February 2011 Blizzard, courtesy: NASA

Click on the image above twice for a high resolution picture.

Calling it one of the largest storms since the 1950s, NASA turned its cameras toward the Midwestern States Tuesday to capture a winter storm stretching across 30 states. Chicago and Oklahoma City were two of the hardest hit cities. Chicago came to a standstill with its 3rd highest snowfall on record, 20. 2″ of snow fell during the blizzard. Blizzard warnings are issued when winds are expected to reach 35 miles per hour. That is one of the reasons this storm was so dangerous. The other reason was ice on the roadways. Warmer air in the upper atmosphere can support other types of wintry precipitation, such as sleet or freezing rain. Freezing rain is rain that freezes on contact with the surface or roadways.

If you want more information on sleet versus freezing rain, read my previous blog entry on wintry precipitation.

A lot of excitement here in New Orleans, Louisiana, as sleet began falling shortly before noon in our viewing area. The mighty Midwest storm yesterday was a rain and wind event for us, with a line of heavy thunderstorms crossing  before the arctic cold front blasted us with freezing temperatures overnight.

Gulf of Mexico Visible Satellite, courtesy: NOAA

Gulf of Mexico Infrared Satellite, courtesy: NOAA

Take a look at these two satellite images from the National Weather Service. The top image shows the visible satellite imagery of the Gulf of Mexico. You can also see the southern outline of Texas, Louisiana, Mississippi, Alabama and Florida in the image. I’m showing you both the visible (or daylight) satellite imagery and the infrared satellite because once the sun goes down, the visible image will be dark. Anyway, what I’m trying to show you is the stream of moisture headed toward Texas and Louisiana. See the bright yellow bands on the infrared imagery? That is cloud cover streaming over the Gulf of Mexico into the southern states. A southern stream of moisture like this usually tells us we’ll have cloudy skies and light rain across the area. It’s not a really unstable atmosphere, so we don’t expect a lot of fireworks with thunderstorms, etc.

What this image is not showing you is how cold it is at the surface. The winter storms that passed through the Midwest  left us with temperatures in the 30s today. Because it was so cold in the lower levels of the atmsphere, this warm and moist southerly flow of precipitation froze once it fell close tothe surface.

Granted, once it landed, it melted, because the air temperature was still above freezing. For snow to occur, you have to have freezing temperatures from the surface to the higher levels of the atmosphere. That’s why it’s tough for southern state to get snow. The tropics and the Gulf of Mexico like to send wam and tropical air masses in our direction. What’s fascinating about the weather pattern we have set up for the next 48-hours, though, is that it will give us a chance for wintry precipitation in the form of sleet or freezing rain because of the warm and tropical air mass.

Because so much warm air is overriding the arctic air mass near the surface, ice crystals that form high in the atmosphere will melt on their way down through the warm, tropical layer, and then freeze again close to the surface. Sleet is a form of precipitation known as ice pellets. It’s actually raindrops that freeze again before hitting the ground. Freezing rain or  black ice, is rain that freezes once it hits the ground.

Once more thing before I let you go.  Some of you may wonder why it will snow in Houston, but not in New Orleans or Mobile? Well, that has to do with the upper levels of the atmosphere. Texas is getting in on some colder air not just at the surface but through all levels of the atmosphere above it.

For the latest weather in your hometown, click on the link to your local TV station.

-Dawn Brown, FOX 8, New Orleans

Hurricane Rick Satellite, Image: NOAA

Baja California is preparing for another strike by a hurricane this season. Resort towns near Los Cabos, Mexico are preparing for a direct hit. Visible satellite imagery above shows a weakening Hurricane Rick, although it still packs winds up to 105 miles per hour this Monday afternoon. In September, Hurricane Jimena made landfall north of resort areas near Los Cabos as a category 2 hurricane, quickly weakening as it moved onshore.

Wind Probabilities Hurricane Rick, Image: NOAA

3 Day Track Forecast Hurricane Rick, Image: NOAA

Currently, National Hurricane Center forecasters believe the storm will still be a hurricane when it approaches Los Cabos on Wednesday. Wave action caused by the storms’ high winds is already being blamed for one death in the Los Cabos resort area. The first image above is a product from the National Hurricane Center that shows the probability of tropical storm or hurricane force winds. Currently there is a 70-80% chance of tropical storm force winds affecting Cabo San Lucas on Wednesday.

Large swells from the storms high winds over the last several days will definitely affect the coast of Baja and Mexico. At one point Rick’s maximum sustained winds topped out at 180 miles per hour. Category 5 hurricanes on the Saffir-Simpson scale are 155mph+.

For the latest on Hurricane Rick, please go to my section on Tracking Hurricanes and the MYL Forums.

For the latest on the high swells, check out the forecast from Surfline. Their blog is on the menu bar on the left hand side. Surfline has some great forecasters with the latest information on wind and wave action.

On the East Coast of the United States, it feels like winter! Cold weather advisories are in effect from Georgia to Pennsylvania.

-Dawn Brown

Today's Snow Depth, Image: NOAA, Click to Enlarge

Look at the snow! This is a picture of the average snow depth across the United States on this Sunday. What’s interesting about this picture is not the fact that five percent of the country is covered in snow. The percentage is not that unusual for the month of October. What is unusual is where the snow is located.  When I look back at the snow analysis for the middle of October for that last ten years, most of the early season snow occurred over the Rocky Mountains. This year, the Great Lakes, Appalachians, Upstate New York and New England have snow accumulations. (Source : National Snow Analysis )

This goes hand-in-hand with the cooler than average summer experienced by the Great Lakes and Eastern Seaboard as well. The upper air pattern continues to bring cooler weather to these regions. However, as I posted on Wednesday, this cool summer is no indication of what winter will look like in the same areas. In fact, NOAA is forecasting a warmer than average winter across the northern tier states. On Thursday, NOAA published its El Nino Outlook, with newer and (much prettier) pictures than I created on my blog last Wednesday, showing folks the climate outlook for this winter.

El Nino Climate Outlook, Image: NOAA

El Nino Climate Outlook 2, Image: NOAA

You can see from the first image above that the Pacific Northwest and Ohio and Tennessee River Valleys are expected to be drier than average. And the entire northern half of the United States is expected to be warmer. Sweet relief will come to the Southeastern States, with a cooler than average winter. Higher than average precipitation is expected for California and the Southern United States. (This the forecast for December through February.)

Today, cold weather warnings have been posted all across the Ohio and Tennessee River Valleys for states from Ohio and Pennsylvania to Alabama and Mississippi. Here’s the latest TV forecasts from FOX Nashville and Biloxi, Mississippi.

Great football weather! Enjoy the games.

-Dawn Brown

Thursday Forecast Highs, Image: NOAA

Friday Forecast Highs, Image: NOAA

The hot and humid weather will soon be coming to an end for folks in Texas, Louisiana, Alabama and Mississippi as a cold front finally slices through the tropical air mass Friday. Look at the forecast highs for Thursday (first image above) and Friday. Thursday, forecast highs will once again approach the upper 80s. When the cooler air mass takes hold Friday, 70s with lower dew points will prevail.

I know TV forecasters throw the dew point around like it’s the actual temperature, but when you live in the south, you might as well go by the dew point temperature when it comes to how you feel. Here’s the thing with the dew point. Generally, when the dew point temperature is 65 or below, most people feel comfortable. Now, in New Orleans during the summer, when temperatures are approaching 95 degrees, and the dew point is 78, if a cold front comes through and the dew point temperatures drops to 70,  A LOT  of people will feel more comfortable!

The reason people feel uncomfortable in humid weather is because our body cools itself by sweating and transferring heat to the air. If the air is warm and moist, it won’t take the heat and moisture we’re trying to give it. Bummer! When the air is drier, it will suck up some of that heat and sweat coming off our bodies. I’m not sure if that description is too simple or simply gross, but that’s the easiest way to explain it.

While cold and dry weather will be the rule across the Upper Midwest, in the Northeast advisories for winter weather are in effect for hilly counties surrounding metropolitan New York and Pennsylvania.

California is drying out and heating up, however, the threat for mudslides will continue during the fall and winter season. In USA Today, there is an article and graphic on how mudslides affect California after a busy fire season.

-Dawn Brown