After having virtually nothing to talk about for the past two months, it appears that the Atlantic Basin is finally starting to show signs of life. Tropical Depression Two formed (then weakened) earlier this week near the coast of Africa. The remnant low of this depression is threatening a comeback this afternoon. It might just make it over the next few days. But east of this remnant low is the big disturbance that the models have been predicting would become a large hurricane for more than a week. I’m not sure that what’s left of Tropical Depression Two will survive for the next five days, though it may well become a weak tropical storm at some point. So I won’t focus on this system. Instead, I’d like to take a good look at the disturbance to its east, Invest 90L, or “Disturbance 33″ as we’ve identified it at ImpactWeather.
In 2005, we were curious as to how many tropical disturbances there were in a typical season so we began counting them in our daily tropical outlook. We just started giving each disturbance a number beginning in May and ending on November 30th. What we’ve found over the past four seasons is that there’s a fairly consistent number of disturbances each season, regardless of how many named storms develop. That number is somewhere between 65 and 75 disturbances. In fact, in 2005 with 28 named storms, there were only 65 disturbances identified.
Back to Disturbance 33, the one in the far eastern Atlantic. Like I said, the models have been extremely bullish on development for the past week or more. Now that it’s out over the water, we’ll see if the models were correct. As of this afternoon, the disturbance appears to have a well-defined circulation, but the thunderstorms aren’t strong enough near the center to classify it as a tropical depression. I think that will change by tomorrow, and we should have Tropical Depression Three over the weekend. The next question is where will it go?
All of the models, tropical and non-tropical are in quite good agreement as far as the first 5-6 days, with the exception of the European model. If you remember from last season, the European did an excellent job with Gustav and Ike, but failed miserably with Hanna. Currently, all the tropical models and the American GFS and Canadian models take Disturbance 33 across the northeast Caribbean next Thursday, August 20th. The European model’s forecast is to the right/north of every other model, taking the center about 300 miles to the north of the northeast Caribbean next Thursday then northward and out to sea. I’ve created graphics to illustrate the forecast positions for 7AM CDT next Thursday below:
GFS, Canadian and European Models Valid 7AM CDT Thursday, August 20th
As you can see, the GFS and Canadian models are in great agreement in taking what they’re forecasting to be a hurricane into the northeast Caribbean just to the east-southeast of Puerto Rico next Thursday morning. The GFS and Canadian models are quite in line with the suite of tropical models, below:
Tropical Models
So, we have reasonably good agreement out for the next week. The purely tropical models don’t forecast beyond 5 days, but the dynamic models like the GFS, Canadian and European models go out as far as 15 days. So let’s see what they’re forecasting after this predicted hurricane passes the eastern Caribbean. The GFS and Canadian are in remarkable agreement today, taking the center to near southern Florida by 7AM CDT on Sunday, August 23rd, while the European is quite different, taking the center well out to sea east of the U.S.
GFS, Canadian and European Models Valid 7AM CDT Sunday, August 23
Beyond Sunday, the GFS and Canadian models turn the hurricane northward up the west coast of Florida and drive it inland across northern Florida and Georgia. That’s today’s runs, anyway. The problem is that though these two models are amazingly close in their predictions today, that hasn’t always been the case. Just yesterday, the GFS model took the center of the hurricane inland into southeast Louisiana. The day before that, the GFS took it northward along the East U.S. Coast. The Canadian model has been more consistent, taking the storm into south Florida for the past 2-3 days. And the European model has been quite consistent in taking the storm northward and safely out to sea after passing well north of the Caribbean.
Where will it go (assuming it actually does develop)? Climatology suggests that the European model may be on the right track. However, about 20-30% of historical storms that have developed in the same region have threatened or impacted the East U.S. Coast. Given the projected pattern in advance of the system, I’m inclined to think that this potential storm may eventually impact the U.S. between Florida and North Carolina. It’ll be interesting to see how this turns out over the next 10-14 days.
