As the US heads towards fall the normal behavior is increased temperature anomaly across the country. One thing I hope these weekly updates will show is just how normal temperature anomalies are in the world. As the fall progresses into winter it will be clear that a single warm week in the autumn can contribute more to a annual amount of warming than a month of the summer can.
In addition the world is in the grip of the warm phase of the AMO (Atlantic Multidecadal Oscillation). Much more on this in the near future, but this year is a poster child for the impact of a warm AMO in the US. The cool northwest being one of primary signals of the warm AMO. This last week is once again a perfect example. In addition the northeast US had a very warm week. Most of the US was near normal for the past week.
The past few weeks are listed below for the annual trend.
This cooler anomaly is much larger this week and this trend of much larger anomalies warm and cool will happen over the next few months. Winter of course is the king of anomalies as very large weekly anomalies can happen anywhere in the country and often do. This will be especially clear in the recent year maps.
The comparable week for the past few years are now shown.
This beginning of September has had 3 out of 4 weeks with significant cooler than average temperatures across the country. Only in 2007 was there no area that was cooler than average. 2008 had much cooler than average temperatures across most of the country. Each of these is dependent on weather, but weather will result in larger temperature anomalies as summer ends. That is the natural cycle of the year.