Cooler Start to the Month of May

The temperature trend this week features highs warming back to, and above, average.  Wednesday afternoon felt great under partly cloudy skies, and Thursday will feel just as nice.  But if we look at the first two weeks of the month of May our average monthly temperature so far has actually been below average.  A little over 3 degrees below average!  (A little look at the rest of the month and it does look like we'll continue to see a warming trend).  

The pattern this spring, at least over the Midwest, has been pretty consistent with the cooler weather.  Yes we've had warm days here and there, but most of our highs have fallen just shy of those daily high temperatures.  What gives?  To understand, we have to look up above our heads at the jet stream level to understand why our overall pattern has been cooler.

For most of May the upper levels of the atmosphere have been warmer over the high latitudes near northern Alaska and the Arctic Circle.  Typically this time of year it is cooler.  So what that 'bubble' of warmth has done has forced our jet stream to dip south and pull down the cooler air that is usually found in the north this time of year.  There are likely a couple causes for that, some extending still back to the winter months, but the tropics may have an answer for our recent chilly snap.

Over the Bay of Bengal near India is a Tropical Cyclone.  Tropical systems and hurricanes are very good at releasing a lot of energy into the atmosphere that can span and effect the weather hundreds of miles away.  It's possible that the energy given off by this cyclone near India has had enough heat - so to speak- that is has caused the warmer air to remain stationary in the higher latitudes over the Northern Hemisphere.

Since this storm won't last forever, as it weakens we should begin to see our pattern break down which will help with the warmth coming late this weekend and into next week.  It's very fascinating to see how weather systems in different parts of the world can affect our weather in the United States.