Friday, April 30, 2010

Drill Baby Drill !!

Nice to see the rain on Friday, a chance to brush cobwebs off of little-used umbrellas, tinker with windshield wipers - complain about the puddles (and hideous commute times). Since March 1 you can count the number of rainy days on one hand - lukewarm sun has been the rule, moderate drought is affecting roughly a third of the state at last report. Yes, the rain was welcome, in spite of washed-out ball games and some really bad hairdo's - but it wasn't nearly enough to pull us out of our deepening dry rut.

I picked up about .39" of rain in my gauge out in Tonka Bay, more than the average across the metro area. Officially MSP received only .07" at Richfield, .13" down the river in St. Paul. That's the nature of spring and summer showers: fickle, sometimes bizarre rainfall patterns. One community gets inundated by 1-2" of rain in a few hours, just 5 miles down the road the sun is out and people are griping about a "lack of rain." During the late fall, winter and early spring months precipitation is more "stratiform", steadier, more widespread rain and snow. This time of year precipitation is "convective", showery, hit-or-miss. All we can do is give probabilities, recite a litany of statistics - "isolated, scattered, numerous" showers, but in spite of all the supercomputer technology and Doppler-speak, we still can't predict EXACTLY which communities will see the most rain. This is one of the real frontiers for meteorology - the 7 Day will always be something of a mystery, but within a few years I think we will be able to make a prediction along the lines of "T-storms in the north metro after 7 pm, no storms in the southern suburbs, the best chance of an isolated tornado is within 10 miles of Mankato around 5:30 pm, plus or minus 60 minutes." That is entirely within the realm of possibility as we improve the models, the data going into the models (more frequent weather balloon launches, tighter grids of "mesoscale" data uploading real-time information). We sometimes refer to this as "Nowcasting", fine-tuning the short-range, 4-12 hour forecast. The average lead time for a tornado warning has increased from 6 to 12 minutes in the last 20 years (meaning the average amount of time between issuing a warning and the onset of tornadic winds is close to 12 minutes, nationwide). There's no reason why that advance lead-time can't increase to 20, even 25 minutes. Fewer Americans are dying because hurricane TRACK predictions are far better than they were a generation ago (landfall predictions are usually +/- 80 miles, about 24 hours out). Forecasting the INTENSITY of hurricanes is still fraught with peril - much tougher for the computer models to handle, but we are making steady progress - fewer Americans than ever are dying from severe weather, in spite of an apparent uptick in tornadoes, floods and hurricanes.

April Recap. What a month - here are the details, day-by-day, if you're feeling nostalgic (or curious). Temperatures for the month ran 8.3 F warmer than average, pretty significant statistically. The metro area had only 8 days with more than .01" of rain. Click here to see the April data from the MN State Climatology Office.

24-Hour Rainfall. Some counties in southeastern Minnesota were soaked by .75 to 1" of rain, nearly 1.5" near Austin and Albert Lea. Most of the MSP metro area saw less than .20" of rain from the latest cool frontal passage. Click here to see 24 hour rainfall for the USA, click on Minnesota to zoom in and get local information.

Friday Almanac. The variation in rainfall around the state - even around the metro area - was pretty significant, from .91" at International Falls to .07" at MSP Airport, .20" in St. Cloud and .48" in Redwood Falls. For a longer list of towns and updated rainfall tallies click here.

Temporary Plan B Saturday PM? This is the "NAM" model output for 3 pm today, a good chance of instability pop-up showers north of St. Cloud and Lake Mille Lacs. NOT an all-day rain, but you may need to spend a little indoor-time between 11 am and 4 pm.

Soggy Kentucky Derby? The same cold front that spawned tornadoes near Little Rock and St. Louis Friday evening may squeeze out heavy rain on today's Kentucky Derby (put your money on the "mudders" - could be a muddy mess at the track). As much as 6-7" of rain is predicted from this slow-moving frontal boundary across the Tennessee Valley over the next 5 days. A southward dip in the jet stream (storm track) will keep Minnesota a bit cooler than recent week - we may actually have to muddle through some 50-degree highs next week. The indignity!

The violent front responsible for major tornadoes near downtown Little Rock, Arkansas and St. Louis, Missouri is pushing east, but lingering moisture behind the front (coupled with a pool of unusually cold air floating a few miles above Minnesota) will spark instability clouds and showers during the midday and afternoon hours Saturday, the chance of 1-2 hours of rain increasing the farther north you drive up I-35. Expect some morning sun, gusty southwest winds (15-30 mph) with clouds increasing as the day goes on. MOST of your Saturday will be dry, even in St. Cloud and Brainerd, but with the strong winds and ragged afternoon clouds it won't be the best day for the lake or beach.

Sunday looks nicer, a little less wind (blowing from the west at 10-20 mph) and sunshine much of the day, enough for highs in the low to mid 60s. Not perfect, but a big step in the right direction. An isolated shower can't be entirely ruled out, but any Sunday showers should affect less than 5% of the state (compared to 30-40% of Minnesota from Saturday afternoon showers/sprinkles).

Overall we seem to be sliding into a cooler, cloudier pattern, a few days next week with highs holding in the 50s (around midweek). I don't see anything severe, no wintry relapses in sight - still pretty quiet out there, all things considered. A "57 F. high next Thursday" is a cool front we all can live with.

Amazing "Couplet". Doppler Radar radial velocity from 8:45 pm Friday evening, showing a violently rotating thunderstorm just east of Little Rock, Arkansas. The bright red-shaded area represents air moving away from the NWS radar site at 70-90 mph, the bright green highlights air moving TOWARDS the radar site at similar speeds, inferring a potential tornado where the two colors meet. Sure enough a large tornado was on the ground - damage reports still coming in from the Little Rock area.

Tornado Signature. Another city, another couplet, evidence of severe rotating southwest of St. Louis, last night around 9 pm. There were reports of another large, potentially violent tornado tracking across the southern suburbs of the St. Louis metropolitan area. This is where Doppler really shines, on the large, long-lasting, long-track EF2+ tornadoes. It's the small, brief twisters, EF0 and EF1 that often get lost in the sauce, much harder to detect in advance with as much lead-time.

Drill Baby Drill! Here are a few of the benefits of offshore drilling - oil slicks so big they show up from outer space. The magnitude of the disaster is starting to set in (oil is still flowing into the Gulf of Mexico from the damaged Deepwater Horizon rig - 5,000 feet below the surface of the Gulf). Officials are trying to burn the oil off the surface of the water, but the ecological impact will be enormous, possibly rivaling the Exxon Valdez spill off the coast of Alaska 20 years ago. We won't know the full extent of the damage for weeks to come, but the impact on coastal Louisiana, Mississippi, Alabama, even Texas, could run into the hundreds of millions of dollars. An update on this slow-motion ecological catastrophe is here.

Political Implications. The BP oil spill is forcing the Obama White House to rethink plans to expand offshore drilling, an essential part of a climate change bill coming up for a vote in Congress. Reuters has a look at how the spill may impact the political sausage-making going on in Washington D.C. What a mess...

Onshore Winds. Here is the NAM prediction for 10 meter winds at 6 pm Saturday - pushing the oil slick onto the Gulf coast, tides running 2-4 feet above normal high tide. There's a very real possibility of low-land flooding along the Louisiana and Mississippi coastline, coastal areas inundated under breaking waves of oil and sludge. A flood of oil - hard to even comprehend how unpleasant and damaging the next few days will be along the Gulf coast.

Paul's Conservation MN Outlook for the Twin Cities and all of Minnesota

Today: Sunny start, then increasing clouds, windy - slight chance of a PM shower (most of the da should be dry). Winds: SW 15-25+ High: 61

Saturday night: Partial clearing. Low: 46

Sunday: More sun, less wind - a drier day statewide. High: 63

Monday: More clouds than sun. High: near 60

Tuesday: Mostly cloudy, milder - a few showers possible. High: 65

Wednesday: Becoming partly sunny, windy and cooler. High: 59

Thursday: Mix of clouds and some sun, coolest day in sight. High: 57

Friday: Mostly cloudy, a bit milder. High: near 60

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