1:00 PM | ***An update on the late week heavy rain threat and east coast tropical system***

[Low-level "weenie" circulation center seen at end of arrow; image courtesy NASA]

Discussion

Sea surface temperatures continue to run at warmer-than-normal levels off the east coast of the US and below-normal in the region between the west coast of Africa and the Caribbean Sea. As a result, this Atlantic Basin tropical season may very well feature more in the way of “home-grown” tropical systems that develop close by as compared with the “African-wave” type of tropical system that travels a long distance across the Atlantic Ocean. Indeed, a weak disturbance now meandering off the east coast of Florida may become just such a “home-grown” type of system that forms nearby over the unusually warm waters off the southeast US coastline.

This disturbance currently features a rather puny looking low-level circulation center (see satellite image; courtesy NASA) and a somewhat disorganized overall appearance with thunderstorms well displaced to the south of the center. Later this week, however, environmental conditions will improve dramatically for substantial intensification and there is a very good chance that this will become the first named tropical storm of the season (Arthur) and, if so, it would be the latest first named storm since 2004 when Alex formed on July 31st. Furthermore, this system could very well become the first official hurricane of the season by the time the 4th of July rolls around. To make matters even more interesting, a strong cold front from the middle of the country will slowly close in on the east coast during the next few days. This front is likely to stall along the Atlantic seaboard for a brief time late this week and - as tropical moisture interacts with the front - heavy downpours are likely to break out along the I-95 corridor from DC-to-Philly-to-NYC from late Wednesday into Friday. By the way, Saturday is likely to turn out to be a beautiful day around here behind any tropical system that does form with a refreshingly cool air mass for this time of year moving in from the Midwest.

Early looks at potential storm tracks (below; courtesy Weather Bell Analytics) from different computer forecast models suggest that the Outer Banks of North Carolina may get directly affected in the Thursday/early Friday time frame and then the tropical system may slide just to the east of the Mid-Atlantic region. However, no matter what the ultimate tropical storm track is, heavy rain is quite likely in the I-95 corridor with the approach of the strong frontal system and the whole situation still needs to be closely monitored. Also, even without a direct hit in the Mid-Atlantic region, rough surf is possible all the way up the coastline at the end of the week. Stay tuned.

For more on the prospects for this Atlantic Basin tropical season: http://thesiweather.com/2014-tropical-and-mid-atlantic-summer-outlooks/

[Map courtesy Weather Bell Analytics at weatherbell.com]