(Image source: NCDC/NOAA)
According to reports from the National Climate Data Center, May 2013 was the third hottest May in the climate record. May 2013′s average temperature was .66 degrees Celsius above the 20th Century average, tying values for May of 2005 and 1998.
Though the Eastern Pacific edged closer to La Nina conditions, this cooling of waters off South America did little to abate near record warmth. Overall ocean temperatures were 5th hottest on record with very high temperatures remaining over much of the Tropical Atlantic and likely providing fuel for the two storms that have already developed in June: Andrea and Barry. Normally, June only hosts one storm every two years. However, in recent years, the number of tropical systems during June has markedly increased, leading some meteorologists to speculate that the Hurricane Season is getting longer.
According to observations from Dr. Jeff Masters at WeatherUnderground, Northern Hemisphere snow cover was also 3rd lowest on record whiles sea ice volume remained in record low territory at 3rd lowest as well. Combined lower sea ice and snow cover, according to Dr. Jennifer Francis of Rutgers University, results in a lessening of the difference in temperatures between the equator and the tropics which can push the Jet Stream into extreme configurations. As I’ve reported over the past month, a number of blocking patterns in the Jet Stream have resulted in periods of severe weather over a number of regions.
According to Dr. Masters:
An extreme jet stream configuration was responsible for the record $22 billion floods in Central Europe in late May and early June, and it is possible that the unusually low May Northern Hemisphere snow cover contributed to the unusual jet stream behavior.
Overall, WeatherUnderground notes 5 major weather disasters during May which exceeded 1 billion dollars in damage, and one, the European Floods, which totaled 22 billion in overall losses. They included:
1) Floods in Central Europe, May – June, $22 billion
2) Drought, Brazil, 1/1 – 5/31, $8.3 billion
3) Tornado in Moore, OK and associated U.S. severe weather, 5/18 – 5/22, $5 billion
4) Tornadoes and severe weather, U.S., 5/26 – 6/2, $2 billion
5) Drought, New Zealand, 1/1 – 5/10, $1.6 billion
Masters does not, however, include the ongoing US drought of 2012-2013 which has already resulted in tens of billions of dollars in damages.
Overall, the 22 billion dollar European flood of 2013 ranked as the 5th most damaging weather disaster outside the US since 1980.
According to NCDC, the period of January to May of 2013 was the 8th hottest on record. With La Nina remaining on the cool side of neutral, natural variability will tend to push 2013 to remain a non-record year. The wild-card, however, is quite a lot of heat that seems to be building up at the Earth’s polar regions. But we’ll have to wait until end of summer to see if this develops into a serious challenge to the El Nino, La Nina base-line.