Dan's Wild Wild Science Journal

Numerical weather prediction model forecast valid at 8 PM U.S. East Coast time Tuesday. This storm will spread tornadoes across the U.S. Midwest and near hurricane force winds on the Great Lakes.

When most folks think of tornadoes they imagine a warm spring afternoon suddenly turning stormy. More often than not this is true but there are glaring exceptions. Last night was one and Tuesday will be another.

A powerful storm system has been winding up  in the Plains. Last night a band of storms from Texas to Alabama brought tornadoes and large hail. Here in North Alabama, I was up for much of the night watching radar.

Winds going toward the radar right next to winds going away from the radar. This is what a tornado looks like on a Doppler radar. Image from Penn. State NEXRAD Archive. Click for larger version.

Large super-cell tornadoes are the easiest to spot and we had only one of those up in Tennessee. The ones you have to really watch for are the smaller more short lived twisters that are embedded in a squall line.

Around 4 AM CDT Monday morning, the Doppler radars indicated a strong circulation in the line over NE Alabama. The little town of Ider, near Fort Payne, was struck with a twister around 4:15.

The tornado looks to be an EF-1 or perhaps briefly an EF-2. An EF-1 tornado has winds of 32-50 meters per second (73-113 mph). That’s the equivalent of up to a category two hurricane on the Saffir-Simpson scale.

The Storm Prediction Center  (SPC) in Norman Oklahoma issues the tornado watches for all of the U.S. They’ve notified Meteorologists like myself and at the local NWS forecast offices that they believe there is a rare “high risk” of tornadoes over Indiana and Ohio on Tuesday. A high risk is rare anytime.

It’s exceedingly rare in autumn.

SPC does only one thing. Forecast severe weather. Meteorologists like myself give high credibility to their forecasts.

The Enhanced Fujita Scale- courtesy of the Storm Prediction Center (NOAA)

There’s been  an amazing technological revolution in forecasting over the last 30 years. In the 1970′s most tornado watches had no reports of tornadoes. Now it is rare for a watch not to verify.

When I was an undergrad meteorology student, I worked on a project at Okla. University in 1980 called SESAME. That stands for Severe Environmental Storms and Mesoscale Experiment. It was a fancy name for trying to correlate what severe storms were doing with what the new Doppler radars were indicating.

I remember being laughed at by people who called it a waste of money. It was anything but.

Doppler radars cover most of the nation now and make it possible for forecasters to give incredibly accurate warnings. An accuaracy I could not have imagined back in 1980.

At 4:15am Monday, the Doppler radar here in North Alabama showed a srong rotation and a tornado warning was issued. We had it on the air in less than 15 seconds from the time the NWS pushed the button. Unfortunately, most people in the little town of Ider were asleep.

The ones who has NOAA weather radios were awake because a loud alarm had gone off. If you live in area where severe weather is likely, you should have one. They only cost about 30$.

It might save your life one night.

You cannot imagine how frustrating it is to break into programming and give a warning while knowing that most people are asleep and will never hear it.

Until it’s too late that is.

Be safe,

Dan

Image form the Climate Prediction Center NOAA. Click to make BIG.

The strong and developing La Nina means that a decent long range forecast of the winter is possible. La Nina, and it’s cousin El Nino, tend to produce predictable weather patterns over the winter months.

Something to keep in mind. The forecast is for the average of the winter months. An above average temperature does not rule out some brief severe cold outbreaks. A drier than normal winter does not mean a certain region will not get a big snow storm.

Image from NOAA.

That said, here is what we can say with the La Nina. The South and Southeast USA will likely be warmer and drier than normal. The Tennessee and Ohio Valleys may see some heavy rains and floods.

Here in North Alabama we could go either way. We are right on the line. 65% of the time we have a milder than normal winter with a La Nina.

La Nina’s tend to bring cold and snowy winters to the NW corner of North America. If you live in Vancouver BC, watch out! It might be a winter to remember!

Kentucky and Ohio look likely to be cool but quite wet.

You can check out the maps but remember this is an average for the winter months!

I took this shot of Ann Posegate in Antarctica.

Ann Posegate, my travel partner to the Pole last January, has a fantastic piece in Weatherwise magazine this month.

It’s all about the difficulties of taking weather observations and forecasting in Antarctica.

Highly Recommended!

Click to read Ann's story.

I never look at an ob from down there without thinking of the people who are there..

Later,

Dan

Pressure pattern at around 18,000 feet (in colour bands) and at the surface (in black lines) for today. The the big high pressure ridge over the East is clearly visible.

For those of you in the Midwestern and Southern parts of America you are likely wondering what the heck happened to fall! Temperatures here in Huntsville in Alabama are running 15 degrees above normal in the afternoon!

This heat wave actually stretches from Oklahoma all the way into Illinois, into Virginia and deep into Old Dixie. It’s really the same heat wave that existed June through August and brought many cities the hottest summer on record.

Same Old Heat Wave

The only difference now is that the days are over an hour shorter and the sun is not as high in the sky. So instead of 106° we see 96°F. Instead of a dew point of 77° we are getting some drier air lingering behind the very weak cool fronts that have managed to break through the upper level ridge. The dew point her ein Huntsville  now is 59°F.

By early next week the pattern changes dramatically with a trough in the east. This means much cooler air and even some desperately needed rain. (Courtesy Unisys weather ECM Model.)

Good news is coming.

The long range numerical weather models are all signaling a pattern change to cooler weather starting this weekend. The strong upper level (heat) ridge will shift to the West and allow the Pacific NW to dry out and see some sun. The East will finally feel some real fall weather.

Right On cue

Click image to read the NRDC report on summer temp. records. Some amazing numbers here.

Meteorological Autumn began back on September first, but most people still use the equinox to denote fall. That occurs at 3:09 GMT Thursday morning. That’s 10:09 PM Wednesday evening (Central U.S. summer time.)

The NRDC has compiled some incredible statistics of the summer heat that are worth taking a look at. You cannot blame any one event or even a brutally hot summer on climate change, but this past summer had some very suspicious patterns to the heat. Patterns that are exactly what you would expect as a result of increasing greenhouse gases.

You can certainly rule out the sun. It has been unusually quiet (see the previous post). You can also rule out  El Nino, since the La Nina has been rapidly developing and this acts to cool the planet.

I enjoy the stories but the day to day forecast is worthless.

I always enjoy reading the stories in the Farmers Almanac. It’s been around for a LONG time and they have good basic astronomical info in it. Although you can get much more precise info from free programs like Stellarium.

About this time every year they release their forecast for the upcoming winter. TV stations everywhere gobble it up and do news stories on what the coming winter will be like.

Great free publicity!

Just to be clear here, the day to day forecasts are made up. They will not have any accuracy over that of a pure guess.

Some real science: An average of all moderate to strong La Nina's shows a milder than normal winter for much of the U.S. and Eastern Canada.

If you want to know what the winter will be like, the only think I can tell you is that with a moderate to strong La Nina brewing, the Southeast will likely have a drier and slightly milder than  normal winter. The odds of this are about 65%. That means there is a 35% chance it will be colder than normal here!

Other parts of the country will vary. See the graphics.

This kind of long range forecast is only possible because the La Nina pattern of colder than normal water in the Equatorial Pacific will cause a fairly predictable shift in the storm track over North America. The affects will actually be felt world wide.

Temperature anomalies for January during La Nina events. Images from NOAA. Click for full size image.

However, not every La Nina winter is the same. Each one is slightly different. Sometimes the La Nina pattern will hardly show up at all in some areas. Sometimes the expected warm areas are super warm.

The temperature anomalies in January for La Nina years shows that it’s quite warm in the Southeast U.S. most of the time but not always. The La Nina winters of 1971 and 1976 were slightly below normal over the Eastern U.S.

A scientific forecast would be for a good chance of having a mild winter in the Southeast. For those of you in Western Canada, a colder than normal winter seems like a good bet. Sometimes it is a super cold winter as well.

Just what you folks in Edmonton wanted to hear, isn’t it!

Later,
Dan