Chinook Posted December 21, 2014 Share Posted December 21, 2014 I recently was browsing some twitter feed of NOAA, and it mentioned the average coldest day of the year, and showed a graphic. I googled it again today, and found some easier-to-read graphics on this,and the average warmest day of the year. I have found some interesting features. Coldest Day Much of the West has its average coldest day around the Winter Solstice, or even earlier. This shows the tendency of sun angle and day length to control the winter climate. Around my area here in Colorado, our coldest daily-mean is around Christmas, and slightly warmer in January. Also, the synoptic-scale troughs tend to deliver very cold air to the West in Nov. and Dec. The immediate West Coast doesn't show any tendency to have the coldest day on March 1st, apparently. The Pacific water temperatures should be at the minimum around then. Much of the East has its average coldest day in January. This shows the tendency of a general 25-day to 30-day lag in Winter-Solstice-to-colest-day. Also, the mean synoptic trough tends to shift eastward in January and February. In the Lake Effect Belts and some interior valleys of Wyoming, Colorado, and Utah, perhaps old, thick, snow cover dominates the coldest day climatology, as some of these areas are February 16th or later. Warmest Day Most of Arizona and New Mexico have their warmest day early in the summer, as the extremely hot dry air peaks out before the southwest monsoon season. These areas receive more clouds and slightly weaker lapse rates when the monsoon is happening. I find it interesting that the Texas, Louisiana, and parts of Tennessee have some of the latest warmest days. Perhaps this is due to warm humid air trapped in upper-level ridges in this area in an early-August time frame. The Pacific Coast areas are dominated by water temperatures, which reach the warmest temps around Labor Day. This is very late in the season compared to most of the continental cities. The Pacific Northwest to North Dakota also seem to have the highest temperature in early August. July 11-20th seems to be a fairly normal date for a lot of the rest of the country. This shows a tendency for a 20-day to 30-day lag from the Summer Solstice (expected for most continental areas.) Link to comment Share on other sites More sharing options...
GaWx Posted December 21, 2014 Share Posted December 21, 2014 Per the maps, it looks like some areas along the Pacific coast go from highest normal to lowest normal in under four months vs. some places that take as long as near or just over 7 months such as in some of those CO valleys! Link to comment Share on other sites More sharing options...
JBG Posted December 25, 2014 Share Posted December 25, 2014 If memory serves me correctly upstate New York and northern New England tends to have warmest temperatures in June or early July and coldest in very late January or early February. Certainly records going back before 1981 bare this out. Link to comment Share on other sites More sharing options...
RodneyS Posted December 27, 2014 Share Posted December 27, 2014 See this thread: http://www.americanwx.com/bb/index.php/topic/38960-recent-january-dca-temperatures-appear-inconsistent-with-1981-2010-normals. The bottom line is that there seems to have been a significant change in the coldest day in DC in recent years. January 13th has gone from being the coldest January day at 33.3 degrees on average during 1872-1983 to the warmest January day at 40.5 degrees on average during 1984-2014 -- an increase of 7.2 degrees. January 21st has been the mirror image of January 13th -- going from the second warmest January day at 36.8 degrees on average during 1872-1983 to the coldest day of the year at 31.8 degrees on average during 1984-2014 -- a decrease of 5.0 degrees. Does anyone know whether this same phenomenon has been taking place in other US cities? Link to comment Share on other sites More sharing options...
RodneyS Posted January 23, 2015 Share Posted January 23, 2015 See this thread: http://www.americanwx.com/bb/index.php/topic/38960-recent-january-dca-temperatures-appear-inconsistent-with-1981-2010-normals. The bottom line is that there seems to have been a significant change in the coldest day in DC in recent years. January 13th has gone from being the coldest January day at 33.3 degrees on average during 1872-1983 to the warmest January day at 40.5 degrees on average during 1984-2014 -- an increase of 7.2 degrees. January 21st has been the mirror image of January 13th -- going from the second warmest January day at 36.8 degrees on average during 1872-1983 to the coldest day of the year at 31.8 degrees on average during 1984-2014 -- a decrease of 5.0 degrees. Does anyone know whether this same phenomenon has been taking place in other US cities? To update this, January 13th was a tad on the cool side in DC this year, bringing the 1984-2015 average for that day to 40.3 degrees -- still an increase of 7.0 degrees from the 1872-1983 average of 33.3 degrees. January 22nd -- the warmest DC January day during 1872-1983 -- was the coldest day of the year in DC during 1984-2015, averaging 32.1 degrees -- a decrease of 5.1 degrees from the 1872-1983 average of 37.2 degrees. Link to comment Share on other sites More sharing options...
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