Weather Watch

Hurricane activity is lower than normal in Atlantic

Most climatologists will tell you that El Niño reduces hurricane activity in the Atlantic Basin.

This phenomenon is caused by the jet stream moving southward; the jet stream creates wind shear in the upper atmosphere, which can disrupt hurricane formation.

The Atlantic hurricane season runs from June 1 to Nov. 30 each year, with the peak on or about Sept. 10. The Eastern Pacific hurricane season runs a little longer, from May 15 to Nov. 30.

So far this year, only two major hurricanes have developed in the Atlantic Basin — which consists of the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico.

Hurricane Bill attained major hurricane status in August and moved northward between the East Coast of the United States and Bermuda.

This storm had little impact, except for generating very large ocean waves that delighted East Coast surfers.

The second major hurricane of the 2009 Atlantic season was Hurricane Fred in September. It moved into an area of strong wind shear in the middle of the Atlantic and quickly dissipated without any impact on land.

In terms of accumulated cyclone energy — which measures combined strength and duration of tropical storms and hurricanes — this season so far is only about a third of the long-term historical average. The Eastern Pacific hurricane season is also running below normal.

The deadliest hurricane to hit the United States was the Galveston, Texas, Hurricane of 1900. At least 8,000 people died in this storm.

The most intense hurricane to hit the United States was the Labor Day hurricane of 1935 that slammed into the Florida Keys. This tropical cyclone, another name for hurricane, had the lowest measured surface pressure ever recorded in North America, reaching an incredible 892 millibars or 26.35 inches of mercury (inHg).

The normal pressure reading at sea level is about 1,013 millibars or 29.92 inHg. To look at it from another perspective, you would have to climb a 3,500-foot mountain to reach the same pressure as was experienced in this hurricane at sea level.

Sustained winds were estimated to have reached 200 mph. It was reported that survivors saw the sky fill with sparks, perhaps from small rocks striking each other in the extreme winds.

Hurricane Camille struck the Mississippi Coast in 1969 and was estimated to have 200 mph sustained winds. The highest gust recorded was 213 mph, which actually broke the anemometer used to measure the wind speeds of the storm.

By the way, the highest surface wind speed ever recorded was 231 mph at the Mount Washington Observatory in New Hampshire in April 1934. The wind was not hurricane related.

This week’s forecast

The 1,027 millibar Eastern Pacific high about 700 miles to the west of San Luis Obispo will continue to produce northeasterly (offshore) winds during late night and morning hours, shifting out of the northwest (onshore) during the afternoon hours.

This condition will give mostly clear and warmer weather during late morning hours, then cooler weather during the late afternoon and evening hours as low stratus clouds develop along the coastline.

Today’s temperatures will range from the high 70s near the coast to the low to mid-80s elsewhere.

Overnight lows will reach the high 40s in the interior and the mid- to high-50s in the coastal valleys and beaches.

Little change is forecast through Monday.

The Eastern Pacific high will strengthen to 1035 millibars while shifting northeastward late Monday.

This condition will set up a steep pressure gradient along the coast. Moderate gale to fresh gale (32- to 46-mph) northwesterly winds and much cooler temperatures will develop Tuesday.

As the Eastern Pacific high moves further eastward, the winds will decrease and shift out of the north to northeast (offshore) Wednesday producing spectacular late October weather with plenty of sunshine and warmer temperatures throughout our area.

An approaching Gulf of Alaska low-pressure system, along with its associated cold front, will move toward the California coastline Thursday, giving light winds and increasing high-level clouds.

Although confidence is medium, current forecast models indicate this system could produce strong to gale force (25- to 38-mph) southerly (prefrontal) winds and rain Friday.

The remnants of Hurricane Neki may provide the additional moisture needed for precipitation.

Rain showers are forecast to linger into the weekend.

Temperatures will be much cooler with snow levels dropping to 4,500 feet by Saturday.

Surf and sea report

This morning’s 5- to 7-foot northwesterly (315-degree deep-water) sea and swell (with a 7- to 12-second period) will decrease to 4- to 6-feet (with a 7- to 14-second period) on Monday.

Increasing northwesterly winds will generate an 8- to 10-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 10-second period) Tuesday.

Note: Sea and swell heights will be much higher at the offshore buoys.

This northwesterly sea and swell will decrease to 7 to 9 feet Wednesday morning, further decreasing to 5 to 7 feet by Wednesday night.

A 3- to 4-foot northwesterly (290-degree deep-water) swell (with an 8- to 11-second period) is forecast for Thursday, followed by increasing southerly (185-degree shallow-water) seas Friday.

An 11- to 13-foot northwesterly (295-degree deep-water) swell (with a 14- to 16-second period) is forecast to arrive along our coastline next weekend.

The model runs are advertising a very intense storm with hurricane-force winds developing off the Kamchatka peninsula in Russia and moving toward the Gulf of Alaska.

If this storm develops, it could produce the season’s first high-energy swell event the following week.

Energy efficiency tip

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John Lindsey is a media relations and nuclear communications representative for Pacific Gas and Electric Co. He is also a meteorologist who specializes in forecasting for San Luis Obispo County. Send him questions to pgeweather@pge.com.

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