© 2019 Terry Swails

EXCESSIVE RAINS POUND PARTS OF THE MIDWEST...WE'RE NOT DONE YET!

September 28, 2019

The past 30 days have featured a wetter than normal weather pattern across the Pacific Northwest, Northern Rockies/Plains, & Midwest. The precipitation footprints from Dorian, Imelda, & remnants of Lorena are also visible. Many southeastern regions were abnormally to historically dry.

The 30 day departures

Attached is September's precipitation-to-date rankings through the 25th. Green Bay, & Salem, OR witnessed their wettest Sept 1-25 on record. Conversely, it's the first time on record that Knoxville, TN and Tallahassee, FL have not reported measurable rainfall through the first 25 days of September.

 

It's really interesting to see how a pattern that brings so much rain to one area can keep another bone dry. These are the September rainfall rankings for some select cities in the central U.S. Dubuque with 12.1" is ranked 2nd all-time for wettest September. Louisville, Kentucky with .04" is currently experiencing their all-time driest.

Pretty wild how a distance of 490 miles can make a foot difference in rainfall in just a matter of 25 days.

It's quite clear that the ring of fire (storm producing jet stream) has been situated over the Midwest bringing the persistent rains. Underneath a sprawling high pressure ridge, subsidence has kept the southeast hot and dry. Here's an example of the overall pattern at 500mb.

Another example using precipitation departures.

The next few days represent only minor pattern alterations so the sensible weather will change little through Wednesday. What it means for my area is mild muggy conditions with continued chances of occasional thunderstorms. Rainfall in this exceptionally moist fall pattern is likely to be generous in all locations and excessive in others. The WPC (Weather Prediction Center) has this for total rainfall through next Friday. Widespread 2-4" amounts are expected and some local areas could see substantially more.

In fact, if the radar estimates are correct, some areas near and east of Peoria may have seen 8-10" in just the past 24 hours. With more to come this could turn into a serious flood situation, especially in parts of Illinois. I don't like the looks of it. The 18 hour rain estimates through 11:48 Friday evening. 

Two positives. Over the rest of the weekend the rains will become more scattered and there should be many dry hours with the excessive rains becoming less widespread and concentrated. They should pick up again Monday or Tuesday as the focused forcing again returns to my specific area. Finally, I do expect a break in the pattern next Wednesday night or Thursday when a short wave will flatten the 50 mb flow bringing cooler and drier conditions. See it here.

However, this may just be temporary trend as the MJO is forecast to remain in phase 1 into mid October. That might signal the persistent eastern ridge will rebuild allowing the mild wet weather to return after a few days reprieve. Until then, it's steady as she goes. Roll weather...TS

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