Tornado Outbreak Next Week?

This storm season has been underwhelming, to say the least.  Only 153 tornadoes have been reported this year, which is a little more than half of the normal value (Image 1).

Image 1: Monthly trend in tornado reports.  Source: The Storm Prediction Center.

Image 1: Monthly trend in tornado reports. Source: The Storm Prediction Center.

What gives?  Well, during the month of March, multiple cold frontal passages removed the rich, “high octane” moisture of the tropics (necessary for explosive supercell thunderstorm development) far from the Plains.  Accordingly, storm chasers lamented, with some openly wondering whether or not to stick a fork into 2013.   Thus, when a big upper trough appeared in the West in the long-range models (Image 2), chasers were thrown into a frenzy of spring-time excitement.

Image 2: Mid-tropospheric trough on Monday, 8 April, as forecast by the 12Z 3 April GFS.  Source: twisterdata.com

Image 2: Mid-tropospheric trough on Monday, 8 April, as forecast by the 12Z 3 April GFS. Source: twisterdata.com

While the details about this system remain muddy – the big picture looks quite tantalizing.  In particular, the global models suggest the development of a broad, strong upper-level low over the western United States that will induce strong, southerly low-level flow and associated moisture advection over the central U.S.  Unlike previous events this year, the moisture quality looks quite decent – courtesy of a nice Caribbean fetch (dewpoints at or above 60 F, perhaps over 65 F at some locations, depending on the model; Image 3).

Image 3: 12Z 3 April GFS forecast of dewpoint temperature for 00Z 9 April.  Source: twisterdata.com

Image 3: 12Z 3 April GFS forecast of dewpoint temperature for 00Z 9 April. Source: twisterdata.com

Given the mean westerly flow this spring – and drought conditions – the elevated mixed-layer also looks primed to create strong instability; indeed, the 12Z 3 April GFS forecast shows over 3500 j/kg in western Oklahoma/western north Texas by Monday evening (April 8th; Image 4).

Image 3: 12Z 3 April GFS forecast of CAPE  for 00Z 9 April.  Source: twisterdata.com

Image 4: 12Z 3 April GFS forecast of CAPE for 00Z 9 April. Source: twisterdata.com

Nevertheless, the severity of the event remains uncertain.  In particular, the timing of upper-tropospheric waves could be the difference between a decent chase day – and a major tornado outbreak.  As usual, exiting waves would lead to less-than-ideal hodographs, while an entering wave would create the familiar “sickle-shaped” hodographs present during major outbreaks.  In all likelihood, though, the timing of the waves won’t be resolved until the event is within 24 hours.

Also of some concern is the quality of the moisture return.  While the GFS continues to insist on high-grade moisture (65 F isodrosotherm near the dryline by game time), the Euro is significantly less bullish (only lower 60s F Tds).  Even if the Euro is correct, tornadoes would still be in the cards, though the event might be less significant (unless the wind fields are stronger than forecast).  It will certainly be interesting to see which model is closer to reality – although we may not get a feel for this until the day before the potential event.  We’ll see!

Advertisements

About Gabe Garfield

I am a research meteorologist from Norman, Oklahoma. In addition to my work, I am interested in storm chasing, sports, philosophy, theology, and culture.
This entry was posted in General. Bookmark the permalink.

3 Responses to Tornado Outbreak Next Week?

  1. Brent Shambaugh says:

    Hey Gabe, this sounds exciting. I hope everyone is safe.

  2. Polly says:

    I see a lot of interesting posts here, i know writing posts is time consuming, but i know unlimited source of content for
    your page , just search in google – rewriter creates an unique article
    in a minute

Leave a reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s