SWIO: Remnants of TC 21S (Hellen)

[dexterlabio]

Hellen is equivalent to a violent typhoon in WPAC as per JMA (115kts 10-min sustained wind). Good call from GFS showing a rapidly intensifying cyclone off Madagascar.

[euro6208]

REMARKS:
301500Z POSITION NEAR 14.9S 44.7E.
TROPICAL CYCLONE (TC) 21S (HELLEN), LOCATED APPROXIMATELY 290 NM
NORTH-NORTHWEST OF ANTANANARIVO, MADAGASCAR, HAS TRACKED
SOUTHEASTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. TC 21S HAS
RAPIDLY INTENSIFIED 80 KNOTS OVER THE PAST 24 HOURS, FROM 50 KNOTS
TO THE CURRENT INTENSITY OF 130 KNOTS, WHICH IS BASED ON DVORAK
INTENSITY ESTIMATES OF T6.5 (127 KNOTS) FROM ALL AGENCIES. ANIMATED
INFRARED SATELLITE IMAGERY DEPICTS AN 11-NM ROUND EYE SURROUNDED BY
A NEAR-SYMMETRIC, 130 NM DIAMETER EYEWALL. THE RAPID INTENSIFICATION
PHASE HAS BEEN FUELED BY EXCELLENT RADIAL OUTFLOW, EVIDENT IN
ANIMATED WATER VAPOR IMAGERY, AND FAVORABLE ENVIRONMENTAL
CONDITIONS. DESPITE WEAKENING OF OUTER CONVECTIVE BANDING DUE TO
LAND INTERACTION, A 301146Z SSMI IMAGE INDICATES THAT THE SYSTEM HAS
MAINTAINED AN INTENSE CORE OF CENTRAL CONVECTION. TC 21S IS TRACKING
SLOWLY SOUTHEASTWARD BUT IS FORECAST TO TURN SOUTHWARD BY TAU 24 AS
IT TRACKS ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE
(STR). AFTER TAU 24, TC HELLEN WILL TURN WESTWARD AS THE STR BUILDS
TO THE SOUTH AND IS FORECAST TO MAKE LANDFALL OVER MOZAMBIQUE BY TAU
120. DYNAMIC GUIDANCE IS IN FAIR AGREEMENT WITH THE EXCEPTION OF
NAVGEM, WHICH ERRONEOUSLY DRIVES THE SYSTEM SOUTH-SOUTHWESTWARD INTO
THE STR. DESPITE THE GENERAL AGREEMENT ON THE FORECAST TRACK,
FORECAST CONFIDENCE REMAINS LOW DUE TO TIMING AND DEGREE OF THE
WESTWARD TURN WITH LAND INTERACTION FURTHER COMPLICATING THE SHORT-
TERM TRACK. TC 21S IS FORECAST TO CONTINUE INTENSIFYING TO A PEAK
INTENSITY OF 140 KNOTS BY TAU 12 (IN FACT, 1230Z IMAGERY SUPPORTS A
T7.0 WHICH EQUATES TO 140 KNOTS). NEAR TAU 12, THE SYSTEM CORE IS
EXPECTED TO BEGIN INTERACTING WITH LAND, WHICH SHOULD RESULT IN A
SHARP WEAKENING TREND THROUGH TAU 48. FURTHER WEAKENING IS EXPECTED
AS THE SYSTEM APPROACHES THE MOZAMBIQUE COAST AND ENCOUNTERS DRY AIR
ENTRAINMENT. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 301200Z IS 35 FEET.
NEXT WARNINGS AT 310300Z AND 311500Z.//
NNNN

2114032600 107S 384E 20
2114032606 107S 390E 25
2114032612 107S 394E 25
2114032618 107S 400E 25
2114032700 109S 405E 25
2114032706 115S 409E 25
2114032712 122S 408E 30
2114032718 124S 408E 30
2114032800 125S 410E 30
2114032806 122S 414E 30
2114032812 126S 419E 30
2114032818 128S 424E 35
2114032900 128S 426E 40
2114032906 130S 428E 45
2114032912 132S 432E 50
2114032918 135S 435E 65
2114032918 135S 435E 65
2114033000 141S 439E 95
2114033000 141S 439E 95
2114033000 141S 439E 95
2114033006 144S 443E 115
2114033006 144S 443E 115
2114033006 144S 443E 115
2114033012 147S 446E 130
2114033012 147S 446E 130
2114033012 147S 446E 130

splendid intensification...bad news for madagascar...

[supercane4867]

Apparently Hellen has become the strongest storm ever observed in Mozambique Channel

21S HELLEN 140330 1800 15.1S 45.0E SHEM 135 922

[Grifforzer]

125 knots (10 mins)

** WTIO30 FMEE 301845 ***
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)
0.A WARNING NUMBER: 12/14/20132014
1.A VERY INTENSE TROPICAL CYCLONE 14 (HELLEN)
2.A POSITION 2014/03/30 AT 1800 UTC:
WITHIN 10 NM RADIUS OF POINT 15.0 S / 45.0 E
(FIFTEEN DECIMAL ZERO DEGREES SOUTH AND FORTY FIVE DECIMAL
ZERO DEGREES EAST)
MOVEMENT : SOUTH-SOUTH-EAST 3 KT
3.A DVORAK ANALYSIS: 6.5/7.0/D 2.5/24 H
4.A CENTRAL PRESSURE: 925 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 125 KT
RADIUS OF MAXIMUM WINDS (RMW) :15 KM
6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 110 SE: 180 SW: 180 NW: 130
34 KT NE: 70 SE: 90 SW: 100 NW: 90
48 KT NE: 60 SE: 60 SW: 70 NW: 60
64 KT NE: 50 SE: 50 SW: 50 NW: 50
7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1008 HPA / 400 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION : DEEP
1.B FORECASTS:
12H: 2014/03/31 06 UTC: 15.7 S / 45.2 E, MAX WIND=110 KT, INTENSE
TROPICAL CYCLONE
24H: 2014/03/31 18 UTC: 16.3 S / 44.8 E, MAX WIND=090 KT, INTENSE
TROPICAL CYCLONE
36H: 2014/04/01 06 UTC: 16.7 S / 44.2 E, MAX WIND=070 KT, TROPICAL
CYCLONE
48H: 2014/04/01 18 UTC: 17.1 S / 43.3 E, MAX WIND=080 KT, TROPICAL
CYCLONE
60H: 2014/04/02 06 UTC: 17.3 S / 42.7 E, MAX WIND=090 KT, INTENSE
TROPICAL CYCLONE
72H: 2014/04/02 18 UTC: 17.7 S / 41.4 E, MAX WIND=100 KT, INTENSE
TROPICAL CYCLONE
2.B LONGER-RANGE OUTLOOK :
96H: 2014/04/03 18 UTC: 18.0 S / 38.7 E, MAX WIND=090 KT, INTENSE
TROPICAL CYCLONE
120H: 2014/04/04 18 UTC: 18.0 S / 35.9 E, MAX WIND=050 KT, INLAND
2.C ADDITIONAL INFORMATIONS:
T=6.5+ AND CI=7.0

AFTER PRESENTING FROM 1100Z TO 1500Z A DT=7.0 ON METEOSAT7 ENHANCED INFRARED IMAGERY, HELLEN EYE IS COOLING FROM +19 DG AT 1300Z TO -36 FG AT 1800Z. 1710Z AND 1533Z SSMIS MICROWAVE IMAGERY STILL NOT SUGGEST ANY EYEWALL CYCLE REPLACEMENT.

HELLEN IS LIKELY TO BE ONE OF THE MOST POWERFULL TROPICAL CYCLONE EVER SEEN OVER THE NORTHERN CHANNEL SINCE THE SATELLITE ERA (1967).

GIVEN THE PAST TRACK OVER THE LAST 6 HOURS MORE SOUTH-EASTERN THAN PREVIOUSLY EXPECTED, THE LIKELIHOOD IS INCREASING FOR AN EXTREMELY DANGEROUS TROPICAL CYCLONE LANDFALL OVER THE NORTHWESTERN COASTLINE OF MADAGASCAR BETWEEN CAPE SAINT-ANDRE AND MAHAJONGA. GIVEN THIS POSSIBILITY, THE RSMC TROPICAL CYCLONE STORM SURGE NWP HAS BEEN RUN THAT SHOWS PHENOMENAL SEA ELEVATIONS IN THE AREA EXPOSED TO THE NORTHERLY WINDS (EAST OF THE FORECAST TRACK).

THIS POTENTIALLY STRENGTHEN AREA IS VERY SENSITIVE BECAUSE ITS BATHYMETRY (PLATEAU)AND STORM SURGE COULD REACH BETWEEN 2M AND 4M IN THE ESTUARY OF THE BETSIBOKA RIVER (MAHAJONGA), MORE THAN 7M IN THE BAY OF BALY (SOALALA) AND BETWEEN 1M AND 4M ON THE COASTLINE EAST OF CAPE SAINT-ANDRE. ALL PREPARATIONS FOR A "WORST CASE" SCENARIO SHOULD BE UNDERWAY THE SYSTEM IS LYING UNDER AN UPPER LEVEL RIDGE AXIS ALOFT. VERTICAL WINDSHEAR IS WEAK TO MODERATE (6.4 M/S ACCORDING TO CIMSS AT 1800Z) AND UPPER LEVEL DIVERGENCE IS GOOD MAINLY POLEWARD IN RELATIONSHIP WITH A WESTERLY SUBTROPICAL JET EXISTING SOUTH OF 18S.UNDER THE STEERING INFLUENCE OF THE MID-LEVELS RIDGE LOCATED NORTHWARD, HELLEN WILL KEEP ON TRACKING SLOWLY SOUTH-EASTWARDS DURING THE NEXT 6 TO 12 HOURS BEFORE BEING WITHIN A TOO SLOW STEERING ENVIRONMENT THAT SHOULD LEAD TO A QUASI-STAT MOTION. A WEAKENING TREND INITIATED BY INDUCED COLD SST MAY TAKEN PLACE BY THAT TIME. ON THE HAND SOME NWP MODELS SUGGEST A TEMPORARILY RISING OF THE VWS TONIGHT. THE INTENSITY FORECAST REMAINS UNCERTAIN ACCORDING TO THE SMALL SIZE OF THE SYSTEM AND ITS SENSIBILITY TO THE VARIATION OF THE ENVIRONMENTAL CONDITIONS. ON AND AFTER MONDAY, THE MID-TROPOSPHERIC NEAR-EQUATORIAL RIDGE IS EXPECTED TO WEAKEN. HELLEN IS THEREFORE EXPECTED TO SLOW DOWN CLEARLY.

BEFORE RE-CURVING WESTWARDS THEN SOUTH-WESTWARDS UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE REBUILDING SOUTHWARD. IF AN OVERLAND TRACK OVER THE NORTHWESTERN MADAGASCAR OCCURS, IT SHOULD WEAKEN THE SYSTEM BUT IT IS EXPECTED TO BE BACK OVERSEA AT A SIGNIFICATIVE INTENSITY.

HELLEN SHOULD KEEP ON TRACKING ON THIS WEST-SOUTH-WEST PATH UP TO A NEW LANDFALL WEDNESDAY NIGHT OR THURSDAY ON THE MOZAMBICAN COASTLINES IN THE AREA OF QUELIMANE. GIVEN THE FAVOURABLE WINDS PATTERN SEEN ON NWP MODELS AT THIS LEAD TIME, THE INTENSITY FORECAST IS AGAIN SIGNIFICANTLY UPGRADED.

GIVEN THE VICINITY OF THE COMOROS ARCHIPELAGO AND MAYOTTE, THE INHABITANTS OF THIS ISLANDS SHOULD STILL CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM.=

[galaxy401]

Wow this is sudden. I think I remember a couple storms in the Mozambique Channel that rapidly intensified too.

[stormkite]

http://rammb.cira.colostate.edu/ramsdis ... display=12

[HurricaneBill]

It seems like years ending in "4" tend to bring destructive cyclones to Madagascar.

1984: Cyclone Kamisy


1994: Cyclone Geralda


2004: Cyclone Gafilo

[wxman57]

Hellen is weakening very fast now. Center is nearly on the coast. I'm estimating winds may be in the Cat 1/2 range now and falling fast.

[euro6208]

AN AREA OF CONVECTION (REMNANTS OF TC 21S) HAS PERSISTED
NEAR 16.1S 44.5E, APPROXIMATELY 225 NM NORTHWEST OF ANTANANARIVO,
MADAGASCAR. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A FULLY-
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) THAT HAD PREVIOUSLY
MOVED BACK OUT OVER THE WATERS OF THE MOZAMBIQUE CHANNEL, BUT HAS
RECENTLY MOVED CLOSER TO LAND AND IS CURRENTLY SKIRTING ALONG THE
NORTHWEST COAST OF MADAGASCAR. UPPER-LEVEL ANALYSIS INDICATES THE
SYSTEM REMAINS IN A FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND
SHEAR AND GOOD OUTFLOW. DYNAMIC MODELS VARY IN SOLUTIONS OF
DEVELOPMENT, BUT GENERALLY AGREE THAT THE LLCC WILL EVENTUALLY BEGIN
TRACKING WEST ACROSS THE MOZAMBIQUE CHANNEL TO THE EAST COAST OF
AFRICA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25
KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1002 MB.
THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS REMAINS LOW.