It will not take much snow to eclipse last year's paltry winter, but are extreme storms the new normal? Bob Ryan takes a look in his winter weather outlook.
OK, I know "more snow than last winter" would not take much. Last winter, the D.C. area (officially at Reagan National Airport) recorded a measly (for snow lovers) two inches of snow. So, what can we look at for some hints of what this coming winter will be here in the D.C. area? As Doug Hill pointed out in his outlook last Tuesday, ENSO is neutral and doesn't offer much of a hint. The latest outlook for El Nino - La Nina is for a "neutral" (tropical oceans neither unusually warm or cool) condition to continue.
The long term trend of temperatures across the U.S. is still more "very warm" periods than "very cold" periods.
And it sure has been a warm year in Washington. Even if the recent chilly pattern continues, this is still likely to be the warmest year in D.C. weather on record. The top line in this multi-year graph is the running temperature year to date for DC
Just looking at all this one is tempted to say that there should be more mild weather ahead and another "easy" winter. But there are hints that what we would call "weather extremes" are becoming more probable in the years ahead. This is one measure of a "Climate Extremes Index" from the National Climatic and Data Center. The green line is the long term trend.
One of the significant atmosphere-ocean changes over the last 30-40 years has been the trend of decreasing Arctic sea ice in summer. This September saw a new record low.
- Some recent studies have suggested that more open water in the Arctic is a factor in upper level jet stream patterns, the so called "westerlies" in the mid-latitudes.
- If this linkage is confirmed by future research, the recent "hints" that weather patterns are becoming more extreme and the extremes more persistent (longer droughts, but also prolonged wet patterns increasing flood risks) will become more widely accepted.
- My friend Stu Ostro has put a lot of thought and time into an outstanding presentation of the footprints of these pattern changes and what may lie ahead. I think what we are seeing recently is not for sure a "new normal" but a pattern that this year will give us a near normal cold winter but also with several chances of major storms for snow lovers.