Will there be a lot of hurricanes in 2013?


The Tropical Meteorology Project at Colorado State University makes annual predictions of hurricane season activity, and they released one of these predictions today. This particular group has a good track record, although I would worry that they tenaciously hold to the idea that global warming is not a factor in hurricane development despite the fact that some of the factors (a disrupted ENSO and high SST) that are most affected in the Atlantic by global warming actually drive their predictions. Still, their predictions seem to be based on good empirical data and are probably robust. (Other season forecast information is to be found below).

El Nino conditions tend to reduce hurricane activity, and the warmer the waters in the North Atlantic, the more likely hurricanes are to form from tropical depressions, the stronger they are likely to be, and the longer they are likely to last.

This year, El Nino conditions are unlikely to develop, and sea surface temperatures in the North Atlantic are unusually high as they have been for a few years.

The TMP has released this PDF of their report, which states:

We anticipate that the 2013 Atlantic basin hurricane season will have enhanced activity
compared with the 1981-2010 climatology. The tropical Atlantic has anomalously
warmed over the past several months, and it appears that the chances of an El Niño event
this summer and fall are unlikely. We anticipate an above-average probability for major
hurricanes making landfall along the United States coastline and in the Caribbean.
Coastal residents are reminded that it only takes one hurricane making landfall to make it
an active season for them, and they need to prepare the same for every season, regardless
of how much or how little activity is predicted.

TMP predicts that there is a 72% chance of at least one category 3 or above hurricane landing somewhere on the US coastline (the average probability over the last century is 52%). There is a 48% of such a landfall along the Atlantic coast plus Florida not counting the panhandle (compared to the century average of 31%) and a 47% probability for the Gulf Coast on the Florida Panhandle and points west to Brownsville (compared to 30%). The chance of at least one category 3 or stronger hurricane hitting points in the Caribbean is 61% (compared to 42%).

The forecast predicts that there will be 18 named storms active over 95 days, of which 9 will be hurricanes, active over 40 days, of which 4 will be Category 3 or above.

The Weather Channel is saying the following about the 2013 season:

The Weather Channel released its first 2013 Atlantic hurricane season outlook on April 8, 2012, calling for another active season.

The forecast calls for a total of 16 named storms, 9 of which are expected to become hurricanes, including 5 major hurricanes (Category 3 or higher on the Saffir-Simpson Hurricane Wind Scale).

These forecast numbers are above the long-term average from 1950-2012 (12 named storms, 7 hurricanes, 3 major hurricanes) and slightly above the averages for the current active era from 1995-2012 (15 named storms, 8 hurricanes, 4 major hurricanes).

The Weather Company's WSI says this:

Weather Services International (WSI) expects another active tropical season this year, with 16 named storms, nine hurricanes, and five intense hurricanes expected (16/9/5). This compares to the 1950-2012 normals of 12/7/3 and the more recent “active period” (1995-2012) normals of 15/8/4.

Researchers at UCL, UK (PDF) predicts 3-4 "intense hurricanes" out of 7-8 hurricanes with 15-16 tropical storms:

The TSR (Tropical Storm Risk) April forecast update for Atlantic hurricane activity in 2013 continues to
anticipate an active hurricane season to moderate probability. Based on current and projected climate
signals, Atlantic basin tropical cyclone activity is forecast to be about 30% above the 1950-2012 longterm norm but slightly below the recent 2003-2012 10-year norm. The forecast spans the period from 1st
June to 30th November 2013 and employs data through to the end of March 2013. TSR’s two predictors
are the forecast July-September trade wind speed over the Caribbean and tropical North Atlantic, and the
forecast August-September 2013 sea surface temperatures in the tropical North Atlantic. The former
influences cyclonic vorticity (the spinning up of storms) in the main hurricane track region, while the
latter provides heat and moisture to power incipient storms in the main track region. At present, TSR
anticipates both predictors will have a small enhancing effect on activity.

Weather Underground's MAweatherboy1 posted this last month:

I foresee a season that will see near to above average activity. One of the main factors we look at to determine this is the ENSO, which involves the temperature of waters in the Pacific Ocean. Warm Pacific waters, called El Nino if the anomaly is greater than 0.5 degrees Celsius, tend to suppress activity in the tropical Atlantic, while cooler than average Pacific waters, called La Nina if the anomaly is greater than 0.5 degrees Celsius, tend to enhance activity. ... This year, I am expecting a very neutral ENSO, with average, season-long (June 1-November 30) Pacific water temperatures that are in the key regions likely not averaging more than 0.2 degrees Celsius above or below average, although I would favor the cooler end of that range if anything. The Southern Oscillation Index (SOI) is an important component in determining ENSO. Positive SOI values promote cooler Pacific waters, and vice versa. SOI values have been mostly negative this winter, though not by much, and I do not foresee any huge changes in this. Neutral conditions like this tend to promote near normal, or in some cases above normal activity. The record breaking 2005 hurricane season was primarily influenced by neutral ENSO conditions.

Photo Credit: NASA Goddard Photo and Video via Compfight cc

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