Feeds:
Posts
Comments

Expanding Snow Cover

Now that it’s December, generally considered winter even though winter won’t officially arrive for a couple of weeks, I thought it would be a good time to take a look at the snow cover across the United States and all of North America.

North America

Here’s the latest map from the National Ice Center:

North America snow cover as of December 2, 2009

United States

What follows is a close-up of the United States and most of Canada–note the snow in southern New Mexico and western Texas, as well as the dot in north-central Texas. I talked about the possibility of southern December snow in a recent post (White Christmas in the South?)–perhaps a preview of things to come?

Snow Haters–Don’t Click on the Following Link

Snow lovers will enjoy this National Ice Center animation, showing the past 31 days (from the current time, not the day the blog was posted). The rest of you should not click on the link until March!

–Paul Yeager

Snow for Christmas (White Christmas) is the most romanticized weather event there is, and the combination of weather factors in December might result in a White Christmas in 2009 for areas that normally don’t receive snow.

Cold Air and Storms in December?

As you know, I don’t focus on specific forecast details (even for Christmas Day) in this blog, but the possibility of widespread cold and an active storm track could result in widespread snow this December.

The coupled forecast system has consistently forecast colder-than-normal weather for much of the country, including the Deep South.

monthly temperature forecasts from the coupled forecast system

In addition, the presence of a strengthening El Nino means that the southern branch of the jet stream should be more active than normal.

An active southern storm track with an abundance of cold air farther to the south…perhaps more residents in this area will have a White Christmas?

–Paul Yeager

Coast-to-Coast Weather News

Here are a few interesting stories from some of my excellent weather blogging friends:

Weather Brains

I recently discovered the Weather Brains Web site, which is host to an informative and entertaining weekly (hour-long) podcast on the weather. If you like the weather (and have a brain!), you’ll love Weather Brains.

Moderate El Nino–Heavy Snow in the East?

Frank Roylance of Maryland weather reports on how a moderate El Nino, like the one going on now, sometimes produces snowy winters in Maryland (NWS: Moderate El Nino winters can be Maryland’s Snowiest), which is something applicable to all Mid-Atlantic residents.

Thanksgiving Tragedy

Erik at MemphisWeather.Net recalls a devastating Tennessee tornado–Remembering the Germantown tornado, 15 years later. What a sad day that was.

Strongest Storm Ever?

Jesse Ferrell of WeatherMatrix reports that Super Typhoon Nida may have been the strongest storm ever recorded.

Want More Sun–Move to Antarctica!

Scott Sistek of Partly to Mostly Bloggin’ recently wrote about how Seattle is gloomier than Antarctica. I know that people talk about moving south to the sunbelt, but this is ridiculous!

Active Weather Pattern?

Tom at PhillyWeather.Net talks about the potential for a stormier pattern during the next week (Potent, Variable Week of Weather Ahead). Again, this is of interest to many eastern residents, not just Philly natives.

–Paul Yeager

Five Weather Seasons?

While it’s common to believe that there are four weather seasons, there are, in fact, five. At least, it seems that way–based on the way people seem to split winter into two seasons, before Christmas and after Christmas.

Winter Before Christmas

Before Christmas, snow is loved and cold is tolerated because the concept of a White Christmas is so ingrained in our culture that what is often considered intolerable weather becomes desirable. In fact, nothing in weather is romanticized as much as the magical White Christmas.

It seems as if every Christmas song sings wistfully of snow falling, sleigh rides, and delightfully frightful weather. Every movie is filled with that perfect Hollywood snow; large and fluffy flakes turn stark villages into magical white kingdoms but somehow never interrupt the joyous green- and red-clad travelers.

We marvel at Christmas lights and decorations as they sparkle in the fresh covering of snow, and even adults are often seen frolicking and building snowmen. We reminisce about how winters used to be much snowier when we were kids–those were the days.

Snow is beautiful, and everyone loves it–at least from Thanksgiving Day through Christmas (and perhaps New Year’s Day).

Winter After Christmas

After Christmas, many of us return to our typical snow-hating ways.

We rip down all of the lights and decorations and stuff them into boxes in the attic; we whine when we have to shovel a driveway or sidewalk. We avoid going outdoors because it’s too slushy, and when a north wind howls, we howl in annoyance at the cold.

We beg for a “January thaw,” make jokes about wishing there were more global warming, and think that the groundhog is an evil beast. If it dare snow in March, it’s best for a meteorologist to invest in Kevlar.

Snow is an awful inconvenience, and everyone hates it.

A White Christmas for Many?

I’ll talk about the weather factors that might lead to a White Christmas for many people across the country during the next couple of days.

Not Everyone Celebrates Christmas (Mini-Rant)

I said the word Christmas many times in this post since that’s what it’s about–a White Christmas. When talking about Christmas, it seems silly to me to randomly insert the word holidays in an attempt to be inclusive of others. A Christmas tree is not more inclusive if it’s called a holiday tree, and Christmas lights are not any less denominational when called holiday lights.

There’s a better way of being inclusive of non-Christians–treat those who don’t celebrate with the respect they deserve.

For example, don’t wish someone who you know celebrates Hanukkah a “Happy Holiday” on December 25 when Hanukkah was three weeks earlier. Wish them a Happy Hanukkah during Hanukkah. Also, don’t be upset if stores cater to people of all religions (or the non-religious) by talking about the entire holiday season rather than focusing on just Christmas.

There is a lot of discussion at this time of year about a war on Christmas by those who believe that Christmas is a national event, not a religious event. I want to remind everyone that Christmas is a religious holiday that is not celebrated by everyone.

–Paul Yeager

Thanksgiving Leftovers

Since I’ve been talking about the computer forecast for Thanksgiving Day for 16 days, the only responsible thing to do is review how well the forecast turned out.

Here’s the map from Thanksgiving morning (7 a.m. EST) (Steve at Weather Talk also talked about the weather for Thanksgiving in Thanksgiving Forecast: The Final Verdict):

Weather map at 7 a.m. EST Thanksgiving Day (courtesy of NOAA)

There was a weak storm in the upper Midwest, which was accompanied by a little snow in the northern Plains, along with some rain along the East. There was also a little rain in the Pacific Northwest. There were no strong storms, which is in stark contrast to the original computer model we looked at (from November 10):

Initial Thanksgiving Day forecast by GFS model (November 10, 12z run)

Five days later, the computer model had begun to back off on the strength of the storm, as is indicated by this map, which shows no big storm–a much better forecast than the original map but still not accurate on the details:

Forecast for Thanksgiving Day (12z run of GFS from November 15, 2009)

The next map we looked at (from a week out) was reasonably accurate, but that’s to be expected:

GFS forecast for Thanksgiving Day (168-hour from November 19, 2009)

Conclusion

Consider this an exercise an example of the big changes that often take place in the long-range operational computer models, but remember, computer models designed for long-range forecasting, often months in advance, are not based on the same mathematical equations, so the same rules do not apply. (See December Forecast.)

–Paul Yeager

Since we’ve been following a computer model (the GFS) forecast for Thanksgiving Day for two weeks now (most recently in Thanksgiving Day Forecast–No Big Storm), I wanted to look at the computer model one more time before the turkey makes its final, fateful landing on the dining room table.

Still No Big Storm

While the original forecast (from November 10) was for a major winter storm, the most recent computer models have only forecast a relatively minor storm. That’s still the case with the forecast from Tuesday morning:

GFS forecast (as of Tuesday, Nov. 24, for Thanksgiving Day

Thanksgiving Day forecast (12z GFS, November 24)

Forecast Details

The point of this exercise has been to give a snapshot of what the computer model is predicting for Thanksgiving Day, not to focus on the details of the forecast for specific locations. This is a snapshot of the forecast for 7 a.m. EST (4 a.m. PST), not a forecast for the entire day. It shows a relatively weak storm, accompanied by cold air and some snow, in the upper Midwest, a little rain moving through Florida, and a rain-bearing cold front approaching the Pacific Northwest.

Note: For a specific forecast for your area for Thanksgiving Day (and related shopping/travel days following), consult your favorite local weather source.

Comparison

By the time the turkey transforms from the perfect holiday meal to dry sandwiches and the type of turkey surprise casserole that makes you wish you had Dominos on the speed dial, I’ll complete our exercise by showing the actual weather map for Thanksgiving morning and compare it to the various forecast iterations highlighted here during the last couple of weeks.

That’ll be much more interesting (and safe!) than going shopping. Black Friday sales won’t be that much better than sales in the coming weeks–when you won’t run the risk of injury going into the store.

–Paul Yeager

December Forecast

When talking about long-range forecasts, as I have often in this blog (long-range forecasts), I’ve noted that we meteorologists base long-range forecasts on more than just whether an El Nino is or isn’t occurring, and I wanted to give an example of one of those other tools today.

Let’s take a look at the NCEP coupled forecast system forecast (is that one too many forecasts?) for December. If it’s right, then much of the United States is in for quite a month!

What It Isn’t

The coupled forecast system is unlike the GFS model I referred to in my series of forecasts about the weather for Thanksgiving Day (Thanksgiving Day Forecast–No Big Storm). The GFS generates a specific daily forecast, hour after hour after hour, and extends a couple of weeks out, typically becoming more and more inaccurate with time since mistakes are magnified by the use of the previous forecast information as the basis for the next forecast iteration.

What It Is:  Specific Long-Range Model

The coupled forecast system is specifically used to generate long-range forecast trends, rather than specific hour-by-hour or day-by-day information (similar to a climate model).

I’ll give details about how the model works in a future post, but the point here is that it generates a general forecast, not a specific forecast. In other words, it forecasts temperature and precipitation deviations from normal, for example, and not the amount of precipitation location/amount on a particular day.

Since that’s what the model is programmed to do, rather than continually generate new forecasts based on the output from a previous forecast time, it doesn’t multiply its forecasting errors. It may not be right, but a bad forecast for one time period doesn’t negatively affect the output for the next time frame, making it possible to create forecasts for months in advance.

Much Colder than Normal in December

The latest coupled forecast system run is predicting a colder-than-normal December in much of the country, with the cold air encompassing the eastern two-thirds of the country. The map is below, but it’s difficult to see since the forecasts for many months are included on one image–and the background is of the entire globe. Go to their site–from the link above or by clicking on the image for more information.

The blue areas indicate colder than normal, and the red is warmer than normal.

Monthly coupled forecast system forecast

 

I recently saw an alternet.org story, How an Entire Town Leveled By a Tornado is Rebuilding Green, about the rebirth of Greensburg, Kansas. It tells a remarkable story of optimism, recovery, and dedication to a single goal.

That’s why I thought it would be good to talk about the Greensburg tornado now.

Overview

If there were one tornado that best symbolizes the way in which a tornado can change life forever, it would be the tornado that destroyed Greensburg, Kansas, on May 4, 2007. And if there’s one story that represents the ability of people to recover from disaster, it’s what’s going on in Greensburg, Kansas, today.

Greensburg History

Greensburg, a small town (only 1.5 square miles) on the farming plains of the southwestern part of the state, was first established in 1886, and it was best known for being the home of the world’s largest hand-dug well. The “Big Well,” 109 feet deep and 32 feet wide, was used as the town’s water supply from 1887 until 1932 and was a major tourist attraction for decades.

Spring in Kansas

Spring is often a dramatic weather time in the Plains, with the building warmth of the upcoming summer competing with the winter cold that is sometimes unwilling to release its grip. This contrast often results in numerous rounds of dangerous thunderstorms, and 2007 was a spring with frequent dangerous storms.

May 4, 2007

Even though May 2007 began without much weather fanfare (after multiple late-winter and early spring tornadoes), a strong late-season storm along the West Coast grabbed the attention of meteorologists. On Friday, May 4, the strengthening spring sun pushed temperatures into the middle 80s in Greensburg, and while the warmth was undoubtedly appreciated, there was an understanding that the warm, humid air mass in combination with the approaching storm would result in dangerous thunderstorms and perhaps tornadoes.

The Tornado

A supercell thunderstorm that had already produced tornadoes in the extreme western part of Kansas approached Greensburg, and at 9:20 p.m., a rapidly intensifying tornado was spotted to the southwest of Greensburg. The National Weather Service issued something called a Tornado Emergency, which is an enhanced tornado warning issued when a violent tornado is headed for a populated area. The intention is to warn residents of Greensburg an immediate, extreme threat.

An EF5 tornado (the strongest category) estimated to be nearly two miles wide (remember–the town was 1.5 miles wide) arrived on the western end of town just before 9:45 p.m. Buildings were no match for the power of the tornado; structures that were not completely blown away were scattered into piles of unrecognizable wreckage. The swirling debris cloud that is associated with a tornado was filled with what had been Greensburg Kansas–two-by-fours, metal plumbing pipes, sofas, broken glass, and everything else became projectiles, projectiles with such force that they would become embedded in any object that they hit.

Two-ton automobiles were lifted from driveways and dumped into crumpled piles hundreds of feet away, railroad cars were overturned, and any trees left standing were stripped of their leaves and bark. Approximately 95% of the town was destroyed.

Aftermath

Greensburg, Kansas, after the tornado

White House photograph of Greensburg, Kansas, after the tornado

Residents who climbed out of storm cellars felt as if they had been transported to another place or time, unable to discern where their homes had been and which direction was West. Even in the black of night, it was clear that everything was gone. They knew that they were standing on their property, but there were no longer homes or any other buildings on the street. Stores that they’d gone to for years were gone. Neighbors that they had talked to hours earlier may have been missing, perhaps safely hiding a cellar or trapped under a pile of debris—or perhaps dead.

According to the 2000 Census, eleven out of the 1,154 residents had been killed, dozens had been injured, and the town was gone. Anyone who wants to understand the power and danger of tornadoes need look no further than Greensburg, Kansas. Life will never be the same.

–Paul Yeager

If you’ve been reading the blog regularly (as if you wouldn’t be!), then you know that I promised to give an update on what one of our computer models is forecasting for Thanksgiving day.

First, though, I want to give you a chance for any new readers (in case you’re not regular readers yet) to look at the previous posts:

No Big Storm

Here is the current forecast map for Thanksgiving Day (168-hour GFS from 12z November 19):

GFS forecast for Thanksgiving Day (168-hour from November 19, 2009)

Remember, the point of this series of blog posts was to show the change in the computer models from whenThanksgiving was day 15 on the model to when Thanksgiving actually arrives; the purpose was not to give specific forecast details for specific locations.

Now that the forecast is just one week away, however, it’s more reasonable to begin to look at the details of the forecast model more carefully–although a lot can still change during a week, so don’t make any plans based on this one computer model.

Forecast Highlights

  • Snow showers in the Midwest and parts of the East (western New York to West Virginia)
  • Unseasonably cold in the Midwest
  • Some rain and mountain snow for the Pacific Northwest
  • Dry and pleasant in the Rockies and Southwest
  • Mild to the southern Plains

One More Update Early Next Week

I’ll have another update early next week, and then we’ll see what actually happens and see how accurate the forecast model was.

–Paul Yeager

I have already extensively covered the forecasts for the upcoming winter (2009-2010), including the following:

One person I neglected to consult, however, is the butcher, who is one pig spleen inspection away from giving us all the answers to the upcoming winter (Predicting Weather with a Pig Spleen).

According to the Old Farmer’s Almanac linked above, the late Gus Wickstrom used the thickness of a pig’s spleen wall to forecast the weather. The details of the method are included in the article, for what it’s worth.

I included some weather wives’ tales in Weather Whys, but I hadn’t heard of this one. I wish I still hadn’t.

–Paul Yeager

Older Posts »