TSR Australian Cyclone Season Outlook

[AussieMark]

'The TSR (Tropical Storm Risk) early September forecast update for Australian-region tropical cyclone activity in 2006/7 anticipates activity ~25% below average. The forecast spans the Australian season from the 1st November 2006 to the 30th April 2007 and is based on data available through the end of August 2006. Our main predictor is the forecast anomaly in October-November Niño 4 sea surface temperatures(SST) which we anticipate will be above-average by 0.64±0.24oC. Since SSTs in this region are linked to vertical wind shear over the Australian region during Austral summer, an above-average Niño 4 SST indicates above-average wind shear and below-average tropical storm activity. Thus we expect Australian basin cyclone activity and landfalling numbers to be below-average in 2006/7. Our forecast reduction since last month reflects a 0.32oC rise on our forecast Oct-Nov Niño 4 SST.'

and as for the probabilities of 'Tropical Storms' forming in the Australian region:

'There is only a 5% probability that Australian-region tropical storm numbers in 2006/7 will be above average (defined as more than 12 tropical storms), a 47% likelihood they will be near normal (defined as between 9 and 12 tropical storms) and a 48% chance they will be below normal (defined as less than 9 tropical storms). The 1975/6-2005/6 climatology probabilities for each category are 29% (above-normal), 36% (near-normal) and 35% (below-normal).'

As for these 'storms' actually striking the coast:

'There is only a 12% probability that Australian tropical storm strike numbers in 2006/7 will be above average (defined as more than 5 landfalling tropical storms), a 52% likelihood they will be near normal (defined as 4 or 5 landfalling tropical storms) and a 36% chance they will be below normal (defined as less than 4 landfalling tropical storms). The 1975/6-2005/6 climatology probabilities for each category are 32% (above-normal), 42% (near-normal) and 26% (below-normal).'

'The key factor behind our forecast for Australian-region tropical storm activity in 2006/7 being ~25% below average is the anticipated supressing effect of early austral summer SSTs in the Niño 4 region.
Warmer than normal SSTs in this region lead to increased atmospheric vertical wind shear over the Australian region during Austral summer; a condition favouring reduced tropical storm activity. Our current forecast SST anomaly (1975-2005 climatology) for October-November 2006 Niño 4 SST is 0.64±0.24oC (up from last month’s value of 0.32±0.32oC). The forecast skill for this predictor at this lead is 88% (assessed using cross-validated hindcasts over the period 1975-2005).'

http://forecast.mssl.ucl.ac.uk/shadow/d ... ep2006.pdf

[P.K.]

'The TSR (Tropical Storm Risk) early September forecast update for Australian-region tropical cyclone activity in 2006/7 anticipates activity ~25% below average.

With all the strong landfalls last year I guess this is good, however you need the rain from what you have been saying.