Category Archives: Meteorology
Thus far the winter has been relatively mild around the Northern Hemisphere. This December was the 14th-warmest December, and the period from Sept. 1 through Dec. 31 was the eighth-warmest since 1948.
Such a prolonged delay to the onset of winter makes one wonder if it will ever arrive this year. Though there is no clear way to be sure about the answer to that question, one potential phenomenon that can encourage a winter-like cold air outbreak is a sudden warming of the lower stratosphere, the layer of the atmosphere between 6 and 20 miles above the surface. Continue reading
The year began with frigid temperatures across Wisconsin. The average temperatures for the first seven days of January were well below normal across southern Wisconsin with most areas at least 15 degrees below normal.
The end of 2018 saw temperatures several degrees warmer than normal, including a record high temperature of 50 F on Dec. 27, tying a record high for the date, last set in 2003, and previously set in 1936 and 1946. Continue reading
In testimony to the infectious appeal of the famous scenes memorialized by Nathaniel Currier and James Ives, prolific lithographers of the middle 19th century, there is an enduring obsession with snow at Christmastime.
A so-called White Christmas is officially observed anytime there is 1 inch of snow on the ground on Christmas morning, whether or not it is snowing at the time. Continue reading
In 1803, British pharmacist and chemist Luke Howard devised a classification system for clouds. It has proved so successful that meteorologists have used Howard’s system ever since, with minor modifications.
According to his system, clouds are given Latin names corresponding to their appearance — layered or convective— and their altitude. Clouds are also categorized based on whether they are precipitating. Continue reading
The atmosphere is actually a fluid. Like water, the pressure at the bottom of a deep column of fluid is larger than the pressure near the top of the column.
Fluids move in response to differences in pressure (the pressure gradient force), always flowing from high toward low pressure. In fact, the wind is driven by pressure differences measured in the horizontal directions. Therefore, the air near the ground (at the bottom of the deep atmosphere) is compelled to move upward toward lower pressure above. Continue reading