El Nino has resulted in in a quiet start to hurricane season in the Atlantic, but things may be changing.
Atlantic Hurricane Season usually (but not always) features below normal activity in the Atlantic Ocean. The main reason for this is high-level wind shear, and that has been the case so far this season, especially across the Caribbean. In the tropics, trade winds resulting in most systems moving from east to west. Wind shear is when you have strong winds in the upper levels of the atmosphere blowing from west to east. As thunderstorms intensity, the strong winds in the upper levels essentially rip the tops off of them, so they cannot fully develop, and thus systems can’t get organized.
The other issue that has caused a relative dearth of storms in the Atlantic has been Saharan Dust. Every year, strong winds blow plumes of dust and sand from the Sahara across the Atlantic and towards the Caribbean and the Gulf. These plumes contain very dry air, inhibiting the development of showers and thunderstorms, and produce very hazy conditions across the islands of the Caribbean. Normally these plumes begin to wane in intensity by mid-to-late July, but this year they have remained fairly strong into early August. Another fairly strong plume will move across the Greater Antilles over the next few days.
Most forecasts, including the most recent update from the team at Colorado State University, continue to show the likelihood of a below-normal season. Thus far, there have only been two named storms in the Atlantic – both in the Gulf. Short-lived Tropical Storm Arthur along the Texas coast in mid-June, and Tropical Storm Bertha, which brough gusty winds and heavy rain from the Florida Panhandle to Louisiana in mid-July. On average, we should have had three named systems by now, with the third one forming around August 3, and the fourth named system of the season forming around August 15 on average. The first hurricane of the season forms around August 11 on average. In terms of Accumulated Cyclone Energy or ACE, which factors storm strength and duration, activity in the Atlantic is only about 22% of normal thus far.
Tropical waves continue to roll off of the west coast of Africa every few days, and as they move into the Atlantic they encounter the Saharan dust and accompanying dry air, the strong wind shear, and water temperatures in the eastern Atlantic that aren’t warm enough to support a tropical system, but that may be changing. Water temperatures in the tropical Atlantic are now warm enough all the way to the coast of Africa to support a system. The last few waves that have moved into the Atlantic have been a bit more robust, with more widespread shower and thunderstorm activity. Forecast models are showing two areas that need to be watched in the Atlantic over the next week for development.
A tropical wave that moved off the west coast of Africa early Friday is now southwest of the Cabo Verde Islands and producing disorganized showers and thunderstorms. Conditions right now are marginally favorable for the system to get organized as it crosses the Atlantic. By the time it reaches the Lesser Antilles, wind shear will increase and conditions will quickly become hostile, eliminating any chance of further development. Another cluster of thunderstorms is moving off the west coast of Africa this evening, but it is farther north than most of the tropical waves, and will likely get choked off by Saharan dust fairly quickly.
Another wave will move off of the west coast of Africa early next week. This wave is expected to be fairly robust, and will likely encounter a less hostile atmosphere as it moves into the Atlantic. Several forecast models have been indicating the possibility that this system could develop into at least a tropical depression, and possibly fairly quickly once it is over water. Of course, this is still days away, and until there is an actual storm for the models to initialize, it is all just speculation. It’s something we’ll continue to monitor for the next several days.
The Atlantic isn’t the only basin where things are getting active. There are three separate systems being monitored for development in the Eastern Pacific, once of which has a slight chance of impacting Hawaii later next week. In the Western Pacific, Typhoon Dolphin will make landfall in eastern China a few hundred miles south of Shanghai on Sunday. Tropical Storm Chan-Hom is expected to make landfall in Japan more than 100 miles north of Tokyo on Tuesday. Tropical Depression Kujira should become a tropical storm and pass a few hundred miles north of the Northern Marianna Islands late Sunday, and another system is expected to develop well northeast of the Northern Mariannas by early next week.
Storm HQ 