2 Major Weather Systems To Watch In The East - Tropical Storm Arthur And A ‘Cut-Off Low’

I awaken to some expected news. The 2020 Atlantic hurricane season has its first named storm of the year. Tropical Storm Arthur is currently located off of the southeastern coast of the United States. Arthur continues a trend in recent years of a named storm prior to the official June 1st start date of the Atlantic hurricane season. However, my meteorological “eye” notices another cyclone that will also impact the eastern U.S., but I suspect that it may not generate the same headlines as a tropical storm. It is called a “cut-off low.” Here is more information on both systems.

Let’s start with Tropical Storm Arthur. The latest information from the National Hurricane Center as of Sunday morning is that a Tropical Storm Warning has been issued for the North Carolina coastal region. Winds in excess of 39 mph and excessive rainfall are expected in that region on Monday. Dangerous surf conditions and rip current threats will be found from the mid-Atlantic region to Florida for the next several days also. As I dissect the National Hurricane Center forecast discussion, there are a couple of key points to highlight. First, the storm is not expected to become a hurricane though some slight strengthening might happen as the storm crosses the warm Gulf Stream. Strong vertical wind shear will ultimately offset this process.. There may also be some slight strengthening in a few days as the storm transitions to a more extratropical (deriving energy from air masses not ocean water) storm. As you see from the official forecast track below, the storm moves pretty close to the Carolina coast before turning out to sea.

Arthur is not the only cyclonic feature worth watching this week in the eastern U.S. Something called a cut-off low will be featured too. For the “meteorologically-uninitiated,” The National Weather Service glossary defines a cut-off low as, “A closed upper-level low which has become completely displaced (cut off) from basic westerly current, and moves independently of that current.” Such systems can remain essentially in the same position for days and even move westward. These things always catch my eye because massive flooding (2009) that we experienced here in Georgia was associated with a cut-off low to the west of us that funneled moisture and rainfall over the state for days.

The cut-off low in the southeastern U.S. (graphic above) is forecasted to sit there for days with its counterclockwise flow pattern. I mention the circulation pattern because much of the eastern U.S. will receive an influx of sustained moisture on the right side of the cyclonic system. The projected rainfall totals from Wednesday to Friday clearly indicate both features discussed in this article: the rainfall in the South and mid-Atlantic associated with the cut-off low as well as the “footprint” of Tropical Storm Arthur. People in the mid-Atlantic and Southeast should expect a wet pattern much of the week so be aware of potential flood threats.

I will close with a shout-out to the meteorological models. They have consistently resolved both of these weather systems for the past week. Kudos to them.