Up until a couple of days ago it looked like there might be some damp weather for the Rose Parade and even a better chance for the Rose Bowl game. An upper level low was the culprit, and they are notoriously difficult to model and forecast. The low is out there, it's just further to the north, and so is the rain.

How likely is rain on New Year's Day in Pasadena? Here's a plot generated on the Western Regional Climate Center web site, that shows the probability of various amounts of rain in a 1-day period at Pasadena. The probability of measurable rain (0.01 inch) in a 24 hour period around January 1 is about 20%, or about 1 in 5. As the rainfall amounts increase, the probability drops. The chance of 1.0 inch of rain is about 4%, or 1 in 25. Keep in mind that the probabilities indicated are for a 24 hour period. The chance of rain for the relatively short two hour duration of the Rose Parade is quite a bit less -- as history demonstrates.

Wednesday's cold front, the latest in our series of surprisingly frequent December weather systems, upped the water year rainfall total at Downtown Los Angeles (USC) to 11.70 inches. As of December 31, L.A.'s rainfall total is about 8 inches above normal, and more than three times the normal amount of rainfall for the water year to date. For the first six months of the 2010-11 water year, the rainfall total for Downtown Los Angeles is the fourth wettest in the 133 years that records have been kept. The water year starts on July 1 and ends June 30.

And we're not done yet. In a normal year, Downtown Los Angeles records about two-thirds of its annual rainfall in the months of January, February and March. This amounts to a little over 10 inches of rain. Depending on how you look at the data, rainfall for Downtown Los Angeles during a La Nina episode is usually about 70%-80% of normal. In addition, the composite plus trend plot for Jan-Feb-Mar precipitation anomaly (from CPC) is particularly dry in coastal Southern California, indicating negative anomalies in excess of 3 inches, with a high frequency of occurrence. Even so, it looks like Los Angeles has a good chance of exceeding the normal amount of annual rainfall of 15.14 inches. All we need before June 30 is another 3.45 inches!

The upper level low postponed on account of the Rose Parade, but due in tomorrow, should help with that. BUFKIT analysis of this morning's WRF ensembles projects anywhere from 0.6 inch to 0.9 inch of rain at Van Nuys through early Monday morning. The 18z NAM isn't as wet, projecting about 0.4 inch. The models are still having difficulties with the forecast, and slight changes in the position and behavior of the upper low could have a significant impact on the amount of rainfall. We'll see!

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

The strong cold front that swept through Southern California Christmas night resulted in 0.90 inch of rain at Downtown Los Angeles (USC), increasing December's rainfall total to 9.67 inches. This makes December 2010 the wettest December in 121 years (since 1889), and the second wettest December since recordkeeping began in 1877.

Rainfall totals from last night's fast moving front generally ranged from about 0.4 inch to 0.9 inch. Here's an archived copy of a Precipitation Summary from the NWS Los Angeles/Oxnard with some rainfall totals from around the area.

This morning's model runs continue to forecast more rain for Wednesday. The 12z NAM projects about 0.5 inch at LAX during the day Wednesday. The 09z SREF puts the probability of more than 0.25 inch of rain in the Los Angeles area at about 50% for the 24 hour period ending 4:00 p.m. Wednesday afternoon.

Depending on how much rain we get Wednesday, for the first six months of the 2010-11 water year (July 1 to December 31), the rainfall total for Downtown Los Angeles will likely rank as the fourth or fifth wettest in the 133 years that records have been kept.

In the medium range outlook, the 12z GFS and 12z ECMWF differ in how they handle an upper level low that they forecast to develop off the California coast New Year's morning. The 12z GFS is quite wet New Year's weekend, but it's too early to put much credence in that forecast. We'll see!

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

After producing phenomenal rainfall totals in Southern California and snowfall totals in the higher elevations of the Sierra, the Pacific low and trough responsible for days and days of wet weather has finally moved east.

Some stations recorded more rain in the last 7 days that would normally be recorded over an entire year. Precipitation amounts over 10 inches were common, and several stations recorded over 20 inches. Tanbark, in the San Gabriel Mountains recorded 24.7 inches, NF Matilija in the Ventura Mountains recorded 24.09 inches, and Lytle Creek in the San Bernardino Mountains recorded an astonishing 26.35 inches!

Here's are snapshots of provisional 7-day rainfall totals in Ventura County and 7-day rainfall totals in Los Angeles County from the Ventura County Watershed Protection District ALERT Map Viewer; and a snapshot of provisional 7-day rainfall totals from the NWS San Diego's Experimental Rainfall Summary Display. And here are archived copies of NWS precipitation summaries with preliminary rainfall totals from the NWS Los Angeles/Oxnard and NWS San Diego offices.

The remarkable amount of rainfall makes December 2010 one of the wettest on record in Southern California. According to preliminary NWS data Downtown Los Angeles (USC) has recorded 8.52 inches of rain so far this December. This ranks it as the third wettest December in Los Angeles since recordkeeping began in 1877, exceeded only by December 1889 (15.8 inches) and December 2004 (8.77 inches). With additional rain a possibility, December 2010 only needs 0.25 inch to surpass 2004. For more detailed info see "A Look at the Record-Breaking Week of Rainfall" a PDF from the NWS Los Angeles/Oxnard.

The Sierra recorded gargantuan snowfall totals, with some of the largest being in the Southern Sierra. In the last week the snow sensor at Farewell Gap recorded 22.6 inches snow water equivalent, which roughly translates to 18 feet of snow. This morning California Cooperative Snow Surveys reports the Southern Section Sierra snowpack at 287% of normal, and the snowpack overall in the Sierra at 207%! Mammoth Mountain reports 167 inches of snow so far this December, a new record for the period 1968 to date, obliterating the records set in 1971 (139.8 inches) and 2002 (134.4 inches).

As of yesterday Downtown Los Angeles (USC) rainfall was a whopping 6.88 inches above normal for the water year. That puts us way, way ahead of what is typical for a La Nina influenced rain season -- at least for a couple of months.

Update December 24, 2010. Looks like there will be two opportunities before the end of December for Downtown Los Angeles (USC) to increase its rainfall total for the month and become the second wettest December since recordkeeping began in 1877. The first chance is Saturday night. For the 24 hour period ending 10:00 a.m. Sunday, the 09z SREF puts the probability of more than 0.25 inch of precipitation in the Los Angeles area at about 70%. The WRF ensembles precipitation forecast for LAX for Saturday night ranges from a low of about 0.25 inch to a high of about 0.7 inch. The 18z GFS says the second opportunity will be Wednesday, and forecasts a little under an inch of rain at LAX. We'll see!

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

If current precipitation forecasts and outlooks validate, December 2010 could become one of the wettest on record in California, and at the higher elevations of the Sierra, one of the most snowy. This morning's 5-day precipitation forecast from the Hydrometeorological Prediction Center, for the 5-day period ending early Wednesday morning, indicates up to 7.9 inches of precipitation locally, and 14.7 inches (water equivalent) in the Sierra. And additional precipitation is forecast beyond the 5 day period.

A large Pacific low working in concert with a low west of Hawaii has established a tropical connection, and is pumping copious amounts of moisture into California. This tropical moisture conveyor belt scenario is currently forecast to continue into next week. Late Sunday, shortwave impulses dig down into the low and elongate it southwestward, creating a large longwave trough. This northern part of this trough is forecast to evolve into another large upper and surface low in the northeastern Pacific. The southern part of the trough is forecast to develop a surface low and front that moves into Southern California Tuesday into Wednesday.

In the short term, BUFKIT analysis of WRF ensemble data for Van Nuys shows precipitation totals through early Sunday morning ranging from about 1.0 inch up to about 3.5 inches. Analysis of 12z NAM data for Van Nuys produces around 1.8 inches through early Sunday morning and nearly 5 inches through early Monday morning. The 09z SREF pegs the probability of more than 1.0 inch of precipitation in Los Angeles area at around 70%. Precipitable water values of over 1.0 inch, high relative humidity, and a strong south to southwesterly inflow of over 30 knots should produce significantly enhanced precipitation on favored slopes -- generally those with a south to southwest aspect.

It's a little early to put much credence in forecasts for next week, other than more rain appears likely. The 06z GFS produced astronomic precipitation totals mid-week -- several inches more than either yesterday afternoon's 00z run (2.75 inches), or this morning's 12z run (4.6 inches). We'll see!

As of yesterday Downtown Los Angeles (USC) rainfall was 0.91 inch below normal for the water year, and much of Southern California was falling behind in the rainfall department. It looks like by next week we'll be ahead of the La Nina game again, perhaps way ahead.

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

Saturday's front wasn't as strong as expected, but still produced some resepectable rainfall totals. Sunday's front was better defined and had better dynamics, but moved through the area relatively quickly. The end result is that water year precipitation totals remain near to above normal for many Southern California locales, and about 0.15 inch below normal for Downtown Los Angeles.

Precipitation totals varied widely. In the Los Angeles basin and surrounding valleys amounts generally ranged from about 0.25 inch to 1.0 inch. Foothill and mountain locations in Los Angeles county recorded about 1.0 to 2.0 inches, but several stations recorded over 2.0 inches. Tanbark in the San Gabriel Mountains recorded 3.51 inches, and Ortega Hill in the Ventura Mountains recorded 5.0 inches! Here's an archived copy of a NWS Los Angeles/Oxnard Public Information Statement with some precipitation totals from around the area.

A drier version of last weekend's system -- with a more inland track -- is forecast to produce more rain and snow in the northern two-thirds of California through midweek, but not much precipitation is expected in Southern California.

This morning's 09z SREF pegged the chance of more than 0.1 inch in coastal Southern California for the 24 hours ending 4:00 a.m. Wednesday at between 30% and 50%, and the chance of more than 0.01 inch at around 90%. The 00z 11/23/10 NAM forecast is slightly wetter south of Pt. Conception than the 18z NAM, but is still forecasting under 0.1 inch in most areas.

It was cold in Southern California last night with lows dipping into the 30's in many valley locations. Malibu Canyon recorded a low of 30°F. Cold overnight temperatures are exepected to continue through Thanksgiving.

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

Thanks to October's unusual amount of rainfall, precipitation totals for many areas of Southern California remain near or above normal for the 2010-11 water year. But November has been relatively dry, and Downtown Los Angeles (USC) is now about 0.30 inch below normal for the month, and for the water year. That's expected to change over the weekend.

A series of impulses on the downstream side of a high amplitude upper ridge is forecast to amplify a trough and generate an energetic upper low along the coast of the western U.S. tonight.

The 00z NAM/WRF shows a strong front moving down the coast and through Southern California on Saturday, a second impulse on Sunday, and possibly a third on Monday.

BUFKIT analysis of this evening's 00z NAM data for Van Nuys project rainfall totals of about an inch over the 24 hr. period ending Saturday at 4:00 p.m., and then another third of an inch or so Sunday. The 00z GFS isn't as generous with the rainfall amounts, generating about 0.5 inch on Saturday and 0.3 inch on Sunday, but appears too fast when compared to current satellite and radar images.

SREF means & spreads suggest amounts across the area should generally range from about 0.5 inch to 1.25 inches, with more expected in the mountains. We'll see!

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

October was an unusually wet month in coastal Southern California. Many areas recorded more than an inch above normal rainfall, and some as much as 3 inches above normal. In a month where around 0.5 inch is considered normal, some areas received several times the normal amount of rainfall.

Most of October's rain resulted from two energetic upper lows, and a relatively strong trough/front that swept through the area October 30th. The front produced a new precipitation record for the date of 1.09 inches at Santa Barbara Airport Here's an archived NWS Public Information Statement with some rainfall totals for that storm.

Last week, an approaching Pacific trough pumped up a thick high pressure ridge over California, sending temperatures soaring and breaking temperature records across the area. November 3rd Long Beach Airport set a new high temperature record for the date of 100°F, and Downtown Los Angeles set a new record of 97°F. November 4th temps were once again in high 90s and several stations broke or tied high temperature records. Here are archived copies of the NWS Record Event reports for November 3 and November 4.

The southern part of the Pacific trough that produced our record high temps cut-off into a small upper low as it approached the coast, and moved onshore north of the Los Angeles basin on Saturday. The remainder of the trough and its associated front moved through the area Sunday evening into Monday. The front held together a little better than expected, and rainfall totals in the Los Angeles basin and valleys generally ranged from about 0.10 inch to 0.30 inch. Here's an archived NWS Public Information Statement with some rainfall totals from around the area..

The latest round of rainfall leaves many areas of Southern California way ahead on rainfall totals for the water year. Downtown Los Angeles (USC) missed out on a couple of the systems, and as of close of business yesterday has recorded 1.10 inch for the water year, which is only 0.06 inch above normal. By comparison, Los Angeles Airport is 0.85 inch above normal, and Camarillo/Oxnard is 0.97 inch above normal. This headstart on the rain season should help keep our rainfall totals a little closer to normal as our La Nina influenced rain season continues.

Speaking of La Nina, the September/October value of the Multivariate ENSO Index (MEI) increased slightly by 0.079 sigma, ending the record plunge from El Nino conditions earlier this year. In the past 30 days there was some decrease in the magnitude of negative SST anomalies in the east-central equatorial Pacific, but subsurface temperatures remain quite cool. Computer models are split on whether Nino 3.4 SST anomalies will continue to decline in magnitude during the Northern Hemisphere winter, but nearly all models indicate decreasing anomalies in early 2011. We'll see!

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