15 December 2009

The little storm that could

That would be TC Laurence, currently menacing the Kimberley region of WA. It is currently a Category 3 storm, with a central pressure of 975 mb. This same system brought a month's worth of rain to Darwin and strengthened into a full blown TC. It is expected to finally move ashore on the afternoon of the 16 Dec, a big (and surprising!) start to the Wet in the western Top End and the Kimberley.  Atypically, the onset of this Wet is not part of the northern monsoon; winds remain easterly across most of the region.

The image, from Aqua MODIS, shows TC Laurence in its full glory on the afternoon of 15 Dec. A cloud-filled but obvious eye is present as are extensive spiral bands swirling in towards the centre.

Initially not expected to have much more than a short-lived regional impact, this TC could  have a major impact on the seasonal climate across a good portion of the continent. The interest here is the effects on the fire weather and climate. The immediate forecast is for the TC to weaken but linger in NW WA for a while, likely finishing off the fire season in the Pilbara and Kimberley.  After that, the forecast becomes uncertain. It's entirely possible, but by no means guaranteed, that this storm (or it remnants...) will effect central and SE Aust, drifting slowly towards the ESE. One 10-day NWP model forecast (unreliable!!) I saw earlier today predicts a major rain event in NSW (on Xmas eve) as the remnants of the TC were absorbed into the extratropics.

It goes without saying that a major widerspread rain event in eastern Australia would be entirely welcome, and help dampen fire activity in those regions. (Of course, high-based thunderstorms with dry lightning would be a disaster...). 'Enough' rain along the storm's path would also reduce fire dangers for the next few weeks. It could also provide soil moisture for abundant growth (fuel for next season) in affected northern areas.

Cape York and the Gulf regions are unlikely to be directly affected from the storm. They will still likely need monsoon onset for the wet season to begin.

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