La Nina Conditions Develop

According to the Climate Prediction Center La Nina conditions developed during this past July as negative sea surface temperature anaomalies strenghtened across the central and eastern equatorial Pacific Ocean.  Nearly all climate models predict La Nina to continue at least through early 2011.  However, there are some uncertainties as to the actual strength.  But since strong cooling has been observed over the last several months - predictions are that La Nina conditions are expected to strengthen and last through Northern Hemisphere Winter 2010-2011.  So what does this mean for us?  A blocking high pattern begins to set up where low pressure systems in the mid-latitudes tend to be weaker than normal in the Gulf of Alaska.  This tends to build up colder than normal air over Alaska and western Canada allowing the cooler air to spill into the northern Plains.  The southeastern U.S becomes warmer and drier than normal while the Great Lakes are stuck in the middle.