Record cold expected.
The Al Gore effect as well as the testimony on Capitol Hill yesterday has caused a massive chunk of Arctic air to descend from Western Canada into the United States. How do temperatures 6o-70F degrees below average sound to folks along the Canadian border? During the next 10-days (or more!), a hemispheric realignment of the large-scale atmospheric circulation will cause a significant decrease in temperatures over North America and Europe. If this regime reinforces itself during the next few weeks, and a negative Arctic Oscillation phase strengthens, the brutally cold temperatures will provide a dramatic reminder that winter is cold regardless of “global warming”. I anticipate plenty of fossil fuel use coming up.
Weather weenie discussion after the break w/maps
With strong anti-cyclones developing over the North Pacific and North Atlantic at the same time, a highly amplified pattern is developing over the Northern Hemisphere. At the permeable barrier separating the troposphere and stratosphere lies the tropopause. On the tropopause, which is often identified by a constant potential vorticity (PV) surface of 2-PV units, one can plot the potential temperature (Θ) to identify upper-level synoptic phenomena such as the jet stream, Rossby-wave breaking, anticyclones, and cut-off lows. From these so-called “dynamic-tropopause” maps, it is relatively easy to see what’s going on.
The warmer potential temperatures ( Θ ) on the tropopause mean it is higher in the atmosphere since Θ increases with height, unlike regular temperature which decreases through the troposphere (before increasing in stratosphere due to ozone absorption of UV). Thus, tropical and subtropical origin air has much higher dynamic tropopause Θ than the Arctic vortex air which is signified by the gray and purple colors on the map above. Often the difference is well over 100-120 degrees Kelvin.
The sharp gradients of dynamic tropopause Θ are typically where the planet’s jet streams are located. During the 180-hour forecast period, the subtropical jet stream is easily identified over the central United States in conjunction with a powerful storm system. The counter-clockwise turning of the Θ represents cyclonic circulations while the opposite, clockwise circulations are associated with anti-cyclonic circulations or ridges.
The flow for the next week comes straight out of the Arctic over North America. Temperatures will easily sink below zero in many places and a hard freeze is likely for a lot of the US. Europe does not escape the bitter onslaught, either. I provide a couple maps below from my FSU website that show the temperatures for the next 180-hours, and the deviations from climatology.
All of this discussion is on the synoptic scale or days to a week time scale. Forecasts longer than this are not particularly skillful, so it is not clear how the La Nina will evolve over the next month. Furthermore, no two La Ninas act the same so averaging together previous events is not particularly skillful either. Main point: the atmosphere rarely matches the “mean state”. Perhaps Heidi Cullen can explain it better than I — after all she was on the Weather Channel.
*snort*
I can walk outside an feel the demonstrable lack of veracity of the prediction.
The map you just posted is 10 degrees warmer at a minimum, virtually everywhere in united states than the prediction map (and also for nov 25 instead of today. The NOAA Map for _this_ morning (Nov 22, the same day as the prediction map above) is even _warmer_.
Highlights include a 40 degree misprediction in central Missouri (actually in the 70’s instead of the predicted 20’s) 30 degrees off in Michigan, Over 20 degrees off in North Dakota.
This was a truly awful and inaccurate prediction, and the smug reactions to it above, accepting it as fact before the evidence was in, quite saddening.
[ryanmaue: Unfortunately, you are not interpreting the minimum temperature plot correctly. It is the coldest temperature to be experienced during the forecast period of 180-hours at each grid point. You need to look at the individual forecast maps for each day … The high in Helena Montana is going to be 4F, which is about 35F below normal for the day.]
Nope. The lows on every NOAA prediction map (1am, and 4am) from now to Saturday are consistently 20 to 20 degrees warmer at a minimum than the prediction map in this article across the country.
As for Helena (aside from the fact it’s 5 now, but that’s the tiniest quibble), the lowest low predicted in the next 10 days is -11 F, whereas the prediction map shows somewhere between -15 and -20 for Helena. Fargo, ND has a predicted lowest low in of about -2, which looks to be among the only hits the prediction map has.
Places like Walla Walla, with a minimum of 4F predicted Tuesday night are still ~20 above this post’s map’s prediction. I stand by the assessment that the posted prediction map is at least 10-20 F colder than NOAA says, on average, for the vast majority of the US.
The NOAA prediction map is based upon the same model I am plotting. There are higher resolution versions… Two different model cores of a similar system: 4-km WRF run minimum temperatures during the next 48-hours for ARW and NMM cores. You must consider the grid spacing of the GFS model results, inherent model bias, the height reduction of the temperature measurement (2-meters), and the forecast lead time. Thus, a 5-day forecast has skill, but clearly not as much as a 24-hour one.
All right, I’m willing to take that grain of salt. I still think this particular 180 hour prediction looks to be significantly overstating minimum temps. But then no predictor is perfect.
The point that winter is cold despite warming trends is something that could do with more recognition. A degree or two of warming will barely register to a local population when the average low temp of a winter region is, say, -5 vs. -7 degrees F.
It’s conversely interesting that the temp anomalies in the arctic – and especially over Greenland and Alaska at this same time are 30-40 or more degrees F _above_ average.
Currently
30-40 or more degrees F below
average in Alberta, Canada.
http://www.wunderground.com/global/CA_AB.html
Yes, but as you say Xeno, a huge change in the Arctic is a small blip against the variability from year to year. The temperature in the Arctic in a given November has a large standard deviation, and of course tails in each direction making it hardly normal. I produce plots which take into account the variability and will put some on my website soon.
Went into DC yesterday and it was 70 degrees, far above normal. But that’s pointless to bring up in a climate discussion, because the real measure we are looking for is climate trends, which is not going to be determined by localized, short term temperature swings. And yes, the lower 48 states are localized, as they represent less than 1.5% of the Earth’s surface.
I can’t believe people here are still struggling with the concept of climate and weather, but then again, there is little skeptics can hang their hat on these days…