A weather buoy tied with 18,000 feet of mooring line to a concrete block at the bottom of the Atlantic Ocean, hundreds of miles east of the Bahamas, stayed put as Hurricane Earl swept by earlier this week. In the past, this wasn’t always the case.
As this major hurricane passed near the 3-meter buoy, the atmospheric pressure dropped to 27.85 inches of mercury and wind gusts reached nearly 100 mph. Gigantic waves from Earl reached the buoy’s location on Wednesday. Later in the day, this buoy (No. 41046) reported the significant wave height of 48 feet, which probably meant the individual waves were close to 100 feet high.
Significant wave height is defined as the average height of the waves in the top third of the wave record. This turns out to be very close to what an experienced mariner — “old salt” — would perceive the wave heights to be. Maximum wave height can be more than twice as high as significant wave height.
Let me tell you, at these tremendous wind speeds and wave heights it is difficult to distinguish the sea from the atmosphere. They almost seem to merge.
Thankfully, Earl weakened as it moved toward the East Coast. Nevertheless, the Cape Hatteras buoy (No. 41001) about 150 miles off the coast of North Carolina in 15,000 feet of water, saw the significant wave height reach nearly 40 feet, with maximum wave heights estimated to be more than 80 feet on Friday. The buoy reported wind gusts over 72 mph.
Often when buoys are subjected to such conditions, the violent motion of these huge and steep waves will break the mooring line, much like a quick tug on a child’s loose baby tooth. Hurricane Ivan capsized a large 10-meter buoy in the Gulf of Mexico in 2004.
These weather buoys provide invaluable weather and ocean-wave data and act as long-range sentinels. Pressure and wind data from these buoys make it much easier to evaluate a hurricane and help determine the correct actions needed to save life and property.
To help buoys survive such conditions, the National Oceanic and Atmospheric Administration has developed a new mooring design called Low-Load Compliant, which has a near-perfect performance record over the past three years. The new mooring system has a 1,500-foot centenary, or horizontal section of line, to absorb wave energy. This new mooring system is also being deployed in the Pacific Ocean.
However, the new mooring system has a much larger watch circle that makes it more vulnerable to vessel traffic because of possible entanglement.
I spoke with the National Data Buoy Center, which requests that mariners make sure their towed gear is at least one-half nautical mile away from the weather buoy’s published position. This should ensure all tow cables, lines and other towed equipment is kept away from the mooring system.
If you are curious, there’s a wonderful website that displays all the buoy data, including the buoys along the Central Coast in easy-to-read format.
The website is: www.lajollasurf.org/buoylist.html.
Weather and surf report
A 1,036 millibar eastern Pacific high centered 1,400 miles northwest of San Luis Obispo will gradually slide eastward while an elongated low pressure trough slowly moves down the West Coast toward Central California by midweek.
Marine low clouds surged inland early this morning but will burn off from the interior and coastal valleys later this morning. Increasing northwesterly (onshore) winds will produce a cooling trend in the North County as cool and moist air from the Pacific filters inland through the coastal passes and gaps.
However, this afternoon’s strong (35 and 31 mph) northwesterly winds will mix out the marine layer from the southwesterly (Avila Beach and Cayucos) facing beaches early this afternoon and will produce beautiful weather for the Pops by the Sea concert at Avila Beach. These winds should also produce a greater amount of sunshine at the northwesterly facing beaches (Los Osos, Morro Bay and Cambria), but a few patches of low clouds will endure.
Temperatures will range from the high 50s to the low 60s along the northwesterly facing beaches, to the low to mid-70s at the southwesterly facing beaches. The coastal valleys will range from the high 70s to the low 80s, while the North County will mostly be in the mid-90s.
The coastal clouds will redevelop tonight, but the winds will turn out of the north by Monday morning and will bring more sun and warmer temperatures to the beaches on Labor Day through Tuesday.
The remainder of the week continues to look cool as the northwesterly winds increase and an expanding marine layer produces temperatures that are well below normal. Still no rain in sight.
Today’s surf report
The northwesterly wind fields moved further eastward towards our shoreline yesterday and will produce a 4- to 6-foot northwesterly (320-degree deep-water) sea and swell (with a 5- to 11-second period) this morning, building to 6 to 8 feet this afternoon through Monday morning. This northwesterly (320-degree deep-water) sea and swell will decrease to 4 to 6 feet on Monday afternoon and will remain at this height and period through Wednesday.
This northwesterly sea and swell will further lower to 4 to 5 feet (with a 5- to 8-second period) on Thursday and will remain at this height and period through Friday.
Arriving from the Southern Hemisphere: Today’s models are indicating a significant storm developing nearly halfway between New Zealand and Chile this week. If this storm develops as advertised, it will produce an energetic Southern Hemisphere swell along our coastline by Sept. 16. Seawater temperatures will range between 51 and 53 degrees through Friday.
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John Lindsey is a media relations representative for PG&E. He is also a local weather expert and has lived along the Central Coast for more than 23 years. If you would like to subscribe to his daily weather forecast or ask him a question, send him an e-mail at firstname.lastname@example.org.