Weather Watch

Buoy failure complicates a forecaster’s job

At our latitude, storms generally move from west to east, directed primarily by the jet stream.

As these storms move in from the Pacific Ocean, the National Oceanic and Atmospheric Administration marine offshore buoy network provides us invaluable weather and ocean wave data.

These offshore buoys are stationed about 500 miles or more off the coast of Northern California, Oregon and Washington and act as long-range sentinels.

It’s interesting that Southern and Central California do not have an offshore buoy network.

While it is rare for storms to reach our coastline from the south-southwest — storms typically decay in the waters off the Central Coast, rather than grow — there have been a few events where such storms have developed, catching us off guard.

Take for example the sudden development of a storm off the Central Coast on Jan. 17 and 18, 1988.

This major storm made landfall near Pismo Beach, where the surface pressure dropped to 989 millibars, an all-time low pressure reading for our area.

The strongest winds occurred south of San Luis Obispo County at Platform Harvest, approximately 16 miles west of Point Conception out at sea, at a sustained speed of 70 knots from the northwest. Without offshore buoys, we did not know that this storm was going to hit our coastline with such intensity.

It is difficult to make an important decision about a storm that you suspect is intensifying in an area where there is very little data. Fortunately, the vast majority of storms move in from the northeastern Pacific or the Gulf of Alaska, where there are offshore buoys.

Two key buoys off the Northern California coastline have become inoperative over the past year.

California marine buoy No. 59, stationed about 357 nautical miles west of San Francisco, went adrift in January 2009 and was recovered in April.

Since that time, there have not been any reports from this station. SE Papa marine buoy No. 06, moored about 600 nautical miles west of Eureka at a water depth of more than 13,000 feet, stopped broadcasting on Jan. 9.

Without these buoys, very little weather or wave data is available from that region, and weather forecasters, such as me, can only hope for a ship report to clarify the situation.

Weather satellites are used to transmit some weather data, but they can not give you atmospheric pressure or wave data.

While ship reports are beneficial, this information is received every six hours.

The buoys report hourly, and with weather, an hour or two can often be the difference between an accurate and inaccurate forecast.

According to the National Data Buoy Center Web site, California buoy No. 59 should be reinstalled by April if weather conditions cooperate.

Hopefully, the U.S. Coast Guard buoy tender ship can inspect the SE Papa buoy about the same time and do any necessary repairs.

This week’s forecast

A series of weather systems will move through the Central Coast this week at roughly two-day intervals. Current models indicate wet weather will continue into at least the first week of March.

This morning’s gentle to moderate (8 to 18 mph) northwesterly winds will shift out of the south later this morning as a very fast-moving cold front approaches the Central Coast.

Rain will spread across our area this afternoon and will continue through tonight. Temperatures today will reach only the mid- to upper 50s across most locations.

The winds will shift out of the northwest tonight and increase to strong to gale-force (25 to 38 mph) levels by Monday morning, producing cold and blustery weather.

Rain will turn to scattered showers Monday morning. A few rain showers may linger over the coastal mountains through Monday afternoon.

Total rainfall amounts will range from 0.55 to 1.05 inches, with higher amounts in the mountains. Snow levels will drop to around 3,000 feet by tonight into Monday morning.

Expect 4 to 10 inches of snow in the Sierra.

Another, much warmer system is expected to produce moderate to fresh (13 to 24 mph) southwesterly winds and periods of moderate rain Tuesday night into Wednesday morning.

Rainfall amounts are expected to range between 1 and 2 inches in the coastal valleys with higher amounts along coastal mountains because of orographic enhancement — precipitation generated by a forced upward movement of air. Snow levels will be over 6,000 feet.

The longer-range charts have been fairly consistent in bringing in another low pressure system that will tap into a warm and moist subtropical air mass Friday. This condition could produce moderate to heavy rainfall late Thursday night into Friday.

Surf and sea report

This morning’s 7- to 9- foot westerly (270-degree deep-water) swell (with an 11- to 13-second period) will shift out of the west-northwest (285-degree deep-water) and decrease to 5 to 7 feet by tonight.

Combined with this westerly swell will be 3- to 5-foot northwesterly (310-degree shallow-water) seas tonight into Monday morning.

A 6- to 8-foot west-northwesterly (285-degree deep-water) swell (with an 11- to 18-second period) will arrive along our coastline Monday, and will remain at this height but with a shorter period through Tuesday.

An 8- to 10-foot west-northwesterly (285-degree deep-water) swell (with a 13- to 20-second period) will arrive along our coastline Wednesday and will remain at this height but with a shorter period through Thursday. This swell will decrease to 4 to 6 feet on Friday.

A 12- to 14-foot west-northwesterly (285-degree deep-water) swell (with an 11- to 15-second period) is forecast along our coastline Saturday.

Seawater temperatures will range between 55 and 57 degrees through this week and seawater visibility should range between 4 and 6 feet along the coast.

Preliminary analysis:

The longer-range charts and models show the potential for high west-northwesterly swell along our coastline March 2.

Conservation tip

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John Lindsey is a media relations 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.