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]:
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).
www.srh.weather.gov 
