Current Weather Conditions:

Tuesday, January 27, 2009

January Thaw

I've recently mentioned the January Thaw in several posts. Being the fanatical weather weenie some think I am, and realizing that I have a worldwide audience (well, the potential for a worldwide audience I suppose...although I do know a couple of kind folks from across the pond have ventured onto my blog a few times), makes me feel compelled to provide an explanation of this regional weather phenomenon.

I'll let Keith C. Heidorn, PhD, (THE WEATHER DOCTOR) provide the technical details.

A January Thaw is expected to fall within the third week of January, usually following a strong cold snap, but need not occur every year. In fact, during the very cold winters of the late 1970s, there were no January Thaws in the New England region during 1978 and 1979. (And they could have used a thaw!) There have also been recent mild winters when the Thaw was absent or hardly noticeable...

In prime January Thaw country, the ideal weather pattern characteristic of the Thaw period unfolds in this manner. It begins after a cold air mass from northern or
western regions has slid over the region (A), eventually moving out over the Atlantic Ocean. As that air mass leaves, the Bermuda High strengthens (B,C,D) and becomes positioned over the southern Atlantic Coast or southeastern US
states while a broad low pressure trough moves slowly across northern Ontario and Quebec (B-E). The juxtaposition of the isobar patterns of these two map features (E) places the northeastern US and southeastern Canada border region into a south-southwesterly flow of warm air from the Gulf of Mexico. This air advects over the northern snow and ice fields and begins a thawing.

Often during this time, the upper air wind patterns are in a period of readjustment, and thus surface weather systems stall or creep slowly across the eastern continent's mid-latitude belt. After several days of warmth, the regional weather again comes under the influence of a strengthened polar high (F,G), and cold weather returns.
Technically,the January Thaw is what is known as a weather singularity, which is a weather phenomenon likely to occur with reasonable regularity around a specific approximate calendar date. That date is typically January 23-25...and those of us living in these parts know that we have not observed any type of thaw over the past several days nor do we have any type of thaw in store over the next few days.

If I had known there would be no January Thaw this year, I would have made a greater effort to get on the bike trainer. Yeah, right!!


Martinator said...

I'm not even thinking about dragging my nice, shiny road bike outside until maybe March. Now if I had a "winter" road bike, or a Cyclocross bike it might be a different story.

As you have read on my blog, I really need to thing about doing some core strength exercises this winter.

I also have a 1982 Schwinn Varsity that I hope to someday make roadworthy once again. Once that project is completed (if I ever really start it) then that would also be a contender for a winter ride.

Did you know that Kenda makes studded snow tires for road bikes?

I would ride more in the winter with a set of these just to say "Oh, I have a set of studded snow tires for my ride..." :-)

Glenn_in_MA said...

My original idea for a winter ride bike was to convert the Peuguot myself. If I stayed with that idea, the bike would still be hanging on the garage wall! I opted to have the LBS do the conversion and they only charged $50 for to me that was a great deal. I'm glad I have the fixed gear to's a different type of ride...much easier to get used to than I was led to believe...and really not too risky (I kept both brakes).

I have no desire to bring my other road bikes out in these conditions.

I'm way behind on winter exercise...happens all the time.

sarah said...

I hope we get a 'February Thaw' to make up for the lack of one in Jan! In the past though, I've thought Feb is colder than Jan here.

Martinator said...


February probably is colder than January here. More snow cover on the ground to reflect away the sun's energy until the vernal equinox and more direct sunshine counters the reflective effect.

Though a February thaw would just mean more crappy roads as the expanding and contracting of the asphalt in New England's wet soil leads to bigger pot holes and chewed up roads in the summer.

Careful what you wish for, you might just get it ;-)

Glenn_in_MA said...

Hey...I'm the resident meteorologist on this site!! LOL!

Sarah, most people do perceive Feb as being colder than Jan, but climatologically it is slightly warmer than Jan. I always think of Feb as the snowiest of the winter months, which is not quite true either.

Martin, at this point I don't think there's much that will change the future condition of the roads...unless we get into a series of freeze-thaw cycles then we're really in trouble. The winter of 95-96 was bad as far as snowfall and I remember it took a HUGE tole on the roads that year. Some of my favorite loops become close to unridable that Spring.

Glenn_in_MA said...

toll, not tole! duh!

sarah said...

If some of the roads around here get any worse, I'll be riding my 'cross bike all the time! There are roads where I've been picking a line like I'm on a trail in the woods.

I just need one really nice day in Feb for my metric century. That's all I ask for! As long as I get that I'll be happy enough on the trainers for the rest ;)