‘Drifting’ buoy data - their effect on

‘Weather’ Analysis and ForecastingIan Hunter S A Weather Service 29/7/2002

Louis Vermaak – DBCP XVIII – Martinique 14-18 October 2002

South African Weather Service (SAWS)

METAREA VII

• Our marine environment

• ‘Fixed platform’ in situ observation sites

• Remotely-sensed marine data

• SAWS marine products/ activities

• Drifters and some case studies

• Comments

SAWS – our Marine Environment

Tropical cyclone ‘Eline’ 22 February 2000

‘Magdalena Oldendorff’ – icebound in METAREA VII

Explosive cyclogenesis south-west of Cape Town

Cut-off low generating heavy SE’ly swell

Heavy SW’ly swell arrives at ‘The Dungeon’ south of Cape Town

Courtesy OSIS Cape Town

Warm Agulhas Current water penetrating the South Atlantic

10% + of world’s seaborne oil trafficrounds the Cape….

Courtesy : MRG Munich

SAWS – our “Fixed Platforms”

Courtesy MRG Munich

cf FA Platform central Agulhas Bank

A visitor to Marion Is (48° S) – March 2002

Bouvet Is. Norwegian AWS v. important for wave forecast models

SAWS AWS on South Thule, South Sandwich Islands

- see ‘ship wave’ clouds, top left.

Remotely-sensed Marine Data

NOAA AVHRR data – Agulhas Current – 5 knots +

MODUS – Terra – Gulf Stream

even higher resolution ...

Scatterometer winds ex QUICKSCAT – not always available

QUICKSCAT sees the pack ice – June 2002

SAWS – our Marine Products/ Activities

SAWS Global Spectral Model (GSM)

SAWS regional Eta model

A few Marine Case Studies in METAREA VII

Heavy, very long-period SW’ly swell to Agulhas Bank

- semi-submersibles unprepared, go into resonance. Damage several $m.

Tropical Cyclone Domoina visits the KwaZulu Natal Coast

Meteosat 7 – 4 September 2001

HmO 10m + off Cape Townwidespread coastal damage

Explosive cyclogenesis 24 May 2002. Heavy swell -> coastal damage/ flooding

Drifting buoy 17513, south-west of Cape Town

August 2002

Antarctic Mesoscale Prediction System model - AMPS

Drifting buoy 71566 – important input for AMPS – wakes up !

NOAA WAVEWATCH model – buoy data please !

Concluding Comments :Marine DATA

Life blood – Bread & butter !

Bouvet AWS data – received 8 hours later ...

International cooperation versus NMS commercialisation

Photo : Brent Appel - SAWB

SA Agulhas returning from Marion Is – August 1999