Tour Periods - Storm Season Explained
Please keep in mind that all tour periods offer the same opportunity and chance to witness severe weather and tornadoes. This section is to help you understand what can be expected with each tour and how they differ throughout the season from the locations where you could be and the severe weather patterns from one tour to another. Also, keep in mind that each severe weather season varies from year to year and mother nature knows no textbook. These graphics represent tornado probabilities using tornado climatology from 1982-2011.
Texas, Oklahoma, and Kansas our typical stomping grounds of "Epic April". Powerful troughs, strong shear and instability create the setting for chaos in the Southern Plains. We wait until mid to late April to begin tours to allow moisture to become more established in southern Tornado Alley. Some of our best chase days have occurred during this time! Late April is no stranger to big outbreaks, big tornadoes and multi-day periods of chasing!
May is Marvelous! Early May combines powerful systems with rich gulf moisture and instability (CAPE, Convective Available Potential Energy). Strong upper-level lows bring powerful troughs into the Alley and can either be slower moving or progressive causing lee side cyclonegenesis (surface low-pressure systems east of Rocky Mountains) This can set the stage for multiple days of severe weather including major tornado outbreaks. Typical areas chased during this phase is Texas, Oklahoma, Kansas, Nebraska.
Mid May the weather can get a bit Extreme! Typically by this time of the season the warm sector is starting to broaden and expand in coverage as moisture is more readily available. Storm systems can traverse the central and southern plains in a parade like fashion bringing multiple days of severe weather. Upslope events in the high plains of the Texas Panhandle and Colorado are starting to get going at this time too. The Southern, Central and High Plains are our playground during this time frame.
Statistically, this period is considered the peak of severe weather season when the mother nature has balanced all parameters needed to produce volatile severe weather and tornadoes. Not that other times won't but the peak does shift from year to year. Typically extreme instability, powerful troughs, very rich moisture all contribute to what can be the perfect time of year. It is the time we all live for. Need I say more? Almost all of Tornado Alley will be susceptible to powerful supercells and tornadoes during this time!
Late May, early June dew points are readily in the upper 60's and low to mid 70's combined with intense insolation gives us extreme instability. CAPE (Convective Available Potential Energy) is a measurement of how much energy is available for convection. The stronger the CAPE the more intense the updraft in return a more powerful storm. This time frame is still what many of us chasers consider prime time. Storms can typically move slower this time of year and can be watched for a while before having to reposition. Warm front action in Nebraska and Iowa can make for some big tornadoes. The upslope regions in the eastern plains of Colorado and Texas Panhandle are starting to peak in tornadic activity as well.
Upslope is a beautiful thing and you will see why for yourself! What is upslope you ask? Upslope is pretty much orographic flow where winds travel up higher terrain and cause lift. When this lift is forced into an unstable air mass the results can be storms! Southeasterly to east flow moves upward into the high plains of eastern Colorado with SW flow aloft (even if weak) tornadic supercells can develop. Photogenic supercells and amazing terrain make this one of our favorite times! It is not just limited to Colorado though. Texas Panhandle, NE New Mexico, Wyoming and Montana are also typical upslope supercell regions. We are very likely to chase in other states in the plains as well. Such as Kansas, Nebraska, Iowa, Illinois, South Dakota and Minnesota.
The jet stream is continuing its northward journey and begins the start of the Northern Plains season. Moisture is well established all the way to the reaches of the Canada border. The Northern Plains are beautiful, add a superbly structured supercell with a photogenic jaw-dropping tornado and you have incredible Violent Skies. The Dakotas, Minnesota, Nebraska, Colorado to the Midwest is a place where dreams are captured and brought home to make friends and relatives who didn't go jealous!
A chasers dream and likely our favorite time to chase!
The Northern Plains are a special place, amazingly flat terrain, great road networks and often times the most photogenic storms of the year. The jet stream by this period resides in the northern reaches of Tornado Alley bringing along with it the storm systems that create some of the best storms of the season. Also, storms can crawl due to the weaker flow aloft. North Dakota, South Dakota, Minnesota, and Montana are some of the places where your jaws will be left open in awe and SD cards filled with incredible structure and once in a lifetime tornado shots.