAD
IN POTENTIAL TRACK SOLUTIONS, PARTICULARLY AFTER TAU 36 WHEN THE
SYSTEM BEGINS TO TURN SOUTHWARD. ACROSS THE CONSENSUS MEMBERS, THE
TRIO OF THE UKMET BASED MODELS INCLUDING UKMET ENSEMBLE, EGRR AND
THE GALWEM ALL DISPLAY THE SAME GENERAL TRACK TYPE AS THE REST OF
THE GUIDANCE BUT TRACK THE SYSTEM EAST OF PORT MATHURIN. THIS
SERVES TO PULL THE CONSENSUS MEAN SIGNIFICANTLY TOO FAR TO THE
EAST. THE REMAINDER OF THE GUIDANCE PACKAGE LIES IN A MORE
TIGHTLY-PACKED ENVELOPE THAT GRADUALLY EXPANDS FROM 100NM AT TAU 48
TO 320NM BY TAU 120, WITH ALL THE MEMBERS CONFINED TO THE WEST OF
THE CONSENSUS MEAN. A MANUAL RUN OF A NEW CONSENSUS WHICH DISCARDS
THE OUTLIERS ABOVE GENERATES A MORE REALISTIC SCENARIO, WITH THE
TRACK PASSING JUST EAST OF MAURITIUS. THE JTWC FORECAST CLOSELY
TRACKS THIS MANUAL CONSENSUS MEAN AND THE ECMWF TRACKER. CONFIDENCE
IS LOW HOWEVER, PARTICULARLY AFTER TAU 48 DUE TO VERY LARGE MODEL
SPREAD. BOTH THE GEFS AND ECENS ENSEMBLES ALSO SHOW A HIGH AMOUNT
OF SPREAD, LENDING EVEN MORE UNCERTAINTY IN THE FORECAST. INTENSITY
GUIDANCE IS MIXED AS WELL, WITH THE GLOBAL-MODEL-BASED SHIPS
GUIDANCE, THE COAMPS-TC (NAVGEM) AND THE HWRF MODELS SHOWING FAR
MORE EXCITEMENT THAN THE OTHER MESOSCALE MODELS SUCH AS HAFS-A AND
THE GFS-BASED COAMPS-TC. THE LATTER MODELS ONLY SHOW MODEST
INTENSIFICATION TO A PEAK BETWEEN 50-65 KNOTS, WHILE THE FIRST
MODELS SHOW A PEAK CLOSER TO 95 KNOTS. ALL AGREE THAT THE PEAK WILL
BE AT TAU 72, FOLLOWED BY A STEADY WEAKENING THROUGH TAU 120. THE
JTWC FORECAST GENERALLY FOLLOWS ABOUT 5 KNOTS LOWER THAN THE SHIPS
GUIDANCE AND SIGNIFICANTLY LOWER THAN THE RAPID INTENSIFICATION
AIDS WHICH ARE TRIGGERING WITH THIS MODEL RUN. CONFIDENCE IS LOW
THROUGH THE FORECAST PERIOD.  

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