The "Dog Days" of summer have been upon us. Generally it means the hottest days of the season when it is hot and stagnant. Thunderstorms bring little relief from the heat and steam.
The term has a history dating back to 1552. The Book of Common Prayer describes the period as being from July 6 to August 17. Despite suspect temperature readings at RDU airport which I believe include today's statewide high of 95, July was near neutral in terms of long term average temperature.
Below is a map showing 200 mb velocity potentials. The easy way to understand is to know that convection and low pressure is favored in the green while brown indicates dry and heat laden high pressure. A supermassive upper level ridge is dominating from the southern Indian Ocean, through Africa, and well into the Atlantic. The ridge serves 2 purposes, to act as a dam which prevents tropical convection from the west from moving to the Atlantic. The secondary function is to keep the intra-tropical convergence zone suppressed and to the south. As a result the East Pacific has been the active tropical storm region this year.
200 mb potential velocities provided by the Climate Prediction Center
There are changes afoot which support the idea that by mid-August the 'Dog Days' will transition to a new and likely tropically active weather pattern. One of the several measures used to define the flow in the atmosphere is the Southern Oscillation Index (SOI). It's recent return into negative territory indicates that the atmosphere is getting some added spin from the tropics. The question facing climate experts and meterologists is whether the boost will be enough to push upper air regions which are more supportive of stormy weather (green) into the west Atlantic.
Therefore, the surrent stretch of hot, humid, thunderstormy weather has just under 2 weeks left. It is especially probable if a tropical storm manages to run the US east coast that we will see an early autumn outbreak of crisp cool air that ends the month.
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