Extreme Weather Event Yeti, Still Going Strong, Aims At Midwest; Fair Weather Event Crocus Interrupted

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The forecast for Saturday calls for freezing rain and snow in a large area of the midwest. Forecast courtesy of NOAA.

The forecast for Saturday calls for freezing rain and snow in a large area of the midwest. Forecast courtesy of NOAA.

Residents of the midwest and northeast, weary of new records for snow and cold which have been set on a daily basis in February, look forward to the change of month on Sunday. Unfortunately Extreme Weather Event Yeti is paying no attention to the calendar.

Whom Will Yeti Stomp On This Week?

The focus of last week’s foulest weather, given various names by The Weather Channel (TWC) — was a swath of freezing rain and sleet from Texas to the Carolinas, with snow to the north. Now warm air is advancing into the Mississippi Valley, and the zone of freezing rain will shift into the midwest.

In the wake of this weekend’s slippery mess, another blast of arctic, actually Siberian, air will probably set new records, not only breaking daily low temperature records, but possibly all-time records for March.

After that, a new round of snow and freezing rain, no doubt christened with a new name by TWC, will march across the middle of the country.

Yeti Eats Potential Energy For Breakfast And It Fuels His Rampage

The strongest temperature gradient (change of temperature with distance) occurs along the edge of the advancing Siberian air. When this cold air meets a flow from the Gulf of Mexico or one that has come across the Pacific Ocean, the gradient is very pronounced.

The strong temperature gradient is a high potential energy state, and the potential energy is constantly increasing. Some of you may say “Wait a minute; energy is conserved; it cannot be created.”

That’s true of a closed system, but the earth is not a closed system. Energy is constantly arriving in the form of solar radiation and being lost in the form of the earth’s microwave radiation. The uneven distribution of incoming solar radiation creates the potential energy.

Solar Heating Decreases With Increasing Latitude

At the equator, the sun strikes at a high angle, while at the poles it strikes obliquely (sometimes not at all). As a result, a given area at the equator receives more sunlight than the same area at the poles.

Movement of air is the primary mechanism for balancing energy in the atmosphere. In the absence of this method, only conduction would redistribute heat, and the earth would resemble the airless planet Mercury, where the temperature contrast is over a thousand degrees from the warmest place to the coldest.

What Does Yeti Do With The Potential Energy?

Atmospheric processes convert potential energy of contrasting temperatures (heat) to kinetic energy (energy of motion — wind) which is then dissipated back into heat by friction. The dissipation of heat takes place at higher latitudes, and the continuing process brings about a long-term steady-state with respect to temperature.

As it turns potential energy into kinetic energy, the atmosphere creates turbulent motions that result in outbreaks of cold air, precipitation, and wind.

Who Will Get The Worst Of Yeti This Weekend?

Bitterly cold air covers the midwest and northeast, and though the warmer flow from the Gulf of Mexico will reach parts of the Mississippi Valley, arctic reinforcements are on the way.

A band of freezing rain will stretch from northern Texas through Missouri, Iowa, Illinois, Indiana, Ohio , and Pennsylvania, and some could reach Atlantic coastal states later in the weekend.. To the north of the freezing rain, snow will fall in moderate amounts. Chicago, which is close to its record snowfall for February, may get a couple of inches, but not quite enough to break the record.

Yeti’s next tantrum, sometime next week, could take place anywhere from the Rockies to the Atlantic coast, as the arctic and Gulf air fight for dominance.

The jet stream forecast for next Friday shows that Yeti still dominates in the eastern US, while Crocus has returned to the west coast. Forecast courtesy of NOAA.

The jet stream forecast for next Friday shows that Yeti still dominates in the eastern US, while Crocus has returned to the west coast. Forecast courtesy of NOAA.

What Happened To Fair Weather Event Crocus?

Last Friday, Decoded Science featured Fair Weather Event Crocus, an unseasonably warm, dry spell of weather on the northwest Pacific coast which coaxed crocuses into an early bloom.

The last few days have seen a return to more typical winter weather in Seattle and Portland: gray and drizzly, with temperatures near 50 degrees.

Movement Of The Long Waves In The Jet Stream

The ribbon of air that surrounds the globe in middle latitudes, called the jet stream, is characterized by waves of every length. Generally a wave number of four or five dominates, which means the waves are separated by about 3,000 miles. These longer waves tend to move very slowly. Within the long wave pattern, shorter wavelengths ripple along. The long waves give weather its overall character, while the short waves produce more localized stormy and fair weather.

Yeti is a long wave dip (trough) over the eastern United States that is unusually pronounced. To its west is a bulge (ridge) that created Crocus. The long wave associated with Yeti has nudged Crocus out temporarily. but in the coming week, Crocus will push back and the weather in the Pacific northwest will return to unusually springlike conditions.

When Will Yeti Leave The Building?

The jet stream forecast for March 10 shows a low-latitude brach returning to California. Forecast courtesy of NOAA.

The jet stream forecast for March 10 shows a low-latitude brach returning to California. Forecast courtesy of NOAA.

Decoded Science has observed that the warm water anomalies in the Pacific Ocean, one at the equator and the other in the Gulf of Alaska, have been jockeying for pole position.

The equatorial warm waters, dubbed El Niño Eggplant by Decoded Science, tends to create a southern branch of the jet stream. That brought record rains to California in November and February.

In January, the ridging caused by the warm waters off the Pacific northwest coast dominated. California was dry; in fact, San Francisco received no rain at all in January.

After early February rains, the ridge associated with Crocus has dominated west coast weather. Longer range forecasts show the low latitude jet returning in a couple of weeks.

Spring Is Bound To Come, But Yeti Is Still Active

In the eastern US, spring won’t start with the change of month. Perhaps with Daylight Savings Time next week, or when the sun crosses into the northern hemisphere on March 20.

What effect has Yeti (or Crocus) had where you live? Do you see any signs of spring?

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