Current Chicago NEXRAD Radar Map : Weather Underground

Current Chicago NEXRAD Radar Map : Weather Underground

Meteorological Winter

Tuesday, December 1, 2009 marked the beginning of Meteorological Winter. Seems a little early huh? There's a diference between Meteorological Winter and Astronomical Winter (also known as the Winter Solstice).

Meteorological Winter is the time of year in which the Northern Hemisphere is the coldest. This period starts on December 1 and ends on February 28.

We are more familiar with Astronomical Winter or the Winter Solstice that begins on December 21-March 20. During this time is when the sun will be furthest away from the Earth.

Pretty inconcievable that Winter is here after experiencing such a mild November and a high of 55 degrees Tuesday at O'Hare. However, today, even though still above normal, we have cooled down falling 10 degrees from Tuesday (45 degrees was the high at O'Hare) with colder weather on the way. Below is a graphic of the 6-10 day temperatures from the Climate Prediction Center.

Colder Blast post Thanksgiving

The GFS remains consistent on an artic blast that is expected to hit the Midwest Thanksgiving week. In addition to this, the Midwest's (especially in Minnesota and Wisconsin) first widespread snowfall is to take place. Chicago may see a few flakes fly come Thanksgiving. Looking further down the road into the first week of December, there is an even larger intusion of cooler air to take place. There are a few indications that supports this. First, is what is called the AO (Artic Oscillation) index. When negative, that means the cold air locked in the Artic typically plunges south into the U.S. providing cooler than normal weather for the northern plains, Midwest, and the Northeast. Opposite conditions when positve. The graphic below shows the Ao index going in a negative direction heading into the first week of December.


Second, the 11-15 day outlook has temperatures from the Plains states to the East coast below normal. The picture below shows this.


The day of this will be December 4 when temperatures will stuggle to make it into the 30s. The graphic below depicts the gfs model of the 850mb temperatures December 4.

Thanksgiving Pattern Change?

Lately, I've been keeping an eye on the consistency of the GFS between the Nov. 24th to Nov. 30th timeframe. So far, the runs have been consistent in showing an outbreak of cold weather around Thanksgiving. The month of November has been everything but what the month of October was. The National Weather Service mentioned that this October was the third coolest October on record and the wettest ever. The pattern for November has been a mild one. In fact, according to the Climate Prediction Center (CPC), next week there will be warm weather over much of the country. The image below gives a graphical depiction of this.


The GFS, while not too good with giving the exact time of a major weather event, does a good job at giving hints of pattern changes. With the current warm up and the morning GFS run continuing to support cold air invading the middle of the country, it will become interesting to see how things will pan out after next week.

It's not important at this time to point out any major storms. However, it is important to note that our current zonal pattern, that has been ushering mild Pacific air into the States, may break in the next couple weeks.

El Nino will be the biggest wildcard in all of this. El Nino has recently gained strength.

This may not necessarily mean that there will be no snow across the middle of the nation or the East Coast. I think that this Winter will experience a split pattern (being active and variable). It will be interesting to see what El Nino does in the next month or so. Models have been showing a decrease in Sea Surface Temperatures (SST) after December which will indicate a stormy second half of this Winter. Only time will tell.

Veteran's Day Tornado Outbreak

Remember the Veteran's Day tornado outbreak Nov. 11, 2002. This was the first major tornado outbreak of the 21st century. 36 lives were lost in 5 states. 83 tonadoes were spawned in 17 different states making this the second biggest tornado outbreak ever for the month of November.

11/11/11 Tornado/Cold Snap

Ever wondered how wild and crazy it would be to have a day of sun with 70 and 80 degree temperatures followed by a tornado outbreak followed by a blizzard/record setting cold snap (leaving behind it temperatures in the single digits)? Well there was a day in which all that happened. It was on this day 98 years ago in which such an event took place in the Midwest. A major storm system spawned numerous tornadoes in the town of Janesville, WI (a town in southern Wisconsin). 9 people lost their lives. The tornado strongest of the tornadoes was an F4. This followed a major cold snapped deemed the "The Great Blue Norther". It's funny too because many cities that day recorded record highs (70s/80s in November). But that same night (YES the same night..some 10 hours later) many Midwest cities were dealing with single digit temps. This was the only day in which a record high and record low was broken on the same day for many cites. Temperatures were in the low 70s in Southern Wisconsin. By nightfall temps drop to around 0. Springfield, IL was the most notable. A high of 80 that afternoon before the cold front passed just to dip to 40 degrees two hours later to 13 degrees by midnight. A 67 degree temperature drop in not even 12 hours. Oklahoma City, OK recorded a record high of 83 degrees and a record low of 17 (66 degree temperature drop). This record still holds today. There was one death from the cold in Monroe, Wi in which a man froze to death.

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