Hurricane Season 2013 Update July 24, 2013: Tropical Cyclone Dorian

The fourth named tropical cyclone of the 2013 Atlantic Hurricane Season has formed, and is the first Cape Verde storm of the season. As of 5:00 pm Wednesday evening Tropical Storm Dorian is centered off the coast of Africa to the west of the Cape Verde Islands. The storm is moving towards the West North West with a forward momentum of 20 miles per hour. Max winds are sustained at 50 miles per hour with gusts as high as 65 miles per hour and a minimum central pressure measured at 1002 millibars. The path of Dorian will be determined by a broad region of high pressure over the Atlantic Ocean. The clockwise flow around this high pressure system will provide the steering winds aloft that will continue to guide Dorian westward over the open waters of the Atlantic.

There are a few factors that are in place that will diminish how fast this tropical system strengthens through the course of the week. One of these factors will be the continuing influence of dry and dusty Saharan air that is being spread westward from the African continent by the same steering winds guiding Dorian, generally the influence of dry air keeps tropical systems from strengthening. Another factor that will keep Dorian from rapidly intensifying are the marginally warm waters of the open Atlantic. Tropical systems rely on warm ocean water temperatures in the 80s to rapidly gain strength, Dorian is currently over waters that are barely warm enough to support tropical development with waters in the lower to middle 70s. For the moment, one factor that is favorable for Dorian to at least remain of Tropical Storm intensity is that it is situated in a relatively low wind shear environment for the time being, this means that the storm isn't likely to be torn apart by strong winds aloft. I do expect this system to continue its westward trajectory through this week as a Tropical Storm.

Thereafter Dorian could become more organized as is moves in to warmer waters and threaten the Virgin Islands and Puerto Rico in the timeframe of Sunday and Monday, however the storm could face stronger wind shear that could keep it from strengthening into anything major. I will continue to monitor this situation as it unfolds.