Fiona May Be Fading, but Two Other Disturbances Still Remain

As mentioned yesterday, the Tropical Atlantic is heating up as it should for this time of year. August is usually a ramp up month in terms of tropical activity as more storms and hurricanes develop during the course of the month as ocean temperatures reach optimum levels, especially in the Eastern Atlantic.

Earlier in the month, we had Hurricane Earl develop in the Caribbean, and eventually come ashore in Belize and Mexico. Then, earlier this week, Fiona developed, and is still hanging in although the storm has been fighting hostile environmental conditions, and isn’t expected to survive though the middle of this coming week.

There are still some threats in the Atlantic. The Cape Verde Season is kicking into overdrive with the emergence of Invest 99L in the East to Central Atlantic, and another tropical wave that just departed the West African coast within the last 24 hours. Both disturbances have been given good odds of developing into tropical cyclones within the next five days.

The more immediate threat of these two disturbances is Invest 99L, which is currently located about 1150 miles to the east of the Lesser Antilles. As of now, the disturbance still remains disorganized, and it is also moving at a fairly fast clip between 15 and 20 miles per hour, which sometimes hinders development. Environmental conditions are also less than ideal right now.

Factors such as upper level winds, humidity, and sea surface temperatures where Invest 99L is headed are currently forecast to be marginal for development over the next several days. As a result, the chances of formation within the next 48 hours is only 20 percent. However, as we get further into the weak, and Invest 99L moves into real estate where environmental conditions are more friendly for formation, the probability of formation increases to about 50 percent.

Moving further to the east, near the Cape Verde Islands and just off the coast of Africa, is another disturbance or tropical wave that has already shown tremendous potential despite just moving into the Atlantic within the last day. The disturbance, Invest 90L, is a tropical wave that already has low pressure associated with it, and conditions appear to be quite favorable for development.

The National Hurricane Center indicates that Invest 90L in the Eastern Atlantic is likely to become a depression over the next several days. The probability of formation over the next 48 hours is at 70 percent and the chances of formation within five days is up to 90 percent. Models have been going a bit crazy with some interesting long range scenarios over the past couple days.

The GFS model with 6 hour average precipitation, mean sea level pressure, and 1000 to 500 millibar thickness indicated in its 18Z run on Friday (August 19th) that a Category Five Hurricane would be bearing down on the Central Florida Gulf Coast by Monday, August 29th. Then, in another run of the full-res GFS at 12Z on August 20th, a Category Four Hurricane is bearing down on Eastern Long Island and Southern New England by September 3rd.

I must caution everyone about these models. While they are eye-popping and interesting, they are going out some 10 days to two weeks, and a lot can change in the atmosphere over that period. Heck, the atmosphere can change a lot in just a day. Nevertheless, it is that time of year where tropical storms and hurricanes develop with greater frequency in the Atlantic, and the United States coastline has been long overdue for a major hurricane (Wilma in 2005 was the last major hurricane to make landfall in the USA). Moral of the story is to be prepared.