Tuesday, August 31, 2010

Hurricane Earl & Tropical Storm Fiona: August 31, Update B

Just a short lunchtime update as interesting things are afoot (and aloft) in the Atlantic.

Earl is still a cat 5, but is slowly slowing down in forward speed. He's now moving at 13mph. Meanwhile, Fiona is still a weak Tropical Storm, but is increasing/moving quickly in forward speed along the same path as Earl (now at 24mph). The two are already interacting, but the question is how much, and in what form...

One scenario we might see is called the Fujiwara Effect (or a Fujiwara Interaction). Basically, if we have two rotating cyclones and they get close to each other (with the western one moving slower than the eastern one) then they start to rotate around each other and around a point between the two systems. Eventually they will spiral in to that central point and merge. This is more frequently seen in the Pacific, but once every few years it happens in the Atlantic. The last time seems to be in 1995 between Iris and Karen.

Another option is straightforward absorption - if Fiona gets much closer, Earl may 'absorb' her.

Yet another scenario is that Fiona slows down, and retains her identity.

Her leading edge is approaching the Leeward Islands now so she is very close to Earl. This proximity complicates everything and I don't know quite how this will play out in terms of track or intensity yet. I'll send another update later.


Disclaimer: read the last one cos I'm sending this via phone & can't get hold of it. But basically - these are my opinions, not those of anyone I represent & listen to your emergency managers, NHC & weather service as they have the best/most up-to-date info.  

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