February 21, 2005

Late last year I made plans on making a visit to California in late February. Part of the reason I chose to visit then was the hopes of having some weather to chase while I visit. My wish became reality on Monday.

I spent the morning in Turlock monitoring conditions in the event of a possible chase. Conditions appeared as if they might be favorable for hail and funnel clouds over the western San Joaquin Valley this afternoon - with surface temperatures warming into the mid 60s, dewpoints in the low 50s, and a core of -25C air at the 500mb level moving overhead. By early afternoon, numerous cells had fired over the Diablo Range, with some activity spilling eastward into the western San Joaquin Valley. I glanced off to the west and could see numerous towering cumulus building to my west, so at 1:45pm I got in my car and headed west in hopes of intercepting these storms.

The original plan was to head west on J17 to Patterson, then head south on I-5. Upon arriving in Patterson, I learned of a tornado warning in Sacramento. So I abruptly changed by plan and blasted north up I-5 towards Sacramento. With the cell more than 80 miles away and moving northwest away from me, this storm would be tough to catch. Numerous severe thunderstorm warnings continued to be issued for this storm over the next hour as I continued north. By the time I arrived in Sacramento at 3:30pm, the storm was within sight to my northwest. The updraft base was low to the ground and looking very ragged, drawing in a low trail of scud in from the east. The storm's precip core was mostly to the northwest of the updraft base, with occasional cloud to ground lightning shooting down from the anvil. I finally caught up with the storm northwest of Arbuckle around 4:15pm. By now the storm was moving over the Coast Range and rapidly decaying. I got out of my car and shot some video and took pictures of what was left of the storm. After a few minutes a cow walked up towards me and started staring at me. Soon after a couple others followed. Then a few others did. Before I knew it I had an angry herd of cattle staring me down and mooing loudly. At that time I took the hint and high tailed it out of there.

Around this time I began hearing reports of a new severe thunderstorm over Solano County, so I picked up I-505 near Dunnigan and dropped south towards Winters. Although this cell was low-topped, it was displaying a photogenic, sculpted shelf cloud reminiscent of ones I've seen on the Plains. The storm was producing frequent cloud-to-cloud and cloud-to-ground lightning, and its precip core had a bluish-green tinge I had never seen in a California storm before. From Winters I drove west towards Lake Berryessa to sample the storm's core. I got into just enough pea-sized hail to cover the road and ground before turning around and heading back east into the valley. This cell rapidly weakened as it moved northwest into the Coast Range and as daytime heating diminished. By now sunset was approaching and it was time to head back to Turlock.

Local TV stations have been showing amazing footage of the tornadoes in the Sacramento area all evening. Most of the footage displayed a white cone about 1/4 way to the ground or a long white rope at a 45 degree angle about 80% of the way to the ground. Perhaps some of the most impressive footage I have seen was taken by a local resident who videotaped shingles being torn off the roof of the house directly across the street no more than 50 feet away. Damage from the tornadoes appears to be very light. Most damage to houses was limited to buckled garage doors and shingles removed from rooftops. Street signs were knocked down, tree limbs were snapped, fences were blown down, and car windows were shattered.

A few interesting observations about the chase.....I was surprised to see how many people were out watching the storm in the Winters area - from local residents in their front yard staring in awe and taking pictures....to passing motorists pulling over along side of the road to take a look at it. Seeing the greenish sky in Winters was also a new revelation for me...I had long assumed that cloud top height was a factor in causing the green sky, and that California storms did not get tall enough to produce the greenish color. Seeing that storm not more than 18,000 to 20,000 feet tall (most Plains storms are 40,000+ feet) produce that green sky now convinces me that it all has to do with heavy precipitation. Others have theorized that hail causes the green sky, although I've seen non-hail producing storms produce a greenish color as well. Still it was nice to see something I had never seen before, not even in the Plains.

Following are some video captures and digital images of this event......

Total Mileage: 341 miles
Total Driving Time: 6 hours, 18 minutes

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