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Warm ocean surface temperatures in the North Atlantic provide the warm and moist air that fuels hurricanes, which develop out of random disturbances in the tropics that provide the spark for these storms. Warmer waters in the North Atlantic generally mean more fuel for the storms. But did you know that surface temperature conditions in [...]

Over the past century, the Arctic was cooler than normal from 1900-1915, warmer than normal during the 20’s, 30’s and 40’s, cooler than normal during the 50’s, 60’s and 70’s and has been warmer than normal from the early 1980’s to today.
Trivia Question: During warm periods in the Arctic, is the Antarctic generally…
a)    Also warmer [...]

In the Southwest U.S., prolonged dry episodes are defined as periods of two months or longer when daily precipitation falls below one millimeter.
Trivia Question: Have such prolonged dry episodes become more or less common over the past 60 years?
a)    More common
b)    Less common
c)    No change
The correct answer is b. Despite drought conditions in [...]

Teleconnections occur when an event in one part of the world impacts another part of the world. One frequent source of teleconnections is the El Niño-Southern Oscillation (ENSO).  ENSO is the periodic shift in wind patterns and sea-surface temperatures over the tropical Pacific Ocean. ENSO’s teleconnections include control over the number of winter storms impacting [...]

Much of our weather in the United States depends on what is happening in the tropical Pacific Ocean. During an El Niño event, which is happening now, the eastern tropical Pacific is warmer than average. During La Niña events, the eastern tropical Pacific is cooler than average. While South America’s west coast may seem far [...]

Winter is ending and the growing or “frost free” season is almost here! The frost free season is defined as the continuous period of the year when the temperature does not drop below freezing. When this season starts and how long it lasts have important implications for the plants and animals that live around us, [...]

Winter is ending and the growing or “frost free” season is almost here! The frost free season is defined as the continuous period of the year when the temperature does not drop below freezing. When this season starts and how long it lasts have important implications for the plants and animals that live around us, [...]

Winter is ending and the growing or “frost free” season is almost here! The frost free season is defined as the continuous period of the year when the temperature does not drop below freezing. When this season starts and how long it lasts have important implications for the plants and animals that live around us, [...]

Winter is ending and the growing or “frost free” season is almost here! The frost free season is defined as the continuous period of the year when the temperature does not drop below freezing. When this season starts and how long it lasts have important implications for the plants and animals that live around us, [...]

Better understanding how fluctuations in climate have affected regional wildfire frequency over the past few centuries may help to improve our ability to predict severe wildfire seasons. Some of the West’s older groves have experienced dozens of wildfires over the past few centuries. The trees that survived these fires recorded black scars in their annual [...]

Snow is both a product of the weather and a weather maker. It has long been recognized that snow exhibits a cooling effect on local and regional scales. Snow reflects more sunlight than bare ground, meaning that it absorbs less energy. More snow cover also means soils stay moist for longer following the spring melting [...]

The amount of solar energy Earth receives varies according to the “11-year solar cycle,” which corresponds to a cycle in the frequency and distribution of sunspots on the sun’s surface. The difference in solar energy between high and low points of the solar cycle is about two watts per square meter. About 35 percent of [...]

Air temperatures are fickle – they fluctuate significantly from day to day, from season to season and from year to year. The temperature of a water body fluctuates as well, but is much more constant than the surrounding air temperature. Water has a higher heat capacity than air, which means it takes far more energy [...]

Temperature records suggest that the Earth’s surface temperatures warmed during the early part of the 20th century, cooled from the period 1940-1970 and have since been warming. While Arctic temperature trends have corresponded to this general warming and cooling pattern, it has followed these trends more severely. During the warming period from 1910-1940, the Arctic [...]

Near the center of Antarctica in the polar vortex, strong westerly winds that blow in a circle around the continent during winter trap an envelope of air near the South Pole, prohibiting this air from mixing with warmer air masses closer to the equator. The extreme cold in the vortex causes clouds to form in [...]

December is East Coast Winter Storm (ECWS) season. These storms are powered by warm water that flows from the Gulf Stream. The Gulf Stream current flows along the Eastern Seaboard past Florida and the Carolinas before reaching Cape Hatteras, where the warm water heads out into the Atlantic. ECWS’s travel northward along the coast causing [...]

Winter storm season is here. Storms will be blowing in from the Pacific, bringing rainfall to lower elevations and snow to the mountains. This year, the eastern tropical Pacific is in an El Niño phase, meaning that its waters are warmer than average. When the eastern Pacific is in an El Niño phase, the northwestern [...]

Winter storm season is here. Storms will be blowing in from the Pacific, bringing rainfall to lower elevations and snow to the mountains. This year, the eastern tropical Pacific is in an El Niño phase, meaning that its waters are warmer than average. When the eastern Pacific is in an El Niño phase, the southern [...]

Winter storm season is here. Storms will be blowing in from the Pacific, bringing rainfall to lower elevations and snow to the mountains. This year, the eastern tropical Pacific is in an El Niño phase, meaning that its waters are warmer than normal. When the eastern Pacific is in an El Niño phase, the southwest [...]

It has long been known that what happens in the tropical Pacific doesn’t just stay in the tropical Pacific. Much of the year-to-year variability in America’s weather, particularly winter weather, can be explained by conditions there. All other things being equal, warm El Niño conditions off the coast of equatorial South America mean a wetter [...]