After posting the climatology of where the first moderate and high risks occur, I’ve received a couple of requests for additional graphics. One that was extremely easy to produce, and also one most frequently requested, is a climatology of moderate and high risks. Using the same Kernel Density Estimation technique described in the original post, I’ve calculated the number of moderate and high risk outlooks an area might expect during a given year, based on data from 1990 through 2008.

Edit to add: Between 1990 and 2008 there were 3454 moderate risks and 243 high risks issued.

Please note that each day consists of multiple outlooks and so it is possible for a grid point to receive multiple “hits” for being located in a Moderate or High risk outlook on the same day. In other words, if your location is located within 2 high risk outlooks, this does not guarantee that you will have two days of high risks. The location might simply be contained within a high risk from two separate outlooks issued for the same day.

For moderate risks, central Oklahoma appears to be the clear winner with nearly 30 moderate risks averaged per year. Increase probabilities extend both north and east from here.

As expected, the average number of high risks per years is considerably less than the average number of moderate risks. (In fact, I had to change the color scale!) Northeast Kansas, northern Missouri, and west-central Illinois are the most likely areas to experience a high risk in a given year with slightly more than 2 expected. A minor axis of increased probability extends southward from the eastern edges of this highest probability band, reaching portions of eastern Arkansas and far northern Mississippi.

Notice how in both of these climatologies, the maximum probabilities are centered in the central United States — east of the Rocky Mountains and west of the Appalachian Mountains. We’ll leave discussion as to why this is for another blog post.

A couple of things I will be watching this evening

• How the cold air interacts with the developing cyclone

The million dollar question (literally) is going to be how the cold air interacts with the developing cyclone. If the cold air plunges more south than southeast, then I would expect the ejecting surface low pressure (and associate low-to-mid-level lows) to move with a more northerly trajectory. If the cold air surges southeast, then the lows will eject with a more eastward component. This has huge implications for who will see the heaviest snows in Oklahoma and southwest Missouri.

The reason for watching how the cold air interacts with the cyclone is the result of how and where the low-level cyclones develop — which on the eastern edge of the “cold-dome”. I strongly believe the surface lows (and associated other lows) will ridge along the edge of the cold dome. Thus, if the eastern extent of the cold air has a more north-south orientation, this is how the surface low will move, placing central Oklahoma in a longer period of heavier precipitation. If the cold air orientation is more southwest to northeast, then expect the heaviest snow to shift east of central Oklahoma, as the surface development will be farther east.

• How the upper-level jet streams interact

Nearly all numerical weather prediction models are forecasting extreme precipitation amounts overnight and through the day tomorrow. It’s a bit perplexing considering the dry ambient environment. This dryness is most likely being overcome by the strong upper-level divergence associated with the ageostrophic response to a couple of a southern and northern jet streak. This strong upper-level divergence results in strong low-level convergence across portions of Oklahoma that will most likely rapidly transport moist air currently in place across eastern Texas, southern Arkansas, and Louisiana. When and where these upper-level jet streams do couple will play a major role in deciding where the heaviest precipitation bands are located.

• How does the precipitation shield evolve overnight

The last several runs of the operational GFS and NAM develop rapidly accumulating snows across eastern Oklahoma with strong low-level frontogenetic forcing. This is in spite of a +0.5C to +1.5C warm nose aloft. This would seem to favor more sleet than snow. However, if lift is strong enough, this might quickly be overcome resulting in 3-4″ per hour snow rates that are currently forecast. Farther west, the 12 and 18 UTC NAM are developing a more classic deformation zone across a large part of central Oklahoma during the late morning and early afternoon hours tomorrow. This deformation zone is more typical of substantial Oklahoma snow falls than the strong, low-level frontogenetic forcing described previously. This large deformation zone is the reason why the NAM has a large area of 6-10″ snow accumulations to the west of the 12-18″+ forecast across eastern Oklahoma.

Also, if a large squall line develops across central Texas and races east too quickly, the squall line might use up a lot of the moisture that is poised to be drawn northward into this cyclone. This would decrease snow totals across portions of Oklahoma, Kansas, and southwest Missouri.

• The evolution of the temperature vertical temperature profile

I hinted at this in a couple of the previous bullets, but how the vertical temperature profile evolves will be crucial in determining snowfall amounts. If a strong warm-conveyor belt does develop overnight, warm air might hang on longer than forecast across portions of Oklahoma. This might lead to an extended period of sleet which would cut down on snowfall totals considerably. However, 1-2″ of sleet, coupled with 2-4″ of snow would be just as bad, if not worse, than a pure 8-12″ of snow.

This week’s “Question of the Week” comes from Trevor Gramling and Ryan Vaughan.

• Climatologically, where is the most likely location to experience the first Storm Prediction Center Moderate Risk of a given year?
• What about High Risk?

Since I do not know the answer ahead of time, this may end up being a two week “Question of the Week” as I write the code to create the answers…

This ought to be fun!

The answers to this week’s “Question of the Week” might surprise some of you. But first, here are the graphs that answer these questions

Here is a choropleth map of January tornadoes by state:

Here is a bar graph showing January tornado counts by state, ordered from most to least:

Keeping the states in descending order of most January tornadoes to fewest tornadoes, here is a bar graph depicting the number of injures by state:

And, once again, keeping the states in descending order of most January tornadoes to fewest tornadoes, here is a bar graph depicting the number of fatalities by state:

And even though this plot is a bit crowded, here is a bar chart that combines the three previous charts into one:

Could you figure out the answers? Well, if not, here they are:

• Which state(s) had the most January tornadoes? Florida (151)

• Which state(s) had the most January tornado injuries? Mississippi (580)

• Which state(s) had the most January tornado fatalities? Mississippi (42)

• Which state(s) had the most injuries per tornado? Deleware (7 per tornado)

• Which state(s) had the most fatalities per tornado? Oklahoma (0.62 per tornado)

And here are the raw numbers,

The answer to last week’s “Question of the Week” sparked a lot of posts on Twitter and at least one question posed in the comments. These comments and questions got me thinking about more ways to dissect the tornado database. Thus, I thought for this week’s installment of QOTW, I would continue with the same theme.

After a small spike from the mid-1960s through the mid-1970s, injuries from January tornadoes decreased slightly and has held relatively steady around 20-25 per year. The exception to this was 1999, which holds the record for most number of January tornadoes, including the largest January tornado outbreak on record. Fatalities appear to follow a similar trend as injuries, albeit with much lower numbers. In total

• January Injuries: 2455 (40.9 per year)
• January Fatalities: 138 (2.3 per year)

We can break down January tornado casualties even more and examine them by F/EF-Scale ratings.

As one might expect, a general increase in casualties is found as F/EF-Scale rating increases. This leads me to this week’s questions.

Above is an image depicting the number of January tornadoes between 1950 and 2009 broken down by county. Using the above image as a guide, between 1950 and 2009:

1. Which state(s) had the most January tornadoes?
2. Which state(s) had the most January tornado injuries?
3. Which state(s) had the most January tornado fatalities?
4. Which state(s) had the most injuries per tornado?
5. Which state(s) had the most fatalities per tornado?

(Hint: A tornado that crosses a county boundary is counted in both counties. Thus, one cannot sum the number of tornadoes per county in a state to find the number of tornadoes per state.)