It’s approaching quickly and the opinions are in. Colorado State has published the extended outlook for the 2012 season. They predict 10 named storms with 4 hurricanes and 2 major hurricanes (6 hurricanes in all). For comparison, an average season consists of 12 named storms, 6-7 hurricanes, and 2 of those as major hurricanes.
The forecast below-average season is due to the potential development of El Niño this summer. Currently the ENSO (El Nino Southern Oscillation) is Neutral. When the oscillation moves towards El Nino (warmer than normal water temperatures in the east Pacific) that typically brings dry air into the Atlantic Ocean, increased wind shear, and diminishing moisture thus hindering tropical development.
The picture below shows ENSO Neutral conditions in the top photo (1993) and ENSO El Nino in the second photo (1997).
This is the Sea Surface Temperature anomaly as it is today…
You can definitely see the warming in the waters on the west coast of South America, indicating a transition to El Nino is coming. How strong it will be is currently unknown. As is when it will officially be classified as El Nino. A certain threshold of Sea Surface Temperature anomaly must be reached first. By the way, the Gulf is extremely warm for this time of year, upwards of 4 degrees higher than normal! Thankfully more than just warm water is needed for hurricane development…much more!!
Okay, enough on the temperatures. So, we are currently ENSO Neutral and will probably be neutral possibly through summer. What does that mean for the Hurricane season?
Looking at the left-hand side of the figure below, we see the average number of hurricane landfalls per year per region. The top most bar graph is the East Coast region followed by Florida, the Gulf Coast, and All Regions. Looking at the third chart down, the Gulf Coast, the La Nina (Cold) events produce nearly 1 hurricane landfall on the Gulf Coast (0.92). Then for Neutral ENSO years, the average falls to 0.74, which is still a high average. That is, statistically, three landfalls on the Gulf Coast out of four Neutral years. Then it drops to 0.52 in El Nino (warm) years.
Link to article: http://journals.ametsoc.org/doi/pdf/10.1175/JCLI4063.1
Clearly El Nino reduces hurricane activity as shown by the last chart in the series for All Regions. However, the difference between Cold (La Nina) and Neutral is fairly small.
The point I want to make here is that we are coming out of a Cold Phase and transitioning into Neutral phase before transitioning into an El Nino phase late summer or fall. Many people hear El Nino and think that there is going to be a security blanket of sorts draped across the Gulf Coast to prevent hurricanes, but we know this is not the case at all. In fact, three out of the top five costliest hurricanes ever occurred in ENSO Neutral years and we will likely be in the Neutral mode for a good part of the hurricane season.
I’m not going to sit here and mock Mother Nature and try to predict the number of storms we will have and where they will make landfall, because in the end…no one knows what the season will look like in terms of landfall locations along the US, if any, and number of storms. Statistically though, the gulf coast has only a slightly lower chance of seeing a landfall this year as it did last year. Last year only two tropical systems made landfall along the gulf coast; Don as a tropical depression on the lower Texas coast and tropical storm Lee in Louisiana. Of course, last year Texas was also dominated by high pressure that kept all tropical storms weak and far away for the most port. Unfortunately, the ensuing drought was terrible.
We shall see what this season has in store. Best to stay prepared.
I’ll keep this going as the season nears and as updates are made to the outlooks and such. I’ll also be tracking and updating on storms as they happen.
Thanks for reading!