Rain Sunday brings brief relief, but no long-term escape from heat or drought
Much of the St. Louis area woke to an unfamiliar sound Sunday morning: rain. With drops falling from Hannibal to the Bootheel, the storm was the most widespread Missouri has seen in quite some time and a rare moment of relief in a summer plagued by historic drought and heat.
But forecasters at the National Weather Service here said it will not matter much in the big picture. With unfavorable weather patterns locked in for the foreseeable future and water deficits running deep, a few hours of rain is no game-changer.
"It's basically a drop in the bucket," meteorologist Jim Kramper said Sunday evening. "We're getting to the point now where we're enough below average where a small little thing like this isn't going to make a difference."
Missouri and Illinois have seen below-average precipitation and above-average temperatures since the beginning of the year. In a report this weekend, the National Weather Service said the first seven and a half months of 2012 have been the hottest on record in St. Louis, with an average temperature 62.4 degrees through July 25. Over the same period, the city has received almost five fewer inches of rainfall than is usual.
But things turned for the worse in early May, when the already-bad conditions began escalating to historic levels. Since then, the city has seen record-breaking temperatures and its rain totals depart even further from normal — more than eight inches less than an average year since May 1.
The conditions have paved the way for drought conditions to blossom in Missouri and much of the country, where conditions have not been much better. Prior to Sunday's rain, 99 percent of Missouri topsoil moisture was considered either short or very short. A report from the U.S. Drought Monitor last Thursday showed that the entire state of Missouri and most of Illinois are now experiencing at least sever drought conditions.
Precipitation totals varied across the area, with more rain falling in the southern portion of of St. Louis County and than at the airport, where St. Louis' official measurements are taken. Valley Park reported one inch of rain, while only nineteen hundredths of an inch fell at Lambert Field.
The national Weather Service estimates it would take 9-15 inches of rain for Missouri to return to near-normal conditions.
Welcome to Phoenix, Ariz.
St. Louis is accustomed to hot summers, just not dry ones. Temperatures routinely rise into the triple digits in June, July and August, and in most cases humidity soars with it, helping to maintain soil moisture levels and spur thunderstorms.
"What's been unusual this year has been how dry it's been. Typically we'll pop up to 100 degrees, but it's very humid out," Kramper said. "We haven't had that (this year). That's been the big change, the dryness."
Kramper, who has forecast in St. Louis since 1992, said this summer's weather is unlike any he's ever seen in St. Louis. In fact, he posited, conditions have been more like Phoenix, Ariz., than Eastern Missouri, and it's all due to a shift in the Jet stream.
"Instead of getting that straight shot of warm, humid air form the gulf (as in a normal year), we're getting it from the southwest, and that air is blowing over the some very dry land on its way," Kramper said.
Forecasters do not know exactly what has caused the jet stream to shift this year, but they do not expect it to change any time soon. Long range forecasts from the weather service's national office call for above-average temperatures through at least August.
While Sunday's rain reined in high temperature forecasted in the upper 90s, the storms totals were not enough to change the outlook, Kramper said.
Forecasted highs for the week ahead are expected to hang in the upper 90s or low triple digits, according to the National Weather Service. The next slight chance of precipitation will not come until next Saturday, the forecast says, when spotty thunderstorms are possible.
As for the possibility of a possible drought-busting hurricane, Kramper is not optimistic.
"If a hurricane should come up and affect us here, you're going to get maybe a day of good rain, but that's going to be it. That's a short-term thing that could create a little relief, but in terms of long-term relief, I wouldn't depend on that to do anything at all," he said.