Drought or no drought?

By From page A4 | January 24, 2014

An examination of the Mountain Democrat rainfall records for the past 139 years finds no precedent for this year’s pathetic precipitation to date.

To recap the rain year that began July 1, 2013, September recorded 0.11 inch of rain. That is not an unusual figure for September, which has averaged 0.54 inch and had zero rainfall 46 times in the past 139 years. October is not a big part of the rain year either. This October recorded 0.05 inch vs. an average of 2.11 inches and 17 Octobers with zero rainfall. November was not bad, recording 1.3 inches, though the 139-year average for November is 4.39 inches and only six Novembers recorded zero rainfall.

December is more problematic, recording only 0.1 inch of rain. The 139-year average is 6.69 inches and only two Decembers have been zero rainfall months.

January has only seen 0.05 inch of rain and the extended forecast from AccuWeather is for continued sunny to partly cloudy days through Jan. 31.

At this point the Placerville rain stats are worse than they were in the drought years of 1975-77. In the 1975-76 rain season, which ended the year with 15.9 inches compared to the average of 39.57 inches, there was more rainfall than we have had so far. October 1975 had 4.86 inches vs 0.05 in 2013. November 1975 had 2.22 inches vs. 1.3 for 2013. December 1975 had 1.24 inches vs. 0.1 in 2013. January 1976 was not that great, recording 0.62, a tad more than 0.05 in 2014.

The figures for 1976-77 were 15.86 total for the year, with 0.15 in October, 1.59 in November, 0.17 in December and 2.9 in January.

So far we are on track for a record low rain year. The high pressure ridge that has kept California sunny and warm, sending storm systems through the Pacific Northwest and Alaska and eventually toward the Midwest, has not budged. An article in the San Jose Mercury News describes it as nearly 4 miles high and 2,000 miles long. No atmospheric scientist or oceanographer has been able to explain why it is so strong for so long. One named it the “Ridiculously Resilient Ridge.”

“It’s like the Sierra — a mountain range just sitting off the West Coast — only bigger,” Bob Benjamin, a forecaster with the National Weather Service in Monterey, told the Mercury-News. “This ridge is sort of a mountain in the atmosphere. In most years, it comes and goes. This year it came and didn’t go.”

A deeper explanation may come from the Pacific Decadal Oscillation. Here is the explanation of the PDO from NASA’s Jet Propulsion Laboratory:

“The Pacific Decadal Oscillation (PDO) is a long-term ocean fluctuation of the Pacific Ocean. The PDO waxes and wanes approximately every 20 to 30 years. From TOPEX/Poseidon (satellite) data together with other oceans and atmospheres data, scientists think we have just entered the ‘cool’ phase. The ‘cool’ phase is characterised by a cool wedge of lower than normal sea-surface heights/ocean temperatures in the eastern equatorial Pacific and a warm horseshoe pattern of higher than normal sea-surface heights connecting the north, west and southern Pacific. In the ‘warm’ or ‘positive’ phase, which appears to have lasted from 1977-1999, the west Pacific Ocean becomes cool and the wedge in the east warms.”

By the way, the PDO was discovered in 1996 by Steven Hare at the University of Washington. He, along with colleagues Nathan Mantua, Yuan Zhang, Robert Francis and Mike Wallace discovered the pattern as part of work on fish populations.

“If the Pacific Decadal Oscillation has switched, we are likely to have 20-30 years with lower rainfall than we have had since the late ’70s. We will still have winter rains, but the number of really wet years is likely to decrease,” according to NASA’s JPL Website.

Though El Nino or La Nina will ride over the PDO, they currently are not in effect at all, according to the National Oceanic and Atmospheric Administration. With no El Nino to give a strong clue about precipitation, NOOA said this about California and the West:

“The rest of the country falls into the ‘equal chance’ category, meaning that there is not a strong or reliable enough climate signal in these areas to favor one category over the others, so they have an equal chance for above-, near-, or below-normal temperatures and/or precipitation.”

The dismal record so far could change in the next two or three months. AccuWeather’s extended forecast calls out five days of rain in February including one of those being a thunderstorm. The Weather Underground’s extended forecast includes the potential for rain the first week in February.

In 139 years of rain measurements both February and March have never had zero years. Fifty-five times February has had less than 5 inches of rain and 18 times less than 2 inches. March has had less than 5 inches 63 times and less than 2 inches 18 times.

Rain is in our future. The question is, how much?

Mountain Democrat

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