The strongest winds in the world

pgeweather@pge.comApril 17, 2010 

Last Sunday’s gale-force southerly winds stoked my curiosity: What were the strongest winds ever recorded throughout the world and along the Central Coast? This is what I discovered.

For many years, the world record was held atop Mount Washington, a 6,288-foot peak in New Hampshire, where in 1934 sustained winds of 186 mph were recorded for five minutes, with a peak gust of 231 mph.

In 1996, Tropical Cyclone Olivia generated a wind gust of 253 mph as it crossed over Barrow Island off the northwest coast of Australia. The gust was measured at the standard measuring height of 33 feet atop a small hill with an elevation of 210 feet.

If you move away from the Earth’s surface, wind speeds tend to increase. In fact, at a height of only 33 feet, the winds often move twice as fast as at the surface because of less friction with the ground.

This wind data remained dormant for many years until a meteorologist with Australia’s Bureau of Meteorology brought it to the attention of the World Meteorological Organization, which verified the data in 2009.

In 1999, a tornado in the town of Moore, Okla., produced a wind gust of 318 mph as measured by Doppler radar. For reference, 200 mph is the threshold for the strongest category of tornado (EF5) on the modified Fujita Scale for damaging winds.

This may or may not be the strongest wind ever seen, it’s just that no other wind event has been measured or recorded with greater wind speeds near the surface.

As you might imagine, winds of these magnitudes apply great forces on any object in their path, producing near total destruction.

Even a small increase in wind speed can greatly increase the force applied to objects, such as the surface of the ocean, buildings or trees. For example, if you double the wind speed from 22 mph to 44 mph, you’re actually quadrupling the amount of force.

A 22 mph wind can only produce a fully developed sea of 5 feet, while 44 mph winds can generate seas of more than 20 feet. The wind-generated waves associated with Cyclone Olivia reached more than 70 feet in height.

Thankfully, winds here have never reached these types of velocities, but they are still strong enough to damage roofs, break tree limbs and even blow trees over, especially if the soil is saturated.

Along the Central Coast, an intense storm in January 1988 produced some of the strongest winds that I know of in this area at Platform Harvest, 16 miles west of Point Conception. The northwesterly reached a sustained speed of 78 mph.

There have been two occurrences of confirmed tornadoes in San Luis Obispo.

The first occurrence happened on April 7, 1926. A Pacific storm from the west produced lightning that struck large oil tanks along Tank Farm Road. As a result, hundreds of whirlwinds formed, but wind speed data is not available from this event.

The second confirmed tornado happened on the morning of May 5, 1998, near Cal Poly. It had the strongest winds that I have ever experienced.

About 5:40 a.m., the rain became heavy and the wind caused my windows to vibrate. At first, I thought it was the train going by. My anemometer was fluctuating between 60 and 70 mph, and the power lines around my home were beginning to arc. Looking out my window, tree branches began to break, and the wind caused debris to rotate in a counterclockwise direction. My anemometer reached 86 mph!

This week’s forecast

A weak, but moist 1,007-millibar low-pressure system about 500 miles southwest of San Luis Obispo will produce variable mid- to high-level clouds, areas of coastal low clouds and fog and light to gentle winds.

Today’s high temperatures are expected to range between the low to mid-70s in the North County, the mid- to high 60s in the coastal valleys and low 60s along the beaches.

The marine layer will deepen tonight, producing cooler temperatures along with night and morning low clouds and fog along the beaches and coastal valleys Monday.

A cool, slow moving 1004-millibar low-pressure system will approach Northern California on Monday, with the associated cold front reaching our area on Tuesday with rain.

Total rainfall amounts should range between a tenth to a quarter of an inch with moderate snowfall accumulations above 4,500 feet across the Sierra.

A strong 1036-millibar eastern Pacific high combined with Tuesday’s low-pressure system will produce a very steep pressure gradient along the California coastline.

This pressure gradient will produce moderate gale to fresh gale-force (32 to 46 mph) northwesterly winds with gusts reaching 55 mph along the coastline late Tuesday all the way into Thursday.

This onshore flow will also bring cooler temperatures. In fact, temperatures will be well below normal for April during the Tuesday through Thursday time period, only reaching the high 50s along the coastline to the mid-60s in the North County.

Warmer and dry weather is forecast Friday through the weekend.

Surf and sea report

Today’s 3- to 5-foot northwesterly (285-degree deep-water) swell (with an 8- to 14-second period) will decrease to 2 to 4 feet on Monday and remain at this height and period through Tuesday morning.

Moderate gale to fresh gale-force (32-46 mph) northwesterly winds with gusts reaching 55 mph along the coast will generate a 7- to 9-foot northwesterly (300-degree deep-water) sea/swell on Tuesday afternoon, increasing to 12 to 14 feet (with a 5- to 16-second period) on Wednesday through Thursday.

This northwesterly swell will decrease 8 to 10 feet (with an 11- to 13-second period) on Friday, further lowering to 5 to 7 feet by Saturday.

Seawater temperatures will range between 53 and 55 degrees through Tuesday, decreasing to 49 to 51 degrees on Wednesday and Thursday.

A word of thanks

I want to personally thank those who came out Saturday to help us with the Earth Day project at Montaña de Oro State Park.

John Lindsey is a communications representative for Pacific Gas and Electric Company. He is also a local weather expert and has lived along the Central Coast for more than 23 years. If you have a question, send him an e-mail at pgeweather@pge.com.

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