Last week, scientists at NOAA and NASA released their report indicating 2018 was the 4th warmest year on record globally and the 14th warmest for the United States. Due to the federal shutdown, the report was delayed a few weeks, pushing it into February. These organizations are already gearing up for the first report of 2019, which will incorporate the whole month of January, and they will notice that the United States was much colder than normal so far.
Now, obviously, winter in the United States means it is going to be cold. Even in a warming world, we will experience cold conditions, just not as much. For more information on cold outbreaks and climate change, check out a good analysis here. Once in a while, it gets to be so cold, that numerous records going back decades can be broken. Why is this the case? Well you may have heard of something called the “Polar Vortex.” First off, it should be noted this is not a new term, as it has been in the American Meteorological Society (AMS) glossary page for many years, with research occurring as far back as the early 1990s. The other thing to note is the polar vortex is always there, it’s just usually up by the poles (hence the name polar). In the wintertime, if the upper air conditions are right, this cold airmass traverses southward into the United States. Depending on the strength of the system, it can stay in the area for a few days, and sometimes even up to a week.
Late in January 2019, a piece of upper level energy came into the northern part of the United States, bringing very cold temperatures into the area. Much of the Midwest experienced sub-freezing temperatures, especially between January 30th and February 1st. In fact, there were a few days where the daytime high temperature was not above 0 degrees Fahrenheit (about -17.8 for those tracking in Celsius). Comparing the last day of January to a thirty year average, most of the United States experienced temperatures more than ten degrees below normal. The maps below depict this information very nicely.
Although not released yet at the time of writing, the January 2019 climate report will certainly show the effects of this cold outbreak. Over 500 weather stations experienced the first month of the year colder than their 1981-2010 counterpart. Not only that, 315 stations experienced both a record breaking overnight low temperature, in addition to having one of their coldest daytime high temperatures. Below are the locations that had either 4 nighttime or 4 daytime records broken:
The upper Midwest, including Minnesota, Wisconsin, Iowa, Illinois, and Michigan, faced the brunt of the polar vortex. Union Grove, Wisconsin, which lies between Chicago and Milwaukee, experienced some of the coldest temperatures. They had 7 overnight low temperature records, and 6 days when the daytime high temperature was at this lowest. There was also a 5 day period where the overnight low temperature hovered between -20 and -25 Fahrenheit, certainly a pipe bursting event for homes in the area.
The most interesting part about this report is that none of the analysis includes wind chill, developed to incorporate the human exposure to heat loss on skin due to both temperature and wind speed. Some areas, experienced wind chills in the -40s. At this rate it wouldn’t necessarily matter what the temperature scale is, as -40 F is the same as -40 C. Nonetheless, I think it can be agreed upon that it was very cold. While there are still 11 more months to go in 2019, it will be interesting to see how this month will effect the values for the entire year.