Monday, November 30, 2009

Snow for Parts of Texas This Week.

An area of low pressure in the upper atmosphere associated with very cold air aloft will move across the state of Texas early this week. Out ahead of this low pressure copious amounts of Gulf Moisture will spread across East Texas. Rain will begin to develop late Tuesday and could be heavy at times Tuesday night.

While heavy rain breaks out across our area Tuesday night, under the actual upper low across west Texas, heavy snow could develop. There are winter storm warnings out for much of west Texas and southern New Mexico where up to 6 to 8 inches of snow could fall. As this area of low pressure moves east, the core of upper level cold air will move with it bringing a threat of snow mixing in with rain across much of west Texas Tuesday night and Wednesday morning.

Will this threat of snow move into East Texas? Although I can’t rule it out completely, there are a few things going against us getting any snow. The main obstacle preventing snow is the fact that our elevation is much lower in East Texas.

Below is an image of the forecast 850mb temperatures. We usually need these temperatures to be below freezing for snow to fall, which they are, running -2 to -4 degrees Celsius.

850mp Temps

Below is an image of the forecast surface temperatures Wednesday Evening. Temperatures are forecast to be between 35 and 40 degrees. In this range snow could reach the surface.

Surface Temps

The final image is the accumulated 6 hour precipitation. This image shows the heaviest wrap around precipitation north of I-30, some of which could be snow. If you look at the surface temperature map again you will see areas north of Mt. Pleasant where temperatures are below 35. This could allow for a light dusting if this verifies on elevated surfaces.

6 Hour Precip

The mid and upper levels of the atmosphere will be plenty cold enough for snow to develop but the depth of above freezing temperatures near the surface is just too great to allow the snow to reach the surface. There are a few areas in East Texas where the elevation is over 700’ and in these locations, it is possible a few wet flakes could reach the surface. If this area of low pressure is slightly stronger than forecast then there could be heavier precipitation under the core and this would drag the colder temperatures aloft to the surface which could lead to a better chance of snow. Many surprise snow events have happened with these upper lows including the snow on Easter of 2007 here in East Texas and the heavy snow event on Christmas Eve of 2004 along the Gulf Coast. So this will need to be watched closely.

One thing is certain. Behind this low, the coldest air of the season will move into East Texas. Temperatures by Thursday morning could be in the upper 20s to lower 30s area wide bringing the first widespread freeze to East Texas.

Thursday, November 19, 2009

Remembering Dr. Fujita

Eleven years ago today the world lost one of the great contributors to the science of meteorology, Dr. Tetsuya Theodore Fujita. Dr. Fujita’s tornado research would later lead to what is now known as the Enhanced Fujita Scale, or EF scale. His original scale of tornado intensity, known as the Fujita Scale, ranged from F-0 to F-12(as seen below).

Through further research based on his findings, this scale was later enhanced and implemented in February of 2007.

Dr. Fujita also studied downbursts and microbursts which eventually lead to a better understanding of how these phenomenons can cause air disasters. He studied two of the most noted airline crashes caused in and around thunderstorms, the 1975 crash of Eastern Airlines flight 66 which crashed at JFK airport killing 122 people and the 1985 crash of Delta flight 191 at Dallas-Fort Worth killing 135 people. It was shortly after Delta flight 191 the Dr. Fujita published is work on the study of microbursts and downbursts which has more than likely saved countless lives.

For more on Dr. Fujita please read the tribute from here.

Friday, November 13, 2009

Warm weather comes to an abrupt end next week

So far the month of November has been warm and dry giving us a chance to dry out from October’s deluge. Normally by now many areas of East Texas would have already experienced their first frost but this November we have been above normal temperature wise delaying the onset of frost and freezing temperatures. It looks as though this spell of mild weather will come to an abrupt end next week. A strong cold front in association with an area of low pressure will bring a chance of showers and thunderstorms late Sunday into Monday followed by much cooler weather. Right now it appears the area of low pressure will stall to our northeast Tuesday keeping cloudy and windy conditions and maybe even a sprinkle or two. The big story will be the temperatures behind the front. High temperatures Tuesday will struggle to reach the middle 50s thanks to lingering cloud cover. As the low finally moves away from the area Tuesday night, clouds should decrease and winds will die down. This is the perfect set up for what we call radiational cooling, were the Earth’s heat is able to escape the atmosphere causing rapid cooling after sunset. Right now it looks as though in our normally cooler locations, temperatures will be able to drop into the lower to middle 30s. This would produce frost in these areas for the first time this year. Right now we are calling for temperatures in the upper 30s to low 40s but looking at the raw data coming late this morning, a frost appears likely for some areas next week. So get ready for some big changes across East Texas.

Sesame Street Visits Good Morning East Texas

Clint, Jennifer, and I had a lot of fun this morning. Here are a few shots of the gang.

Remembering one of the worst tornado outbreaks in East Texas

Sunday will mark the 22nd anniversary of one of the biggest tornado outbreaks in the History of East Texas. On this day, four long track F3 tornadoes moved across parts of East Texas and a total of 50 tornadoes occurred over a 48 hour period from the Southern Plains to the Southeast United States. One of the most noted tornadoes was the F3 that caused considerable damage to Palestine in Anderson County. This tornado was on the ground for 11 miles and unfortunately claimed one life and injured 59 other people.

The most tragic tornado of the day tracked through Cherokee and Smith counties through Jacksonville, Mixon, and Whitehouse. This tornado was on the ground for 33 miles, claimed 4 lives, and injured an additional 81 people. Based on times and tracks , this tornado appears to be the second tornado in East Texas and fourth overall produced by a single supercell thunderstorm that developed along a dryline in Central Texas. This storm appears to have gone on to produce a total of eleven tornadoes including another F3 tornado in Cass County near Marietta, making a total of four F3 tornadoes from a single thunderstorm.

Later, in the early evening hours, another supercell developed near Lufkin and moved to the northeast. This storm would go on to produce a long track F3 tornado near Center in Shelby County and continue northeast through southeastern Panola County into Louisiana. Thankfully this tornado caused no deaths in East Texas but it did injure 15 people.

Unfortunately since this event happened before the internet age, there is very little information. A matter of fact, this may be one of the largest tornado outbreaks with very little research or information available. I would like to change that. Over the next few weeks I plan on researching this event to find out as much information as possible. For one thunderstorm to produce eleven tornadoes is a very unusual and extreme event. If you have any images or stories of this event you would like to share, please email them to me. With your help, we can learn more about the environment that lead to such a tragic event.


Wednesday, November 11, 2009

The November 11th Blue Norther of 1911

On November 11th, 1911, an intense area of low pressure developed over the Midwest leading to extreme weather across a good deal of the nation. Many areas of the country saw record warmth late that afternoon only to be shocked by the intense arctic blast to follow hours later. In Oklahoma City, a record high of 82°F was set in the afternoon before a cold front raced through the area. Just before midnight, the temperature was 16°F establishing a new record low for the same date. Other Cities such as Springfield, MO set record highs in the 80s that afternoon followed by record lows in the teens just before midnight.

Take a look at some of these temperature extremes from highs on the 11th to lows on the 12th:

Oklahoma City 82°F/14°F
Amarillo, TX 70°F/10°F
Palestine, TX 82°F/28°F
Springfield, MO 80°F/8°F
Fort Worth, TX 86°F/20°F

So why the big difference in temperatures? The image at the top shows the weather map for the morning of November 11th, 1911. You will notice an intense area of low pressure developing across northwest Missouri at this time. This low brought with it a large amount of warm moist air that would lead to severe thunderstorms, as I will discuss farther down, but also brought with it dry air as winds blew down the front range of the Rockies causing a dryline to form from Oklahoma down into Texas. The air mass behind this dry line was still out ahead of the main cold front so temperatures were allowed to soar. Much of southwestern Missouri, Oklahoma, and Texas were in this warm dry air mass with temperatures soaring into the 80s to near 90 in a few locations. Shortly after sunset the arctic front raced through these same areas causing temperatures to plummet, as much as 30°F in one hour. It was the unique combination of warm dry air ahead of a fast moving cold front which allowed such a large range of temperatures to occur on the 11th.

In addition to the significant temperature change, an outbreak of severe weather occurred across parts of the Midwest. Numerous tornadoes were reported across Indiana, Illinois, Michigan, and Wisconsin. An F2 tornado hit Waterloo, IN and 2 people were killed in Michigan with tornadoes. The strongest tornado was in Jamesville, WI where an F4 tornado killed 9 people. Less than an hour later blizzard conditions with wind chill temperatures near 0°F were hampering the cleanup efforts.

Monday, November 9, 2009

Ida Now A Tropical Storm

Ida moved back into the warmer waters of the Caribbean Sea late Saturday and re intensified to a hurricane yesterday. Ida reached its peak intensity yesterday at 6PM when the top winds reached 105 mph, making Ida a category two storm. Ida's top winds continue to decrease now as it enters the northern Gulf of Mexico where water temperatures are much cooler. As of this update top winds were 70 mph making Ida a strong tropical storms before making landfall along the north central Gulf Coast. Some continental, drier air will also wrap into the system causing Ida to lose her tropical characteristics. Very heavy rain and isolated tornadoes can be expected along the central Gulf Coast over the next couple of days along with very gusty winds. The current forecast track is below and will update as new advisories are released.

Thursday, November 5, 2009

Ida Could Be Heading For The Gulf.

The 2009 Hurricane season does not want to end just yet. Our ninth named tropical system has now made landfall in Nicaragua as Hurricane Ida. In the process, Ida became one of the fastest developing tropical systems on record becoming a hurricane in just 24 hours. The fastest system to develop from depression to hurricane occurred two years ago off the Texas Gulf coast, Hurricane Humberto.

Now that Ida has made landfall, she will rapidly decrease in strength over Nicaragua and Honduras and will more than likely become a depression tonight. By Friday afternoon we expect Ida to move back into the Caribbean Sea and once again reach tropical storm status. Notice the current forecast track. The center of Ida comes very close to hitting the Yucatan Peninsula by Monday morning. If Ida remains over warm water, she could once again become a hurricane as she enters the Gulf.

The good news for Texas, it looks as though a cold front that will move through the area Monday will help steer Ida of to the east. Areas along the Gulf Coast from Alabama to the Florida Keys should pay very close attention to Ida as this appears to be the most likely area of landfall next week.