Updraft: April 26, 2011 Archive

Super Soaker: 1" to 2"+ rain, snow? Tornadoes swarm south

Posted at 9:22 AM on April 26, 2011 by Paul Huttner (1 Comments)
Filed under: Rainfall, Severe weather, Winter/spring 2011

Update 9:45 am:

1.22" rainfall (and counting) at the Huttner Weather lab in the west metro as of 9:45am.

***Orignal post 9:02am***

Talk about April showers...on steroids.

A major Midwest storm is wringing out steady moderate to heavy rainfall in Minnesota & western Wisconsin today.

The storm is producing some impressive rainfall totals. Rains have already topped 1 inch in southeast Minnesota, and will likely top 2"+ in some areas by early Wednesday.

To the south, another severe weather outbreak has left at least 7 dead in Arkansas overnight. Preliminary SPC reports indicate as many as 38 tornadoes swept across Texas, Arkansas & Tennessee Monday & Monday night.

The same area remains under a moderate to high risk for severe weather and tornadoes today according the latest convective outlook from SPC.

Here's the alarming verbiage form SPC today.

"The Storm Prediction Center is forecasting a major severe weather outbreak today and/or tonight. Details below."

The culprit:

A powerful spring storm is responsible for both our soggy Tuesday and the deadly severe outbreak in the Southern Plains.

The surface low is winding up in eastern Iowa this morning, and will stall over Wisconsin through tomorrow.

Potent surface low in eastern Iowa spreads rain north.
(Click all images to enlarge)

The slow motion storm will mean rain (and some snow) will linger over the Upper Midwest, with another day of severe weather along the trailing cold front in the south.

Soaking rains:

Rainfall totals are already impressive. Over an inch has fallen near Rochester, with a healthy .95" in the weather lab Deephaven rain gauge as of 8:20 am.

Here are some other rainfall totals as of 7 am this morning.

This NWS storm total rainfall estimate map may end up on the conservative side.

Wind too!

A strong steady wind is howling today as the storm winds up and wraps into Minnesota. Winds are gusting to over 30 mph in some areas.

Radar with wind gusts overlay.

Snow mixes in tonight & Wednesday?

It does appear the lowest mile of the atmosphere will be just cold enough to mix in some wet snowflakes late tonight and early Wednesday. The best chance for accumulating snow will be north & east of the metro. There could be a few inches of slush early Wednesday morning in Rice Lake, Hayward & Spooner up toward the Brule River.

Any snow that does mix in in the metro will not stick with temps above freezing.

Severe April 2011: All time USA tornado record?

The swarm of tornado outbreaks this month is simply freakish, off the charts crazy.

Remember these are preliminary numbers, but check out these stunning numbers so far in April from SPC.

559 (and counting daily) - Preliminary USA tornado count so far in April 2011.

267 - Previous April tornado record set in 1974 (Year of the "Super Outbreak.")

543 - All time monthly USA tornado record set in May 2003.

39 - tornado fatalities so far this month. (3 year running April average is 6.)

12 - "Killer tornadoes" so far this month. (Annual average is 22.)

38 - Additional tornado reports Monday.

Even with the expected "downward adjustment" from preliminary to final tornado numbers in April, it seems clear we have already smashed the previous April record of 267 tornadoes from the "Super Outbreak" year of 1974.

As we add more tornaodes today, it's possible we may make a run at the all time monthly record of 543 set in May 2003 when the final numbers are counted.

It is clear that this April will be one for the (tornado) record books.

The Big Question: Why?

There is consensus that tornadoes increase in the central plains in La Nina years like 2011.

Here's a post from the excellent 'Capital Weather Gang" blog.

"A study that examined the relationship between sea surface temperatures in the Pacific and the number of tornadoes in the U.S. found a weak correlation between La Nina and a greater number of tornadoes. Another study found tornadoes during La Niña years had longer than average track lengths, more violent tornadoes, and a good probability of having an outbreak of 40 or more tornadoes. Brooks points out that both the Palm Sunday tornado outbreak in 1965 and the Super Outbreak in 1974 occurred during La Nina years."

There is also evidence that though overall annual tornado numbers have increased dramatically since the 1950s. Some (much?) of that increase is due to increased and more accurate reporting of tornadoes.

Today's Doppler networks, high resolutions satellite, TV weather wars and caravans of nomadic storm chasers roaming the plains with digital video cameras and cell phones leave very few tornadoes undetected.

What we don't know is why some years like this year are so off the charts, out of control tornado spawning beasts.

I've had the pleasure if sharing interviews and dinner with folks like Greg Carbin at SPC and Howie Bluestein who are featured in the NY Times piece that came out Monday. It is because of dedicated people like Greg & Howie (and thousands of others) that we have success stories like Friday's EF-4 (possible EF-5?) tornado in St. Louis where NWS warnings gave a 22 minute lead time and nobody was seriously hurt or killed.

We did not get so lucky last night in Arkansas, where violent tornadoes and flash flood claimed multiple lives.

Here in Minnesota we can take away a couple of things. Last year's all time Minnesota tornado record (final tally of 113?) may not have been a freak occurrence. Our overall tornado numbers have nearly doubled since the 1950s from around 26 per year to nearly 50.

Also, severe weather season will move north over the next 4-6 weeks. Now is the time to be ready, so that if the St. Louis & Arkansas type tornadoes move north you'll be prepared.

PH

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