January 2002. Moderate to heavy snows hit parts of Georgia, the Carolinas, and Virginia during the first week of January.
The original definition of El Niño goes back to the eighteenth or nineteenth century when Peruvian sailors coined the term to describe a warm southward current that appeared annually near Christmas off the Peruvian coast. Hence the name El Niño, Spanish for "the Child," referring to the Christ Child.
Winter storms are generated, as are many of the thunderstorms of summer, from disturbances along the boundary between cold polar and warm tropical air masses—the fronts where air masses of different temperatures and densities wage their perpetual war of instability and equilibrium. The disturbances may become intense low-pressure systems, churning over tens of thousands of square miles in a great counter-clockwise sweep.
During the past century, global surface temperatures have increased at a rate near 1.1°F per century, but this trend has dramatically increased to a rate approaching 3.6°F per century during the past 25 years. There have been two sustained periods of warming, one beginning around 1910 and ending around 1945, and the most recent beginning about 1976.
Meteorologists estimate that, at any given moment, some 1,800 thunderstorms are in progress over Earth's surface, and about 18 million a year around the world. It is estimated that approximately 100,000 to 125,000 thunderstorms occur in the United States each year.
A tornado is a local storm of short duration (usually 5–10 minutes) formed of winds rotating at very high speeds, usually in a counter-clockwise direction (in the Northern Hemisphere). This storm is visible as a vortex—a whirlpool structure of winds rotating about a hollow cavity in which centrifugal forces produce a partial vacuum.
There is nothing like the hurricane in the atmosphere. Even seen by sensors on satellites thousands of miles above Earth, the uniqueness of these powerful, tightly coiled storms is clear.
The transformation of a tranquil river or normally dry wash into a destructive flood occurs hundreds of times each year, in every part of the United States. Every year, floods drive some 75,000 Americans from their homes; on the average, 127 persons are killed each year.
The planet Earth is believed to consist of a thin crust 2–3 mi thick under the oceans and as much as 25 mi thick beneath the continents that covers the large, solid sphere of the rock mantle, which descends to about 1,800 mi. Below the mantle is the fluid outer core, and, at about 3,200 mi depth, the apparently solid inner core.
Volcanic activity has played a dominant role in shaping the face of Earth. Much of the natural beauty of the land, its mineral wealth, and the fertility of the soil is owed to volcanism, especially in the western states.
Air pollution is a general term that covers a broad range of contaminants in the atmosphere. Pollution can occur from natural causes or from human activities.
Weather is the state of atmospheric conditions (i.e., hot/cold, wet/dry, calm/windy, sunny/cloudy) that exists over relatively short periods of time (hours to a couple of days). Weather includes the passing of a thunderstorm, hurricane, or blizzard, and the persistence of a heat wave, or a cold snap.
Air is a mixture of several gases. When completely dry, it is about 78% nitrogen and 21% oxygen.
The National Weather Service (NWS) continues full-scale redevelopment of its systems and its organization.
Temperature extremes depend upon a number of factors, important among which are altitude, latitude, surface conditions, and the density and length of record of observing stations.
The distribution of temperature over the world and its variations through the year depend primarily on the amount of distribution of the radiant energy received from the sun in different regions. This in turn depends mainly on latitude but is greatly modified by the distribution of continents and oceans, prevailing winds, oceanic circulation, topography, and other factors.
Local Climatological Data (LCD) are data observed at principal meteorological stations by trained observers or automated equipment that has been tested and accepted by the controlling agency. The stations are located worldwide and are operated by agencies of the United States government.
Birmingham is located in a hilly area of north–central Alabama in the foothills of the Appalachians about 300 miles inland from the Gulf of Mexico. There is a series of southwest to northeast valleys and ridges in the area.
Mobile is located at the head of Mobile Bay and approximately 30 miles from the Gulf of Mexico. Its weather is influenced to a considerable extent by the Gulf.
Anchorage is in a broad valley with adjacent narrow bodies of water. Cook Inlet, including Knik Arm and Turn again Arm, lies approximately 2 miles to the west, north, and south.