Many people have been asking for the first half of the 2010 season “where are all the hurricanes?” Well, I think we’ve found them. Since August 21st, 8 named storms have formed, including three Category 4 hurricanes and Category 2 Julia (Julia reached Category 2 strength at 8PM CDT this evening and could reach Category 3-4 strength tomorrow). As of this afternoon, we have newly-formed Tropical Storm Karl in the western Caribbean, which I think is destined to become Hurricane Karl in the Bay of Campeche on Friday. The last 30 days have been extremely active across the tropics, one of the busiest 30-day periods on record. So far, though, all the big hurricanes have mostly stayed out to sea (Earl reached eastern Canada possibly as a Category 1 hurricane). But there are signs in the long-range models that the development region may be shifting westward toward the Caribbean Sea and the Gulf of Mexico in the coming weeks.
For the past 3-4 weeks, the Caribbean Sea and Gulf of Mexico region has been dominated by high pressure and sinking air. The massive ridge over the southern U.S. has kept the region free of any significant storms up until now, but that high pressure area won’t be around forever. Summer comes to an end next week, and the transition to fall is just the thing that could make the western Atlantic Basin come alive with development. One long-range signal, the Madden-Julian Oscillation (MJO) is predicting that an upward motion pulse will reach the western Atlantic Basin in the next week or so.
The MJO is a pulse of increasing upward motion and tropical cyclone development that starts in the Indian ocean and travels eastward across Asia, the Pacific and eventually to the western Atlantic Basin. Wherever this MJO pulse travels, we typically see an increase in tropical cyclone development. Once it reaches the East Pacific, there is often a significant increase in development across the Gulf of Mexico and the Caribbean Sea. Just such an MJO pulse is now forecast to reach the East Pacific later this week. It’s not a strong MJO, but it could significantly increase thunderstorm activity across the Gulf and Caribbean, leading to the development of several storms in the region.
In addition, some of the longer range computer models have been forecasting the development of a hurricane in the central to western Caribbean Sea between about the 21st and 25th of the month (next week). For 3-4 days now, each run of the American GFS model has forecast such development. Even the European model is hinting at this development now. The models are forecasting the high pressure area across the Gulf to break down next week, leading to development in the Caribbean. I think that there is a very good chance that the models are correct in forecasting such development.
So while the 2010 season has just passed the half way point, it’s looking like the last half of the season will likely bring several hurricane threats to the Caribbean Sea and to the U.S. Gulf Coast, and quite possibly to the southeast U.S. as well. The strong La Niña out in the Pacific could keep the 2010 season going through October and well into November. Don’t look for a rapid shut down of the tropics in late September this year. The worst of the season may be yet to come as far as landfalling hurricanes.