Friday, January 6, 2012

A Seesaw Pattern

The first cold outbreak of the season hit the midlands of South Carolina as New Years Day came to a close.  A high temperature in Columbia on that Sunday was 73 degrees F followed by a high of 40 degrees F just two days later.  It was the coldest weather so far for this winter.

Now a warming trend has returned temperatures to the unseasonably warm levels.  This Saturday will see high temperatures in the upper 60s to low 70s for the Midlands whereas normal high temperatures for this time of year are in the mid 50s.  It appears that the unseasonably warm weather will last into at least the middle of next week.

This seesaw pattern will last for much of January.  The bitter cold air remains lock up in the polar regions with only brief cold outbreaks for this part of the country.  Much of the country will experience above normal temperatures.

As mentioned in previous blog posts this winter's warm weather is fueled primarily by the Arctic Oscillation (AO).  This oscillation has seen the wildest swings ever recorded over the past six winters.  Records of the oscillation date back to 1950.

The pattern has re-established itself over North America and it will be unseasonably warm through the middle of next week for much of the Southeast.  There will be some light rain possible for the Midlands Sunday night into Monday morning.  The better chance for rain will come on Wednesday as a storm system moves from the western Gulf region to the Northeast.  This will bring a surge of moisture northward and rain will be likely.  The center of the storm system will pass well north of the area so no snow is expected.

Fig. 1 - The surface weather pattern for Wednesday, January 11, 2012, at 18z as depicted by the GFS computer model.  The scale at bottom is for rainfall in inches for the past six hours.  Image Credit: WSI
A cold front will pass through the Midlands late on Wednesday and this will signal the next change in the weather.  Colder, drier air will be pushing into the region.  It will settle over the area by the next weekend with the coldest temperatures likely Saturday morning according to the European model (ECMWF) or Sunday morning by the American model (GFS).

Fig. 2 - Surface temperatures for 12z Sunday morning, January 15, 2012, as depicted by the GFS.  Image Credit: WSI
This next cold outbreak will not be as cold as the one earlier this month.  Low temperatures will only drop into the mid to upper 20s for the weekend.  Temperatures will moderate again into the new week (January 16th time frame).

Much of the southwestern half of South Carolina is either in a severe or extreme drought as depicted by the U.S. Drought Monitor.  The rain mid-week will not be enough, but it will be much needed.  We need all the rain we can get to build up soil moisture for the planting season ahead.  Unfortunately we have begun 2012 as we ended 2011 with dry conditions.  Last year ended 8 inches below normal for the year.