WDXS32 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (ENALA) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.8S 71.1E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 778 NM EAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
EXTREMELY SMALL TROPICAL CYCLONE, WHICH PEAKED AT OR JUST PRIOR TO
1800Z AND IS NOW ALREADY WEAKENING. EARLIER MICROWAVE IMAGERY
AROUND 231308Z SHOWED A VERY CLEAR MICROWAVE EYE FEATURE, AND LATE
VISIBLE IMAGERY PRIOR TO SUNSET SHOWED INDICATIONS OF A NASCENT EYE
FEATURE, WHICH HAS SINCE DISSIPATED. THE CENTRAL DENSE OVERCAST
(CDO) SEEN IN THE EIR HAS BECOME INCREASINGLY RAGGED IN JUST THE
PAST HOUR AS WELL. DUE TO THE STEADILY DETERIORATING CDO, THERE IS
A WIDE SPREAD IN THE AGENCY FIX POSITIONS AND A LACK OF RECENT
HIGH-RESOLUTION MICROWAVE IMAGERY, MEANS THE INITIAL POSITION IS
ASSESSED WITH LOW CONFIDENCE. THE INITIAL INTENSITY IS SET WITH
MEDIUM CONFIDENCE AT AN AGGRESSIVE 75 KNOTS, WHICH WHILE ABOVE THE
MAJORITY OF THE AGENCY FIXES, IS SUPPORTED BY THE PGTW FIX, THE ADT
AND AIDT ESTIMATES AS WELL AS A 231630Z ASCAT-B PASS WHICH SHOWED
WINDS EXCEEDING 60 KNOTS IN THE CENTER OF THE SYSTEM. APPLYING THE
10-15 KNOT LOW-BIAS CORRECTION FOR ASCAT WINDS AT THIS SPEED EASILY
SUPPORTS A 75 KNOT INTENSITY. THE SYSTEM IS TRACKING SOUTHWESTWARD
THROUGH A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY WARM
SSTS, ROBUST POLEWARD OUTFLOW AND MODERATE TO HIGH NORTHWESTERLY
VWS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T4.0 - 65 KTS
   FMEE: T4.0 - 65 KTS
   FIMP: T4.0 - 65 KTS
   CIMSS SATCON: 69 KTS AT 231719Z
   CIMSS ADT: 74 KTS AT 231800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECAST TRACK HAS SLOWED TO
QUASI-STATIONARY AT THE END OF THE FORECAST AND THE INTENSITY TREND
HAS SHIFTED TO INTENSIFICATION AT THE END OF THE FORECAST. 

FORECAST DISCUSSION: TC 14S (ENALA) HAS UNDERGONE A SHORT BURST OF
VERY QUICK INTENSIFICATION OVER THE PAST 6-12 HOURS. WHILE
ENVIRONMENTAL CONDITIONS WERE NOT OPTIMUM FOR THIS BURST OF
ACTIVITY, THE COMPACT NATURE OF THE SYSTEM ALLOWED FOR A RAPID
CONSOLIDATION OF AN INNER CORE OF DEEP CONVECTION, WHICH WAS ABLE
TO PUSH BACK AGAINST THE MODERATE SHEAR. HOWEVER, EVEN OVER THE
PAST FEW HOURS, AN UPTICK IN THE NORTHWESTERLY SHEAR AND AN INFLUX
OF DRY AIR IN THE MID-LEVELS, HAS LED TO DETERIORATION IN THE
SYSTEMS SUBSEQUENT TO THE PEAK WHICH OCCURRED AT OR JUST PRIOR TO
231800Z. OVER THE NEXT 48 HOURS, THE SYSTEM WILL CONTINUE TRACKING
SOUTH-SOUTHWESTWARD ALONG THE WESTERN SIDE OF A DEEP-LAYER STR
WHICH IS ENTRENCHED TO THE NORTH. BY TAU 72, THE SYSTEM WILL SLOW
SIGNIFICANTLY, MOVING INTO A WEAK STEERING PATTERN CREATED BY THE
PASSAGE OF AN UPPER-LEVEL TROUGH WHICH BREAKS DOWN THE STEERING
RIDGE. THIS GENERAL PATTERN IS ANTICIPATED TO REMAIN IN PLACE
THROUGH THE END OF THE FORECAST, LEADING TO A SLOW, MEANDERING
TRACK THROUGH TAU 120. IN TERMS OF INTENSITY, HIGH-RESOLUTION MODEL
FIELDS AND CROSS-SECTIONS INDICATE CONTINUING DRY AIR INTRUSIONS
FUELED BY STEADY MODERATE NORTHWESTERLY VWS THROUGH THE NEXT 72
HOURS. THESE NEGATIVE FACTORS WILL BE OFFSET SOMEWHAT BY THE
STRONG, DIVERGENT, POLEWARD OUTFLOW WHICH WILL SLOW THE PACE OF
WEAKENING, BUT NOT BE ENOUGH TO SUPPORT INTENSIFICATION OR
MAINTENANCE OF THE INTENSITY. AS THE SYSTEM SLOWS DOWN AT THE END
OF THE FORECAST, IT DRIFTS OVER A SLIGHTLY WARMER POOL OF WATER AND
SIMULTANEOUSLY VWS IS FORECAST TO DECREASE AND UPPER-LEVEL OUTFLOW
BECOME RADIAL DUE TO DEVELOPMENT OF A POINT SOURCE ALOFT. THE
COMBINATION OF FACTORS WILL LEAD TO REINTENSIFICATION AT THE END OF
THE FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
GOOD AGREEMENT THROUGH THE FIRST 72 HOURS OF THE FORECAST, WITH
JUST 100NM SPREAD BY TAU 72. THINGS GO OFF THE RAILS AFTER TAU 72,
WITH DETERMINISTIC GUIDANCE SHIFTING TO MORE A SQUASHED SPIDER
LOOK, WITH EACH CONSENSUS TRACKER SHOWING A DIFFERENT VECTOR TO THE
TAU 120 POSITION. ENSEMBLE GUIDANCE ALSO SHOWS SIGNIFICANT SPREAD
AFTER TAU 72 WITH SOLUTIONS SPREAD ACROSS MORE THAN 600NM. THE JTWC
FORECAST TRACKS THE NORTHERN SIDE OF THE ENVELOPE THROUGH TAU 72
WITH HIGH CONFIDENCE. AFTER TAU 72, THE JTWC FORECAST TRACKS THE
GFS DETERMINISTIC AND ENSEMBLE MEAN, THOUGH CONFIDENCE IS VERY LOW
DUE TO THE WIDE SPREAD IN THE ENSEMBLE GUIDANCE. SIMILARLY,
INTENSITY GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 AND THE JTWC
FORECAST FOR THE MOST PART TRACKS THE CONSENSUS MEAN, ALBEIT
SLIGHTLY LOWER AFTER TAU 48. HOWEVER, IN THE EXTENDED RANGE, MODELS
SHOW SIGNIFICANT DIVERGENCE, WITH HWRF PREDICTING A PEAK OF 90
KNOTS AT TAU 120, WHILE DECAY-SHIPS INDICATES 25 KNOTS AT THE SAME
TIME. THE COAMPS-TC DETERMINISTIC ALSO SHOWS SIGNIFICANT
INTENSIFICATION AFTER TAU 72, WHILE COAMPS-TC ENSEMBLE SHOWS A
STRONG PROBABILITY (70 PERCENT) OF MODERATE INTENSIFICATION IN THE
LATER TAUS. HOWEVER, THERE HAS BEEN A LARGE AMOUNT OF RUN-TO-RUN
VARIABILITY WITH THIS STORM, AND THIS IS THE FIRST MODEL RUN
DEPICTING INTENSIFICATION IN THE LATER TAUS, HENCE THE JTWC
FORECAST HAS YET TO BITE ON THAT BAIT, AND WHILE INDICATES SOME
INTENSIFICATION AFTER TAU 96, REMAINS BELOW THE MORE AGGRESSIVE
GUIDANCE. 

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