Weathernotes Archive January 2001

Weathernotes for Sunday, January 28, 2001

Friday's rain brought the season's rainfall total for Los Angeles (USC) to within 0.60' of normal for the date. Los Angeles received 0.71" from the storm, with amounts around the area generally ranging from about 0.50" to 0.75".

A weak shortwave should bring some showers or light rain to Northern California tomorrow, but at the moment the southern extent of the precipitation is expected to be about Fresno.

This ensemble forecast Spaghetti Plot shows a ridge over California at the beginning of February. This ridge builds in mid-week and according to yesterday's ensembles, lasts about week. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weathernotes for Friday, January 26, 2001

A cold front associated with a well developed low off the Northern California coast brought rain to Southern California for a second time this week, nudging Los Angeles rainfall totals more near to normal.

This radar loop (from Intellicast) shows the cold front working its way through the area this morning.

This system resulted in heavy rain in Northern California yesterday. So far rainfall totals around the basin have generally ranged from about 0.25"-0.50 inch. Additional rain appears likely, with isolated thunderstorms possible in the unstable conditions behind the front. The low is forecast to move south over Southern California later today and depending on its actual track could result in additional showers or thundershowers.

The Week 2 Precipitation Probabilities issued by the CDC continue to depict below average precipitation probability for Southern California for the 7 day period centered on February 6. Yesterday's 6-10 day and 8-14 day outlooks also specified below normal precipitation for Southern California. This is due in part to a mean ridge forecast to be over the West Coast around February 1. Current ensembles show the ridge flattening after about a week. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weathernotes for Tuesday, January 23, 2001

Last week medium range models suggested a chance of rain mid-week and rain is in the forecast.

A complex, cold, upper level low and trough is expected to result in up to an inch of rain in Northern California and along the Central Coast later today and tonight. HPC currently forecasts about 0.25"-0.50" of precipitation in the Los Angeles area for the 24 hour period ending Thursday morning with up to 0.75" in the Southern Sierra.

This system is forecast to produce two main centers of vorticity in the trough that dumbbell around each other in the low's counter-clockwise circulation. The UKMET shows the more northerly center eventually merging with the next shortwave upstream. This shortwave is expected to result in more rain for the area Thursday night into Friday, with showery weather possibly continuing into the weekend.

The Week 2 Precipitation Probabilities issued by the CDC depicts a below average precipitation probability for Southern California for the 7 day period centered on February 3. Yesterday's 6-10 day and 8-14 day outlooks also specified below normal precipitation for Southern California. This is due in part to a mean ridge forecast to be over the West Coast around February 1. Current ensembles show the ridge flattening, and the flow becoming more zonal a few days later. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weathernotes for Tuesday, January 16, 2001

Our impressive January 10-12 storm brought Los Angeles (USC) to within a half-inch of normal for the period since July 1. The storm also brought the Sierra snowpack to just under 50% of normal for the date.

Lower thicknesses associated with a trough over the Southwest have resulted in some low temperatures around the area and a few snow showers, with some snow and ice on passes such as the Grapevine and El Cajon Summit. Yesterday, snow was reported (traffic reports) as low as 2000 ft. At the moment it is mostly clear over much of Southern California.

There's a lot of new snow in the mountains surrounding Los Angeles. (Photo courtesy of the UCLA Dept. of Astronomy Mt. Wilson Towercam. That's the Hooker 100 inch telescope with the higher peaks of the San Gabriel Mountains in the background.)

Current medium range forecasts suggest the possibility of more rain the middle of next week. The Week 2 Precipitation Probabilities issued by the CDC depicts an above average precipitation probability for Southern California for the 7 day period centered on January 27. However yesterday's 6-10 day and 8-14 day outlooks both specified below normal precipitation for Southern California. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weathernotes for Thursday, January 11, 2001

So far, a vigorous Pacific storm has behaved pretty much as forecast, resulting in copious amounts of rain in Southern California, particularly along south and southwest facing foothills and mountain slopes. This can be clearly seen in the Intellicast radar based 24hr precipitation estimate ending 12z this morning.

Precipitation amounts have more or less followed those forecast by HPC. Some selected amounts as of early this morning: Upper Matilija Cyn 5.43; Santa Paula Creek 7.05; Rocky Peak 4.45; Downtown/USC 3.26; Newhall 3.98; San Gabriel Dam 3.19; Mt. Baldy 2.60.

At 8:45 this morning the frontal zone was located south of Los Angeles. Today's HPC QPF forecast shows rain continuing in Southern California. There is considerable instability and dynamics associated with the low and it is forecast to move down the coast as the day progresses. An experimental GOES sounder remote vertical profile from a point south of the low center earlier this morning recorded an LI of -4 and CAPE of 611 J/Kg.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weathernotes for Wednesday, January 10, 2001

The HPC QPF forecast issued early this morning for the 24 hour period ending early Thursday morning shows some impressive, orographically enhanced, rainfall totals in the Southern California mountains, and more rain is forecast to follow on Thursday.

Yesterday's 12z AVN and 12z ETA were in relatively good agreement. Earlier today there were some differences in the06z AVN and 06z ETA, with the ETA not quite as wet, but today's 12z model runs are generally back in sync.

SSMI derived water vapor from MOST/NOAA/NESDIS depicts a plume of approximately 30-35 kg/m2 being entrained by the system. The 1530z NOAA GOES water vapor image (UW-Madison) suggests a powerful combination of moisture and dynamics in the southeast quadrant of the system. (The wave-like pattern of enhancement is interesting.)

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weathernotes for Tuesday, January 9, 2001

The downtown Los Angeles (USC) weather station recorded 0.27 inch of rain on Monday, ending the count of days with 0.01 inch or less of rain at 70. The last significant rain was on October 29 when 0.53 inch was recorded at this station. So, since then there has been 2 days in October, 30 days in November, 31 days in December, and through Sunday, 7 days in January, for a total of 70.

The 12z ETA and 12z AVN have essentially the same message for Southern California: We are going to get very wet. If these forecasts verify, there will be rain, heavy at times, Wednesday night and Thursday. Current HPC QPF forecasts show copious rainfall amounts on Wednesday and Thursday.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weathernotes for Monday, January 8, 2001

The question of the day was whether or not Los Angeles (USC) would get enough rain out of today's frontal passage to break the 70 day string since Los Angeles has seen more than a dribble of rain.

This morning's radar looked very promising, but radar echoes and rainfall rates diminished as the front moved through the L.A. basin.

Light rain has been falling in the area with amounts ranging from zero up to about 0.15 inch in the basin; and up to 0.5 inch or so at some Santa Barbara and Santa Maria area stations. As of about 1:30 PM the Malibu Hills RAWS has recorded about 0.25 inch and the Beverly Hills RAWS about 0.08 inch. And yes, as of 1:00 PM the official Los Angeles weather station at USC had recorded 0.19 inch of rain, so the string of days without "significant" rain appears to be at an end.

If there is some doubt about today's rainfall being significant, wait until Wednesday night. If current forecasts verify there will be no question that the "days without significant rain" string has been broken. The !2z AVN from COLA/IGES shows up to an inch of precipitation over the area during the 12 hours ending Thursday morning. The HPC QPF forecast for the same period generally shows 0.5"-0.75" over the area with some higher amounts in the coastal mountains to the north of Los Angeles.

The Multivariate ENSO Index (MEI) for November/December is -0.63, indicative of a moderate La Nina. Earlier this year neutral ENSO conditions were expected this Winter with a forecast rend toward a warm episode El Nino later in the year. Current ENSO forecasts for Fall 2001 are now trending neutral.

The current 6-10 day outlook, 8 to 14 day outlook, and ensemble based precipitation probability depict more or less normal precipitation amounts in Southern California in the period from January 14 to January 22. (These outlooks can change dramatically from day to day.)

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Weathernotes for Tuesday, January 2, 2001

This morning, as I prepared to go to the office, I wondered if I should grab a jacket. No, I thought; it would be a little chilly, but the car heater would soon take effect. As I walked out the door, I was startled by the warmth. Was this July? It felt like the temp was in the high sixties! It was 6:30 in the morning and I was in short sleeves!

A nearby RAWS recorded a temperature of 65 degrees at 7:00 a.m.. At noon the temp had reached 83!. While the winds were not yet strong, the predicted Santa Ana was heating things up. If the sun's declination was not at wintertime lows the highs today would have certainly reached triple digits.

Remarkably, 64 days since Los Angeles (USC) has had more than 0.01 inch of rain, there is still a little standing water trapped in some deeply shaded potholes in the Simi Hills. This photo was taken on Christmas Day. At that time the five foot long pothole was up to 18 inches deep!

The good news is, there's a chance that "days of dry weather" count could end somewhere around 70+. If medium range forecasts verify, Southern California could see some rainfall early next week. Current ensemble forecasts of precipitation probability suggest that most of California could get a good shot of precipitation. CDC's Week 2 Precipitation Probability shows a continuing above average chance of precipitation for California for the seven day period centered on January 13.

More information concerning Southern California weather can be found using our WEATHER LINKS page.