West vs. East Coast Beaches: The best of both worlds

Today's blog post was written by guest blogger, Donna Fitzgerald, of Wilmington, NC. Donna has lived in Wilmington for 7 years and enjoys taking visits to the beach with her two daughters. Donna is an avid reader and writer- what better place to compose than on the sandy shores!

Thanks, Donna, for researching this topic and sharing with the Beach Blog!

The beaches throughout the United States all offer some varying levels of beauty. Many will argue which area of the country contains the best beaches. For some, it's the surfing conditions that make a beach the best. For others, the beach terrain and weather conditions may make one coast more favorable than another.

There are many differences between the coastal beaches of California and the shoreline of North Carolina. Some differences are notable and evident to the average beach-goer. Other aspects are less obvious and require research and understanding of the varying geographic areas.

Sandy beaches and dunes are typical along the Outer Banks of North Carolina.

Physical Differences

The coast of North Carolina is mostly made up of barrier island chains that allow visitors to travel over many bridges to get from one island to the next. One of the most famous areas, the Outer Banks, is completely made up of thin island chains and sandy beaches separated from the mainland by large shallow bays. The coast of western beaches - California in particular - contains mostly beaches that are immediately adjacent to the mainland areas. Barrier islands and inlets are few and far between.

As we all know, the coast of California is under constant watch for tectonic activity. The east coast is what is referred to as a passive margin, while the California coast is on an active margin. With this being said, California is much more prone to earthquakes and unpredictable tectonic shifts.

Climate

The eastern shores of the United States are much more prone to experiencing tropical cyclones that form off the Atlantic. With these storms comes the risk of tropical depressions, tropical storms, and hurricanes that can impact the coast. With this being said, the climate in each area varies greatly. In general, the beaches of the Pacific Northwest (northern California, Oregon, and Washington) receive the highest amounts of precipitation. East coast beaches receive moderate precipitation and central and southern California beaches receive the least. El Niño cycles can greatly affect the distribution of precipitation along the west coast.

The waves roll in at Pacific State Beach, about 15 miles south of San Francisco.

Other Differences

Sandy beaches mostly make up the shorelines of east coast beaches. To the north, you may find a few New England beaches that feature rocky, jagged shorelines. The east coast primarily features sandy shores that make beach time more enjoyable and relaxing for visitors.

The west coast beaches, like those along the coast of California often feature rocky terrain and steep slopes. The California shoreline often contains many more steep hills and cliffs, like those along Big Sur in central California. These can pose threats to visitors and special cautions should be exercised.

One of the biggest advantages of west coast beaches in comparison to the east coast beaches is the consistent wave climate. California beaches are known for having higher, longer period waves due to the offshore wave climate and narrower continental shelf along the west coast. Surfing conditions are more ideal on the west coast compared to the east coast, where waves are less consistent. This being said, great east coast surfing spots can be found.

Steep beaches with waves make for fun skimboarding at Montara State Beach, about 30 miles south of San Francisco.

Visitors

If you are visiting either coast, be sure to take note of these unique differences. Some tend to favor visiting the east coast beaches because of their sandy shorelines and enjoyable temperatures. Others believe California and west coast beaches are better to visit because of their geographic diversity and great surfing conditions.

Which coast do you prefer?

Sunset near Cape Hatteras, on the Outer Banks of North Carolina.

El Niño could more than double number of King Tides this winter

In case you haven't been following the latest developments in the equatorial Pacific, a potentially strong El Niño condition has been taking shape over the last few months (check out the LA Times El Niño Q&A here). NOAA's Climate Prediction Center has issued an El Niño Advisory, and currently projects a greater than 90% chance that El Niño conditions will continue through the winter, and an 80% chance it will last into early spring.

El Niño is characterized by coupled oceanic and atmospheric conditions which lead to a slackening or reversal of the equatorial trade winds, which typically blow from east to west. This allows a warm pool of equatorial ocean water to migrate eastward towards the coast of South America. The changes in the ocean and atmosphere as a result of El Niño produce more southerly storm tracks, which bring increased precipitation and coastal storm events (storm surge and waves) to the California coast. The warm water associated with El Niño also exacerbates storm surge conditions through thermal expansion of ocean waters, which can further elevate high tides by 0.5 to 1.0 feet above normal.

The figure below shows the average sea surface temperature (SST) anomalies for July 1, 2015 relative to typical conditions. As can be seen, the entire northeast Pacific basin is warmer than usual, with SSTs running up to 3 deg C above normal in the eastern equatorial Pacific.

Nearly all models predict an El Niño of some magnitude to continue through the winter, with many models predicting a strong event at its peak strength. The thick yellow line in the figure below represents the average of the dynamical models (models based on physics, not statistics), which show El Niño conditions peaking in the Oct-Nov-Dec time frame and then tailing off after January. The average prediction shows the SST anomaly holding steady just above 1.5 deg C through the Dec-Jan-Feb time period. The 1.5 deg C threshold is the level used by NOAA to declare a strong El Niño event (read more about the Oceanic Nino Index here).

So what does this all mean for the California coast? Well, if the historical record tells us anything, it's that any old run of the mill El Niño is not a guarantee of wet weather, extreme tides, and large waves. Wet and stormy winters are most likely to occur during strong El Niño events. The most severe El Niños in recent memory - the 1982-83 and 1997-98 events were strong El Niños that persisted for the duration of the winter. Strong El Niño conditions persisted from September through March in 1982-83 (with a peak index of 2.2) and from July through February in 1997-98 (with a peak index of 2.4).

Both winters brought intense rainfall, extreme tides, and large storm waves to the coast. In fact, many tide stations along the California coast recorded their highest ever tide levels during these two events (read more about California coastal flood processes here). We can use our historical record of past El Niño events combined with predicted astronomical tides and El Niño forecast to project the likelihood of extreme tide flooding along the California coast for the coming winter. To accomplish this, I analyzed the storm surge patterns during past El Niño events and developed statistical relationships to project the occurrence of extreme tide events for the coming months.

First, let's take a look at the occurrence of extreme tide events during a typical winter - one characterized by neutral El Niño conditions. A commonly used benchmark for high winter tides is the King Tide which represents the highest annual winter tides each year (read more about King Tides here). The figure below shows the highest predicted tides during February 2016. I typically consider a King Tide to be around 7 ft, so these high tides are pretty close. We know that when we get tides around 7 ft, we start to see some nuisance flooding impacts along areas such as San Francisco's Embarcadero and other areas such as Mill Valley. So we'll use the 7 ft threshold to define a significant tide event in San Francisco Bay.

Predicted tides at San Francisco showing King Tides around February 7-9, 2016.

I paired the predicted tides for November through April with the historical storm surge climatology for neutral El Niño conditions to produce a baseline for the expected number of King Tide days for the coming winter, in the absence of El Niño conditions. And you know what? This year is not a great year for King Tides. Based on my analysis, I project we will have approximately four King Tide days this year (i.e., tides that exceed the 7 ft benchmark). So, depending on the timing of Pacific storm events relative to the high tides we may see more or fewer than four - but that's my best estimate. Four King Tides is the median, or expected, value based on the statistical analysis - the 95% confidence limits on that estimate are between 0 and 12 King Tide days. The figure below shows the projected tide conditions for February 2016 for neutral El Niño conditions. The most likely timing for King Tides appears to be around February 7-9.

Projected tide conditions for February 2016 under neutral El Nino conditions.

Given the projected El Niño conditions for the coming fall and winter, however, we can expect to see much more frequent storm surge events and generally elevated water levels as a result of the prevailing El Niño conditions. This means that if we have a moderate or strong El Niño in the coming months, we will see a much greater frequency of King Tides this year. How many more? Well, it depends on the strength and duration of the El Niño conditions and the timing of storm events with high tides.

If we have a moderate El Niño event through the winter, we can expect to see approximately nine King Tide events. The figure below shows the projected tides for February under moderate El Nino conditions. During moderate El Niños, higher than normal tides can occur; however, not with the same severity as during strong El Niños. Looking at the projected tide levels, you can see that the tides are generally shifted upwards, and a greater number of high tides have the potential to exceed the King Tide benchmark.

Projected tide conditions for February 2016 under moderate El Nino conditions.

If we have a strong El Niño event that lasts through the winter, we can expect to see approximately 30 King Tide events! That's on par with the 1982-83 and 1997-98 winters, which saw approximately 31 and 32 King Tide events, respectively. The figure below shows the projected tides for February under a strong El Nino event. What's remarkable about this projection is the long string of nearly equal high tides between February 12-21 - all of which have the potential to exceed the King Tide benchmark. That will be a critical time period for communities to be prepared for flood impacts.

Projected tide conditions for February 2016 under strong El Nino conditions.

We can also look at hybrid scenarios. For example, if we start off with a strong El Niño which decreases in strength to moderate after January, that puts us at approximately 18 King Tide events. I'll stop there because we've essentially bookended the possible scenarios.

I've summarized the results by month for neutral, moderate, and strong El Niño conditions in the table below. What's interesting about the strong El Niño events is that while 30 King Tides sounds like a lot, the 95% confidence limits on the projection puts the upper limit at 48 King Tide events. That is extremely unlikely to occur and is more a product of the statistical analysis methods used in the simulations - truly a worst-case scenario. Anything greater than 30 will be extraordinary but 48 events would definitely be one for the record books!

Projected Number of King Tide Events for Neutral, Moderate, and Strong El Niño Winter (2015-2016)

	Neutral			Moderate			Strong			1982-83 Winter	1997-98 Winter
	Low	Mid	High	Low	Mid	High	Low	Mid	High
November	0	1	2	0	1	2	2	5	7	4	7
December	0	1	3	0	2	4	1	4	7	6	8
January	0	1	3	0	2	5	1	5	8	9	11
February	0	1	3	0	2	5	4	8	13	6	6
March	0	0	1	0	2	5	3	8	13	6	0
Total		4			9			30		31	32

So stay tuned for more as we continue to watch the developing conditions in the Pacific. The timing of this year's El Niño on the heels of our historic drought highlights the extreme nature of the California climate. A strong El Niño this year would be both a blessing and a curse, as the same storms that would fill our reservoirs may wreak havoc on our coastline.

Fort Cronkhite Loop Trail, Marin Headlands

Rodeo Lagoon is one of my favorite spots on the central California coast. This past February, we took advantage of some remarkably dry weather to hit the trails in the Marin Headlands. It was Super Bowl Sunday and we enjoyed a late afternoon ridge hike and practically had the place to ourselves!

Here is a nice view of the Wolf Ridge high above Fort Chronkhite from the parking lot at Rodeo Beach. We took a 5.2 mile loop hike which traverses a portion of the ridge.

The hike starts at Rodeo Beach, one of my favorite spots in the Marin Headlands.

A few surfers jockeyed for waves at the north end of the beach. The surf was pretty calm and it looked like a nice day to be out in the water.

A couple hundred feet up the trail you can look back down on the lagoon and beach. This is one of my favorite views in the bay area. I don't know why - it just is.

After a few more minutes of hiking, we came upon the Battery Townsley, constructed in 1938. Park Service volunteers were conducting tours and a very friendly lady gave us the last tour of the day through the tunnels buried in the hillside. During WWII, this entire installation would have been carefully camouflaged to hide it from spying eyes.

A little bit higher up the ridge we got an even better view of the beach, looking over towards Point Bonita, with San Francisco in the background. Sutro Tower is visible on the ridge in the background (in my neighborhood!), with the hills around Pacifica (Montara Mountain and Point San Pedro) stretching out to the south.

This is the site of the massive 68-foot long artillery gun mounted in the hillside at Battery Townsley. With a range of 25 miles, the idea was that you could triangulate on an enemy warship, project its speed and trajectory, and hit the target within three shots. Seems kind of improbable to me, but the Park Service volunteer assured us that the crew was quite capable.

Here's a photo of a gun similar to that mounted at Battery Townsley.

We saw a few folks up on the trail but we mostly had the ridge to ourselves since it was close to sunset. This is the view looking north towards Tennessee Valley.

There is a paved trail at the top of the ridge that takes you up to Hill 88 (elevation 988 ft), which has a history as a radar site for nearby Nike missile installations.

There are quite a few abandoned buildings at the top of the hill. This one provides a view of Ocean Beach in San Francisco, through the window.

Once on top of the ridge, we found sweeping views of the Pacific Ocean to our west.

Looking west along the ridge at sunset. It was a beautiful day to be up in the Marin Headlands.

This is the view coming down from Hill 88. You have to backtrack just a little bit to pick up the rest of the Wolf Ridge trail, which drops down on the backside of the ridge and then joins the Miwok trail to loop back around to Rodeo Lagoon.

We got a late start and took an unexpected tour of Battery Townsley so we ended up hiking down the road back to the car in the dark. It was worth it though!