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Category Archives: Seasons
Is winter winding down?
Despite a prolonged deep freeze that straddled the end of December and the first week of January, during which we had below-zero morning low temperatures on 12 of 13 consecutive days, the month of January is likely to end at just about normal for Madison.
We are not, however, out of the woods just yet. Climatologically, the last week of January/first week of February is the coldest time of the year as a result of several physical factors. Continue reading
What is a ‘bomb cyclone’?
The term “bomb cyclone” refers to the formation and rapid development of a mid-latitude cyclone. A mid-latitude cyclone is a large-scale, low-pressure system, characteristic of the middle latitudes, that has counter-clockwise flow around its center (in the Northern Hemisphere).
A primary measure of development in these storms is a drop in the atmospheric pressure at the center of the storm. Air near the ground is forced to move inward to the center of the circulation — this is known as convergence. Continue reading
How does frost form?
Frost on objects is just water vapor in the air that has deposited itself as ice onto a surface. Frost forms on objects close to the ground, such as blades of grass.
At night, a blade of grass loses energy by emitting radiation (a non-lethal kind) while it gains energy by absorbing the energy emitted from surrounding objects. Under clear nighttime skies, objects near the ground emit more radiation than they receive from the sky, and so a blade of grass cools as its energy losses are greater than its energy gains. If the temperature of a grass blade gets cold enough and there is sufficient water vapor in the environment, frost will form on the grass. Continue reading
Do trees need cold weather?
Extreme cold weather can kill trees, and cold weather at the wrong time can damage trees. For example, a warm February and March in Michigan in 2012 brought early blooms to apple trees that then were killed by an April frost.
Some trees require cool temperatures, such as some fruit trees (peaches, cherries and blueberries) and nuts (almonds). Cold air along with less sunlight that comes with winter halts tree growth, preparing the tree to withstand freezing temperatures and then resume their growing the following spring. Continue reading
What’s up with all the wild weather?
Another week of destructive weather around our country culminated in the passage of Hurricane Maria over the island of Puerto Rico on Wednesday of last week. Some of the rainfall totals from automated stations on the island were of truly biblical proportions.
Though still subject to verification and a check on accuracy, 12.20 inches of rain fell in one hour at Gurabo Abajo, one of several stations on the southwest side of El Yunque, the high mountainous area in the northeast. Continue reading
