Tropical Cyclone Ian - Tonga

[jamie]

Has been a very quiet start to the season. Sorry if there is already a topic for this.

Ian has formed just north of Tonga http://www.stuff.co.nz/world/south-paci ... ward-Tonga

[Nev]

Thanks Jamie. That's a shocking piece of journalism though...

From the link above…

The 2013-14 South Pacific cyclone season has been slow to get started and it is the first time there have been no cyclones between July and December.

What? In the last 13 years alone, 5 have had no TC's between May and December.

In the 2012-13 season there were 24 cyclones, including Evan which killed 14 people in Samoa.

Huh? There were only 8 named TC's last season in the South Pacific and Coral Sea region combined.

There have been an average of 27 cyclones a year between 1981 and 2012.

According to RSMC Nadi and TCWC Brisbane, there are on average 7.4 TC's per year in the South Pacific and about 4 in the Coral Sea (although some TC's may count for both regions).

[Nev]

Anyways, doesn't look like this little puppy is going anywhere fast…

RSMC Nadi initially had TC Ian peaking at Cat 3, but promptly revised that yesterday...

TROPICAL DISTURBANCE ADVISORY NUMBER A6 ISSUED FROM RSMC NADI
Jan 06/1348 UTC 2014 UTC.

TROPICAL CYCLONE IAN 07F CENTRE 995HPA WAS LOCATED NEAR 18.9S 175.9W
AT 061200 UTC. POSITION POOR BASED ON MTSAT/GOES IR IMAGERY WITH
ANIMATION AND PERIPHERAL SURFACE REPORTS. CYCLONE SLOW MOVING.
MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT ABOUT 35
KNOTS, INCREASING TO 45 KNOTS BY 071200UTC.

…

ORGANISATION HAS SLIGHTLY IMPROVED AND CONVECTION REMAINS PERSISTENT
PAST 24 HOURS. SYSTEM LIES IN A LOW SHEARED ENVIRONMENT UNDER AN
UPPER RIDGE. OUTFLOW FAIR TO THE NORTH BUT RESTRICTED ELSEWHERE. SST
AROUND 29 DEGREES CELCIUS. THE SYSTEM IS SLOW MOVING AS IT IS LOCATED
WITHIN A WEAK STEERING ENVIRONMENT BETWEEN A LOW LEVEL NEAR
EQUATORIAL RIDGE LOCATED TO THE NORTH AND A LOW LEVEL SUBTROPICAL
RIDGE LOCATED TO THE SOUTH. DVORAK ANALYSIS BASED ON 0.45 WRAP
YIELDING DT OF 2.5. PT=3.0 AND MET=3.0. FT BASED ON MET THUS,
T3.0/3.0/D0.5/24HRS.

MOST MODELS AGREE ON A NORTHWESTWARDS MOVEMENT THEN RECURVING
SOUTHEAST WITH
GRADUAL INTENSIFICATION.

[jamie]

I thought this numbers were high. I couldn't work out what they ment cause I always thought it was around the 10 mark.

[Nev]

Compact TC Ian appears to continue to exceed forcasters expectations. On Wednesday it was upgraded to Cat 2, yesterday Cat 3 and last night Cat 4 …

WTPS31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 07P (IAN) WARNING NR 008//
…
REMARKS:
090900Z POSITION NEAR 16.9S 176.4W.
TROPICAL CYCLONE 07P (IAN), LOCATED APPROXIMATELY 302 NM EAST-
NORTHEAST OF SUVA, FIJI, HAS TRACKED EAST-SOUTHEASTWARD AT 02 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS THAT OVER THE PAST 12 HOURS THE SYSTEM HAS UNDERGONE A PERIOD
OF RAPID INTENSIFICATION. ALTHOUGH TC 07P REMAINS A COMPACT SYSTEM,
THE LOW LEVEL CIRCULATION CENTER (LLCC) AND SUPPORTING UPPER LEVEL
ENVIRONMENT HAS ALLOWED FOR THE DEVELOPMENT OF A WELL-DEFINED EYE
FEATURE. A RECENT 090552Z SSMIS MICROWAVE PASS INDICATES A PINHOLE
EYE REMAINS AND HAS BEEN USED IN THE PLACEMENT OF THE SYSTEM. OVER
THE PAST FEW HOURS THE TRACK HAS STARTED TO MOVE EASTWARD AND
APPEARS TO BE BECOMING MORE ENGAGED BY THE NEAR EQUATORIAL RIDGE
(NER) AS A MID-LATITUDE TROUGH CONTINUES TO TRACK OVER NEW ZEALAND,
WEAKENING THE SUB-TROPICAL RIDGE (STR) TO THE SOUTH OF TC 07P. MODEL
GUIDANCE INDICATES THE TROUGH WILL CONTINUE TO SHIFT THE STR,
EVENTUALLY MERGING WITH THE NER CAUSING AN INCREASE IN TRACK SPEED
FOR TC 07P AROUND TAU 36 TO 48. IN THE LATER TAUS, INTERACTION WITH
THE MID-LATITUDE WESTERLIES WILL LEAD TO A WEAKENING TREND BY TAU
72. TC 07P IS FORECAST TO BEGIN EXTRA-TROPICAL TRANSITION BY TAU 96.
AS THE CURRENT POSITIONING ALIGNS WITH THE PREVIOUS FORECAST, THERE
HAS BEEN A SLIGHT INCREASE IN THE CONFIDENCE FOR THE FORECAST TRACK,
BUT OVERALL CONFIDENCE REMAINS LOW DUE TO THE RECENT NATURE OF THE
TRACK CHANGES. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 090600Z IS 20
FEET. NEXT WARNINGS AT 092100Z AND 100900Z.//
NNNN

[Nev]

RSMC Nadi upgraded Severe TC Ian to Cat 5 last night, with winds near the centre of 200 km/h, gusting to 290 km/h and a central pressure of 930 hPa. It's expected to make landfall at Vava'u in the northern islands of Tonga in the next few hours…

TROPICAL DISTURBANCE ADVISORY NUMBER A21 ISSUED FROM RSMC NADI
Jan 10/1348 UTC 2014 UTC.

SEVERE TROPICAL CYCLONE IAN 07F CENTRE 930HPA CAT 5 WAS LOCATED NEAR
18.2S 174.9W AT 101200 UTC. POSITION GOOD BASED ON HR MTSAT EIR
IMAGERY AND PERIPHERAL SURFACE REPORTS. CYCLONE MOVING
SOUTH-SOUTHEAST AT ABOUT 04 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS
NEAR THE CENTRE ESTIMATED AT ABOUT 110 KNOTS.

EXPECT WINDS ABOVE 63 KNOTS WITHIN 20 NAUTICAL MILES OF CENTRE,
ABOVE 47 KNOTS WITHIN 40 NAUTICAL MILES OF CENTRE AND
ABOVE 33 KNOTS WITHIN 80 NAUTICAL MILES OF CENTRE.

DEEP CONVECTION REMAINS PERSISTANT PAST 12 HOURS. EYE DISCERNIBLE AND
WARMING. CLOUD TOPS COOLING RAPIDLY PAST 6 HOURS. IAN LIES IN A LOW
SHEARED ENVIRONMENT JUST SOUTH OF AN UPPER RIDGE. OUTFLOW FAIR TO
SOUTH AND EAST BUT RESTRICTED ELSEWHERE. SST AROUND 28 DEGREES
CELCIUS. SYSTEM IS MOVING SOUTHEASTWARDS ON THE SOUTHERN PERIPHERY OF
THE NEAR EQUATORIAL RIDGE TO THE NORTHWEST OF THE SYSTEM. DVORAK
ANALYSIS BASED ON EYE PATTERN WITH OW EYE SURROUNDED BY W EMBEDDED IN
CMG YIELDS DT OF 6.5, MET=6.0 AND PT=6.5. FT BASED ON DT THUS,
T6.5/6.5/D2.0/24HRS.

GLOBAL MODELS AGREE ON A SOUTHEASTWARD MOVEMENT WITH GRADUAL
WEAKENING AFTER 24 HOURS.
...

[Nev]

Visable sat-pic of Ian passing over Late Island, west of Va'vau on a SE track about an hour ago…

[jamie]

Wow the models have not done well with this storm. Was initially supposed to be no more than like a Cat 2 and dive south quite quickly.

Impressive storm!

[Manukau heads obs]

not good for Tonga...some saying worst TC for 50 years?

[Willoughby]

Amazing storm!!

[Willoughby]

Special Weather Bulletin Number TWENTY SIX for Tonga ON SEVERE
TROPICAL CYCLONE IAN ISSUED FROM RSMC NADI
Jan 10/2242 UTC 2014 UTC.
TROPICAL CYCLONE WARNING.

A HURRICANE WARNING REMAINS IN FORCE FOR THE VA'VAU GROUP AND HA'APAI
GROUP.
A GALE WARNING REMAINS IN FORCE FOR THE TONGATAPU GROUP.
A STRONG WIND WARNING REMAINS IN FORCE FOR THE REST OF TONGA.

SEVERE TROPICAL CYCLONE IAN CENTRE [938HPA] CAT 4 WAS LOCATED NEAR 19
DECIMAL 2 SOUTH 174 DECIMAL 6 WEST OR ABOUT 45 NAUTICAL MILES
SOUTHWEST OF VA'VAU AND 40 NAUTICAL MILES NORTH-NORTHWEST OF HA'APAI
AT 102200 UTC. IAN IS CURRENTLY MOVING SOUTH-SOUTHEAST AT ABOUT 06
KNOTS. CLOSE TO ITS CENTRE, THE CYCLONE IS ESTIMATED TO HAVE AVERAGE
WINDS UP TO ABOUT 105 KNOTS WITH MOMENTARY GUSTS TO 145 KNOTS.

ON THIS FORECAST TRACK, THE CYCLONE IS EXPECTED TO BE LOCATED ABOUT
115 NAUTICAL MILES SOUTH OF VA'VAU AND ABOUT 50 NAUTICAL MILES
SOUTH-SOUTHEAST OF HA'APAI AT 111000 UTC AND ABOUT 205 NAUTICAL MILES
SOUTH OF VA'VAU AND ABOUT 145 NAUTICAL MILES SOUTH-SOUTHEAST OF
HA'APAI AND ABOUT 110 NAUTICAL MILES EAST-SOUTHEAST OF NUKU'ALOFA AT
112200UTC.

DESTRUCTIVE WINDS MAY BEGIN SEVERAL HOURS BEFORE THE CYCLONE CENTRE
PASSES OVERHEAD OR NEARBY.

FOR THE VA'VAU AND HA'APAI GROUP:
EXPECT VERY DESTRUCTIVE HURRICANE FORCE WINDS WITH AVERAGE SPEED OF
105 KNOTS AND MOMENTARY GUSTS TO 145 KNOTS. HEAVY RAIN AND SQUALLY
THUNDERSTORMS. FLOODING INCLUDING SEA FLOODING OF LOW LYING COASTAL
AREAS. PHENOMENAL SEAS. DAMAGING HEAVY SWELLS.

Not looking good there at all over the next few hours.

Islands in question where the eye will pass over: http://goo.gl/maps/cGwvU

[ben g]

It looks so flat, I hope they have high ground? The storm surge will be nasty

[NZstorm]

The most recent metar I can find from Haapai Aiport is 1pm.

NFTL 110000Z 08055G75KT 9999 -RA SCT008 BKN015 OVC100 26/25 Q0976

55knots gusting 75 knots. Baro 976hpa.

[Nev]

RSMC Nadi have upgraded TC Ian to Cat 5 again, after dropping back to Cat 4 this morn.

TROPICAL DISTURBANCE ADVISORY NUMBER A24 ISSUED FROM RSMC NADI
Jan 11/0746 UTC 2014 UTC.

SEVERE TROPICAL CYCLONE IAN 07F CENTRE 935HPA CAT 5 WAS LOCATED NEAR
20.4S 173.9W AT 110600 UTC. POSITION GOOD BASED ON HR MTSAT EIR
IMAGERY AND PERIPHERAL SURFACE REPORTS. CYCLONE MOVING TOWARDS
SOUTH-SOUTHEAST AT ABOUT 10 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS
NEAR THE CENTRE ESTIMATED AT ABOUT 110 KNOTS.

EXPECT WINDS ABOVE 63 KNOTS WITHIN 15 NAUTICAL MILES OF CENTRE,
ABOVE 47 KNOTS WITHIN 30 NAUTICAL MILES OF CENTRE AND
ABOVE 33 KNOTS WITHIN 60 NAUTICAL MILES OF CENTRE.

CYCLONE HAS INTENSIFIED WITH CLOUD TOPS COOLING IN PAST 6 HOURS. EYE
REMAINS WELL DEFINED. SYSTEM LIES IN A LOW SHEARED ENVIRONMENT JUST
SOUTH OF AN UPPER RIDGE. OUTFLOW ENHANCED TO THE SOUTH BY JET STREAM
LOCATED ON DOWNSTREAM SIDE OF THE APPROACHING UPPER TROUGH. SST
AROUND 28 DEGREES CELCIUS. SYSTEM IS MOVING SOUTH-SOUTHEASTWARDS ON
THE SOUTHERN PERIPHERY OF THE NEAR EQUATORIAL RIDGE TO THE NORTH OF
THE SYSTEM. DVORAK ANALYSIS BASED ON EYE PATTERN WITH WMG EYE IN B
SURROUND EMBEDDED IN W YIELDING DT OF 6.5, MET=6.5 AND PT=6.0. FT
BASED ON DT THUS, T6.5/6.5/D1.0/24HRS.

GLOBAL MODELS AGREE ON A SOUTH-SOUTHEASTWARD MOVEMENT WITH GRADUAL
WEAKENING.
...