Monday, May 17, 2010

Insurance: Accuweather Calls for Wild Hurricane Season (AIG; ALL; BRK.B; CB; TRV)

UPDATE: "Insurance: Here Come the Catastrophe Bond Offerings (AIG; BRK.B)"
Original post:
First, take a look at the sea surface temperature anomaly map:

Unisys' Sea Surface Temperature Map.

Current Sea Surface Temperature Anomaly Plot

In the post below, Accuweather's Joe Bastardi mentions the rapid warming of the Gulf of Mexico this season. Just as concerning is the elevated temps in the main development region off the coast of Western Sahara and Mauritania.
First up, Accuweather:

The upcoming hurricane season could be a top 10 active year, a stark contrast from the relatively calm 2009 season. Chief Hurricane Meteorologist Joe Bastardi predicts a total of 16-18 storms this season. To put that in perspective, only eight years in the 160 years of records have had 16 or more storms in a season.

The season should start early with one or two threats by early July, and stay late with additional threats extending well into October.

His forecast team expects at least six storms to impact the United States coastline--slightly more than one out of every three. In a normal year, one out of every five named storms (20 percent) in the Atlantic basin impacts the United States. In the 2005 season, 36 percent of the storms affected the United States, while 50 percent impacted the United States in 1998 and 2008.

"From the standpoint of number of storm threats from the tropics to the United States coastline, we will at least rival 2008, and in the extreme case, this season could end up in a category only exceeded by 2005," Bastardi said.

Bastardi observes a rapid warming of the Gulf of Mexico and the collapsing El Nino pattern, which were both characteristics of the 1998 and 2005 seasons....MORE

From Dr. Jeff Masters' Wunderblog:

Record Atlantic SSTs continue in the hurricane Main Development Region

Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest April on record, according to an analysis 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. The area between 10°N and 20°N, between the coast of Africa and Central America (20°W - 80°W), is called the Main Development Region (MDR) because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.) SSTs in the Main Development Region (10°N to 20°N and 20°W to 85°W) were an eye-opening 1.46°C above average during April. This is the third straight record warm month, and the warmest anomaly measured for any month--by a remarkable 0.2°C. The previous record warmest anomalies for the Atlantic MDR were set in June 2005 and March 2010, at 1.26°C.

Figure 1. The departure of sea surface temperature (SST) from average for May 13, 2010. Image credit: NOAA/NESDIS.

What is responsible for the high SSTs?
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. The AO and NAO are climate patterns in the North Atlantic Ocean related to fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores-Bermuda High.

If the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), this creates a weak Azores-Bermuda High, which reduces the trade winds circulating around the High. During December - February, we had the most negative AO/NAO since records began in 1950, and this caused trade winds between Africa and the Lesser Antilles Islands in the hurricane Main Development Region to slow to 1 - 2 m/s (2.2 - 4.5 mph) below average. Slower trade winds mean less mixing of the surface waters with cooler waters down deep, plus less evaporational cooling of the surface water. As a result, the ocean heated up significantly, relative to normal, over the winter. Negative AO/NAO conditions have been dominant much of this spring as well, resulting in further anomalous heating of the MDR waters.

This heating is superimposed on the very warm global SSTs we've been seeing over the past few decades due to global warming. Global and Northern Hemisphere SSTs were the 2nd warmest on record this past December, January, and February, the warmest on record in March, and will likely be classified as the warmest or second warmest on record for April, since NASA just classified April as the warmest April on record for the globe. We are also in the warm phase of a decades-long natural oscillation in Atlantic ocean temperatures called the Atlantic Multi-decadal Oscillation (AMO). This warm phase began in 1995, and has been partially responsible for the high levels of hurricane activity we've seen since 1995....MORE