Weather Watch

From high winds to rain and ‘king tides’: It’ll be a weather watcher’s dream this week

A February 2014 storm swamped Point San Luis Lighthouse.
A February 2014 storm swamped Point San Luis Lighthouse.

If you’re a surfer, fisher or scuba diver, you’ve undoubtedly noticed an increased in ocean temperatures over the past few weeks as persistent southerly winds have produced a northerly flowing current that has brought a warmer body of seawater from the south to the Central Coast.

Since 1976, PG&E’s Diablo Canyon Power Plant environmental monitoring team has maintained seawater temperature recorders housed in steel canisters and placed at fixed locations in the intertidal and subtidal zones along the Pecho Coast, which lies between Point San Luis and Point Buchon.

These calibrated instruments have recorded millions of seawater temperatures over the decades.

The average seawater temperature for the month of January is around 55.8 degrees Fahrenheit; however, this January it’s currently close to 59 degrees.

The warmest January on record was 59.9 degrees recorded in 1998; by the way, that year was one of the strongest El Niño events on record. That event produced 43.98 inches of rain at Cal Poly (the official home of climatology for San Luis Obispo) and 28.24 inches at the Santa Maria Airport, the most rainfall ever recorded there since 1948.

Currently, the water temperatures are in El Niño territory, (warmer than average sea surface temperatures in eastern Equatorial Pacific), but the atmosphere hasn’t responded yet. There’s still a 90 percent chance El Niño will form this winter according to NOAA’s Climate Prediction Center, but even if it doesn’t, it won’t mean the Central Coast won’t see a rainy winter.

“Although there was a very modest El Nino this year, it’s probably not strong enough to be having a big effect on the storms,” Josh Willis, oceanographer and climate scientist at NASA’s Jet Propulsion Laboratory in Pasadena, told me. “It was mild to begin with, and it’s already fading. This is just a nice parade of winter storms to give us a bit of relief from our long-enduring drought – a drought that won’t be cured by a single set of storms, or even a single winter. However, it’s nice to see the rain.”

Nevertheless, the next series of storms starting Sunday night and continuing through Thursday should put a dent in the ongoing drought.

After Friday’s rain, Chris Arndt of SLOweather.com reported about 118 percent of average rainfall for this time in the rain season with 10.81 inches, while the Santa Maria Airport has recorded 5.06 inches or about 96 percent of normal.

If the charts and models verify, these averages will dramatically increase by Friday. You see, a 540-decameter upper-level trough of low-pressure along the California coastline will direct a series of surface lows and frontal systems into the Central Coast. These storms will produce prolonged periods of moderate gale-force to fresh gale-force (32 to 46 mph with possible gust 55 mph) southerly winds along our coastline and moderate to heavy rain, especially along the southerly facing slopes due to orthographic enhancement.

The European Centre for Medium-Range Weather Forecasts and NOAA’s Global Forecast System models are predicting that the cumulative rainfall totals will range between 3 and 7 inches of rain throughout the Central Coast by Friday with Big Sur receiving as much as 9 inches over this period.

These southerly winds and warmer seawater temperatures may also create higher than expected tides. When the water warms, it causes thermal expansion in the upper levels of the ocean. Consequently, seawater levels can be several inches higher than those predicted in the tide tables. The southerly winds can cause storm surge along the southerly facing beaches combined with high waves can further rise sea level.

This condition will be especially critical with the upcoming King Tides. The earth will be at perigee (the closest point in its orbit around the sun).

Gravitational forces exerted by the moon and sun create the timeless tides.

This tugging produces a tidal “bulge,” or area of higher sea level on the ocean’s surface. As the Earth rotates eastward on its axis, California moves into this bulge, which produces a flood tide, and eventually a high tide. As the Earth continues to spin, we move into an area of below-normal sea level, or nodes, which produces an ebb tide, eventually reaching low tide. The slack tide is when the sea is not coming in or going out. Typically, we experienced two low and high tides per day.

Starting next Saturday and continuing through Tuesday, Jan. 22, some of the highest and lowest tides of the year, separated by less than 12 hours, will occur.

The highest will happen at 9:17 a.m. Monday, Jan. 21, when the predicted tide will reach 6.9 feet — and it could be much higher. That will be accompanied by a low tide of -1.7 feet at 4:35 p.m. later that day on Monday.

In other words, the level of the sea will shift 8.6 feet in a little over seven hours. Talk about ripping currents in Morro Bay.

By the way, on Jan. 20, a total lunar eclipse (blood or copper moon) will take place with totality of the event between 8:41 and 9:43 p.m. It’ll coincide with the super moon, which will be at perigee and will appear approximately 14 percent larger and 30 percent brighter than usual. This will also be a wolf moon (first full moon of the year). Consequently, this will be called a super wolf blood moon. The Central Coast should be between storms on Sunday for partly cloudy skies for viewing.

To get an idea of what this will look like in the not-too-distant future, the California King Tides Initiative is encouraging the public to document these tides that occur along the state’s coast. The organization’s goal is to document changes to our shoreline and give the public a glimpse of what’s to come.

If you’re going to photograph these tides, please be safe. Never turn your back to the ocean, and always be aware of your surroundings, weather and oceanographic conditions.

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