CSU and TSR predict above average 2012 Atlantic hurricane season
Jeff Masters

5:17 PM GMT on December 07, 2011

Above-average Atlantic hurricane activity is likely for 2012, but there is a 40% chance of an El Niño event that will keep hurricane activity below average, according to the latest seasonal forecast issued today by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). For the first time in twenty years, the CSU team is not issuing a December forecast with a specific number of tropical storms and hurricanes. Instead, they have issued a more qualitative forecast, which I think is a great idea, since their quantitative December forecasts have shown no skill. Their outlook for the 2012 Atlantic hurricane season:

15% chance: Very active season with 14-17 named storms, 9-11 hurricanes, 4-5 major hurricanes
45% chance: Active season with 12-15 named storms, 7-9 hurricanes, 3-4 major hurricanes
30% chance: Inactive season with 8-11 named storms, 3-5 hurricanes, 1-2 major hurricanes
10% chance: Very inactive season with 5-7 named storms, 2-3 hurricanes, 0-1 major hurricanes

An average season has 11 named storms, 6 hurricanes, and 2 intense hurricanes. The main reason that CSU's December forecasts have shown no skill is because we have no skill predicting El Niño events nine months or more into the future. When an El Niño event occurs, bringing much above average wind shear over the tropical Atlantic, hurricane activity is substantially reduced. Making successful seasonal hurricane forecasts requires that one make a successful El Niño forecast.


Figure 1. Forecasts of El Niño conditions by 20 computer models, made in November 2011. The longest range forecasts for July-August-September (JAS) at the right side of the image show that 3 models predict weak El Niño conditions, 8 predict neutral conditions, and 1 predicts a weak La Niña. El Niño conditions are defined as occurring when sea surface temperatures in the Equatorial Pacific off the coast of South America (the "Niño 3.4 region) rise to 0.5°C above average (top red line). La Niña conditions occur when SSTs in this region fall to 0.5°C below average (blue line.) Image credit: Columbia University.

What will El Niño do in 2012?
We currently have a borderline weak to moderate La Niña episode in the Eastern Pacific, characterized by cooler than average waters off the equatorial coast of South America. While we can say with good confidence that La Niña will continue through the winter and into spring, it is highly uncertain what might happen next summer and fall to La Niña. In April and May, we typically see La Niña fade to neutral, and in many cases, a full-blown El Niño will develop by the fall. As the CSU team notes, there have been fourteen years since 1950 which had La Niña conditions that were similar to what we are experiencing this December. During the following years' hurricane season, an El Niño event developed 36% of the time, in those fourteen years. In 2012, the odds of a fall El Niño may be higher than this, since we have gone three years since the last El Niño, and these events typically occur every 3 - 7 years. Of the 12 El Niño/La Niña computer models that made November predictions for the July-August-September 2012 portion of hurricane season (Figure 1), only 3 (20%) predicted that El Niño would arrive. However, these models have no skill predicting El Niño so far in advance.

2012 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR), issued their 2012 Atlantic hurricane season forecast today. TSR is calling for an above-average year, with 14.1 named storms, 6.7 hurricanes, and 3.3 intense hurricanes. TSR predicts a 49% chance of an above-average hurricane season, 30% chance of a near-normal season, and a 21% chance of a below normal season. TSR bases their December forecast on predictions that sea surface temperatures next fall in the tropical Atlantic will be above about 0.1°C above average, and trade wind speeds will be about 0.2 m/s slower than average. The trade wind speed prediction is based on a forecast for neutral El Niño conditions in August - September 2012.

I like how TSR puts their skill level right next to the forecast numbers: 3% skill above chance at forecasting the number of named storms, 0% skill for hurricanes, and 7% skill for intense hurricanes. That's not much skill, and really, we have to wait until the June 1 forecasts by CSU, NOAA, and TSR to get a forecast with reasonable skill.


Figure 2. Forecast skill of the TSR, NOAA (National Oceanic and Atmospheric Administration) and CSU (Colorado State University) seasonal hurricane outlooks 2002-2011 as a function of lead time. NOAA does not release seasonal outlooks before late May. It is clear there is little skill in forecasting the upcoming number of Atlantic hurricanes from the prior December. Skill climbs slowly as the hurricane season approaches. Moderate skill levels are reached by early June and good skill levels are achieved from early August. Image credit: Tropical Storm Risk, Inc (TSR).

US forecaster sees average 2012 Atlantic hurricane season

(Reuters) - The 2012 Atlantic hurricane season will likely see average storm activity with sea surface temperatures forecast to be cooler than last year, the director of the U.S. National Hurricane Center said on Monday.

The comments by Bill Read came less than a month before major forecasters are expected to begin unveiling their predictions for the hurricane season, which officially starts on June 1 and ends November 30.

Read did not make any specific forecasts on the number of hurricanes he expected but he did say preliminary reports suggest water temperatures could be less conducive this year for hurricane formation.

"There is some early indication that it's cooler than it was (last year) in the eastern Atlantic," he said, speaking at an annual hurricane conference in Charleston, South Carolina.

"We may not see the rapid development far out east like we had last year," he said.

On average, the Atlantic-Caribbean hurricane season brings 12.1 tropical storms, with 6.4 of those strengthening into hurricanes. The region is still in the midst of a multi-decade busy period, and 2011 saw 19 tropical storms, with seven growing into hurricanes, including three major ones.

In an early pre-season forecast released in December, Weather Services International (WSI), a private weather forecaster, predicted a relatively tame 2012 Atlantic season with a total of 12 named storms and seven hurricanes.

During 2011, Irene was the only hurricane to hit the United States and the first since Hurricane Ike struck southeastern Texas in 2008.

Read said forecast models suggest there is less of a chance of the La Nina phenomenon, which fosters hurricane formation.

"Last year, we had a big honking La Nina," he said. "It was a more active year than normal. Looking at the ocean forecast models, they're all saying that the La Nina went by."

The Colorado State University hurricane forecasting team, led by Bill Gray and Phil Klotzbach, is expected to issue its hurricane season forecast on April 4.

The National Hurricane Center will release its prediction during the second half of May, Read said. (Additional reporting by Jane Sutton in Miami; editing By Kevin Gray and Todd Eastham)

SOURCE

Very Early Thoughts On The 2012 Hurricane Season

I wanted to post some very early preliminary thoughts I have regarding the 2012 Hurricane Season, which starts, unbelievably, in a little more than two months.

First off, as far as I can determine, we are out of the La Nina phase of the ENSO and are in neutral conditions. I think for the upcoming 2012 Hurricane Season, we will be on the warm side of neutral and transitioning into a weak El Nino as we get into September, October and November. Additionally, the eastern Atlantic is colder in terms of ocean water temperatures as compared to recent years. This, I think, means that long tracked storms will be very far and few between and our development will be in-close, mainly west of 55 and 60 West Longitude.

Looking at the weather pattern from this winter and into the spring, there are quite a few years that pop out at me for analog years. They are:

1910:

1921:

1946:

1951:

1954:

1957:

1975:

1976:

1979:

2002:

The top analog years out of those that I am looking at are #1: 2002, #2: 1976 and #3: 1957.

One relatively big thing that all of these years have in common are low overall numbers for storms and hurricanes, but a more significant threat and impact on land. Some examples include: Hurricane #5 impacting just south of Tampa in 1910, the Tampa hurricane of 1921, a hurricane into the west coast of Florida in 1946, Hurricanes Carol and Edna into New England in 1954 and Hurricane Hazel into southeastern North Carolina in 1954, Hurricane Eloise into the Florida Panhandle in 1975, Hurricane Belle impacting New England in 1976, Hurricanes David and Frederic in 1979 and finally Isidore and Lili in the Gulf of Mexico in 2002.

So, I think the US East Coast and particularly the Gulf of Mexico are at risk this year from storms that develop relatively close to land rather than the long-tracked storms like Irene from last year. Additionally, the fact that 1910, 1921 and 1946 were years that had significant hurricanes impacting the Tampa area makes me kind of nervous. Additionally, the northern and western Caribbean may be at risk this year from any storms developing in-close (within 250-300 miles of the Lesser and Greater Antilles).

Finally, I think next winter (2012-13) has the potential to feature a cold El Nino meaning that there will be a ridge in the western United States and a trough of low pressure in the eastern United States. This potentially could mean a snowier and colder than average winter east of the Rocky Mountains and especially east of the Mississippi River.

So, in summary:

1. I am looking at relatively low numbers in terms of named storms, probably on the order of 9 or 10 named storms. Those storms have the potential to develop in-close or be of home-grown variety.

2. In terms of threats, the Gulf of Mexico, in particular, has the potential to be fairly active in terms of development with threats to the US Gulf coast. The US East Coast also has the potential to be at least threatened by a tropical storm or hurricane this hurricane season.

3. I am also looking at the possibility of development in May. Some of the analog years, including 1951 and 1976 had development in May, including Category 3 Hurricane Able in 1951.

I will continue to look at things over the coming couple of months and I will keep you all updated.

CROWN WEATHER