Friday, July 16, 2010

Hurricane Watch: "June SSTs in the tropical Atlantic set a new record"

From WunderBlog:
...Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest June on record, according to an analysis I did of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. SSTs in the Main Development Region (10°N to 20°N and 20°W to 80°W) were 1.33°C above average during June, beating the previous record of 1.26°C set in June 2005. 

June 2010 is the fifth straight record warm month in the tropical Atlantic, and the third warmest anomaly measured for any month in history. The only warmer anomalies were 1.51°C and 1.46°C, set in May 2010 and April 2010, respectively. As I explained in detail in a post on record February SSTs in the Atlantic, the Arctic Oscillation (AO) and its close cousin, the North Atlantic Oscillation (NAO), are largely to blame for the record SSTs, though global warming and Atlantic Multidecadal Oscillation (AMO) also play a role. The magnitude of the anomaly has fallen over the past month, since trade winds over the tropical Atlantic have increased to slightly above-normal speeds. These higher trade wind speeds are due to the fact that the Bermuda-Azores High has had above-normal surface pressures over the past month. The Bermuda-Azores High and its associated trade winds are forecast to remain at above-average strength during the next two weeks, according to the latest runs of the GFS model. 

This means that Atlantic SST anomalies will continue to fall during the remainder of July. However, keep in mind that we are talking about anomalies--the ocean will continue to warm until its usual early September peak in temperature, and it is likely that we will have the warmest or second warmest SSTs on record over the tropical Atlantic during the peak part of hurricane season, mid-August through mid-October.