Tips for "Other" Hurricane Outlooks

Location: New York
Author: Weather 2000
Date: Wednesday, April 6, 2011

Amidst the Yo-Yo in robustness of Atlantic Hurricane Seasons the past Decade, it is important to note that Tropical Storm formation has not been decisively below the long-term average (9-10 Named Storms) since the 1997 Season - when only 7 Storms were Named that year. Hype following the historic 2005 Season didn't help prepare one for the tame 2006 Season, nor did bearishness following the 2009 Season help prepare one for the active 2010 Season. With oceanographic/atmospheric conditions in 2011 slightly less favorable than they were in 2010, a less voluminous Season than last year (19 Named Storms), is statistically logical and common sense. Lest we forget, Seasons with large Tropical Storm counts can have minimal USA landfall impact [e.g. 2010 did not have a single storm > 40 knots make USA landfall] and Seasons with modest Storm totals can have devastating impacts [e.g. 1992].

The CSU Team initially releases a pre-Season Tropical Outlook in December, for the upcoming Hurricane Season.  Several other forecast services then use this outlook as the foundation for their outlooks in the Spring, perhaps adjusting a number or two here/there, or tossing in a different causal explanation.  Proper statistical meteorology practices require fixed-width or fixed-confidence ranges to be provided, but the "single-number Storm prediction" has nonetheless captured the attention of the public/user/media community over the years.

There are basically 2 camps of vendor "Hurricane Outlooks" disseminated each Spring which you will come across. The majority of these will always cover the upside, with high-number predictions which both attention-grab and take a "better to over-forecast than under-forecast" insurance paradigm. Considering we're in the middle of an active AMO cycle since 1995, simply taking the average of all these years yields 15 Named Storms, 8 Hurricanes, and 4 Intense Hurricanes. So you will likely see a lot of outlooks stick close to [15 / 8 / 4], with a variety of rationales, but really it's the 15-year Mean.

The other camp will typically wait for the large-number outlooks to come out, and scout out ways to be contrary. Ironically, you'll never see vendors release "Below Normal" outlooks [such as 8 / 3 / 1] due to the destructive consequences of having more storms than announced. However, the "Spring Hump" causes many computer models each year to pre-maturely and artificially intensify El Niño Events following a La Niña or Neutral Winter. So some (short-term) forecasters either get perennially tricked by this, or use it as a rationale to separate themselves "from the pack" and subsequently hedge closer to the long-term average of [10 / 6 / 2].

Tips for pre-Season Ocean/Atmosphere parameters:

It's unfortunate that spin is used for Tropical prediction in light of the potential consequences, but it exists regardless. For example, the proclamation "25% fewer storms than last year!" could be made, but it conceals from the reader that the statement would still translate to 14+ Named Storms (a Season similar to 2004).  Furthermore, the percentage of Tropical Storms that evolve into Hurricanes and the number of Hurricanes that make U.S. landfall any given year, are very much at the whim of local environmental conditions and synoptic steering patterns that can only be accurately assessed as the Season is underway. So be wary of headlines such as "Could this be the year New York City gets the Big One?" - of which there is nothing inherently wrong with the question itself, except for the fact that some folks make this prognostication EVERY Spring for the past 25 years.

Another perennial approach (either innocently or agenda-driven) is over-weighting of Sea Surface temperatures and anomalies [SSTAs] in the early Spring months. SSTAs can ebb, flow and flip signs 3-4 times between March and July, so their Seasonal credence in early Spring is worth about the same as Opening Day stats has on one's Baseball Season.  In much the same way as weekly NINO 3.4 aberrations are not appropriate to assess multi-month ONI status, monthly Atlantic SSTA aberrations are not appropriate to assess multi-Decadal AMO status.  In recent history, cool SSTs across the Gulf of Mexico and Caribbean into May obviously did not inhibit Hurricane IVAN in 2004, and cool SSTs across the Main Develop Region [MDR] into June obviously did not inhibit 16 Tropical Storms from forming in 2008. FWIW, SSTAs are currently unseasonably warm across the Gulf of Mexico, Bahamas and Eastern Atlantic, but not so across the Caribbean Sea. We will of course keep you abreast of the Season's evolution, storm prospects, and our Hurricane intensity & path predictions.

Tips for popular CSU Hurricane Outlooks:

Despite some fanatical proclamations which sprout every year, there is quality tropical research and statistical predictions emanating from a variety of legitimate scientific entities.  Over the past decade, the most popular and widely heralded of these "Hurricane Forecasts", has come out of Colorado State University [CSU], more commonly coined simply "Dr. Gray's Forecast" (referring to Professor Emeritus Dr. William Gray who headed the Tropical Team).  Dr. Gray has mostly moved on to other climate projects, and now Dr. Klotzbach heads the team responsible for what is still the benchmark of Seasonal Atlantic Hurricane Outlooks. 

On Wednesday April 6th, they are scheduled to issue their first Hurricane Season Forecast of 2011 which will undoubtedly garner media, public and industry attention.  Below is our best estimate of the key numbers they will declare (along side historical averages), to help you prepare for any impacts they may cause:

                    Long-Term Average:  OUR Anticipated CSU Forecast: 

Named Storms               10                      16                   

Hurricanes                  6                       9                           

Intense Hurricanes          2                       5  

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