The first -40º F or colder temperatures of the season (in the Lower 48 States)
January 13th, 2009
GOES-12 10.7 µm IR images
A strong “Alberta Clipper” system ushered in some of the coldest air of the 2008/2009 winter season on 12 January 2009 — in fact, it was so cold that AWIPS images of the GOES-12 10.7 µm IR channel data (above) showed that surface brightness temperatures as low as -20º to -40º C (cyan to green color enhancement) were surging southward from south-central Canada into the north-central US in the wake of the clipper.
A closer view using GOES-12 IR imagery with a different color enhancement (below) displayed a large area of IR brightness temperatures colder than -40º C (violet colors) across much of eastern North Dakota and northwestern Minnesota during the pre-dawn hours of 13 January. The coldest GOES-12 IR brightness temperature values seen were -47º C (-53º F) at 13 UTC (7am local time) just to the north of Waskish (station identifier KVWU) in northeastern Minnesota.
GOES-12 10.7 µm IR images
The 1-km resolution MODIS 11.0 µm IR image at 08:57 UTC (3:57 am local time) on 13 January (below) showed similar values of cold IR brightness temperatures, with a minimum of -48º C (-54º F). The coldest surface air temperature reported that morning was -42º C (-44º F) by the National Weather Service Cooperative Observer at Embarrass in northeastern Minnesota, with lows of -41º C (-42º F) at Babbit, Bigfork, Effie, and International Falls. Prior to this date, the coldest temperature recorded in the Lower 48 states this winter season was -39º C (-38º F) at Simpson, Montana on 21 December 2008.
MODIS 11.0 µm IR image
– 15 January Update –
GOES-12 10.7 µm IR images
On the morning of 15 January, the core of the coldest air in the north-central US was found from central North Dakota into northeastern South Dakota — Bismarck in North Dakota dropped to -42º C (-44º F) (only 1 degree F shy of their all-time record low), while Aberdeen in South Dakota recorded a low of -41º C (-42º F) (which was only 4 degrees F shy of their all-time record low). However, GOES-12 10.7 µm IR images (above) displayed surface IR brightness temperatures as cold as -47º C (-53º F) in North Dakota.
A comparison of 1-km resolution MODIS and 4-km resolution GOES-12 surface IR brightness temperatures at around 08:45 UTC or 3:45 am local time (below) displayed very similar minimum values of -48º C (-54º F) and -47º C (-53º F), respectively.
MODIS 11.0 µm IR + GOES-12 10.7 µm IR images
With such a cold and dry air mass in place over the region, the GOES-12 6.5 µm “water vapor channel” imagery (below) was able to display a signature of the large surface temperature contrast between the relatively warm waters of the Great Lakes and the St. Lawrence River and the surrounding colder land surfaces. GOES-12 water vapor weighting functions calculated using the Detroit MI rawinsonde data indicated that many of the GOES imager and sounder water vapor channels were peaking at unusually-low altitudes.
GOES-12 6.5 µm water vapor images
MODIS true color imagery showed that ice formation was rapidly increasing over far western and southern Lake Michigan with the presence of the cold air over the Great Lakes region.
