© 2019 Terry Swails

A COOL WET START TO SUMMER...

May 3, 2019

I was looking through the new EURO EPS Weeklies and I have to tell you I was impressed by two things. One, the extent of the wet weather the next 6 weeks. And two, the amount of cool air that remains in the pattern. I suspect the primary reason for the below normal temperatures is the rain and how it impacts the environment it falls into. There's a proven correlation to wet soils and cool weather. In fact, there is even a long term climate model based on the relationship between soil moisture, evaporation, and temperatures. This model is called CAS (constructed analog soil moisture). It's output is based on on the GFS forecasts of precipitation, moisture, and existing soil moisture out to 2 weeks

 

The latest long CAS forecast for May, June, and July shows strong chances for above normal precipitation and below normal temperatures over most of the nation's heartland.

Below you can see the existing soil moisture conditions and those projected at the end of July. No shortage of rain and no projections of drought. Thus, the idea of cooler than normal temperatures through summer is established.

If you buy this link to rainfall (which I think has plenty of merit) the EURO weeklies also make sense. Just look at the widespread heavy rain it's projecting the next 46 days. 

 

The associated precipitation anomalies.

The EPS control is even more aggressive than the EPS mean over my area with some 6 week totals of up to 15"+ in northern Iowa. Needless to say, excessive amounts like this are bound to cause problems for farmers, rivers, and streams if this forecast comes close to verifying. It is a red flag and very concerning due to the large areas impacted.

Moving on to temperatures, based on the high volume of rain, vast amounts of soil moisture, and limited evaporation that temperatures would be below normal, especially highs. The EPS mean temperature departure certainly shows that through June 3rd.

The U.S. climate model the CFSv2 is also on the cool and wet bandwagon. Here's the next 30 days of temperature departures in 10 day increments.

 

Days 0-10

Days 10-20 

Days 20-30 

Here's the associated 30 day precipitation forecast on the CFSv2

Do you see where this is going? Wet weather and cool temperatures go hand in hand. End of story.

 

I like to end on a positive note and that is the fact that Saturday and Sunday look warmer. Highs should reach the upper 60s north to low 70s south, a welcome change. It seems as though dry weather should last through most of the day Sunday when the pattern turns active once again. I'm still expecting heavy precipitation to return to the central Midwest early next week. More on how that's shaping up in my next post. Happy Friday to you and as always, roll weather...TS

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