Hot and dry pattern to reverse 

Posted: 7:19 am Friday, July 27th, 2018

By Kirk Mellish

We are in a new heat wave, something that has been few and far between this summer.

The American Meteorological Society Glossary of Meteorology defines a heat wave by convention as at least 3 days of at least 90F for a daytime high:

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Many parts of the metro area have been 90 or so since the 24th and we have at least three more days to go. But overnight low temperatures are running a bit below average thanks to the dip in the humidity. We are between 😍 and 😐 for the next couple days.

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While a stray or “rogue” late day thunderstorm can’t be ruled out FRIDAY THROUGH SUNDAY most of us will stay dry with a decent amount of sunshine each day and modest humidity.

Beat the Heat, check the back seat for kids and pets:

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However, after Sunday as we’ve seen so often this summer the pattern changes back to one with more clouds, more humidity, lower temperatures and higher than normal odds of a shower or storm.

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See below how the pattern aloft changes as the jet stream goes from a mostly dry West/Northwest flow to a moist flow from the Southwest. Changing the source of our air mass from drier continental air to muggy air from the Gulf of Mexico:

CURRENT JET STREAM FLOW:

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JET STREAM FLOW NEXT WEEK:

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Rain goes from below normal the next 3 days to above-normal most days next week and beyond.

The UKMET model agrees with the ensembles from the GFS, ECMWF, and Canadian GEM:

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3-DAY AVERAGE RAINFALL ESTIMATE:

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DAY 4-5 AVERAGE RAINFALL ESTIMATE:

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Surface frontal systems and low pressure become more active as a result of the synoptic flow change in the jet stream:

5dayfcst_wbg_conus

Follow me on Twitter @MellishMeterWSB.

 

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