Hurricane Outlook & Perspectives

It's late-April, and that means it's time for the parade of Hurricane Season Forecasts.  With 12 active Seasons in the past 15 years, many forecast services perennially become contrarian or overly-bullish - often reflecting "markets over meteorology".  Two of the more popular claims this year will be:

[1.] The potential emergence of La Niña conditions. While emerging weak/moderate La Niña conditions tend to enhance development of tropical cyclones, too strong of a Pacific SST cool down can actually cause the opposite effect. And don't forget that ONI is the proper ENSO metric, NOT weekly values; 3-D character (skewness, thermocline) is more important than simply a NINO temperature reading.

[2.] Warm Atlantic waters. Atlantic waters following an El Niño episode tend to warm during the Spring over the Main Development Region. A common temptation will be to compare Spring SSTs to those of 2005's record shattering season, but be mindful that SSTs/SSTAs are merely one of many contributory variables.

Despite prophetic or magnanimous claims you may hear, the percentage of Tropical Storms that evolve into Hurricanes and the number of Hurricanes that actually make U.S. landfall any given year, are very much at the whim of local environmental conditions & synoptic steering patterns which can only be accurately assessed as the Season is underway. 

Adjustments to 2009 Atlantic Hurricane Season Official Record:

* CLAUDETTE's peak intensity was upgraded to 50 knots from the operationally designated 45 knots.

* ERIKA's peak intensity was downgraded to 45 knots from 50 knots.

* GRACE's peak intensity was downgraded to 55 knots from the original 60 knots . 

Much of the comments below have been carried over from recent past Seasons, but the crux of these insights & paradigms are important to instill throughout this Decade and beyond.

HURRICANE LESSONS, COMMENTS AND OUTLOOK [for 2010 SEASON]:

10.)  The record-setting 2005 Atlantic Hurricane Season was undoubtedly going to set a benchmark after which all ensuing Seasons would seem anti-climatic. Following a psychological lull in 2006 [an average 10 Tropical Storms formed], the pendulum swung up again in 2008 when 16 Tropical Storms developed including a record 6 consecutive USA landfalls. In 2009, a near normal total of 9 storms formed. These pendulum swings in Tropical Storm production should not obscure the bottom line which is 12 of the past 15 Seasons have produced more Storms than the long-term average (with only 1997 being decidedly below), and this trend is likely to continue during this active cycle of which we are in the midst.

9.)  In 2005, Hurricane Emily was the strongest Atlantic Hurricane ever prior to August [160 mph], with Dennis being the 2nd strongest ever prior to August [150 mph].  This cautions that intense Tropical Storms can be a legitimate threat in the early stages of the Summer. Furthermore, Hurricane #1 in March 1908 [100 mph], Hurricane Abel in May 1951 [115 mph], Hurricane Lenny in November 1999 [155 mph], Hurricane Paloma in November 2008 [145 mph], and Hurricane #2 in December 1925 [100 mph], demonstrate that legitimate Hurricanes can and do form on the periphery of the official "Hurricane Season". 2009 also marked the 3rd consecutive year in which a Tropical Depression or Storm was classified before June 1st.

8.)  2009 {2006} were subtly resilient in that even an average number of 9 {10} Tropical Storms were able to form in light of 2 inhibitory factors that evolved.  Firstly, a moderate El Niño event emerged quite during the 2006 & 2009 Summers, creating disruptive shear patterns and helping to shut down the very end of the Season [but only after 5 Hurricanes formed in September 2006!].  More significantly, the perennial Saharan Air Layer (or SAL) was substantially more robust and persistent than usual, essentially "choking" numerous potential Tropical waves before they could organize, in August and October.  If you exclude these 2 variables from the equation (as was the case in 2007, 2008 and likely again in 2010), you can easily see 25%-50% more Tropical Storms and/or Hurricanes.

7.)  Those who set their sights only on the U.S., may not realize what a dangerous bullet was dodged in 2007: For the 1st time in recorded history, 2 Category 5 Hurricanes made landfall in North America in the same year (Dean in Mexico and Felix in Nicaragua).  You nudge either of those 2 storms just 50 miles further North when they were in the Eastern Atlantic, and you get an alarming GOM situation.  This is exactly what transpired in 2008 when 5 Tropical Cyclones entered the GOM and a record 5 consecutive months featured the formation of a Major Hurricane. GOM Hurricane landfalls may be skewed later in the Season due to the cool start to that basin's SSTs, but our research concludes that there are above-average odds both that a Major Hurricane will enter the GOM and a Major Hurricane will make landfall in the North America in 2010.

6.)   Louisiana has lost 2,500 square miles of (essential buffering) wetlands and bayou forest from 1937-2009 alone, due to coastal development (including urban subsidence and river channeling), and subsequent erosion.  Similar huge losses of these natural silt and vegetative buffers have taken place during the past Century from Texas to Maine.  Building, living in, and manipulating coastal areas satisfies the needs of industry, commerce and residents, but exponentially increases the vulnerability of these regions to storm devastation.

5.)   You might be surprised to learn that not a single Hurricane made USA landfall the past 5 years as a Category 4 or Category 5 storm; Charlie [CAT 4] in 2004 was the last, and then you have to go back to Andrew [CAT 5] in 1992 before that.  Thus, things could have been worse since 2004, on isolated bases, believe it or not.  Furthermore, IKE in 2008 was the first Hurricane in decades to make a direct hit on major hubs such as Houston/Galveston, and we still have had only 3 Hurricanes of Category 4/5 striking anywhere from Brownsville Texas to Tampa Florida since 1950.  

4.)   Mostly due to geography, but not to be overlooked, is the fact that no Hurricane since 1950 has ever directly struck from the upper Outer Banks of North Carolina to New York City (a Mid-Atlantic coastal zone that represents Scores of Millions of people). The region has been impacted by storms traversing up the Atlantic States (i.e. Floyd - 1999, Hanna - 2008), but time will eventually run out on avoiding direct primary landfalls.  Due to steering mechanisms and SST projections, our research concludes that there are higher odds that at least 1 Hurricane will impact the U.S. Northeast/Mid-Atlantic Coast in 2010 (i.e. closer than Bill in 2009).

 - We completed an ongoing compendium of historical New York Coast Hurricanes which you might find of interest:

http://www.weather2000.com/NY_Hurricanes.html

3.)   From Loop Current, MDR Thermocline, and Oceanic Heat Content projections, our research concludes that there remain decent odds that an Atlantic Hurricane could exceed winds of 180 mph during the 2010 Season (Dean and Felix in 2007 came close with 175 mph sustained winds).  There is also no reason why the top Atlantic pressure intensities recorded of < 900 mb couldn't be challenged in 2010.

2.)  Our research has detected an evolution over the past Decade of the Inter-Tropical Convergence Zone [ITCZ] shifting further southward toward the Equator.  This now places traditional "Hurricane-Proof" islands like Aruba, Bonaire and Curaço in Tropical Storms' line-of-sight along along with several Central American Countries (such as Felix in 2007 remaining below 15°N latitude it entire life). Furthermore, this also allows for the turning radius of low-latitude storms to intersect the GOM (like Dennis, Emily and Wilma in 2005). Similar to 2005, the range of Latitudes within which Tropical Storms will likely form, and the length of the Season (i.e. earlier onset to the "Cape Verde Season") are both likely to be enhanced in 2010.

1.)  Much attention is typically given to pre-Season Sea Surface Temperature Anomalies [SSTA's] - which, by the way, are presently much warmer-than-normal across the sub-basins of the Caribbean, Eastern Atlantic, and the Main Development Region [MDR]. Most importantly, regardless of anomalies, Tropical Storms only require ocean temperatures above 75°F to form (even cooler for Sub-Tropical formation), and such temperatures are plentiful throughout the entire Atlantic Basin.  More technically, for the past 3 years we have been tracking the elevated iron ore concentrations being deposited via African Dust across the Atlantic, which can contribute to steep SST escalations across the GOM & MDR as the Season progresses [by lowering Specific Heat Capacity requirements of basins]. In summary, Oceanographic and Atmospheric environments  should be conducive for Tropical development during the 2010 Atlantic Hurricane Season.