Hard Freeze Grips U.S. Central Gulf Coast Region
By late Sunday evening on 3 December, 2006 surface arctic high pressure had developed southeastward and was poised to bring the coldest temperatures of the 2006-2007 Fall-Winter Season thus far to the U.S. Deep South. By Tuesday morning, 5 Dec, surface high pressure was in firm control, and under clear skies and relative light wind conditions, surface temperatures fell into the upper teens to upper 20s across a large portion of the Central Gulf Coast Region. A Hard Freeze Warning was issued early Monday (4 Dec 2006, 4 AM CST) for Tuesday morning's hard freeze event that was forecast to occur north a Wiggins, MS to Mobile, AL to Crestview, FL line (see dashed white line in images below). A Hard Freeze Warning means that at least 5 hours of surface temperature below 26 deg (F) is expected. People, Pets, Plants and pipes definitely need protection from this type of cold weather.
Surface Temperatures by Midnight, 5 December had already fallen into the lower 20s over interior portions and that ranged to the mid 30s along the coast. The see surface temperature observations and satellite imagery estimates of colder temperatures around the region for various hours click on each the images below [NOTE: The digital portion of the images below is what is referred to as 'satellite skin temperature' and in this case was found to be about 2 deg (F) colder than the actual surface temperature which is measured at 2 m (or 6 feet) above ground. In this manner, and in the absence of clouds overhead, we can estimate the surface temperature within approximately 1-2 deg(F) of the actual for most locations]:
Midnight, 5 Dec 2006 3 AM CST, 5 Dec 2006 6 AM CST, 5 Dec 2006
Typically, in situations like this that are characterized by strong arctic-origin surface high pressure, relative light winds and clear sky conditions, if you live near a river valley and very close to the water you will be warmer than surrounding areas (as shown along major river basins like the Alabama, Tombigbee and Pascagoula in the images above). Also, if you live on hill tops where winds are a bit higher (i.e., a light wind is defined as less than or equal to 6 mph), you may also be a little warmer. However, if you are away form the coast and live within the interior valleys with no water source (such as positions of interior southeastern Mississippi, along the Alabama-Florida border and over far inland portions of southwestern Alabama (e.g., Butler County), you will experience some of the coldest minimum surface temperatures. This indeed happened in this event! Typically, and not necessarily related to this case, as surface high pressure builds further east the second night behind a cold (and sometimes even the third night, albeit more rare) will actually be colder than the first night due to the winds dying off and the evaporation of any rainwater that may fallen in association with the cold front.
Additional Monday afternoon (4 December) maximum and Tuesday morning (5 December) minimum surface temperatures over portions of interior southeastern Mississippi, southwestern Alabama and the extreme northwestern Florida Panhandle can be view by <clicking here>. A Freeze Watch was issued much earlier for this event on Saturday, 2 December.
Acknowledgments: This narrative was produced on Tuesday 5 December 2006 by Jeffrey M. Medlin (Science an Operations Meteorologist) and posted to the .www by Ray Ball (Information Technology Officer).