Spotty Pockets of Heavy Rain
I mentioned last week that we might experience a period of enhanced rainfall this week. Let’s start off with a look at where rain has fallen over the past 4 days. At first glance, you might notice that most of the Southeast U.S. has received some rain. However, there have been a couple of exceptions. Parts of the Carolinas and southern Alabama seem to have missed most of the rain. Areas in blue represent relatively modest amounts of rain –
0.50 to 0.75 inches. In fact, most of the Southeast U.S., over the past 4 days, received less than 0.50 inches of rain.
There have been spotty pockets of heavier rainfall (1.0 inch or more). I have outlined these areas in red.
A source of deep-layer moisture seems to be in place. Here is an estimate of precipitable water (PW). PW reflects the total amount of moisture (vertically) within a column of the atmosphere. It is a good indicator for the potential for heavy rainfall.
The region in brown (outlined by the red line) shows the highest levels of PW. To put this in perspective, here are anomalies of PW. PW values of 150% or greater cover most of the Southeast U.S., with readings nearing 200% over higher elevations of the Carolinas.
Thunderstorms that have formed over the past several days have produced periods of tropical downpours, reflecting this deep atmospheric moisture. The overall lift however, has been more modest, thus resulting in scattered rainfall coverage.
A front will pass through Wednesday and Thursday. This will provide additional lift. The enhanced lift ahead of the front, along with high PW already in place, should increase rainfall intensity and coverage through midweek.
Once this front passes, it looks like about a 5-day period without any significant rainfall