(Fremont County, WY) – From record breaking rainfall, to multiple instances of tornadoes or tornado-like conditions, to massive hail storms, Fremont County has been on receiving end of quite the onslaught of active/severe weather this spring and early summer, and County 10’s Meteorologist Dave Lipson is here to provide some answers.
We asked some of the most common questions we have been receiving at County 10; here’s what he had to say.
County 10: – Is this behavior normal in Wyoming weather cycles?
Dave Lipson: The synoptic pattern that has been responsible for a lot of our active weather this spring and early summer has been a closed low pressure center, within the long wave, “semi permanent” trough, typically located somewhere along the Pacific Coast, or in the Great Basin to our west and southwest.
(A trough is “An elongated area of relatively low atmospheric pressure, usually not associated with a closed circulation, and thus used to distinguish from a closed low.”)
These weather features have been churning up moisture from the southwest out ahead of these synoptic scale weather features.
The circulation around a low pressure center swirls counterclockwise, so it stands to reason that the winds around these weather features would transport moisture from the Pacific Ocean way out ahead of it, northeast toward Wyoming.
County 10: What’s with the frequency of storms?
Dave Lipson: This weather pattern seems to have been very persistent this season, so, as long as the general weather pattern remains, with long wave “troughiness” to the west of us, the frequency of thunderstorms will continue. This is not particularly normal for this time of year for this long.
You may remember, a couple of years ago when the large high pressure system that typically begins to set up over Texas, or the Southern Plains, shifted farther northwest than usual, and we had several days in a row with high temperatures a couple of degrees above 100, even before the summer solstice, without much rainfall.
What usually happens in our neck of the woods is thunderstorms will develop over the mountains and affect us, then when they encounter juicier moisture over Eastern Wyoming, they can become severe, well to our east.
During the annual Southwest United States monsoon in July, we will often be on the fringes of that activity, as they round the ridge, which typically is located over the south central part of the country, in a clockwise fashion, putting our area under the “ring of fire” with garden variety thundershowers, and sometimes dry lightning, potentially causing fire starts. That has not been the case this year thus far.
(The Southwest United States Monsoon is a “pattern of pronounced increase in thunderstorms and rainfall over large areas of the southwestern United States and northwestern Mexico, typically occurring between June and mid-September.)
County 10: What’s specifically causing this continuous run of strong storms?
Dave Lipson: With help of Pacific moisture in the mid and upper levels, and even the influx of gulf moisture in the lower levels from the southeast (which is not necessarily typical, but is an occasional aspect of our weather), it can turn our garden variety thunderstorms severe.
This happens because of the release of heat due to a process known as the release of “latent heat of evaporation.”
(Latent heat of vaporization is the “amount of heat energy required from the environment to change the state of a liquid to a gas.”)
When the warm summer sun heats the earth’s surface, the earth’s surface heats the lower layers of the troposphere. Then, resulting parcels of warm buoyant air rises.
Once the air rises high enough to cool down, due to cooling due to expansion because of less air pressure higher in the troposphere, the air condenses and forms clouds.
Once clouds form, the rising parcels of air cool more slowly due to the warming effect of the latent heat of evaporation.
This causes the rising air to be that much relatively warmer than the environmental air it is rising through, casing the air to rise even faster and higher, producing, taller, stronger, and heavier thunderstorms.
The “semi permanent” long wave trough to the west of us,has been emitting “short wave troughs” toward our area. You can think of long wave troughs as the railroad tracks to guide the shortwave troughs along.
When short wave troughs track across our area, colder air aloft advects into the mid and upper atmosphere overhead, and encourages the rising air to rise even faster, because of the relative difference of the temperature of the rising parcels of air through the environment.
These weather systems are transported to us via the jet stream. The jet stream increases our winds high above. This causes an evacuation of mass at the surface, resulting in more lift at the surface to fill in the void, strengthening thunderstorms to potentially become severe.
County 10: Are other states on the receiving of uncharacteristic severe weather, or is it just Wyoming?
Dave Lipson: We are not the only ones experiencing severe weather active weather. The Deep South and the Midwest have been having their fair share of killer tornadoes and severe weather.
The Red Rocks Amphitheatre in Morrison, Colorado recently was hailed on, causing head
injuries during a performance.
Do you have any more specific questions you like us to ask Lipson? If so email us at [email protected]!