Still stuck in a fairly quiet pattern despite daily tornado threats… that’s what a stubborn cut-off low will get you on most occasions. The start of next week has the lowest potential for tornadoes, but things pick up again briefly around the middle of next week.

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Thursday

Central and southern High Plains, Texas, southern Louisiana — TORNADO RANGE: 1-4 — CONFIDENCE: Normal
Expected Tornado Hotspot: Central High Plains
Pros: Good directional shear, decent/good speed shear, low to moderate instability, good upper-level forcing in the High Plains.
Cons: Morning and afternoon clouds and showers contaminating the atmosphere, potential high LCL issues in the southern High Plains, no notable upper-level forcing in the southern parts of the risk area.

Friday

Central and southern Plains, Louisiana — TORNADO RANGE: 1-4 — CONFIDENCE: Normal
Expected Tornado Hotspot: West-central Plains, central Texas
Pros: Good directional shear, low to moderate instability, good upper-level forcing in the central Plains.
Cons: Potential veer-back-veer wind profiles in the central Plains, weak speed shear in the eastern parts of the risk area, no notable upper-level forcing in the southern parts of the risk area.

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An EF-4 churns near Rozel, Kansas on May 18, 2013. (Jeremy Perez via Flickr)

An EF4 tornado churns near Rozel, Kansas on May 18, 2013. (Jeremy Perez via Flickr)

It’s the age of the wedge tornado. At least in reports.

The continued popularization of storm chasing, and weather as a whole, has brought certain geek words out front in recent times. Often, they are incorrectly used.

True wedge tornadoes — appearing at least as wide as they are tall — make up only a fraction of all types and shapes. Despite the seeming appeal to “run to wedge,” other terminology is largely intuitive and it helps everyone be better informed.

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Abridged version because I was chasing some cherry blossoms earlier today. Cut-off low in the back half of the week offers low forecast confidence in both day-to-day tornado potential (likely to be low each day), and in where the exact tornado threat areas are.

1-3 Day
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Monday

Texas — TORNADO RANGE: 0-2 — CONFIDENCE: High
Expected Tornado Hotspot: None

Tuesday

Western Gulf Coast — TORNADO RANGE: 0-2 — CONFIDENCE: High
Expected Tornado Hotspot: Southern Texas

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Tornado highlights covering the week of April 5-April 11, and a brief look ahead.

An EF4 tornado near Rochelle, Illinois on April 9, 2015. (Jodi Mair via Flickr)

An EF4 tornado near Rochelle, Illinois on April 9, 2015. (Jodi Mair via Flickr)

As anticipated, last week was the most active of the season so far when it comes to severe weather. While parts of the severe weather episode did not perform as expected, others did and then some.

Among the barrage of about two dozen tornadoes April 8-9, the first violent twister of the 2015 season touched down to the northwest of Chicago on April 9, killing 2.

The upcoming week shouldn’t be a total snoozer, but it seems rather unlikely to produce anything quite on the level of events we just went through.

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Famous picture of F4 tornado with two distinct funnels destroying the Midway Trailer Park near Dunlap, Indiana. Photo by Paul Huffman. (NWS Indianapolis, Indiana)

Famous picture of F4 tornado with two distinct funnels destroying the Midway Trailer Park near Dunlap, Indiana. Photo by Paul Huffman. (NWS Indianapolis, Indiana)

On April 11, 1965, and over a time span of approximately 12 hours, one of the most infamous tornado events in United States history took place across the Southern Great Lakes region. Commonly known as the Palm Sunday Tornado Outbreak (more precisely, the second Palm Sunday Tornado Outbreak, following one in 1920 and preceding another in 1994), numerous fast-moving tornadoes were unleashed upon the states of Iowa, Illinois, Wisconsin, Indiana, Michigan, and Ohio.

The twisters claimed over 260 lives, injuring thousands of others and causing hundreds of millions of dollars in damages. It was the worst tornado outbreak in Indiana’s history with nearly 140 killed in the state alone. In modern tornado history, this ranks second to the Super Outbreak of April 3-4, 1974 in terms of violent tornado count in a single North American outbreak, with 17 F4+ tornadoes.

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Spring is alive with the sights and sounds of tornadoes! There aren’t a lot of them, but the day-to-day numbers will start to add up as we head into the middle of the month.

1-3 Day
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Thursday

Midwest, central Miss. Valley — TORNADO RANGE: 3-8 — CONFIDENCE: Normal
Expected Tornado Hotspot: West-central Illinois
Pros: Good speed shear, decent low-level directional shear, moderate instability, good upper-level forcing.
Cons: Fairly unidirectional flow aloft, storms lining out along the cold front, pre-frontal cloud cover and showers/storms stabilizing the atmosphere.

Friday

Southeastern Mid-Atlantic, northeastern North Carolina — TORNADO RANGE: 0-1 — CONFIDENCE: High
Expected Tornado Hotspot: None
Pros: Good speed shear, low to moderate instability, possible local enhancement of backing winds at the surface.
Cons: Poor directional shear, storms lining out along the cold front.

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It’s spring and we are back with bi-weekly forecasts for the 2015 tornado season! I’ll be keeping to the same format as last year, running new 7-day forecasts every Monday and Thursday until things get quiet again. The only exception will be during our annual chasecation, which is set for late May into early June this year.

Time to throw out the first pitch…

1-3 Day
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Monday

No tornadoes expected.

Tuesday

California — TORNADO RANGE: 0-1 — CONFIDENCE: High
Expected Tornado Hotspot: None
Pros: Good upper-level forcing, decent directional shear.
Cons: Low instability, hints of a veer-back-veer wind profile, weak mid-level speed shear.

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Tornado highlights covering the week of March 29-April 4, and a brief look ahead.

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A trio of tornado warned supercells in Kansas on April 2.

Here we go again. The historical peak of the tornado year has arrived, and it usually runs through June. Given that the period often has regular storminess, Tornado Digest returns for its weekly run over the next few months.

Severe weather has already awakened. Despite the exceptionally quiet start to the year across the country, both of the last two weeks have featured systems creating big thunderstorms and dropping tornadoes.

The outlook ahead appears to indicate the calendar is finally taking over, and tornado numbers are likely to be on the rise. A multi-day run of severe weather, including the risk for tornadoes, is increasingly probable during the week ahead.

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These maps break down April tornadoes based on where they begin.

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Cumulative monthly tornado counts (since 1950) more than double moving from March to April. It’s the classical beginning of the three-month peak of the year.

Once we get into April, the migration of tornado zones away from the cold-season home near the Gulf of Mexico is increasingly apparent.The month is known as one with eyes on big-city targets from the southern Plains to the Southeast and up into the Midwest and lower lakes.

Where tornadoes form: October, November, December, January, February, March

Depending on the averaging period and length, April typically delivers about 150 to 170 tornadoes across the country.

The month is well known for extremely violent and devastating tornado episodes, partly due to dynamic early-season jet stream configurations and also because the month tends to focus its fury on more densely populated areas compared to May and June.

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2015-map

April 7 update: As mentioned in the original text, there are perils to writing about current tornado numbers too quickly. At least 4 additional tornado reports came in late to SPC after the article was completed. They were all from March 31 in Arkansas, the southeast part of the state on top of the warnings shown in the map above. This brings the March preliminary to 13 per NOAA accounting. Please consider that change when looking at the stats below. I generally bounded them with the expectation that numbers could increase to about this level, so the place in history can still be well judged by reading!

Original post from April 1 at 9:10 a.m. EDT: March 2015 will be remembered for being as quiet as it gets for tornadoes. Twisters slept till late in the month as cold air dominated the eastern two thirds of the country. Despite the low numbers, one was fatal on March 25.

The month just ended was only part of a historically timid start to the 2015 tornado year. Seemingly the continuation of a trend in recent years?

While we expect the March-May period to finish below average for tornadoes, it appears an uptick in activity should be along as we get into April. Spring will of course take hold eventually.

In the meantime, let’s take a quick look at where we are and how it compares…

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