Updraft: May 22, 2008 Archive

Timing is everything

Posted at 7:00 AM on May 22, 2008 by Paul Huttner

It looks like we just may salvage a pretty great Memorial Day Weekend if everything works out right.

Back when I was getting started in meteorology, one "old school" technique we used was to time the "short waves" in the jet stream that produce precipitation. These mini waves are embedded in the jet stream, and produce lift and spin in the atmosphere ahead of them, and generate bands of showers and thunderstorms in summer.

Craig Edwards and I sometimes chat about these old school techniques with fond memories. Today's forecast models break down every conceivable parameter and display them in 6 hour increments. Often that's of incredible value, but sometimes the old school techniques still carry the day, and the forecast. Keep it simple, as they say.

The main short wave this weekend appears to be headed for Minnesota Saturday night. If it comes through then, we would see our best chance of rain overnight Saturday night into Sunday morning. If that happens, it will mean more sunshine during the day Saturday and Sunday, and warmer temperatures.

Potential weekend precip timing

If the timing is off by 6 to 12 hours, we may see storms during the day, which will keep our temperatures down, so the passage of this wave is critical to the kind of weather you will experience this weekend.

Our spring has been cool and wet, but has also featured relatively low dew points. We have not seen big incursions of moisture rich Gulf of Mexico air moving north. That may change this weekend, and we may see and feel our first 60 degree dew point in parts of Minnesota Sunday.

Overall I still expect a pretty good weekend, with just a few hours of showers and thunderstorms. Let's hope we can get the timing right, and bring most of them through at night!

PH

Start your engines

Posted at 2:12 PM on May 22, 2008 by Craig Edwards

For the fifteen years I worked at Indianapolis, the Thursday before Memorial weekend presented the most important opportunity of the year to establish credibility with the weather forecast.

As Paul Huttner noted earlier, not only is it about the chances of showers and thunderstorms, but it is about the timing. Back in the Circle city Office we focused on the weather window; the six hours of dry weather required for the pre-race ceremonies and the greatest spectacle in racing, the Indianapolis 500. If it rained prior to 7 am and after 3 pm, dampness was not an issue. However the hundreds of thousands of spectators favored dry weather all day.

I remember numerous times providing a detailed forecast by phone to the media, friends and neighbors on the morning of the race when rain was either already falling or in the forecast. Anxiety mounted if multiple yellow flags slowed the race, favoring a better chance of afternoon thunderstorms when precious minutes added to the checkered flag.

Looks like no problem for the Indy 500 this year. Forecast for Indianapolis

It really is about the timing. If we predict showers and thunderstorms for your Saturday night and Sunday and the rain falls from midnight to 6am on Sunday, it has a much lower impact on your holiday festivities.
Brainerd Lake Area Forecast

Remember, we are just the messengers. For this holiday weekend, let's try to emphasis the positive. It still looks like a run at 80 degrees is possible on Sunday.

Play it safe with the chilly lake temperatures; not nearly warm enough for taking a plunge.
CE