Mid-summer review

Back on June 3rd I produced a post titled “Summer weather outlook for Kentucky” and promised to provide periodic updates throughout the summer. Since meteorological summer is officially half over (June-August), consider this the mid-summer review. I will break down each of my original predictions and summarize with my expectations for the rest of the summer.

1) A developing La Nina will keep the jet stream and storm systems to the north along the Canadian border

While dynamical models still predict the evolution of a La Nina over the next 1-3 months, statistical models and observations predict a slower evolution and possibly the continuance of neutral ENSO conditions.

2) Quasi-stationary heat ridges supported by severe droughts over the Southwest and Southeast will weaken any storm that does move southward

This has been true for the most part. Aside from the last week of June, when a cold front interacted with the upper level energy over the southern plains to produce several inches of rain over west-central KY, most of the Mid-South has been very dry. Several cold fronts that the models predicted would produce widespread 0.50 – 1.0 inches of rain instead produced a few sprinkles or at least very hit or miss rainfall. Interestingly, the synoptic positioning of the two Southwest and Southeast heat ridges have allowed the cut-off upper level energy over TX, OK, and KS to basically saturate those states with record summer rainfall (think of the low as a small counterclockwise gear spinning between two large clockwise gears).

3) Those same ridges could act as a saving grace by steering the remnants of an active Atlantic hurricane season into the mid-south

Too early to tell since hurricane season has not really started yet.

What to expect: Based on these three indicators, I think the summer of 2007 could be the warmest since 1999 and I think drought conditions will worsen across the Commonwealth. I

Well, so far it looks like I’m half right. Drought conditions have worsened across the Commonwealth and most notably in Tennessee as seen here. However, the very wet and stormy pattern over the southern plains has kept the hot and dry air masses that originate over the desert southwest from impacting our area. Temperatures over the first half of summer have ranged from 0.8 (Bowling Green) to 2.0 (Louisville and Nashville) degrees above normal. It has been hot, but not extraordinarily so. The hottest day thus far across the Mid-South has been 95 degrees but I do expect that there will be several 95-99 degree days over the next six weeks. Whether or not we reach 100 or not is debatable.

2nd half of summer outlook: The Climate Prediction Center believes that drought conditions will persist across the Mid-South through at least the rest of the summer. Synoptically, there is nothing to change for my summer forecast, so I will continue to predict warm and dry conditions for the remainder of the summer.

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