Saturday, June 20, 2009

Forecasting a heat wave

Believe it or not, there are a few interesting things that play into a forecast like the one we have right now - which calls for plenty of sun and mid 90s or higher through the middle of next week (at least). Being that I am a perfectionist, with a forecast like this, it's the little things that make it right.

The heat wave we're experiencing is due to a huge ridge of high pressure positioned from the surface all the way to the upper levels of the atmopshere. It is this high pressure that is steering the storms we had a week ago well to our north now. The best place to start with a forecast during conditions like this is persistence - what did it do yesterday and the day before and how will it be different today? The only differences are those "little things" - the strength and position of the ridge (stronger=hotter), the amount of moisture in the atmosphere (more moisture=more clouds and less ability to warm), the moisture near the surface, which affects the dewpoint (recent rains=moister ground=higher dewpoints and less ability to warm, but higher humidity), and wind (more wind=more mixing of the atmosphere and less ability to warm). So when deciding whether it will be 95 and 98, one has to take into account all of these factors.

As we head into early next week, many of these factors will be working to try and offset each other. While the ridge of high pressure will tend to move away and weaken slightly (promoting slightly cooler temps), without rain the ground is getting drier by the day, thus promoting lower dewpoints during peak heating, but causing the near-surface air to warm more freely. The result would be temperatures continuing to be nearly as hot, while heat index values lower slightly. Combine that with a few more clouds during the afternoons as the high moves slightly further west, and perhaps we'll see the Heat Advisories dropped by early next week.

Until then, the ridge holds, the sun beats down relentlessly, and the heat continues. Please take all necessary precautions against the heat - the longer it lasts, the more prone to heat exhaustion you will become. Be sure to check on the elderly and young children, as well as your pets, during this early season heat wave.

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