SOUTH PACIFIC OCEAN: TC 30P MAILA. WARNING 4 ISSUED BY JTWC @05/1500 UTC.
TC WARNING GRAPHICS
PROGNOSTIC REASONING
WDPS31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 30P (MAILA) WARNING NR
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 9.3S 154.6E
INITIAL INTENSITY: 75 KTS
GEOGRAPHIC REFERENCE: 687 NM NORTHEAST OF CAIRNS, AUSTRALIA
MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 02 KTS
SIGNIFICANT WAVE HEIGHT: 22 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SYSTEM
RELATIVELY SYMMETRICAL CENTRAL DENSE OVERCAST (CDO) WHICH HAS
REMAINED FOR THE MOST PART UNCHANGED FOR THE PAST 12 HOURS. WHILE
AN EYE HAS YET TO APPEAR IN THE CDO, A 050753Z WSF-M COLOR-ENHANCED
37GHZ IMAGE REVEALED A WELL-FORMED MICROWAVE EYE IS PRESENT UNDER
THE CDO. ONE POSSIBLE REASON FOR THE LACK OF A FASTER PACE OF
INTENSIFICATION IS THE PRESENCE OF SOME EVIDENT DRY MID-LEVEL AIR,
EVIDENCED BY A MOAT BETWEEN RAIN BANDS IN THE MICROWAVE IMAGERY,
WEDGING UP THE WESTERN SIDE OF THE EYE FEATURE. ADDITIONALLY,
MESOSCALE MODEL-DERIVED SOUNDINGS INDICATE THE PRESENCE OF HIGH
(20-25 KNOT) MID-LEVEL EASTERLY SHEAR, WHICH IF PRESENT, WOULD ALSO
INHIBIT A FASTER RATE OF INTENSIFICATION. EVEN WITH THESE NEGATIVE
FACTORS, TC 30P HAS STEADILY INTENSIFIED OVER THE PAST 12 HOURS.
THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE, WITH THE
WSF-M IMAGE PROVIDING THE ONLY LOOK UNDER THE HOOD. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE AS WELL, BASED ON A
BLEND OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED
BELOW. ENVIRONMENTAL CONDITIONS ARE FAVORABLE, WITH WARM SSTS,
MODERATE WESTERLY OUTFLOW ALOFT, AND LOW DEEP-LAYER SHEAR, OFFSET
BY DRY MID-LEVEL AIR AND MODERATE TO HIGH MID-LEVEL EASTERLY SHEAR.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: COMPETING AND BALANCED STEERING
PATTERN, WITH A DEEP-LAYER NEAR EQUATORIAL RIDGE (NER) ALONG THE
EQUATOR, AND A SUBTROPICAL RIDGE (STR) OVER NORTHERN AUSTRALIA.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T4.5 - 77 KTS
KNES: T4.5 - 77 KTS
ABRF: T4.0 - 65 KTS
CIMSS ADT: 61 KTS AT 051130Z
CIMSS AIDT: 65 KTS AT 051130Z
CIMSS D-MINT: 86 KTS AT 050754Z
CIMSS D-PRINT: 88 KTS AT 051200Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: MODERATE WESTWARD
OTHER FACTORS: MODERATE TO HIGH MID-LEVEL SHEAR.
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: TROPICAL CYCLONE (TC) 30P HAS MAINTAINED A
QUASI-STATIONARY MOTION OVER THE LAST 12 HOURS AND REMAINS TRAPPED
IN A COMPETING STEERING ENVIRONMENT AS DESCRIBED ABOVE. THERE ARE
AS OF YET NO SIGNS OF ANY SIGNIFICANT CHANGE IN THE STEERING
PATTERN FOR THE NEXT 48 TO 60 HOURS AND TC 30P WILL MEANDER SLOWLY
AROUND THE SOLOMON SEA THROUGH THAT TIMEFRAME. THE FORECAST CALLS
FOR A SLOW EASTWARD PROGRESSION THROUGH TAU 36, THEN A TURN
NORTHWARD BY TAU 48. HOWEVER, THE BOTTOM LINE IS THAT THE TRACK
WILL BE BOTH HIGHLY ERRATIC AND HIGHLY UNCERTAIN, THOUGH THE SYSTEM
IS EXPECTED TO REMAIN IN A FAIRLY SMALL AREA THROUGH TAU 48. BY TAU
72, THE NER TO THE NORTH MOVES AWAY TO THE NORTH AND THE TROUGH
ASSOCIATED WITH TC 31P NEAR FIJI MOVES AWAY TOWARDS THE SOUTHEAST,
WHICH WILL ALLOW THE STR OVER AUSTRALIA TO BUILD EASTWARD TO THE
SOUTH OF TC 30P. BEYOND TAU 96, THE STR OVER AUSTRALIA MOVES
QUICKLY EASTWARD, POSITIONING ITSELF TO THE SOUTH OF TC 30P. THIS
EVOLUTION OF THE STEERING PATTERN WILL ALLOW TC 30P TO BE EJECTED
WESTWARD AFTER TAU 72, ULTIMATELY TRANSITING CLOSE TO THE SOUTHEAST
TIP OF PAPUA NEW GUINEA BY THE END OF THE FORECAST PERIOD.
REGARDING INTENSITY, DEEP-LAYER SHEAR IS FORECAST TO CONTINUE TO
WEAKEN IN THE NEAR-TERM, AND MID-LEVEL SHEAR IS ALSO EXPECTED TO
SLACKEN, ALLOWING THE VORTEX TO FULLY ALIGN. ONCE THIS OCCURS, THE
SYSTEM IS FORECAST TO RAPIDLY INTENSIFY (RI), TO A PEAK OF 110
KNOTS BY TAU 36. OCEAN HEAT CONTENT IN THE REGION IS HIGH (125-150
KJ PER CM2), SO THE WARM WATER IS DEEP ENOUGH TO ALLOW FOR ABOUT 36
HOURS OF UPWELLING BEFORE THE COOL WATERS REACH THE SURFACE.
BEGINNING AT TAU 48, THE SYSTEM RAPIDLY WEAKENS AS IT LOSES ITS
ENERGY SOURCE. BY TAU 72, TC 30P WILL REACH ITS MINIMUM AND AS IT
BEGINS TO MOVE TO THE WEST AND AWAY FROM THE COOL UPWELLED POOL, IT
WILL BEGIN TO INTENSIFY ONCE MORE. HOWEVER, PROXIMITY TO TERRAIN
AND A MARGINAL INCREASE IN SHEAR WILL SERVE TO CAP THE INTENSITY
THROUGH THE END OF THE FORECAST PERIOD.
MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN SIGNIFICANT
DISAGREEMENT, PARTICULARLY IN THE LONGER-RANGE FORECAST TAUS.
THROUGH TAU 48, THE BULK OF THE CONSENSUS MEMBERS, AS WELL AS BOTH
GEFS AND ECEPS, DEPICT A SLOWLY MEANDERING, BUT GENERALLY EASTWARD
TRAJECTORY. THE AI MODELS (EC-AIFS, GDM AND THE AI CONSENSUS) BEGIN
TO DEVIATE EQUATORWARD AND BREAK FROM THE PACK BY TAU 48. BY TAU
72, THE BULK OF THE CONSENSUS TRACKERS LOOP THE SYSTEM BACK TOWARDS
WEST OR SOUTHWEST WHILE THE AI MODELS CONTINUE THEIR TRACK
EQUATORWARD. BY THE END OF THE FORECAST PERIOD, THE AI MODELS ARE
ARRAYED IN A FAN HEADED WEST-NORTHWEST FURTHER INTO THE SOLOMON
SEA. THE REMAINDER OF THE CONSENSUS (ECMWF, ECEPS, GFS, GEFS,
NAVGEM, EGRR AND GALWEM) FAN OUT ON A SOUTHWESTWARD TRAJECTORY,
WITH A 210NM SPREAD BETWEEN THE GFS AND GEFS ON THE NORTHERN EDGE
AND THE NAVGEM ON THE SOUTHERN. THE JTWC FORECAST IS PLACED CLOSE
TO THE CONSENSUS MEAN THROUGH TAU 96, THEN MUCH SLOWER, IN A BLEND
BETWEEN THE ECMWF AND GEFS AT TAU 120. CONFIDENCE IS LOW,
ESPECIALLY GIVEN THE VERY WIDE SPREAD IN THE ENSEMBLE MEMBERS.
INTENSITY GUIDANCE IS MIXED. NEARLY EVERY RI AID IS TRIGGERED,
DEPICTING A PEAK INTENSITY BETWEEN 110-130 KNOTS BY TAU 36.
MEANWHILE, THE HWRF AND COAMPS-TC SUGGEST LITTLE IN THE WAY OF
ADDITIONAL INTENSIFICATION AND THE HAFS-A IS ROUGHLY BETWEEN THE
TWO EXTREMES. AFTER THE PEAK AT TAU 36, THE GUIDANCE IS SPLIT, WITH
THE SHIPS, GFS AND CONSENSUS INDICATING A FLAT INTENSITY TREND
THROUGH THE REMAINDER OF THE FORECAST, WHILE THE COUPLED MODELS
DEPICT A SHARP WEAKENING THROUGH TAU 72 BEFORE RESUMING A SLIGHT
INTENSIFICATION. THE JTWC FORECAST IS PLACED GENERALLY NEAR THE
HAFS-A, BUT CONFIDENCE IS LOW DUE TO THE FACT THAT THE TREND WILL
IN LARGE PART BE DRIVEN BY THE FORECAST TRACK, CONFIDENCE IN WHICH
IS LOW.
FORECAST CONFIDENCE:
TRACK 00-72 HR: LOW
TRACK 72-120 HR: LOW
INTENSITY 00-72 HR: LOW
INTENSITY 72-120 HR: LOW//
NNNN
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 30P (MAILA) WARNING NR
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 9.3S 154.6E
INITIAL INTENSITY: 75 KTS
GEOGRAPHIC REFERENCE: 687 NM NORTHEAST OF CAIRNS, AUSTRALIA
MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 02 KTS
SIGNIFICANT WAVE HEIGHT: 22 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SYSTEM
RELATIVELY SYMMETRICAL CENTRAL DENSE OVERCAST (CDO) WHICH HAS
REMAINED FOR THE MOST PART UNCHANGED FOR THE PAST 12 HOURS. WHILE
AN EYE HAS YET TO APPEAR IN THE CDO, A 050753Z WSF-M COLOR-ENHANCED
37GHZ IMAGE REVEALED A WELL-FORMED MICROWAVE EYE IS PRESENT UNDER
THE CDO. ONE POSSIBLE REASON FOR THE LACK OF A FASTER PACE OF
INTENSIFICATION IS THE PRESENCE OF SOME EVIDENT DRY MID-LEVEL AIR,
EVIDENCED BY A MOAT BETWEEN RAIN BANDS IN THE MICROWAVE IMAGERY,
WEDGING UP THE WESTERN SIDE OF THE EYE FEATURE. ADDITIONALLY,
MESOSCALE MODEL-DERIVED SOUNDINGS INDICATE THE PRESENCE OF HIGH
(20-25 KNOT) MID-LEVEL EASTERLY SHEAR, WHICH IF PRESENT, WOULD ALSO
INHIBIT A FASTER RATE OF INTENSIFICATION. EVEN WITH THESE NEGATIVE
FACTORS, TC 30P HAS STEADILY INTENSIFIED OVER THE PAST 12 HOURS.
THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE, WITH THE
WSF-M IMAGE PROVIDING THE ONLY LOOK UNDER THE HOOD. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE AS WELL, BASED ON A
BLEND OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED
BELOW. ENVIRONMENTAL CONDITIONS ARE FAVORABLE, WITH WARM SSTS,
MODERATE WESTERLY OUTFLOW ALOFT, AND LOW DEEP-LAYER SHEAR, OFFSET
BY DRY MID-LEVEL AIR AND MODERATE TO HIGH MID-LEVEL EASTERLY SHEAR.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: COMPETING AND BALANCED STEERING
PATTERN, WITH A DEEP-LAYER NEAR EQUATORIAL RIDGE (NER) ALONG THE
EQUATOR, AND A SUBTROPICAL RIDGE (STR) OVER NORTHERN AUSTRALIA.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T4.5 - 77 KTS
KNES: T4.5 - 77 KTS
ABRF: T4.0 - 65 KTS
CIMSS ADT: 61 KTS AT 051130Z
CIMSS AIDT: 65 KTS AT 051130Z
CIMSS D-MINT: 86 KTS AT 050754Z
CIMSS D-PRINT: 88 KTS AT 051200Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: MODERATE WESTWARD
OTHER FACTORS: MODERATE TO HIGH MID-LEVEL SHEAR.
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: TROPICAL CYCLONE (TC) 30P HAS MAINTAINED A
QUASI-STATIONARY MOTION OVER THE LAST 12 HOURS AND REMAINS TRAPPED
IN A COMPETING STEERING ENVIRONMENT AS DESCRIBED ABOVE. THERE ARE
AS OF YET NO SIGNS OF ANY SIGNIFICANT CHANGE IN THE STEERING
PATTERN FOR THE NEXT 48 TO 60 HOURS AND TC 30P WILL MEANDER SLOWLY
AROUND THE SOLOMON SEA THROUGH THAT TIMEFRAME. THE FORECAST CALLS
FOR A SLOW EASTWARD PROGRESSION THROUGH TAU 36, THEN A TURN
NORTHWARD BY TAU 48. HOWEVER, THE BOTTOM LINE IS THAT THE TRACK
WILL BE BOTH HIGHLY ERRATIC AND HIGHLY UNCERTAIN, THOUGH THE SYSTEM
IS EXPECTED TO REMAIN IN A FAIRLY SMALL AREA THROUGH TAU 48. BY TAU
72, THE NER TO THE NORTH MOVES AWAY TO THE NORTH AND THE TROUGH
ASSOCIATED WITH TC 31P NEAR FIJI MOVES AWAY TOWARDS THE SOUTHEAST,
WHICH WILL ALLOW THE STR OVER AUSTRALIA TO BUILD EASTWARD TO THE
SOUTH OF TC 30P. BEYOND TAU 96, THE STR OVER AUSTRALIA MOVES
QUICKLY EASTWARD, POSITIONING ITSELF TO THE SOUTH OF TC 30P. THIS
EVOLUTION OF THE STEERING PATTERN WILL ALLOW TC 30P TO BE EJECTED
WESTWARD AFTER TAU 72, ULTIMATELY TRANSITING CLOSE TO THE SOUTHEAST
TIP OF PAPUA NEW GUINEA BY THE END OF THE FORECAST PERIOD.
REGARDING INTENSITY, DEEP-LAYER SHEAR IS FORECAST TO CONTINUE TO
WEAKEN IN THE NEAR-TERM, AND MID-LEVEL SHEAR IS ALSO EXPECTED TO
SLACKEN, ALLOWING THE VORTEX TO FULLY ALIGN. ONCE THIS OCCURS, THE
SYSTEM IS FORECAST TO RAPIDLY INTENSIFY (RI), TO A PEAK OF 110
KNOTS BY TAU 36. OCEAN HEAT CONTENT IN THE REGION IS HIGH (125-150
KJ PER CM2), SO THE WARM WATER IS DEEP ENOUGH TO ALLOW FOR ABOUT 36
HOURS OF UPWELLING BEFORE THE COOL WATERS REACH THE SURFACE.
BEGINNING AT TAU 48, THE SYSTEM RAPIDLY WEAKENS AS IT LOSES ITS
ENERGY SOURCE. BY TAU 72, TC 30P WILL REACH ITS MINIMUM AND AS IT
BEGINS TO MOVE TO THE WEST AND AWAY FROM THE COOL UPWELLED POOL, IT
WILL BEGIN TO INTENSIFY ONCE MORE. HOWEVER, PROXIMITY TO TERRAIN
AND A MARGINAL INCREASE IN SHEAR WILL SERVE TO CAP THE INTENSITY
THROUGH THE END OF THE FORECAST PERIOD.
MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN SIGNIFICANT
DISAGREEMENT, PARTICULARLY IN THE LONGER-RANGE FORECAST TAUS.
THROUGH TAU 48, THE BULK OF THE CONSENSUS MEMBERS, AS WELL AS BOTH
GEFS AND ECEPS, DEPICT A SLOWLY MEANDERING, BUT GENERALLY EASTWARD
TRAJECTORY. THE AI MODELS (EC-AIFS, GDM AND THE AI CONSENSUS) BEGIN
TO DEVIATE EQUATORWARD AND BREAK FROM THE PACK BY TAU 48. BY TAU
72, THE BULK OF THE CONSENSUS TRACKERS LOOP THE SYSTEM BACK TOWARDS
WEST OR SOUTHWEST WHILE THE AI MODELS CONTINUE THEIR TRACK
EQUATORWARD. BY THE END OF THE FORECAST PERIOD, THE AI MODELS ARE
ARRAYED IN A FAN HEADED WEST-NORTHWEST FURTHER INTO THE SOLOMON
SEA. THE REMAINDER OF THE CONSENSUS (ECMWF, ECEPS, GFS, GEFS,
NAVGEM, EGRR AND GALWEM) FAN OUT ON A SOUTHWESTWARD TRAJECTORY,
WITH A 210NM SPREAD BETWEEN THE GFS AND GEFS ON THE NORTHERN EDGE
AND THE NAVGEM ON THE SOUTHERN. THE JTWC FORECAST IS PLACED CLOSE
TO THE CONSENSUS MEAN THROUGH TAU 96, THEN MUCH SLOWER, IN A BLEND
BETWEEN THE ECMWF AND GEFS AT TAU 120. CONFIDENCE IS LOW,
ESPECIALLY GIVEN THE VERY WIDE SPREAD IN THE ENSEMBLE MEMBERS.
INTENSITY GUIDANCE IS MIXED. NEARLY EVERY RI AID IS TRIGGERED,
DEPICTING A PEAK INTENSITY BETWEEN 110-130 KNOTS BY TAU 36.
MEANWHILE, THE HWRF AND COAMPS-TC SUGGEST LITTLE IN THE WAY OF
ADDITIONAL INTENSIFICATION AND THE HAFS-A IS ROUGHLY BETWEEN THE
TWO EXTREMES. AFTER THE PEAK AT TAU 36, THE GUIDANCE IS SPLIT, WITH
THE SHIPS, GFS AND CONSENSUS INDICATING A FLAT INTENSITY TREND
THROUGH THE REMAINDER OF THE FORECAST, WHILE THE COUPLED MODELS
DEPICT A SHARP WEAKENING THROUGH TAU 72 BEFORE RESUMING A SLIGHT
INTENSIFICATION. THE JTWC FORECAST IS PLACED GENERALLY NEAR THE
HAFS-A, BUT CONFIDENCE IS LOW DUE TO THE FACT THAT THE TREND WILL
IN LARGE PART BE DRIVEN BY THE FORECAST TRACK, CONFIDENCE IN WHICH
IS LOW.
FORECAST CONFIDENCE:
TRACK 00-72 HR: LOW
TRACK 72-120 HR: LOW
INTENSITY 00-72 HR: LOW
INTENSITY 72-120 HR: LOW//
NNNN
RIPA FORECAST
SOUTH PACIFIC OCEAN: TC 31P. WARNING 2 ISSUED BY JTWC @05/1500 UTC
TC WARNING GRAPHICS
PROGNOSTIC REASONING
WDPS32 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 31P (VAIANU) WARNING
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 14.9S 172.4E
INITIAL INTENSITY: 55 KTS
GEOGRAPHIC REFERENCE: 290 NM NORTHEAST OF PORT VILA, VANUATU
MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 04 KTS
SIGNIFICANT WAVE HEIGHT: 21 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
RAPIDLY CONSOLIDATING, COMPACT CENTRAL DENSE OVERCAST (CDO), WITH A
NASCENT EYE BEGINNING TO DEVELOP IN THE MOST RECENT FRAMES IN THE
ANIMATION. A 051210Z GMI 89GHZ IMAGE REVEALED WELL-DEFINED SPIRAL
BANDING FEATURES WRAPPING IN A WIDE ARC INTO A QUICKLY SEPARATING
INNER CORE OF DEEP CONVECTION, WITH A SMALL MICROWAVE EYE FEATURE.
DEEP CONVECTIVE HOT TOWERS ARE DEVELOPING IN THE CENTRAL CORE
REGION OF THE CDO, SURROUNDING THE EYE, AND ACCOMPANIED BY A ROBUST
INNER-CORE LIGHTNING BURST, A POTENTIAL INDICATOR OF NEAR-TERM
RAPID INTENSIFICATION (RI). THE INITIAL INTENSITY IS ASSESSED WITH
HIGH CONFIDENCE BASED ON THE MICROWAVE EYE IN THE GMI IMAGERY. THE
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON THE
SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES AVAILABLE AT ANALYSIS
TIME, THOUGH IT IS ALREADY LIKELY TOO LOW BASED ON THE RAPIDLY
DEVELOPING SITUATION. ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE
FOR RI, WITH LOW VERTICAL WIND SHEAR (VWS), WARM SSTS, HIGH OHC,
AND ROBUST POLEWARD OUTFLOW.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED SOUTH OF SAMOA.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.5 - 55 KTS
KNES: T3.5 - 55 KTS
PHFO: T3.5 - 55 KTS
NFFN: T3.0 - 45 KTS
CIMSS ADT: 57 KTS AT 051140Z
CIMSS AIDT: 43 KTS AT 051140Z
CIMSS D-PRINT: 60 KTS AT 051300Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
VWS: 5-10 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
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: TROPICAL CYCLONE (TC) 31P (VAIANU) IS FORECAST
TO TRACK POLEWARD ALONG THE WESTERN FLANK OF THE DEEP STR THROUGH
THE MAJORITY OF THE FORECAST PERIOD. ONLY AFTER TAU 96 WILL THE
TRACK DEVIATE TO A MORE SOUTHWARD TRAJECTORY, AS IT IS BOTH PULLED
SOUTHWARD INTO A DEEP-LAYER TROUGH AND PUSHED SOUTH ALONG THE
WESTERN PERIPHERY OF A VERY STRONG RIDGE REACHING ALL THE WAY TO
45S ALONG THE 160W LONGITUDE. REGARDING INTENSITY, TC 31P IS PRIMED
TO RI IN THE NEAR-TERM, UNDER VERY FAVORABLE ENVIRONMENTAL
CONDITIONS. THE WINDOW OF OPPORTUNITY HOWEVER, IS FINITE, AND THE
CONDITIONS WILL ONLY LAST FOR ABOUT 36 HOURS. THEREAFTER, SHEAR
WILL RAPIDLY INCREASE, TO MORE THAN 30 KNOTS BY TAU 48, MORE THAN
50 KNOTS BY TAU 96 AND HIGHER STILL BY THE END OF THE FORECAST
PERIOD AS THE SYSTEM PASSES UNDER A POLAR FRONT JET STREAK AND
BEGINS EXTRA-TROPICAL TRANSITION (ETT). THE RAPIDLY INCREASING
SHEAR WILL ALSO USHER IN EXTREMELY DRY MID-LEVEL AIR, HELPING TO
SQUASH TC 31P. WHILE THE SYSTEM WILL BE DECAPITATED BY TAU 72 AND
SMOTHERED BY DRY AIR AFTER TAU 96, IT WILL STILL TAKE TIME TO SPIN
DOWN IN INTENSITY. BY THE END OF THE FORECAST PERIOD, BAROCLINIC
FORCING WILL FURTHER SLOW THE RATE OF WEAKENING AS THE SYSTEM
BEGINS ETT.
MODEL DISCUSSION: TRACK GUIDANCE IS IN STRONG AGREEMENT, WITH
NAVGEM THE ONLY OUTLIER AMONGST THE CONSENSUS MEMBERS, DEPICTING A
TRACK FAR OUT TO THE EAST TOWARDS TONGA. THE REMAINDER OF THE
CONSENSUS MEMBERS ARE CONFINED TO A GRADUALLY EXPANDING ENVELOPE THAT
WIDENS TO 105NM BY TAU 72 AND 280NM BY TAU 120. THE LARGER ISSUE IS
ALONG-TRACK SPREAD, PARTICULARLY BETWEEN THE AI MODELS (EC-AIFS, GDM
AND THE AI CONSENSUS) AND THE REMAINDER OF THE GUIDANCE. AT TAU 72,
ALONG-TRACK SPREAD IS ABOUT 80NM, INCREASING TO 250NM BETWEEN THE
SLOW GFS AND FAST AI MODELS, BY TAU 120. THE JTWC FORECAST IS
POSITIONED CLOSE TO THE CONSENSUS MEAN (MINUS NAVGEM) THROUGH TAU 72,
THEN ALONG THE TRACK LINE OF THE MEAN, BUT SLIGHTLY FASTER, HEDGED
TOWARDS THE AI CONSENSUS. CONFIDENCE IS HIGH THROUGH THE ENTIRE
FORECAST PERIOD. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT. NEARLY
EVERY RI AID IS TRIGGERED, INDICATING A PEAK INTENSITY BETWEEN 105-
130 KNOTS. ALL MODEL GUIDANCE SHOWS THE PEAK OCCURRING NEAR TAU 36,
THEN A MORE OR LESS RAPID WEAKENING THROUGH THE REMAINDER OF THE
FORECAST PERIOD. THE JTWC FORECAST IS PLACED CONSISTENT WITH THE RI
AIDS THROUGH TAU 36, THEN CLOSE TO THE CONSENSUS MEAN THEREAFTER,
WITH MEDIUM CONFIDENCE.
FORECAST CONFIDENCE:
TRACK 00-72 HR: HIGH
TRACK 72-120 HR: HIGH
INTENSITY 00-72 HR: MEDIUM
INTENSITY 72-120 HR: MEDIUM//
NNNN
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 31P (VAIANU) WARNING
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 14.9S 172.4E
INITIAL INTENSITY: 55 KTS
GEOGRAPHIC REFERENCE: 290 NM NORTHEAST OF PORT VILA, VANUATU
MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 04 KTS
SIGNIFICANT WAVE HEIGHT: 21 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
RAPIDLY CONSOLIDATING, COMPACT CENTRAL DENSE OVERCAST (CDO), WITH A
NASCENT EYE BEGINNING TO DEVELOP IN THE MOST RECENT FRAMES IN THE
ANIMATION. A 051210Z GMI 89GHZ IMAGE REVEALED WELL-DEFINED SPIRAL
BANDING FEATURES WRAPPING IN A WIDE ARC INTO A QUICKLY SEPARATING
INNER CORE OF DEEP CONVECTION, WITH A SMALL MICROWAVE EYE FEATURE.
DEEP CONVECTIVE HOT TOWERS ARE DEVELOPING IN THE CENTRAL CORE
REGION OF THE CDO, SURROUNDING THE EYE, AND ACCOMPANIED BY A ROBUST
INNER-CORE LIGHTNING BURST, A POTENTIAL INDICATOR OF NEAR-TERM
RAPID INTENSIFICATION (RI). THE INITIAL INTENSITY IS ASSESSED WITH
HIGH CONFIDENCE BASED ON THE MICROWAVE EYE IN THE GMI IMAGERY. THE
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON THE
SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES AVAILABLE AT ANALYSIS
TIME, THOUGH IT IS ALREADY LIKELY TOO LOW BASED ON THE RAPIDLY
DEVELOPING SITUATION. ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE
FOR RI, WITH LOW VERTICAL WIND SHEAR (VWS), WARM SSTS, HIGH OHC,
AND ROBUST POLEWARD OUTFLOW.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED SOUTH OF SAMOA.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.5 - 55 KTS
KNES: T3.5 - 55 KTS
PHFO: T3.5 - 55 KTS
NFFN: T3.0 - 45 KTS
CIMSS ADT: 57 KTS AT 051140Z
CIMSS AIDT: 43 KTS AT 051140Z
CIMSS D-PRINT: 60 KTS AT 051300Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
VWS: 5-10 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
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: TROPICAL CYCLONE (TC) 31P (VAIANU) IS FORECAST
TO TRACK POLEWARD ALONG THE WESTERN FLANK OF THE DEEP STR THROUGH
THE MAJORITY OF THE FORECAST PERIOD. ONLY AFTER TAU 96 WILL THE
TRACK DEVIATE TO A MORE SOUTHWARD TRAJECTORY, AS IT IS BOTH PULLED
SOUTHWARD INTO A DEEP-LAYER TROUGH AND PUSHED SOUTH ALONG THE
WESTERN PERIPHERY OF A VERY STRONG RIDGE REACHING ALL THE WAY TO
45S ALONG THE 160W LONGITUDE. REGARDING INTENSITY, TC 31P IS PRIMED
TO RI IN THE NEAR-TERM, UNDER VERY FAVORABLE ENVIRONMENTAL
CONDITIONS. THE WINDOW OF OPPORTUNITY HOWEVER, IS FINITE, AND THE
CONDITIONS WILL ONLY LAST FOR ABOUT 36 HOURS. THEREAFTER, SHEAR
WILL RAPIDLY INCREASE, TO MORE THAN 30 KNOTS BY TAU 48, MORE THAN
50 KNOTS BY TAU 96 AND HIGHER STILL BY THE END OF THE FORECAST
PERIOD AS THE SYSTEM PASSES UNDER A POLAR FRONT JET STREAK AND
BEGINS EXTRA-TROPICAL TRANSITION (ETT). THE RAPIDLY INCREASING
SHEAR WILL ALSO USHER IN EXTREMELY DRY MID-LEVEL AIR, HELPING TO
SQUASH TC 31P. WHILE THE SYSTEM WILL BE DECAPITATED BY TAU 72 AND
SMOTHERED BY DRY AIR AFTER TAU 96, IT WILL STILL TAKE TIME TO SPIN
DOWN IN INTENSITY. BY THE END OF THE FORECAST PERIOD, BAROCLINIC
FORCING WILL FURTHER SLOW THE RATE OF WEAKENING AS THE SYSTEM
BEGINS ETT.
MODEL DISCUSSION: TRACK GUIDANCE IS IN STRONG AGREEMENT, WITH
NAVGEM THE ONLY OUTLIER AMONGST THE CONSENSUS MEMBERS, DEPICTING A
TRACK FAR OUT TO THE EAST TOWARDS TONGA. THE REMAINDER OF THE
CONSENSUS MEMBERS ARE CONFINED TO A GRADUALLY EXPANDING ENVELOPE THAT
WIDENS TO 105NM BY TAU 72 AND 280NM BY TAU 120. THE LARGER ISSUE IS
ALONG-TRACK SPREAD, PARTICULARLY BETWEEN THE AI MODELS (EC-AIFS, GDM
AND THE AI CONSENSUS) AND THE REMAINDER OF THE GUIDANCE. AT TAU 72,
ALONG-TRACK SPREAD IS ABOUT 80NM, INCREASING TO 250NM BETWEEN THE
SLOW GFS AND FAST AI MODELS, BY TAU 120. THE JTWC FORECAST IS
POSITIONED CLOSE TO THE CONSENSUS MEAN (MINUS NAVGEM) THROUGH TAU 72,
THEN ALONG THE TRACK LINE OF THE MEAN, BUT SLIGHTLY FASTER, HEDGED
TOWARDS THE AI CONSENSUS. CONFIDENCE IS HIGH THROUGH THE ENTIRE
FORECAST PERIOD. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT. NEARLY
EVERY RI AID IS TRIGGERED, INDICATING A PEAK INTENSITY BETWEEN 105-
130 KNOTS. ALL MODEL GUIDANCE SHOWS THE PEAK OCCURRING NEAR TAU 36,
THEN A MORE OR LESS RAPID WEAKENING THROUGH THE REMAINDER OF THE
FORECAST PERIOD. THE JTWC FORECAST IS PLACED CONSISTENT WITH THE RI
AIDS THROUGH TAU 36, THEN CLOSE TO THE CONSENSUS MEAN THEREAFTER,
WITH MEDIUM CONFIDENCE.
FORECAST CONFIDENCE:
TRACK 00-72 HR: HIGH
TRACK 72-120 HR: HIGH
INTENSITY 00-72 HR: MEDIUM
INTENSITY 72-120 HR: MEDIUM//
NNNN
RIPA FORECAST
SATELLITE FIXES @05/1430 UTC
TPPS10 PGTW 051447
A. TROPICAL CYCLONE 30P (MAILA)
B. 05/1430Z
C. 9.36S
D. 154.55E
E. FIVE/GK2A
F. T4.5/4.5/D1.5/24HRS STT: S0.0/03HRS
G. IR/EIR
H. REMARKS: 46A/PBO EMBD CNTR/ANMTN. LLCC EMBEDDED IN CMG YIELDS A
DT OF 5.0. MET YIELDS 4.0. PT YIELDS 4.5. DBO PT.
I. ADDITIONAL POSITIONS: NONE
RUCKER
TPPS11 PGTW 051454
A. TROPICAL CYCLONE 31P (VAIANU)
B. 05/1430Z
C. 14.96S
D. 172.50E
E. FIVE/HMWRI9
F. T3.5/3.5/D1.5/24HRS STT: S0.0/03HRS
G. IR/EIR
H. REMARKS: 38A/PBO SBC/ANMTN. CNVCTN WRAPS 1.10 ON LOG10 SPIRAL
YIELDING A DT OF 4.0. MET YIELDS 3.0. PT YIELDS 3.5. DBO PT.
I. ADDITIONAL POSITIONS: NONE
RUCKER
TPXS10 PGTW 051441
A. TROPICAL CYCLONE 29S (INDUSA)
B. 05/1430Z
C. 30.12S
D. 71.88E
E. FIVE/MET9
F. T2.5/3.5/W1.5/24HRS STT: S0.0/03HRS
G. IR/EIR
H. REMARKS: 63A/PBO PRLY ORGNZD LLCC/ANMTN. LLCC LOCATED WITHIN
75NM OF COLD OVERCAST GREATER THAN 90NM ACROSS YIELDS A DT OF 2.0.
MET YIELDS 3.0. PT YIELDS 2.5. DBO PT.
I. ADDITIONAL POSITIONS: NONE
RUCKER
A. TROPICAL CYCLONE 30P (MAILA)
B. 05/1430Z
C. 9.36S
D. 154.55E
E. FIVE/GK2A
F. T4.5/4.5/D1.5/24HRS STT: S0.0/03HRS
G. IR/EIR
H. REMARKS: 46A/PBO EMBD CNTR/ANMTN. LLCC EMBEDDED IN CMG YIELDS A
DT OF 5.0. MET YIELDS 4.0. PT YIELDS 4.5. DBO PT.
I. ADDITIONAL POSITIONS: NONE
RUCKER
TPPS11 PGTW 051454
A. TROPICAL CYCLONE 31P (VAIANU)
B. 05/1430Z
C. 14.96S
D. 172.50E
E. FIVE/HMWRI9
F. T3.5/3.5/D1.5/24HRS STT: S0.0/03HRS
G. IR/EIR
H. REMARKS: 38A/PBO SBC/ANMTN. CNVCTN WRAPS 1.10 ON LOG10 SPIRAL
YIELDING A DT OF 4.0. MET YIELDS 3.0. PT YIELDS 3.5. DBO PT.
I. ADDITIONAL POSITIONS: NONE
RUCKER
TPXS10 PGTW 051441
A. TROPICAL CYCLONE 29S (INDUSA)
B. 05/1430Z
C. 30.12S
D. 71.88E
E. FIVE/MET9
F. T2.5/3.5/W1.5/24HRS STT: S0.0/03HRS
G. IR/EIR
H. REMARKS: 63A/PBO PRLY ORGNZD LLCC/ANMTN. LLCC LOCATED WITHIN
75NM OF COLD OVERCAST GREATER THAN 90NM ACROSS YIELDS A DT OF 2.0.
MET YIELDS 3.0. PT YIELDS 2.5. DBO PT.
I. ADDITIONAL POSITIONS: NONE
RUCKER
