Tropical Cyclone Yalo

[Nev]

Yesterday evening JTWC issued a TC Formation Alert for the developing Tropical Depression between Rarotonga in the Cook Islands and Tahiti in French Polynesia. RSMC Nadi in their first advisory earlier this morning also have a moderate to high risk of TC formation in the next 24 to 48 hours…

WTPS21 PGTW 240730
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
200 NM EITHER SIDE OF A LINE FROM 15.8S 157.6W TO 21.5S 150.5W
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS
IN THE AREA ARE ESTIMATED TO BE 25 TO 30 KNOTS. METSAT IMAGERY AT
240700Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 16.8S
156.5W. THE SYSTEM IS MOVING SOUTHEASTWARD AT 14 KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 16.0S
158.0W IS NOW LOCATED NEAR 16.8S 156.5W, APPROXIMATELY 275 NM WEST
OF BORA BORA. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS
A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER WITH IMPROVED
CONVECTIVE BANDING. A 240520Z SSMIS 37 GHZ IMAGE SHOWS CONVECTIVE
BANDING WRAPPING TIGHTLY INTO A WELL-DEFINED CENTER. UPPER-LEVEL
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND
SHEAR AND GOOD POLEWARD AND EQUATORWARD OUTFLOW. DYNAMIC MODEL
GUIDANCE INDICATES A STEADY SOUTHEASTWARD TRACK OVER THE NEXT TWO
DAYS WITH GRADUAL INTENSIFICATION DUE TO THE FAVORABLE CONDITIONS.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
250730Z.//
NNNN

TROPICAL DISTURBANCE ADVISORY NUMBER B1 ISSUED FROM RSMC NADI
Feb 241358 UTC.

TROPICAL DEPRESSION 11F CENTRE 1000HPA WAS LOCATED NEAR 17.2S 156.3W
AT 241200 UTC. POSITION POOR BASED ON HR GMS GOES EIR AND PERIPHERAL
SURFACE REPORTS. CYCLONE MOVING SOUTH-SOUTHEAST AT ABOUT 11 KNOTS.
MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT ABOUT 25
KNOTS.

DEEP CONVECTION HAS INCREASED AND ORGANISATION HAS IMPROVED SLIGHTLY
IN PAST 24 HOURS.SST AROUND 29 DEGREES CELCIUS. SYSTEM LIES UNDER AN
UPPER RIDGE IN A LOW SHEARED ENVIRONMENT. CYCLONE CIRCULATION EXTENDS
UP TO 500HPA. SYSTEM IS BEING STEERED TO THE SOUTHSOUTH-EAST BY THE
DEEP LAYER MEAN NORTH-NORTHWESTERLY WIND FLOW.
DVORAK ANALYSIS BASED ON 0.35 WRAP YEILDS DT=2.0. MET=2.0 AND
PT=1.5.FT BASED ON DT. THUS, YEILDING T2.0/2.0/D1.0/24HRS.

GLOBAL MODELS HAVE PICKED UP THE SYSTEM AND SLOWLY MOVE IT SOUTHEAST
WITH GRADUAL INTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 HOURS IS MODERATE TO HIGH.


FORECASTS :
AT 12 HRS VALID AT 250000 UTC 18.5S 155.7W MOV SSE AT 07KT WITH 25 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 251200 UTC 19.5S 154.8W MOV SE AT 07KT WITH 35 KT
CLOSE TO CENTRE

OUTLOOK :
AT 36 HRS VALID AT 260000 UTC 20.5S 153.2W MOV SE AT 35KT WITH 35 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 261200 UTC 21.6S 151.1W MOV SE AT 10KT WITH 35 KT
CLOSE TO CENTRE.

THE NEXT TROPICAL DISTURBANCE ADVISORY ON TROPICAL DEPRESSION 11F
WILL BE ISSUED AROUND 242000 UTC.

[Nev]

JTWC referring to the low between the Cook Islands and French Polynesia as a TC this afternoon, based on 1-minute mean-winds. Earlier today RSMC Nadi had a moderate to high risk in the next day or two...

WTPS32 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/240721Z FEB 16//
AMPN/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. TROPICAL CYCLONE 14P (FOURTEEN) WARNING NR 001
02 ACTIVE TROPICAL CYCLONES IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
250000Z --- NEAR 18.5S 155.9W
MOVEMENT PAST SIX HOURS - 165 DEGREES AT 04 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
...
REMARKS:
250300Z POSITION NEAR 18.7S 155.9W.
TROPICAL CYCLONE 14P (FOURTEEN), LOCATED APPROXIMATELY 273 NM
NORTHEAST OF RAROTONGA, HAS TRACKED SOUTH-SOUTHEASTWARD AT 04
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS CURVED DEEP CONVECTION BANDING INTO A VERY
COMPACT CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC). A 241940Z
AMSU-B 89 GHZ MICROWAVE IMAGE SHOWS A MODERATELY WELL-DEFINED CENTER
WITH DEEP CONVECTION LIMITED TO THE WESTERN SEMI-CIRCLE, SUPPORTING
THE INITIAL POSITION WITH MODERATE CONFIDENCE. THE INITIAL INTENSITY
IS ASSESSED AT 35 KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF T2.5
(35 KNOTS) FROM ALL REPORTING AGENCIES. ENVIRONMENTAL ANALYSIS
INDICATES THAT THE SYSTEM IS CURRENTLY IN A FAVORABLE ENVIRONMENT
WITH LIGHT (10-15 KNOTS) VERTICAL WIND SHEAR (VWS), GOOD POLEWARD
AND EQUATORWARD OUTFLOW AND HIGH SEA SURFACE TEMPERATURES (SSTS)
NEAR 29 CELSIUS. TC 14P IS FORECAST TO TRACK GENERALLY SOUTH-
SOUTHEASTWARD THROUGH THE ENTIRE FORECAST PERIOD, ALONG THE WESTERN
PERIPHERY OF A DEEP-LAYER, NORTH-SOUTH ORIENTED RIDGE TO THE EAST.
TC 14P IS FORECASTED TO INTENSIFY SLOWLY THROUGH TAU 24 AS IT
REMAINS IN A FAVORABLE ENVIRONMENT. BY TAU 36 VWS BEGINS TO INCREASE
AS TC 14P INTERACTS WITH A DEEP MID-LATITUDE TROUGH APPROACHING FROM
THE WEST. BY TAU 72, THE SYSTEM WILL DISSIPATE OVER WATER AS SHEAR
AND SST VALUES BECOME UNSUPPORTIVE OF SUSTAINING THE SYSTEM.
MAXIMUM SIGNIFICANT WAVE HEIGHT AT 250000Z IS 16 FEET. NEXT
WARNINGS AT 251500Z AND 260300Z. THIS CANCELS AND SUPERSEDES REF A
(WTPS21 PGTW 240730). REFER TO TROPICAL CYCLONE 11P (WINSTON)
WARNINGS (WTPS31 PGTW) FOR SIX-HOURLY UPDATES.//

TROPICAL DISTURBANCE ADVISORY NUMBER A3 ISSUED FROM RSMC NADI
Feb 250118 UTC.

TROPICAL DEPRESSION 11F CENTRE 998HPA WAS LOCATED NEAR 18.6S 155.8W
AT 250000 UTC. POSITION POOR BASED ON HR GMS GOES EIR AND PERIPHERAL
SURFACE REPORTS. DEPRESSION MOVING SOUTH-SOUTHEAST AT ABOUT 08
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 30 KNOTS.

DEEP CONVECTION HAS INCREASED AND ORGANISATION HAS IMPROVED SLIGHTLY
IN PAST 24 HOURS.SST AROUND 29 DEGREES CELCIUS. SYSTEM LIES UNDER AN
UPPER RIDGE IN A LOW SHEARED ENVIRONMENT. CYCLONE CIRCULATION EXTENDS
UP TO 500HPA. SYSTEM IS BEING STEERED TO THE SOUTHSOUTH-EAST BY THE
DEEP LAYER MEAN NORTH-NORTHWESTERLY WIND FLOW.
DVORAK ANALYSIS BASED ON 0.50 WRAP YEILDS DT=2.5. MET=2.0, AND
PT=2.5. FT BASED ON DT. THUS, YEILDING T2.5/2.5/D1.0/24HRS.

GLOBAL MODELS HAVE PICKED UP THE SYSTEM AND SLOWLY MOVE IT SOUTHEAST
WITH FURTHER INTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 HOURS IS MODERATE TO HIGH.

FORECASTS :
AT 12 HRS VALID AT 251200 UTC 19.7S 155.2W MOV SSE AT 06KT WITH 30 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 260000 UTC 20.6S 153.8W MOV SE AT 08KT WITH 35 KT
CLOSE TO CENTRE

OUTLOOK :
AT 36 HRS VALID AT 261200 UTC 21.5S 152.1W MOV ESE AT 09KT WITH 35 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 270000 UTC 22.3S 150.6W MOV ESE AT 08KT WITH 40 KT
CLOSE TO CENTRE.

[Nev]

TC Yalo was named by RSMC Nadi this evening…

TROPICAL DISTURBANCE ADVISORY NUMBER A4 ISSUED FROM RSMC NADI
Feb 250728 UTC.

TROPICAL CYCLONE YALO CENTRE 995HPA CATEGORY 1 WAS LOCATED NEAR 19.5S
155.4W AT 250600 UTC. POSITION POOR BASED ON HR GOES EIR IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING SOUTH-SOUTHEAST AT ABOUT
10 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED
AT ABOUT 35 KNOTS.
…
DEEP CONVECTION REMAINS PERSISTENT WITH CONVECTIVE BAND TRYING TO
WRAP AROUND LLCC. ORGANISATION HAS IMPROVED IN PAST 24 HOURS. SST
AROUND 28 TO 29 DEGREES CELCIUS. SYSTEM LIES JUST SOUTH OF AN UPPER
RIDGE IN A LOW SHEARED ENVIRONMENT. SYSTEM IS BEING STEERED TO THE
SOUTH-SOUTHEAST BY THE DEEP LAYER MEAN NORTH-NORTHWESTERLY WIND
FLOW.DVORAK ANALYSIS BASED ON 0.60 WRAP YEILDS DT=3.0, MET AND PT
AGREE. FT BASED ON DT. THUS, YEILDING T3.0/3.0/D1.5/24HRS.

FORECASTS :
AT 12 HRS VALID AT 251800 UTC 20.4S 154.6W MOV SE AT 06KT WITH 45 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 260600 UTC 21.1S 153.2W MOV ESE AT 07KT WITH 45 KT
CLOSE TO CENTRE

OUTLOOK :
AT 36 HRS VALID AT 261800 UTC 22.0S 151.6W MOV SES AT 09KT WITH 40 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 270600 UTC 22.9S 150.3W MOV SE AT 08KT WITH 35 KT
CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON YALO WILL BE ISSUED AROUND
251400 UTC.

[Nev]

Probably not the most significant TC this season, but I don't think one has formed this far east since 1998, although 24-hr Mike came close in 2014.

Some good flaring overnight, but main convection looks a little sheared to the SE. Yalo's environmental conditions look to be very marginal for further development. Interesting to see that JTWC have her heading off to the SE into NZ's AOR, while Nadi have been consistent with a turn to the west at about 23S this weekend…

TROPICAL DISTURBANCE ADVISORY NUMBER A6 ISSUED FROM RSMC NADI
Feb 251957 UTC.

TROPICAL CYCLONE YALO CENTRE 993HPA WAS LOCATED NEAR 20.8S 153.7W AT
251800 UTC. POSITION POOR BASED ON HR GOES EIR IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING SOUTHEAST AT ABOUT 08
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 40 KNOTS.
…
DEEP CONVECTION REMAINS PERSISTENT WITH CONVECTIVE BAND TRYING TO
WRAP AROUND SUPPOSED LLCC. ORGANISATION HAS IMPROVED IN PAST 24
HOURS. SST AROUND 27 TO 28 DEGREES CELCIUS. SYSTEM LIES IN A MODERATE
TO STRONG UPPER DIVERGENCE REGION AND IN A MODERATE TO HIGH SHEARED
ENVIRONMENT. SYSTEM IS BEING STEERED TO THE SOUTHEAST BY THE DEEP
LAYER MEAN NORTHWESTERLY WIND FLOW.DVORAK ANALYSIS BASED ON 0.70 WRAP
YEILDS DT=3.0, MET AND PT AGREE. FT BASED ON DT. THUS, YEILDING
T3.0/3.0/D1.0/24HRS

FORECASTS :
AT 12 HRS VALID AT 260600 UTC 21.8S 152.9W MOV SE AT 06KT WITH 40 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 261800 UTC 22.4S 152.3W MOV SE AT 04KT WITH 45 KT
CLOSE TO CENTRE

OUTLOOK :
AT 36 HRS VALID AT 270600 UTC 22.7S 152.2W MOV SSE AT 02KT WITH 45 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 271800 UTC 22.7S 152.6W MOV W AT 02KT WITH 45 KT
CLOSE TO CENTRE

WTPS32 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL CYCLONE 14P (YALO) WARNING NR 002
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
251200Z --- NEAR 19.9S 154.9W
MOVEMENT PAST SIX HOURS - 130 DEGREES AT 08 KTS
POSITION ACCURATE TO WITHIN 040 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
…
REMARKS:
251500Z POSITION NEAR 20.2S 154.6W.
TROPICAL CYCLONE 14P (YALO), LOCATED APPROXIMATELY 334 NM WEST-
SOUTHWEST OF PAPEETE, TAHITI, HAS TRACKED SOUTHEASTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS SHALLOW CONVECTIVE BANDING WRAPPING INTO A
CIRCULATION CENTER THAT HAS BECOME INCREASINGLY SYMMETRIC OVER THE
LAST SIX HOURS. SUBSTANTIAL CENTRAL CONVECTION IS ALSO BEGINNING TO
BE OBSERVED WITH ASSOCIATED BROAD OVERCAST OBSCURING THE LOW LEVEL
CIRCULATION CENTER, GIVING LOW CONFIDENCE TO THE INITIAL POSITION.
THE INITIAL INTENSITY IS ASSESSED AT 50 KNOTS AND IS BASED ON
MULTIPLE FIXING AGENCIES REPORTING DVORAK ESTIMATES BETWEEN T3.0 AND
T3.5 (45 AND 55 KNOTS RESPECTIVELY). TC YALO IS CURRENTLY TRACKING
SOUTHWARD AS IT RIDES ALONG THE WESTERN BOUNDARY OF A SUBTROPICAL
RIDGE POSITIONED TO THE EAST. CONDITIONS CURRENTLY SUPPORT A SHORT-
TERM INTENSIFICATION TO 55 KNOTS BY TAU 12 AS SEA SURFACE
TEMPERATURES ARE WARM (27 CELSIUS) AND MODERATE (20 TO 25 KNOTS)
VERTICAL WIND SHEAR (VWS) IS PRESENT WITH A STRONG POLEWARD OUTFLOW
CHANNEL. HOWEVER, BY TAU 24 TO 36 TC YALO WILL RAPIDLY WEAKEN AS ITS
SOUTHWARD TRACK MOVES IT OVER COOLER WATERS AND A LONGWAVE TROUGH
MOVES IN FROM THE WEST SUBSTANTIALLY INCREASING VWS. TC YALO IS
FORECAST TO DISSIPATE BY TAU 48. MAXIMUM SIGNIFICANT WAVE HEIGHT AT
251200Z IS 18 FEET. NEXT WARNINGS AT 260300Z AND 261500Z.//

[Nev]

RSMC Nadi have corrected that earlier turn to the west this morning. Not looking too good for Yalo today, although Nadi appear to be slightly more optimistic than JTWC. Convection appears to be weakening and has become more displaced from her LLCC due to strong NW shear…

TROPICAL DISTURBANCE ADVISORY NUMBER A7 ISSUED FROM RSMC NADI
Feb 260115 UTC.

TROPICAL CYCLONE YALO CENTRE 993HPA WAS LOCATED NEAR 21.9S 152.8W AT
260000 UTC. POSITION POOR BASED ON HR GOES EIR IMAGERY AND
PERIPHERAL SURFACE REPORTS. CYCLONE MOVING SOUTHEAST AT ABOUT 11
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 40 KNOTS.
…
DEEP CONVECTION REMAINS PERSISTENT WITH CONVECTIVE BAND TRYING TO
WRAP AROUND SUPPOSED LLCC. ORGANISATION HAS IMPROVED IN PAST 24
HOURS. SST AROUND 27 TO 28 DEGREES CELCIUS. SYSTEM LIES IN A MODERATE
TO STRONG UPPER DIVERGENCE REGION AND IN A MODERATE TO HIGH SHEARED
ENVIRONMENT. SYSTEM IS BEING STEERED TO THE SOUTHEAST BY THE DEEP
LAYER MEAN NORTHWESTERLY WIND FLOW.DVORAK ANALYSIS BASED ON 0.60 WRAP
YEILDS DT=3.0, MET AND PT AGREE. FT BASED ON DT. THUS, YEILDING
T3.0/3.0/D1.0/24HRS.

FORECASTS :
AT 12 HRS VALID AT 261200 UTC 23.5S 151.2W MOV SE AT 11KT WITH 40 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 270000 UTC 24.8S 149.8W MOV SE AT 09KT WITH 35 KT
CLOSE TO CENTRE

OUTLOOK :
AT 36 HRS VALID AT 271200 UTC 25.7S 149.1W MOV SE AT 06KT WITH 45 KT
CLOSE TO CENTRE
AT 48 HRS VALID AT 280000 UTC 26.2S 149.0W MOV S AT 02KT WITH 45 KT
CLOSE TO CENTRE

WTPS32 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL CYCLONE 14P (YALO) WARNING NR 003
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
260000Z --- NEAR 21.7S 153.3W
MOVEMENT PAST SIX HOURS - 145 DEGREES AT 10 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
…
REMARKS:
260300Z POSITION NEAR 22.0S 153.0W.
TROPICAL CYCLONE 14P (YALO), LOCATED APPROXIMATELY 327 NM
SOUTHWEST OF PAPEETE, TAHITI, HAS TRACKED SOUTHEASTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS SHALLOW CONVECTIVE BANDING WRAPPING INTO A
CIRCULATION CENTER THAT HAS BECOME INCREASINGLY ASYMMETRIC OVER THE
LAST SIX HOURS. CORE CONVECTION HAS BEEN WANING WITH NOTICEABLE
WARMING OF THE CONVECTIVE CLOUD TOPS, WHICH ARE OBSCURING THE LOW-
LEVEL CIRCULATION CENTER (LLCC). AS A RESULT, THERE IS LOW
CONFIDENCE IN THE INITIAL POSITION. THE CURRENT INTENSITY IS
ASSESSED AT 40 KNOTS, BASED ON DVORAK INTENSITY ESTIMATES OF T2.5
AND T3.0 (35 AND 45 KNOTS, RESPECTIVELY) FROM MULTIPLE FIXING
AGENCIES. TC YALO HAS WEAKENED SUBSTANTIALLY SINCE THE PREVIOUS
WARNING, WITH MODERATE TO HIGH (30-35 KNOTS) VERTICAL WIND SHEAR
(VWS) BEGINNING TO DECOUPLE THE SYSTEM. THERE ARE INITIAL
INDICATIONS THAT THE LOW LEVEL CIRCULATION CENTER IS STARTING TO
BECOME EXPOSED DUE TO THIS NORTHWESTERLY SHEAR. TC YALO IS FORECAST
TO TRACK SOUTHEASTWARD THROUGH THE FORECAST PERIOD AS IT RIDES ALONG
THE WESTERN BOUNDARY OF A SUBTROPICAL RIDGE POSITIONED TO THE EAST.
ENVIRONMENTAL CONDITIONS WILL RAPIDLY DETERIORATE OVER THE NEXT 12
TO 24 HOURS AS TC YALO MOVES OVER INCREASINGLY COOLER SSTS AND INTO
AN AREA OF VERY HIGH (50 TO 60 KNOTS) VWS ASSOCIATED WITH AN
APPROACHING UPPER-LEVEL LONGWAVE TROUGH. THESE EFFECTS WILL LEAD TO
DISSIPATION OF THE SYSTEM BY TAU 24. MAXIMUM SIGNIFICANT WAVE HEIGHT
AT 260000Z IS 18 FEET. NEXT WARNINGS AT 261500Z.//

[Nev]

Just for the record, RSMC Nadi downgraded Yalo to an Ex-TC around midnight last night…

TROPICAL DISTURBANCE ADVISORY NUMBER A9 ISSUED FROM RSMC NADI
Feb 261304 UTC.

EX-TROPICAL CYCLONE YALO TD11F CENTRE 998HPA WAS LOCATED NEAR 23.3S
150.8W AT 261200 UTC. POSITION FAIR BASED ON HR GOES EIR IMAGERY AND
PERIPHERAL SURFACE REPORTS. DEPRESSION MOVING SOUTHEAST AT ABOUT 13
KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT
ABOUT 30 KNOTS.

LLCC EXPOSED. DEEP CONVECTION HAS DECREASED AND IS DISPLACED TO THE
SOUTHEAST OF LLCC. SST AROUND 25 TO 26 DEGREES CELCIUS. SYSTEM LIES
IN A HIGH SHEARED ENVIRONMENT. SYSTEM IS BEING STEERED TO THE
SOUTHEAST BY THE DEEP LAYER MEAN NORTHWESTERLY WIND FLOW.DVORAK
ANALYSIS BASED ON SHEAR PATTERN WITH LLCC LESS THEN
1 1/4 DEGREES FROM STRONG TEMPERATURE GRADIENT YEILDS DT=2.0, MET AND
PT AGREE. FT BASED ON DT THUS, YEILDING T2.0/2.5/W1.0/24HRS.

FORECASTS :
AT 12 HRS VALID AT 270000 UTC 24.5S 149.8W MOV SE AT 08KT WITH 30 KT
CLOSE TO CENTRE
AT 24 HRS VALID AT 271200 UTC 25.1S 149.6W MOV SSE AT 03KT WITH 25 KT
CLOSE TO CENTRE.

THIS WILL BE THE FINAL TROPICAL DISTURBANCE ADVISORY ON EX-TC YALO
TD11F.

WTPS32 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL CYCLONE 14P (YALO) WARNING NR 004
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
261200Z --- NEAR 23.4S 150.7W
MOVEMENT PAST SIX HOURS - 135 DEGREES AT 12 KTS
POSITION ACCURATE TO WITHIN 040 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
...
REMARKS:
261500Z POSITION NEAR 23.7S 150.4W.
TROPICAL CYCLONE 14P (YALO), LOCATED APPROXIMATELY 359 NM SOUTH
OF PAPEETE, TAHITI, HAS TRACKED SOUTHEASTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS THE PRESENCE OF INCREASING VERTICAL WIND SHEAR (VWS) OVER
THE LAST SIX HOURS AS THE BULK OF CONVECTION IS NOW DECOUPLED FROM
THE SYSTEM REVEALING A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER
(LLCC). THE CURRENT INTENSITY IS ASSESSED AT 35 KNOTS BASED ON
DVORAK ESTIMATES FROM PGTW AND PHFO REPORTING CURRENT INTENSITIES OF
T2.5 (35 KNOTS). CURRENTLY TC YALO IS EXPERIENCING SIGNIFICANT (35
TO 40 KNOTS) VWS DUE TO AN APPROACHING LONGWAVE TROUGH FROM THE
WEST, AND SEA SURFACE TEMPERATURES (SST) ARE COOL (25 CELSIUS)
CONTRIBUTING TO THE RAPID WEAKENING. DUE TO THE DETERIORATING
ENVIRONMENT TC YALO WILL NO LONGER BE AT TROPICAL STORM STRENGTH BY
TAU 12. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT
TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED
FOR SIGNS OF REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 261200Z
IS 15 FEET.