Tropical Storm Gaston

If Hurricane Earl and Tropical Storm Fiona were not enough to keep the National Hurricane Center busy, than Tropical Storm Gaston surely will be. The Storm was named this afternoon, and just complicates matters for the NHC who already have their hands full.

Tropical Storm Gaston, as of the 5 PM EST National Hurricane Center advisory, is located in the central Atlantic at 12.9°N 37.0°W. Currently it is a minimal tropical storm with winds of 40 miles per hours. It is moving due west at 15 miles per hour. The official track has Gaston moving slowly over the next 48 hours, before picking up forward speed on Saturday. The 5 day projected path brings Gaston about 300 miles East of the Leeward Islands on Monday. From there forecasts get more complicated. Several computer models have it entering the Caribbean Sea. As for intensity, it will likely strengthen to a category 1 hurricane by this weekend.

Hurricane Fiona 2010

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.

Tropical Storm Fiona

There's no absolute certainty in weather forecasting. But the future of Tropical Storm Fiona, the most recent in a trio of named storms, is more uncertain than the storm's two immediate predecessors, Danielle and Earl.

As of this evening, Tropical Storm Fiona had a sustained wind of 40 mph and was roughly 850 miles to the east of the Leeward Islands.

The official National Hurricane Center forecast is for the tropical storm to slowly strengthen but remain below hurricane strength as it takes a track very similar to that of Earl for the next few days. Forecasters expect the storm to be centered just to the north of the Lesser Antilles on Wednesday, where Hurricane Earl was early today.

At this point, there are as many questions as answers about Fiona's future.

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Since both Danielle and Earl blossomed into major hurricanes over the open Atlantic when moving through an environment with warm water and little wind shear (upper-level wind flow that inhibits hurricane formation), it might be expected that the same type of intense development would follow with Fiona.

But Fiona has been slower to organize, and government forecasters point to dry air and a lack of organization as factors that will continue to slow the storm's development during the next couple of days. The risk is that Fiona could fight off the dry air in its way and begin to take advantage of the very warm water and develop regardless of the current lack of organization.

In addition, Fiona is expected later this week to move into an environment with wind shear, which could also inhibit development. One of the reasons for the expected shear may very well be Fiona's proximity to Earl in a few days. Since Fiona is moving more quickly than Hurricane Earl -- 24 mph versus 15 mph as of this evening -- the upper-level wind being created by Earl might slow the development of Fiona.

The weaker and less organized Fiona is at the time it encounters shear, the more likely it is to be weakened by shear.

The forecast track of Fiona also carries some uncertainty. Forecasters are confident that the storm will track northwestward -- similar to Earl -- for at least the next few days, and there's a good chance that the storm will remain to the east of the United States. But changes in the overall weather pattern from the weekend and beyond mean that other forecast tracks are possible.

With so many questions, it's important that anyone with interests from the northeastern Caribbean to the United States continue to monitor the progress of Fiona in the coming days.