Snow present in 49 of the 50 U.S. states
January 11th, 2011
04:38 PM ET

Snow present in 49 of the 50 U.S. states

After big snow and ice events in the Southeast, Plains, and Midwest this week, 49 out of the 50 states currently have snow on the ground -  yes, even Hawaii, where snow falls in Mauna Loa and Mauna Kea all winter. 

The only state that has avoided this icy blast is Florida.  Does that make you want to go on a nice, warm vacation to the Sunshine State?  You're not alone.

Put another way, that means snow is present in 69.4 percent of the lower 48, which is more than double than December.  This is extremely unusual, though it's hard to put a date on when this last happened because records aren't kept on this kind of event.

The National Operational Hydrologic Remote Sensing Center combines ground reports and images from satellites in space to determine how much of the country is covered in snow.  That's what you see in the image above.  The images tell how deep and widespread the snow is, and that's important not only for images like this one, but also for computer weather models, which use the data to generate accurate forecasts. Such forecasts were very useful in predicting this week's winter storms.

Earlier this week, two storms began to churn: one in the northern Plains and Midwest, and one in Texas.  The southern winter storm took a track across the Gulf Coast, pulling warm, moist air over an extreme arctic blast that set up over the eastern half of the United States late last week.  This provided fuel for the storm to carve a path of snow, sleet, and freezing rain from Texas to the Carolinas. 

Here in Atlanta, we're still coated in snow and ice and probably will be for the next couple of days.  No one in the Southeast escaped the wrath except, of course, Florida.

But it's not over.  Now that the southern-track storm has moved into the Atlantic and is moving north, the other Midwest storm is going to merge with it, creating a Nor'easter event that could dump up to two feet of snow in the Northeast.  Winter storm warnings and advisories have been posted for the event - 32 states have winter storm advisories issued, by the way.

Here's how the snow forecast breaks down for some major cities:

Washington DC: 2-4 inches
Philadelphia, Pennsylvania: 4-6 inches
New York, N.Y.: 6-12 inches
Hartford, Connecticut: 15-20 inches
Boston, Massachusetts: 12-16 inches

The snow and cold started early this winter and has been extreme for most of the country.  Usually the Southeast avoids the blast, but not in 2011.  We're all feeling a little "snowed in" this winter.

Winter solstice: What does it really mean?
December 21st, 2010
03:29 PM ET

Winter solstice: What does it really mean?

Today, December 21, is the winter solstice, and what we like to refer to as the first day of winter.

But what does that really mean? Hasn't winter already started? In November and December, we've already seen extreme winter storms, and now there's a storm for the record books in the Southwest: Parts of  California recorded 9 feet of snow from Friday to Sunday, and could be looking at 20 feet by the time the storm ends.

So why do we wait so long to declare winter?

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Record freeze: Extreme weather battering East Coast
December 14th, 2010
12:48 PM ET

Record freeze: Extreme weather battering East Coast

Winter is getting off to an early start this year as the bitter cold continues after this past weekend’s storm.

Strong northerly winds are ushering in an arctic blast that is setting records across the eastern half of the U.S.

Record lows were set Tuesday morning from Virginia to Florida. High temperatures are 30 degrees below average for this time of year. And to make matters worse, snow and ice are in the forecast, making even day-to-day commutes difficult and dangerous.

Florida farmers continue to take protective measures against freezing temperatures this week. And although it hasn’t been a catastrophic event, long stretches with lows below freezing could have a detrimental impact on strawberries and citrus.

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Filed under: U.S. • Weather
November 25th, 2010
11:48 AM ET

This year's winter outlook: Extreme, again?

Last year's winter season dumped massive snowfalls and left people across the country trying to shovel their cars out.

Meteorological winter technically doesn’t start until December 1, but that didn’t stop two storms from spreading some snow across the Rockies and Upper Midwest this week. The second storm, which is making its way toward the Northeast on Thanksgiving Day, is ushering in an arctic blast of cold air behind the precipitation.

Cities in Montana hit record lows around 20 degrees below zero, and high temperatures on Thursday will be 10 to 20 degrees below average from California to the Great Lakes.

With this early start to winter, one can’t help but wonder what’s in store this year. Last year was record-breaking, with “Snowmaggedon” and “Snowpocalypse” making their way into our vocabulary. Although it’s always hard to say with certainty what an entire season will bring and whether we’ll see a repeat of last winter, some climate indicators from the National Oceanic and Atmospheric Administration make it easy to forecast what regions will see precipitation and temperatures that are out of the ordinary.

La Nina set in this year and is expected to strengthen over the next few months. If we look at what other La Nina events have bestowed on North America, we can say with some confidence:

The Northwest will be colder and wetter than average.

This includes rain and snow, but if the past week is any indication, the Northwest should be prepared for above-average snowfall. Seattle, Washington, has already set snowfall records this year and will probably continue to do so through February.

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Filed under: U.S. • Weather
July 30th, 2010
12:04 PM ET

NOAA confirms record breaking hailstone in South Dakota

A hailstone that fell from a severe thunderstorm in South Dakota has been officially declared the largest ever recorded in the United States, in terms of both diameter and weight, according to the NOAA National Climate Extremes Committee.

The stone was 8.0 inches in diameter, 18.62 inches in circumference, and weighed one pound, 15 ounces.

This is just short of the size of a soccer ball.

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July 23rd, 2010
06:23 PM ET

Louisiana's invisible shield: wind shear

Bonnie is currently making its way across the Florida peninsula, and is set to enter the Gulf of Mexico on Friday night. When it does so, it will encounter some of the warmest waters the Gulf has ever seen – and in some places even warmer than the waters that Katrina crossed over in 2005. So what’s the difference between Bonnie and Katrina? It's all in the upper levels.

Over the past few days, CNN Hurricane Headquarters has been monitoring an area of low pressure at the top of the troposphere, which is the place where all the weather happens in Earth's atmosphere. Tropical cyclones (the generic term we use for tropical depressions, tropical storms, and hurricanes) thrive in "low-wind" environmental conditions. This sounds counter-intuitive but it makes sense when you think about it. Strong winds in the environment where the tropical cyclone seed is trying to grow is going to rip it apart. We call this "wind shear," and it literally shears a storm apart. A tropical cyclone seed needs to plant its roots in weak winds and warm waters so it can build the vertical structure that it needs to churn into a hurricane.

The upper-level low that we have been monitoring is causing some strong wind shear over the Gulf of Mexico, and its why we didn’t see Bonnie strengthen when it was over the Bahamas, and it’s going to prevent strengthening over the Gulf of Mexico as well, assuming the wind shear sticks around. So even though the main ingredient for a strong hurricane is present (warm sea surface temperatures), we probably won’t see Bonnie strengthen much past 50 mph wind speeds.

The northern Gulf will still see relatively strong winds, especially over the Deepwater Horizon site, but it won’t be the worst case scenario: a major hurricane rolling into Louisiana with catastrophic impacts to the oil spill clean up effort.

And we shouldn’t take Louisiana’s Invisible Shield for granted though, because as the season rolls on, the wind shear tends to decrease. We can’t be sure the Gulf will be as lucky next time.