As you can see on the frequency diagram below, the first week of August typically marks the real beginning to the hurricane season. About 90-95% of all named storms occur between August 1st and October 15th in a typical season. The chart below actually shows the frequency distribution of tropical depressions, tropical storms, hurricanes and major hurricanes. The very peak of the season is generally considered to be the 10th of September. And like clockwork, the 2010 season seems to be slowly coming alive this week.
Just a few days ago, Tropical Storm Colin formed east of the Caribbean Sea. Although I think that Colin may have been named a little too quickly (later data indicated that Colin lacked a well-defined circulation center), it still indicates that the tropics are becoming more active. But just as quickly as Colin developed, it ran into wind shear associated with an upper-level low which tore the newly-formed storm apart. The same thing happened to Bonnie a few weeks ago, if you recall. This does indicate that there are still some pockets of strong wind shear across the tropics, something that’s not uncommon for early August.
Colin may be down, but I’m not sure he’s “out” just yet. Surprisingly, many of the models still indicate that Colin will get past the shear zone produced by the upper-level low and regenerate into a tropical storm. The hurricane-specific models even take Colin to hurricane strength in 2-3 days as it passes a few hundred miles off the East U.S. Coast. That’s certainly possible, but it does look like Colin’s strong winds would not impact any land areas.
In the Caribbean, there’s a disturbance we’ve identified as Disturbance 31. It’s actually a tropical wave that we have been tracking since it moved off the west coast of Africa about 12 days ago. Many tropical waves weaken after emerging off the west coast of Africa in the early part of the season, only to strengthen once they reach the Caribbean. Really, it’s just the associated thunderstorms that weaken, not the waves themselves. Disturbance 31 is certainly looking more impressive today as it moves westward at 15-20 mph. There may be a 40% chance that the disturbance will become at least a tropical storm before it reaches the Yucatan Peninsula on Friday night or Saturday morning. Some models even take it to hurricane strength by then, but those models already assume it’s a tropical depression, something it’s not.
The good news for those across the northern Gulf of Mexico is that the same high pressure that’s been producing the above-normal temperatures should remain in place for at least another week. That means any developing storm in the western Caribbean Sea would be driven westward toward Mexico rather than turn toward the northern Gulf of Mexico. Therefore, we think that Disturbance 31 will probably remain to the south of 23N-24N latitude, whether or not it develops.
Finally, out in the far eastern Atlantic is Disturbance 32. The disturbance certainly has a good bit of energy associated with it, though it is somewhat lacking as far as its organization. A number of computer models indicate that this disturbance will develop into a tropical storm in 4-5 days as it passes well north of the eastern Caribbean. Both the American GFS model and the European ECMWF model take the system safely north and east of the Caribbean and out to sea into the open Atlantic next week. As far north as the disturbance is now, I’d say that such a track out to sea is most likely.
All in all, the various computer models which extend out to 10-15 days are showing an increase in development over the coming weeks, something that I’d expect to see in early August. Over the last 15 years, we’ve witnessed about 1 named storm per week forming in the month of August, and I don’t think that this August will be much different. Look for activity to gradually ramp up over the next week or two as wind shear slowly declines. Longer range signals are pointing to a very active September, but that’s the subject of my next update here.
