Monday, August 30, 2010

Hurricane Earl and Tropical Storm Fiona - 310001Z

Hurricane Earl intensified this afternoon and became a category 4 cyclone. In short, this system is big and powerful. It is tracking through minimal wind shear and very warm sea surface temperatures which will likely see it intensify even further over the next 48 hours. It is still tracking slightly north of west at about 13 knots (24 kmh/15 mph).

While the storm is still expected to recurve northward, its continued forward speed to the west has shifted the forecast track somewhat west. This brings the forecast even closer to the US eastern seaboard and should give Nova Scotia some moment of pause. While it is still far too early to forecast a landfall, most models have this cyclone reaching as far west as Maine or as far east as seaward of Nova Scotia as a possible category 2 hurricane.

Invest 97L was upgraded to a tropical storm and is now TS Fiona with rain bands starting to appear in wind fields of about 35 knots. Whether Fiona intensifies or not is difficult to say. It is tracking almost due west at 21 knots (39 kmh/24 mph) which means it is moving closer to Earl.

I know the immediate response to this is to expect that the two cyclones will merge to form an even bigger storm, however, that's not what happens. Earl is generating strong upper outflow winds which will create strong wind shear in Fiona's path. With that happening, and with Earl robbing Fiona of moist air, there is a fairly decent chance that Fiona will lose its energy and dissipate. If... it keeps moving at its current speed. If it slows down Fiona could become a whole different story.

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