Late June-August signals mixed 

Posted: 7:22 pm Sunday, June 4th, 2017

By Kirk Mellish

Models and analog methods are hotter and drier for mid to late June through August.

They depict the jet stream storm track retreating toward if not into Canada while high pressure ridging aloft expands from California, Mexico and the Desert SW into much of Dixie.

A standard method in synoptic meteorology used to indicate summer-level heat trends even without looking at model temperature output, is to look for a jump north by the 588dcm contour of constant height at 500MB, and/or the northward lurch of the 576dcm measure of 1000-500mb thickness value.

500mb height levels in summer of 582 or less are common, but 588 values are often hot and 591 values very hot. What is more when 500mb values grow above 588 thunderstorms become rare.

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Although they both at least hint at some weakness and/or NW flow opportunities in the SE region that may allow enough scattered thundershowers to keep heat and drought from coming on too strong or too long.

The weak Pacific Ocean signals tilt toward neutral to weak warm or positive in the ENSO regions. Still clearly borderline.

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The trend toward a possible “Modoki” style El Nino is visible with the cooler than normal waters closer to South America (Eastern Tropical Pacific) and the warmer anomalies further west.

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This has summer implications at odds with Numerical Weather Prediction output and analogs.

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We will have to continue to monitor trends to see if the El Nino Modoki continues to come on or backs off. It’s also important to see if El Nino weather signals from the SOI and MJO confirm or conflict with an El Nino summer. If they fail to fall in line then a hotter and drier pattern will be more likely.

Follow me on Twitter @MellishMeterWSB

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