Tuesday, July 16, 2013

Does Rainfall Effect High Temperatures?

90 degree heat is here and its been a long time coming. After a rainy/cooler than normal spring along with the more recent 8-10 inch rainfalls over the last two weeks, this round of warmth is a welcome break. I don't want to lessen the significance of the flooding last week since many areas are still cleaning up. But the heavy rains and subsequent saturated ground is a welcome sign as the daytime highs soar north of 90.

FOX8 Front yard on July 13th -- Lush Green Grass!

I talked about this earlier in the spring and summer:  WET GROUND SUPPRESSES HIGH TEMPERATURES!  Large scale factors like the heat dome overhead can override this effect somewhat depending on how large in extent the wet ground goes.

Here is a map of the rainfall numbers compared to normal for the first 14 days of July.

Here is the location of this VERY STRONG AND DEEP heat dome. The center is right over Ohio. The 600dm (decameters--height of the high pressure dome) is a rarity over Ohio. In fact, last summer, I don't recall the heat domes over ANY part of the US pushing above 600.

When you superimpose the heat dome location over the rainfall map, you see that the center is over the saturated ground over Ohio and Kentucky. High temperatures on Monday only hit 91.

Last year, the heat dome was well west of Ohio yet daytime highs in July reached 98 TWICE. The ground in the first weeks of July was incredibly dry!
Historically, 42% of our 90 degree days occur in July.

We had many more days above 95 in the 1940s and 1950s than we've had since.

So will the wet ground override the effects of the strong OHIO CENTERED heat dome over the next few days keeping temperatures in the 90 to 93 degree range versus what happened last year at this time? 

I say YES.  Check back on Friday as the heat retreats west.

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