By Nathan McCollumnTROPICS — Over the past few days, a large mass of convection has been organizing east of the Leeward Islands. This afternoon, Air Force Reconnaissance aircraft investigated this area and found a broad, closed circulation with sustained winds of 50mph. Therefore, Tropical Storm Erika has been declared by the National Hurricane Center. The long-term path of Erika will be dependent on the forward movement. Basically, Erika will move west-northwest for several days as it stays south of the southern boundary of a high pressure ridge. Then, we have a couple of scenarios that could happen. Everyone should know that the current forecast has a low confidence level because we need to see how strong Erika becomes over the next few days. Shear is not a problem today, but shear will likely increase as Erika reaches the southeast boundary area. If Erika becomes a hurricane (stronger storms tend to follow ridge boundaries easier than weak storms), it is likely that the system will take a path much like Bill and Danny. If Erika is impacted by the shear sometime in the next 48-72 hours, it may tend to stay on a more westerly track. We have plenty of time to see how Erika develops before making a definitive decision on any impact to Florida. The location of Tropical Storm Erika is Latitude 17.2N – Longitude 57.3W, or about 390 miles east of the Leeward Islands. Erika has sustained winds of 50mph with a central pressure of 1007mb, moving west-northwest at 9mph.
The visible satellite image shows the broad center located in the western part of the convection area. The center will likely move more toward the center of the convection over the next 24 hours. The infrared picture shows a large amount of convective energy that will likely strengthen Erika as it moves west. The attached water vapor picture shows Erika south of the subtropical high pressure ridge. The southeast part of the ridge appears to be near the central Bahamas. No shear area is near Erika.
While the forecast map does not include Florida in the “error cone”, we should continue to monitor this storm. As I mentioned, there is a low confidence in the current forecast because of the forward speed of Erika. At only 9mph, this system is going to be around for awhile. The slow movement is due to the lack of strong steering currents. So, we will watch this system overnight and give the models a chance to analyze the airplane data. The new forecast models should be better tomorrow with the new data to analyze.
The next advisory will be Wednesday.