Upper levels producing flooding in South Carolina and record cool temps locally

An upper-level weather pattern that is fairly unusual is combining with the strongest hurricane of the year to produce varying rare conditions locally and across the Southeast.

Starting outside the Mid-South, Hurricane Joaquin has gotten even stronger today as it departs the rain and wind-lashed Bahamas, heading on a northeast track that will take it well offshore the U.S. and side-swiping Bermuda.

Major Hurricane Joaquin with 155 mph wind departs the Bahamas heading northeast into the western Atlantic.

Just a notch below category 5 status at 155 mph sustained wind, the hurricane is not having a direct impact on U.S. weather. However, indirectly it is contributing to a potentially catastrophic flooding event, as described by NOAA, over parts of the southeast U.S., most directly in the Carolinas and northeast Georgia. As shown in the graphic below, a river of water-logged air extends from Joaquin into SC, which is feeding persistent heavy rain, dropping multiple inches per hour in some cases!

Precipitable water (PW) values of 2″+ (red) are clearly seen being drawn into SC from Joaquin this afternoon, creating flooding rainfall. Graphic courtesy WxBell.
Portions of South Carolina are experiencing record rainfall and possible catastrophic flooding along the lines of a 500-1,000-year event, according to the Weather Prediction Center.

Areas like Charleston, SC are receiving record rainfall that are being attributed to Joaquin by some, but really is the result of a deep upper-level low pressure system over the southeast U.S. (shown below) that is helping to draw Joaquin’s moisture into the region.  That same upper low is also responsible for our overcast and chilly conditions in the Memphis metro.

A large upper level low over the southeastern U.S. is drawing abundant moisture from Joaquin (lower right), as well as creating cloudy, cool conditions over the Mid-South. Graphic courtesy WxBell.

On the backside of the low, in the Mid-South, persistent northerly flow around the low and moisture wrapping around said low has created cloudy skies the past couple of days, keeping temperatures well below normal. In fact, today’s high temperature will be a record cool max topping out (so far) at 59° in the wee hours of this morning. Add a north wind at 10-15 mph and sweatshirts and jackets have been retrieved from the closet as fall has arrived!

Early afternoon visible satellite imagery shows persistent cloud cover over all of the southeastern U.S., including the Memphis metro.

Over the next couple of days, the southeast upper low will weaken a bit and move east as Joaquin moves out, allowing for some sunshine to re-appear in the Mid-South sky. A little is possible tomorrow afternoon, which will help temperatures warm back to the mid 60s to near 70 depending on how long how solar radiation we receive.

By mid-day Monday, the upper low will have shifted offshore and weakened slightly, allowing high pressure to build into the Mid-South, warming temperatures and bringing more sunshine. Graphic courtesy WxBell.

By Monday, we’ll be back near 80 with more sunshine expected. Conditions remain dry into next week as temperatures warm back into the mid 80s for much of the week, a result of high pressure at the lower and upper levels taking hold. The next chance of rain doesn’t appear until late in the week as the next frontal system approaches. Keep track of the latest forecast on our mobile website or in the MWN mobile apps (link below).

Erik Proseus
MWN Meteorologist

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