State of our Surf: Summer 2007

As with any summer season, our surf will change from that during the months of winter and spring. Surf-producing systems will shift hemispheres, with Pacific storms brewing at lower latitudes near the Antarctic and the Tropical Pacific as well. East coasters on the other hand will be watching the horizon for hurricanes as the tropical storm season gets underway.

Taking into consideration the state of our planet's climate and weather, this change into summer has some interesting twists and turns. This report will first discuss the primary factors influencing weather and surf for the coming season with a brief synopsis. What follows are sections discussing these effects on California, the East Coast of the U.S., and popular travel destinations as well.

Synopsis

The El Niño Southern Oscillation (ENSO) has shifted wildly over the past few years. In 2005, the cycle was in a La Niña phase, which was partly responsible for the strong hurricane season then. A rapid shift last year to El Niño changed all that for the east coast. The El Niño was expected to continue into winter, which would have stirred up good-sized swells for California and Hawaii. But as we entered the winter of 2006-2007, El Niño quickly faded into oblivion and the ENSO cycle went neutral.

Currently, the latest ENSO report from NOAA's Climate Prediction Center calls for a transition from the now neutral state of the ENSO cycle to La Niña conditions. This could have effects on both the Pacific and Atlantic in the way of waves for the coming months.

For Pacific locales, El Niño conditions in the summer can strengthen the jetstream by Antarctica, keeping swell-producing storms tight in its grip, not allowing as much southerly swell to traverse northward. El Niño can also create warmer waters for ideal hurricane formation in the Tropical Pacific. But, since we may be headed into a La Niña, the opposite would be true.

For east coast locales, summertime El Niño conditions tend to strengthen and lower the jetstream over hurricane alley, increasing vertical wind shear that blows the tops off of forming hurricanes. This results in less tropical storm activity. A La Niña though has the opposite effect with a tendency for exacerbated hurricane formation. Right now, wind shear is low, which is good news for hurricanes, but bad news for those in the paths of these destructive storms.

The ENSO though is neutral for now, and the La Niña (if it does develop) would likely be weak. This will have to be monitored over the next few months, but confidence is high that we'll be trending towards La Niña conditions in the coming months. More information on the ENSO cycle and its effects on our oceans and climate can be found in chapter four of my latest book, Is it Hot in Here.

The Pacific Decadal Oscillation (PDO) can accentuate an ENSO event (something I also discuss in more detail in Is it Hot in Here). Since we're now in a neutral-to-negative PDO cycle, the ENSO neutral-to-La Niña conditions will have continued support, likely resulting in more noticeable La Niña conditions in the Pacific.

The Atlantic however is facing a different issue. Since the Atlantic Multidecadal Oscillation (AMO) is in a positive phase conducive to hurricane formation, hurricane benefits of a La Niña could get further backing. So while the Pacific may not see many tropical storms this year, the Atlantic very well could.

Sea Surface Temperatures (SSTs) though are a major player in tropical activity for both Pacific and Atlantic regions. SSTs are not all that anomalous at the moment (click here to see global SST model). This ho-hum state of temps coincides of course with the neutral ENSO. There are however some above normal SSTs around the tropics -- both Atlantic and Pacific. With the lack of notably cold water, tropical storm formation would not easily be deterred in these regions.

Taking all of this into account, here's how the State of our Surf is stacking up so far for this summer's surf season:

California

California got some early season southern hemi SW swells in the early spring as the jetstream near Antarctica remained mild, allowing even moderate storm formation to drift northward. And right on cue, as would be expected in an ENSO neutral phase, NW ground swell systems originating in the Western Pacific waned in recent weeks as the winds of spring stirred up choppier swell along the coast.

The southern hemisphere continues to show signs of life with numerous storms forming in the lower 50s, typical of the upcoming season. The big question though for these distant storms, is how the jetstream will react in coming months, determining whether they'll drift -- and subsequently throw their energy -- northward. This looks favorable over the next few months.

With the ENSO shifting towards La Niña, the southern jet should relax enough for this favorable northward drift of Antarctic storms. In fact, as of this report, the southern jet is relatively weak with comparatively ineffectual winds in many places along its circumferential route (click here to see image). By allowing storms to drift northward, southern hemi swells this summer will likely result in far less angular spreading decay. This would result in more surf being directed at California this summer. Nevertheless, although aim would be ideal, without storms, there won't be surf. Storms will need to be produced to make the jetstream trend worthwhile. So far, giving the PDO and ENSO phases coupled with trends in recent storms so far this year, moderately sized southern hemi storm formation is highly likely.

Meanwhile, the northern hemisphere is reflecting the zero-sum nature of the changing seasons with a decrease in activity in the Western Pacific and Aleutian Chain regions being diametric in relation to the southern hemisphere activity. While NW ground swells are not likely to form over the next few months (typical of the summer season) wind swell still has a chance to develop along the coast, but in moderation correspondent to an ENSO neutral year.

On the hurricane front, things are looking rather ho-hum for the Eastern Pacific. Sea surface temperatures are only slightly above normal in this region, and cold water is predominant outside of this immediate area. Wind shear is also rather high right now in the tropics, which is bad news for hurricane formation. While there's no doubt that the Tropical Eastern Pacific region will have storm formation this summer, conditions are not conducive to excessive hurricane development. In fact, tropical storm activity will likely be below normal.

Winds though could be a concern, at least for the next few weeks until summer gets fully underway. Winds are caused by a difference in pressure between high and low pressure systems with wind blowing from the high to the low. This is evident during the Santa Ana season when high pressure over Utah interacts with lows in the Pacific, resulting in wind being blown from land to the sea (offshore winds). During a La Niña season, the north eastern Pacific (i.e. near the Gulf of Alaska) remains under the influence of dominant high pressure. While this typically results in a pattern that blocks wintertime storms -- something we'll need to look at later this year -- it also sets up a hair-trigger for winds, that is, if any lows should form to the south of the high near the coast. If lows should form at lower latitudes (i.e. Baja in through Central America), the northern high could interact with these systems, creating gradients near our shores, resulting in NW winds. This kind of wind pattern though is more characteristic of our spring seasons, so the next few weeks (in through June) could be subjected to some stronger than normal onshores. If also these winds become strong enough from the NW, then upwellings would be a concern as well. The likelihood though for anomalous wind effects is low, especially given the fact that the ENSO is still neutral, and an impending La Niña would likely be weak.

In summary: it looks like California will see a near-normal summer for swells with the usual winds we see during a normal summer season. There should be a fair amount of moderately sized southern hemi swells lasting a few days at a pop, thanks to northward drift from a weak jetstream near Antarctica. Super-sized southern hemi swells are of course likely during any summer season, but so far, these look to be fewer this year. Tropical storm formation though will more than likely be very low this summer with the better swells coming in from the far reaches of the southern hemisphere.

The East Coast

All eyes are focused on hurricane alley this summer. Although 2006 turned out to be a dud of a year for tropical storm formation in the Atlantic, jitters still linger from 2005. The relative tranquility of the 2006 summer season was in large part due to a rapidly evolving El Niño. This increased wind shear across hurricane alley, killing off hurricanes in their infancy. SSTs were also lower in 2006 than in 2005, and the position of the Bermuda High was not in a position to direct storms at the U.S. like it was in 2005 (something I explain at greater length in chapter 5 of Is it Hot in Here).

At this point, it is difficult to determine how the Bermuda high will react for the summer season. All other elements though are in play for an above average hurricane season. In fact, the latest report from the Department of Atmospheric Science at Colorado State University is calling for an above average hurricane season (you can find that report online here). Although their reports have been known to be flawed (see The Grey Matter in chapter 5 of Is it Hot in Here), these reports more often than not concur with NOAA's National Hurricane Center early season forecasts. The Colorado State University report asserts that the number of named storms in the Atlantic will total 17, a normal year has about 10. As for Hurricanes, their call is for 9, where a normal year sees about 6. And as far as intense hurricanes, the Colorado State University forecast calls for 5, about twice as many as a normal year.

NOAA's Climate Prediction Center released its hurricane assessment report for the 2007 hurricane season today, which pretty much agrees with the Colorado State University report, with 3-5 major hurricanes comprising what is seen as a year to be 75% above normal for hurricane activity. You can find the full report from NOAA here.

Atlantic hurricanes have been historically more prominent from late August through early October( see month details here and incident history here). Since we're just now approaching the beginning of summer, tropical storm activity will likely be quiet for at least the next few weeks or longer. Still, elements are conducive to hurricane formation right now.

Vertical wind shear is low within the hurricane-forming regions of the Atlantic (around 20-25° north). While some of this could be attributed to La Niña (and the consequential weakening of the jetstream over hurricane alley), persistent high pressure near the U.S. has decreased the west to east upper atmospheric flow, allowing the opposing African Easterly Jet to ride unabated. This has set up an ideal course for hurricanes that would form off the coast of Africa this summer. If the Bermuda high gains strength this year and/or shifts its position slightly towards the U.S., the combined effects would result in ideal conditions for hurricane trajectories aimed at the east coast.

In summary: the main feature for surf and weather along the eastern seaboard is the high likelihood of an above normal hurricane season. Although surf would no doubt be on the rise from such storms, if conditions continue as they are trending now, then storms may come far too close to the coast to be surfable in most of the southern states; instead, coastal damage could be high from these storms. Areas farther north could benefit from swell from these storms, but we'll need to see how the Bermuda High and various elements of the approaching La Niña react over the coming months.

Travel Destinations

With the southern hemisphere now showing signs of life and tropical storm activity likely in the coming weeks, Costa Rica and south Pacific locales will subsequently see more swells in the coming months -- typical of the summer season. With coastal waters being slightly above normal off the coast of Central America now though, that particular region could experience frequently occurring lows. Although these lows would not likely get a chance to become strong hurricanes due to cold water immediately beyond the outer waters of the Central American region (linked with the La Niña), their potential increases the chance for wind swell and thunderstorms for at least the next month or longer along the coastlines of Central America.

Hawaii though can expect similar surf conditions as California, with southern hemi action becoming the dominant feature and NW activity diminishing. In all, the Hawaiian Islands are likely to have a normal summer surf season.

With the hurricane season winding up, Caribbean locales will once again become a concern for tropical storm formation. With an overly active season anticipated this summer, additional caution is warranted for all locales within the Tropical Atlantic.

As always, Mother Nature continues to call the shots. Our world of weather and the surf created by nature’s most powerful storms across our planet’s oceans are controlled not only by the laws of physics, but also chaos and unpredictability. While confidence is high on this forecast, only time will tell the truth as we keep an eye on the horizon, and watch time and weather unfold before us.

--Nathan Cool

Nathan Cool is the founder of WaveCast, the Chief Forecaster for WetSand.com, an associate member of the American Meteorological Society, a professional member of the American Association for the Advancement of Science, and host of GreenhouseTruth.com. Nathan has authored a number of books including The WetSand WaveCast Guide to Surf Forecasting, and his recently released, Is it Hot in Here? -- The simple truth about global warming. More information on Nathan can be found at his web site:
http://nathancool.com/