Winter Storm Maximus produced snow in Chicago and Detroit on Saturday. Now The Weather Channel is calling the storm that is moving into the northeast ….. Maximus. The situation illustrates the problem in naming winter storms.
Why Name Winter Storms?
The idea of naming winter storms was born of good intentions. Forecasters can follow areas of bad weather as they move generally from west to east, and it is convenient to be able to refer to these areas by some designation.
Better a name, even one like Maximus, than just “that snowstorm in the midwest.” The World Meteorological Organization names hurricanes and there has been no controversy over that practice since it started including men’s names. But winter storms are different.
What Is a Winter Storm?
Generally speaking, winter storms are like hurricanes in that they are associated with low pressure. But the analogy to tropical systems breaks down after that point. A tropical storm is a defined low pressure center with winds exceeding 39 miles per hour. How do we define a winter storm? By pressure? by snow? By wind? It’s actually quite subjective.
The Pressure Distribution in a Winter Storm
The polar vortex is pronounced in the winter, covering the general area of the pole (hence the name), and is surrounded by a jet stream that circles the globe in the middle latitudes, dipping here and there, but generally oriented west to east. Under the strongest part of the jet stream is the line of demarcation between cold arctic air and warmer tropical or sub-tropical air. Depending on their origins, these air masses can be dry or saturated.
The boundary of warm and cold air is in a state of high potential energy. Eventually that energy must be dissipated, because more is being produced by the sun’s differential heating of the equator and pole. Substantial amounts of energy can be released when a low pressure system forms, develops into a nor’easter, and mixes the cold and warm air. The areas around the low pressure center receive a lot of precipitation, either snow or rain.
The boundary between warm and cold air masses, called a front, marks a long line of low pressure. Bad weather can form along this line with only a minor low pressure center developing — or none at all. Just a modest movement of the warm air over the cold or the cold air under the warm will cause lifting. If the air contains sufficient water vapor, precipitation will occur. Since a few tenths of an inch of melted precipitation (a summer shower’s worth) is equivalent to several inches of traffic-snarling snow — or even worse, a coating of power-outaging ice — it doesn’t take much to cause what most people would consider a storm.
Why the Weather This Winter Has Been So Stormy
The contrast between cold and warm air over the United States in the winter of 2014 has been very pronounced.; the potential energy has been high. But most of the storms have been produced by ripples along the front, in places where warm air rides over cold or cold air wedges beneath warm, producing stormy weather, but not releasing much of the potential energy. The exception was Janus, which became a classic nor’easter with deep low pressure. This storm released some potential energy and was followed by a period of relative calm.
The Current Weather System
The Weather Channel is calling the disturbed weather that will move through the east coast today Maximus, but I suggest it is not the same Maximus that dumped snow on Chicago and Detroit over the weekend.
On the weather map for Saturday, the precipitation from Maximus can clearly be seen centered on Chicago, along a front but not connected to any low pressure center. The small low over Texas is what has become the new storm. Let’s call it Son of Maximus.
Whatever we call it, this storm will bring heavy rains to parts of the south and snow farther north — possibly over six inches in some places. Son of Maximus will not develop into a deep low pressure system, so a lot of potential energy will remain across the United States.
The Weather Channel has already named the next storm, Nika — in fact, they named it on Friday, rather prematurely — and expects it to move from Texas to New England in the next few days. Nika also looks like it will depart without developing into a significant low pressure system.
A Look at the Weather Ahead
Some extended forecast models show another storm affecting the same general areas as Maximus, Son of Maximus, and Nika next weekend. Indications are that this could become a vigorous nor’easter, with deep low pressure. If that happens, potential energy could be released (converted to wind), and there could be a respite from the awful weather that much of the country has experienced. Wouldn’t that be nice!