Fresno Bee Newsroom Blog

An unexpected 110 degrees — what happened?

Low pressure spinning off coast of California was the culprit on Monday.

Fresno spiked 110 degrees on Monday, the hottest day of the year. It broke a 121-year-old record and surprised a lot of folks who had seen forecasts of about 100.

What happened? It was sunnier than expected in the morning, and the San Joaquin Valley got a wind-blown taste of the southwest desert. Then the lightning and thunder show started in the evening.

The culprit was low pressure spinning in a counterclockwise direction in the Pacific Ocean, said meteorologist Paul Iniguez of the National Weather Service in Hanford.

“The counterclockwise spin brought a flow of air up from the desert,” he said. “It was hotter in the Valley than many desert locations. In eastern Kern County desert, the temperatures were in the 90s.”

Meteorologists call this kind of low pressure a “cutoff low,” because it is separated from the jet stream — the high elevation blast of wind coming across the Pacific eastward into the West Coast.

Without the jet stream to move it along, the low could sit in one place and spin winds into California.

The high temperature in Fresno was reported at 109, but it actually climbed to 110 after 5 p.m., Iniguez said.

The flow of air coming from the east continued into the evening and thunderstorms began to appear. There were power outages and fires. In Kern County, there were 1,600 lightning strikes, Iniguez said.

“There were probably more people who saw lightning than people who saw rain,” Iniguez said. “I wouldn’t call this weather unusual in August, but it’s not typical.”

Fresno already has 31 triple-digit days this summer

How hot has it been? Fresno already has 31 days at 100 degrees or higher this year, and the average for an entire summer is 36.

But the heat will have to keep blasting for Fresno to equal last year’s total — 48.  As I have written already, August was very warm last year with 23 days at or above 100 degrees.

There was one other thing I saw in the 2012 numbers that seemed interesting: October had two triple-digit days. I checked October data all the way back to 1996, and did not find a 100-degree day.

I have emailed the National Weather Service in Hanford to find out how long ago there was another triple-digit Fresno day in October.

Hot July, yes, but August 2012 was torrid

The streak of 100-degree-plus days in Fresno came a little early this year, and I’ve heard a lot of people talking about how comfortable July 2012 was in comparison.

It was. But don’t forget about last August. Fresno had 23 days of triple digits in August — 19 of them consecutive.

The all-time record is 21 in a row, set in 2005. Last August narrowly missed it. The 19-day streak was preceded by two 99 degree days. And the two 99-degree days were preceded by three 100-plus days.

If those two 99-degree days in early August last year had been just a little warmer, the new record would have been 24 in a row.

But July 2012 had only 13 days of 100-degree readings. On July 17 last year, the high temperature was 85. That might feel pretty good right now.

Heat drama unfolding as big story in California

California heat and drought are becoming the story of summer 2013 as reservoirs drop and wildfires burn.

Fresno is nearing two consecutive weeks of 100-plus temperatures. The record is 21 consecutive days, set in 2005. Bakersfield has a similar streak, along with a 110-degree day on July 2.

Wildfires have blackened nearly three times more acreage than last year. The foothills in Fresno County around Shaver Lake are considered in extreme fire danger in the foothills this year.

Probably the most unique story so far:  a giant sequoia that caught fire in June 2012 and continued right through the winter. It’s amazing because Sierra winters can be brutally cold and wet at 7,000 feet where this tree lives.

The San Joaquin Valley’s notorious dirty air has been worse on other years, but it has exceeded the federal ozone standard 10 of the last 11 days.

Yosemite Falls, which usually begins dwindling in early July, is almost dry.  If you look around other Sierra web cams, you’ll see a very dry watershed.

But, here’s the kicker for the San Joaquin Valley, take a look at two key reservoirs: Pine Flat and San Luis.

Pine Flat Reservoir in Fresno County is down to 30% of capacity. San Luis Reservoir in western Merced County is at 20%. With most of July and all of August still ahead, farmers and small towns may get the worst of this summer.

First March ozone violations since 2007

The ozone standard has been breached twice this week in the San Joaquin Valley — both in Maricopa at the southwest end of Kern County. They are the first March violations since 2007.

The late-winter warm spell gets the blame. At the same time, it’s worth mentioning that the usual suspects — Fresno, Clovis, Bakersfield and Sequoia National Park — are not spiking ozone problems.

The point is that it’s hard to escape ozone problems in the 25,000-square-mile San Joaquin Valley when nature switches on the heat.

The Valley’s run of five years without a March violation is memorable if only because such early season problems were pretty common a few years ago.

March violations happened in every year between 2001 and 2004. And there were nine violations in 2004.

Those were the bad old days of ozone here. The Valley averaged 155 violations over that span. From 2008 to 2012, the average was 105.

The goal in cleaning up the Valley’s air is zero violations. Last year, the Valley had 105 violations. But the first one didn’t happen until the third week in April.

Temperature records fell all over state

Meteorologist Steve Johnson, a private consultant in the Fresno area, posted a list of California records set on warm Wednesday this week.

It was topped by Fresno’s 85 degrees, which broke the 2007 record for the day by one degree.  Burbank broke its record by eight degrees.

From reading the list, it looks like 2007 was pretty warm, too. But there are also some very old records that were broken. The Riverside record was more than a century old.

Here’s the list, which includes the place, the new record and the old record:

Fresno,  85°  (84° set in 2007), South Lake Tahoe, 69° (64° set in 2007), Burbank,  93° (85° set in 1951), Sandberg,  77° (76° set in 2007),  Woodland Hills, 94° (92° set in 2007), Ramona, 86° (84° set in 2007), Riverside, 95° (90° set in 1902), Thermal, 97° (96° set in 1997), Alpine, 84° (81° set in 1994), El Cajon, 86° (81° set in 2004), Elsinore, 92° (88° set in 1926), Escondido, 87° (86° set in 1951).

If warm weather continues, the snowpack in the Sierra Nevada will come rolling down a little sooner than usual. The snowpack is about 60% of average right now — better than last year when it was about 45% as spring began in late March.