Weather in the Central California Interior in 2000
The following is account of significant weather by month that I have observed or worked through from March 12, 2000 when I moved here through the end of 2000.
March 2000 - The first portion of the month was cool and wet. I figured when I arrived I would bring down some snow from Montana. Well it didn't happen. Maximum temperatures were frequently well into the 70's and not a drop of rain was to be seen. There wasn't much fog either. Just some light fog in the morning on a few days. During my second week the extended progs (on three consecutive days) were actually calling for record low temperatures and snow on the valley floor (5200 meter thickness) during the early portion of the following week (28th and 29th). Everyone was blaming me for this since this is common for southern Canada. As it turned out, the models moderated as the event neared. Temperatures only dropped to seasonal levels, and we had some strong winds for a few hours as a strong cold front pushed through. The main system was an "inside slider" type system which drops southeast to the east of the Sierra Crest. These systems trend to be dry in this area. Statistics have proven it although there are forecasters (the TV clowns included) who have never learned this. I learned about coordination problems between offices too as there is often a fine line in the North Valley between Merced and Modesto. Climatological averages prove this too.
April 2000 - The first portion of the month saw a heat wave which changed the record books. Temperatures surged into the 90s in many locations. Temperatures moderated some toward the middle of the month as the large high pressure area which had dominated for several days weakened. On the 12th I finally felt a few rain drops. I worked my first convective event, and first significant weather event since my move, on the early afternoon of the 13th. Around 12:30 just after I sent the TWEBs out, some strong cells popped up in the northern zones. I was one of two forecasters who was put on the radar in the anticipation of a severe outbreak. Even SPC was concerned as lapse rates indicated the potential for severe storms. I just watched in frustration for 90 minutes as all of the real fireworks were to the north of our area of responsibility. We warned once later in the afternoon for one storm that did produce large hail. By then I had already been relieved, and was home following the event online. The best part of that day; though was I noticed that the extended progs were calling for a "southwester" to nail us on the 17th. A southwester is a large warm low pressure system that hits California from the southwest. They usually produce heavy rainfall and can cause hydrology problems as they produce tons of runoff. The storm nailed us as predicted and produced urban flooding, but runoff was not a problem. I was on annual leave that day, and I spent that day unpacking. I actually was called in the two previous days (from annual leave) to cover for sick leave (the office was understaffed at this time). The remainder of the month was dry with fluctuating temperatures. After another long warm spell, a modified arctic front hit us on the night of the 28th. I was actually outside the Sequoia Mall at the time when the front hit. Arctic fronts feel like being whipped in the face. Having listened to a stream of KRKX while I was working out I actually flashed back, and actually believed that I was in Billings on Grand Avenue until the road west just went on forever through dairies. The month turned out to be wet and unusually warm.
May 2000 - The month began with a warm and dry week followed by a cooler and unstable airmass which arrived over the weekend. This brought some light rain showers to the area. The next several days were mild with daytime highs only reaching the 70s for the most part. A late season pacific storm north of our area brought a cold front through on the 15th. This system produced numerous thunderstorms in the valley. I was the lucky one who on the radar that evening. Several of these storms produced heavy rain. One of which was almost warned on, but it was a pulse type storm which quickly weakened. The storms kept going overnight as an unusual phenomena called CISK (Conditional Instability of the Second Kind) or CSI (Conditional Symmetric Instability) occurred in an area of high shear behind the front. The result was the shattering of several daily rainfall records. After a couple of mild days, a large upper ridge built into the area. Temperatures soared into the triple digits on the 21st through the 23rd. The heat combined with the financial woes of the local power companies to threaten the area with power outages. A marine intrusion on the 24th brought some welcome relief. After a warmup (low level ageostrophic forcing from the southeast can warm up the valley by mixing our marine air in a few hours), another intrusion followed on the 30th. The month ended up just like April. It was warm and wet.
June 2000 - The month began with a short heat wave which ended with a cold front passage on the 5th. As the airmass near the surface warmed, temperatures aloft remained quite cool for June. When what appeared to be a weak vort max crossed Central California on the morning of 8th, a line thunderstorms fired up and crossed the valley before crashing into the Sierras and precipitating out. These storms produced locally heavy rainfall which produced some urban flooding, and numerous daily precipitation records were shattered. The one day alone made this month one of the wettest June's of all time. I can remember a system much like this one that produced heavy snowfall across Southern Montana on March 5, 1999. All that is needed is a persistent unstable airmass, and a weak upper level system. After a four day cool spell with April like temperatures the heat wave returned for the rest of the month as high pressure kept temperatures well above normal and precipitation out of the area until the 28th when a thunderstorm produced large hail over parts of Yosemite Park. The month ended up warm and wet just like the previous two.
July 2000 - Temperatures were well below normal for the first half of the month as surges of marine air continuously spilled into the valley. Summer returned in full force for the second half of the month as highs usually neared the century mark. July is typically free of precipitation, and this month was. The dry conditions make conditions ideal for large wild fires and one fire (The Manter Fire) just went on and on and on in the southern Tulare County Mountains during the second half of the month, burning close to 75,000 acres. At least the month was cooler than normal and free of high humidity.
August 2000 - The month began with three days of intense heat. Climatology rules were broken on the first as monsoonal moisture helped trigger thunderstorms on the afternoon of the first. The storms produced stream flooding in Yosemite Park and large hail in the Tehachapi Valley. The valley even picked up a few drops. Lightning form some of these storms also started numerous wild fires. One of which burned over 3,000 acres in the Kern County Mountains. Another round of thunderstorms hit the mountains on the 3rd. I helped lay the smackdown on three severe thunderstorm warnings for the mountains (I even had two warnings out at one time fir the first time in almost a year). I was only able to verify one of the warnings (which hit Yosemite Village), but the two other cells both had higher reflectivity, VIL's and stronger tilt to them. These storms only passed over hiking trails where there are no spotters around to report large hail and strong winds. A long dry spell followed. High temperatures in the valley hovered around the century mark until a welcome cold front pushed through on the 28th. The front also triggered a round of pulsating thunderstorms in the Kern County Mountains on the afternoon of the 28th. The month ended with three pleasantly cool days with high temperatures around 80 in the valley. This month ended up slightly warmer than average, and also wetter thanks to the three days of afternoon convection.
September 2000 - The month began with an unusual weather event as round of moderate to locally heavy thunderstorm rains fell in the valley and mountains on the morning of the first. This was the result of a low pressure system near Salt Lake City undergoing rapid intensification known as "bombogenesis". This monster system was able to pull up Gulf of Mexico moisture, wrap it around itself, then spread it into Central California from the northeast. Several daily rainfall records were shattered and the raisin crop sustained heavy damage. The remainder of the month was dry. The first week of the month was unusually cool, but the heat returned by the third week. A strong cold front crashed through on the 21st lowering temperatures again just in time for fall. Temperatures averaged close to normal, and precipitation was generally above normal.
October 2000 - The first week of the month resembled a return to summer, but an intense cold front pushed through on the 9th. Following the frontal passage was a dust storm which reminded me of my days in Lubbock then a round of thunderstorms. I worked one of my most controversial shifts in my career that evening as I put out the "Weird Al" warning. Yes, it cancelled an outdoor Weird Al show. The warning did not verify even though cross sections of it even suggested tornadic characteristics. I felt that it was better to be safe than sorry. The first winter storm of the season hit the following day producing urban flooding (one half to one inch amounts were common) in the valley and heavy snowfall in the mountains. A supercell thunderstorm dropped southeast through the western valley that afternoon. We warned on it three times (this was a large hail producer) as I had some fun on the radar. Temperatures were well below normal for several days in the wake of the early season storm. A dry cold front from an inside slider system brought strong northwest winds to the area on the 21st and 22nd. The next winter storm moved through on the 26th and 27th bringing another round of rain to the valley and heavy snows to the mountains. A stronger storm crossed to our north on the 28th and 29th. A cold front with this system pushed through on the 29th. As the cold air pushed down over Central California a line of thunderstorms broke out across the valley. The office was ready for it as extra staffing was called in. The sky resembled that of days when I filmed tornadoes in Texas and Oklahoma. Not long after I arrived in the office that afternoon I smacked out a severe thunderstorm warning which I soon upgraded to a tornado warning after the TVS (tornado vortex signature) popped up on the radar. This was the first time (in over six years with the NWS) that I put out a tornado warning. As a result, the sirens went off in Visalia and Tulare. The storm produced large hail and funnel clouds, but no tornado. Another supercell thunderstorm produced large hail later that evening near Merced. The month ended up as one of the wettest October's of all time with temperatures averaging slightly below normal.
November 2000 - An upper tough over the Great Basin and an offshore ridge left our area in a cold northwest flow pattern for most of the month. Temperatures were below normal almost every day as this was one of the coldest November's of all time. Hard freezes hit the valley on the 12th and 13th. The month was also unusually dry. Most of the valley remained free of precipitation. Inside slider systems clipped Yosemite Park with some high elevation snows on the 10th and 14th while the rest of the area remained dry. Another round of morning freezes hit from the 17 to the 20th, but the month was free of arctics. Dense morning fog became a problem in the valley toward the end of the month.
December 2000 - The offshore ridge pushed slightly inland early in the month which left the area in a more stagnant ridging pattern. The result was persistent dense smog in the valley. Several inside sliders helped mix out the air during the second week of the month. These systems were mostly dry and brought little precipitation. The second half of the month was almost a repeat every day. Dense fog and subfreezing temperatures in the morning followed by a sunny and mild afternoon. The month ended up being warmer than normal and unusually dry.
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