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# Tuesday, 21 November 2017

The following chart compares various climate parameters for cold ENSO episodes that have occurred since 1949. Except where noted the cold episodes listed are those specified in the CPC's tabulation of Cold & Warm Episodes by Season. The cold and warm episodes are based on the Oceanic Niño Index (ONI), which is calculated using the three month running mean of ERSST.v5 SST anomalies in the Niño 3.4 region with multiple-centered 30 year base periods. A description of the parameters follows the chart. With the exception of years prior to 1957, a Nov-Mar GWO phase space plot is included for each episode. Data for 2017-18 will be updated periodically.

Year ERSST
Version
Nov-Mar
AAM
Peak MEI4 Peak MEI Season Peak
ONI
Peak ONI Season L.A. Rain GWO
Phase Plot
1949-501,2 v5 -- -1.445 APRMAY -1.5 DJF 9.94 --
1950-511,3 v4 -- -1.261 NOVDEC -0.8 NDJ, DJF 8.21 --
1954-551 v5 -- -1.528 MAYJUN (54) -0.9 ASO 11.94 --
1955-561 v5 -- -2.209 MAYJUN (55) -1.7 OND 16.00 --
1956-571 v3b -- -1.490 MAYJUN (56) -0.4 Several 9.54 --
1961-62 v2 -0.515 -1.087 DECJAN -0.3 ASO, SON 18.79 Click for Nov-Mar GWO Phase Space Plot
1962-63 v3b -1.264 -0.863 JANFEB -0.4 OND, NDJ 8.38 Click for Nov-Mar GWO Phase Space Plot
1964-65 v5 -1.150 -1.476 JULAUG -0.8 ASO - DJF 13.69 Click for Nov-Mar GWO Phase Space Plot
1967-683 v4 -0.773 -1.106 APRMAY -0.7 JFM 16.58 Click for Nov-Mar GWO Phase Space Plot
1970-71 v5 -0.980 -1.870 MARAPR -1.4 DJF, JFM 12.32 Click for Nov-Mar GWO Phase Space Plot
1971-72 v5 -0.174 -1.439 AUGSEP -1.0 OND 7.17 Click for Nov-Mar GWO Phase Space Plot
1973-74 v5 -1.336 -1.939 DECJAN -2.0 NDJ 14.92 Click for Nov-Mar GWO Phase Space Plot
1974-75 v5 -0.846 -1.251 OCTNOV -0.8 OND 14.35 Click for Nov-Mar GWO Phase Space Plot
1975-76 v5 -0.716 -1.968 SEPOCT -1.7 OND, NDJ 7.22 Click for Nov-Mar GWO Phase Space Plot
1983-84 v5 -1.099 -0.529 JANFEB -1.0 OND 10.43 Click for Nov-Mar GWO Phase Space Plot
1984-85 v5 -0.600 -0.715 APRMAY -1.1 NDJ 12.82 Click for Nov-Mar GWO Phase Space Plot
1988-89 v5 -1.144 -1.501 AUGSEP -1.8 OND, NDJ 8.08 Click for Nov-Mar GWO Phase Space Plot
1995-96 v5 -0.227 -0.612 DECJAN -1.0 SON - NDJ 12.46 Click for Nov-Mar GWO Phase Space Plot
1998-99 v5 -0.544 -1.140 JANFEB -1.6 NDJ, DJF 9.09 Click for Nov-Mar GWO Phase Space Plot
1999-00 v5 -0.784 -1.210 JANFEB -1.7 NDJ, DJF 11.57 Click for Nov-Mar GWO Phase Space Plot
2000-01 v5 -0.801 -.714 OCTNOV -0.7 OND - DJF 17.94 Click for Nov-Mar GWO Phase Space Plot
2005-06 v5 -0.616 -0.575 NOVDEC, MARAPR -0.8 NDJ, DJF 13.19 Click for Nov-Mar GWO Phase Space Plot
2007-08 v5 -1.015 -1.579 FEBMAR -1.6 NDJ - DJF 13.53 Click for Nov-Mar GWO Phase Space Plot
2008-09 v5 -0.599 -.726 SEPOCT -0.8 DJF 9.08 Click for Nov-Mar GWO Phase Space Plot
2010-11 v5 -0.598 -1.888 AUGSEP -1.7 SON, OND 20.20 Click for Nov-Mar GWO Phase Space Plot
2011-12 v5 -0.371 -0.993 DECJAN -1.1 SON, OND 8.69 Click for Nov-Mar GWO Phase Space Plot
2016-17 v5 0.088 -0.363 SEPOCT -0.7 ASO - OND 19.00 Click for Nov-Mar GWO Phase Space Plot
2017-185   -0.247            
1. AAM and AAM tendency anomaly data not available.
2. Based on ONI values beginning with DJF 1949-50.
3. ONI did not meet threshold of 5 consecutive overlapping seasons using ERSST v5.
4. MEI values are normalized and may change as new data is added. Specified values were current as of April 24, 2012.
5. Data as of November 17, 2017. Data for 2017-18 will be updated periodically.

ERSST Version: The most recent ERSST version for which the episode was designated a cold episode. (See Peak ONI below.)

Nov-Mar AAM: The mean of the global relative atmospheric angular momentum anomaly for the period November 1 to March 31 of the following year. GWO phase space data is calculated using code from the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Peak MEI: The peak seasonal value of the Multivariate ENSO Index (MEI). Reference Wolter and Timlin, 1993, 1998. MEI values are normalized and may shift as new data is added.

Peak MEI Season: The peak bi-monthly season(s) for which the MEI is computed.

Peak ONI: The peak Oceanic Niño Index (ONI) based on SST anomalies in the Niño 3.4 region. Reference Climate Prediction Center Cold & Warm Episodes by Season (Multiple centered 30-year base periods.)

Peak ONI Season: The peak tri-monthly season(s) for which the ONI is computed.

L.A. Rain: The July-June rainfall year precipitation total in inches for Downtown Los Angeles (USC). Reference WRCC LOS ANGELES DWTN USC CAMPUS, CA. See Precipitation>Quantity>Monthly Precipitation Listings>Monthly Totals.

GWO Phase Space Plot: Plot of global relative atmospheric angular momentum anomaly vs. global relative atmospheric angular momentum tendency anomaly for the period November 1 to March 31 of the following year. Data is calculated using code from the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Tuesday, 21 November 2017 14:00:44 (Pacific Standard Time, UTC-08:00)  #    Disclaimer  |   | 
# Sunday, 03 April 2016

Following is a chart comparing the 2015-16 El Nino to warm ENSO episodes that have occurred since 1950. The warm episodes are based on the revised Oceanic Niño Index (ONI) which is calculated using the three month running mean of ERSST.v4 SST anomalies in the Niño 3.4 region with multiple-centered 30 year base periods. Unless noted the warm episodes are those specified in the CPC's tabulation of Cold & Warm Episodes by Season. A description of the parameters follows the chart. With the exception of years prior to 1957, a Nov-Mar GWO phase space plot is included for each warm episode.

Year Jul-Sep
AAM
Nov-Mar
AAM
Peak MEI Peak MEI Season Peak
ONI
Peak ONI Season L.A. Rain GWO
Phase Plot
1951-521 -- -- 0.822 JULAUG 0.9 SON 26.21 --
1952-532 -- -- 0.788 APRMAY 0.7 FMA-AMJ 9.46 --
1953-542 -- -- 0.484 AUGSEP 0.8 ASO, SON, OND 11.99 --
1957-583 -- 0.773 1.474 DECJAN, JANFEB 1.7 DJF 21.13 Click for Nov-Mar GWO Phase Space Plot
1958-59 -0.919 -0.206 0.788 JANFEB 0.6 NDJ, DJF, JFM 5.58 Click for Nov-Mar GWO Phase Space Plot
1963-64 0.005 0.046 0.867 OCTNOV, DECJAN 1.2 SON, OND 7.93 Click for Nov-Mar GWO Phase Space Plot
1965-66 -0.826 -0.748 1.436 JULAUG 1.8 OND 20.44 Click for Nov-Mar GWO Phase Space Plot
1968-69 0.130 0.513 0.844 JANFEB 1.0 JFM 27.47 Click for Nov-Mar GWO Phase Space Plot
1969-70 0.358 0.413 0.670 OCTNOV 0.8 ASO, SON, OND 7.77 Click for Nov-Mar GWO Phase Space Plot
1972-73 -0.096 -0.239 1.827 JUNJUL, JULAUG 2.0 OND 21.26 Click for Nov-Mar GWO Phase Space Plot
1976-77 0.284 -0.828 1.029 AUGSEP 0.8 OND,NDJ 12.31 Click for Nov-Mar GWO Phase Space Plot
1977-78 -0.646 1.008 0.993 SEPOCT, OCTNOV 0.8 OND, NDJ 33.44 Click for Nov-Mar GWO Phase Space Plot
1979-804 0.496 -0.013 0.996 NOVDEC 0.6 NDJ, DJF 26.98 Click for Nov-Mar GWO Phase Space Plot
1982-83 0.938 2.337 3.011 FEBMAR 2.1 OND,NDJ, DJF 31.25 Click for Nov-Mar GWO Phase Space Plot
1986-875 0.232 0.019 2.140 APRMAY87 1.2 JFM 7.66 Click for Nov-Mar GWO Phase Space Plot
1987-885 1.153 1.000 1.982 JULAUG 1.6 JAS, ASO 12.48 Click for Nov-Mar GWO Phase Space Plot
1991-92 -0.008 0.808 2.269 MARAPR 1.6 DJF 21.00 Click for Nov-Mar GWO Phase Space Plot
1994-95 -0.422 0.764 1.419 SEPOCT 1.0 NDJ 24.35 Click for Nov-Mar GWO Phase Space Plot
1997-98 1.811 1.481 3.049 JULAUG,AUGSEP 2.3 OND, NDJ 31.01 Click for Nov-Mar GWO Phase Space Plot
2002-03 0.047 0.324 1.199 DECJAN 1.3 OND 16.49 Click for Nov-Mar GWO Phase Space Plot
2004-05 -0.020 0.747 1.055 FEBMAR 0.7 JAS-NDJ 37.25 Click for Nov-Mar GWO Phase Space Plot
2006-07 0.143 -0.322 1.322 OCTNOV 1.0 NDJ 3.21 Click for Nov-Mar GWO Phase Space Plot
2009-10 -0.103 0.303 1.521 JANFEB 1.3 NDJ,DJF 16.36 Click for Nov-Mar GWO Phase Space Plot
2014-156 -0.526 -0.297 0.997, 1.567 MAYJUN14, APRMAY15 0.6 OND, NDJ 8.52 Click for Nov-Mar GWO Phase Space Plot
2015-167 1.313 1.637  2.527 AUGSEP 2.3 NDJ 9.36 Click for Nov-Mar GWO Phase Space Plot

1. AAM and AAM tendency anomaly data for 1951-52 not available.
2. Continuous warm episode from DJF 1952/53 to DJF 1954.
3. AAM anomaly is average for Jan-Mar 1958.
4. Warm episode per ERSST.v4, but not ERSST.v3b.
5. Continuous warm episode from ASO 1986 to JFM 1988.
6. Warm episode per ERSST.v3b, but not ERSST.v4.
7. Data as of April 3, 2016.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric angular momentum anomaly for the periods July 1 to September 30 amd November 1 to March 31 of the following year. GWO phase space data is calculated using code from the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Peak MEI: The peak seasonal value of the Multivariate ENSO Index (MEI). Reference Wolter and Timlin, 1993, 1998. MEI values are normalized and may shift as new data is added.

Peak MEI Season: The peak bi-monthly season(s) for which the MEI is computed.

Peak ONI: The peak Oceanic Niño Index (ONI) based on SST anomalies in the Niño 3.4 region. Reference Climate Prediction Center Cold & Warm Episodes by Season (Multiple centered 30-year base periods.)

Peak ONI Season: The peak tri-monthly season(s) for which the ONI is computed.

L.A. Rain: The July-June rainfall year precipitation total in inches for Downtown Los Angeles (USC). Reference WRCC LOS ANGELES DWTN USC CAMPUS, CA.

GWO Phase Space Plot: Plot of global relative atmospheric angular momentum anomaly vs. global relative atmospheric angular momentum tendency anomaly for the period November 1 to March 31 of the following year. Data is calculated using code from the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Sunday, 03 April 2016 08:46:40 (Pacific Daylight Time, UTC-07:00)  #    Disclaimer  |   | 
# Tuesday, 28 July 2015

NRL GOES E/W Composite VIS/IR (Day/Night) - Saturday, July 18, 2015 5:00 PM PDT Click
NRL GOES E/W Composite VIS/IR (Day/Night)
Post-tropical remnant low Dolores is west of Baja
Saturday, July 18, 2015 5:00 PM PDT.

Downtown Los Angeles (USC) ended the 2014-2015 rainfall year (July 1 - June 30) with 8.52 inches of rain; well below the normal of 14.93 inches. It was the fourth consecutive year of below normal rainfall in Los Angeles and much of Southern California.

To kick off the new new rainfall year two waves of moisture and instability associated with ex-hurricane Dolores, other tropical sources, and a strong monsoonal flow from Baja resulted in record-setting rainfall in Southern California from Saturday July 18 to Monday July 20.

Constructive interference of the El Nino base state by the active phase of the MJO resulted in negative 200-hPa velocity potential anomalies and enhanced convection in the Eastern Pacific during the first half of July. This appears to have contributed to the rapid development of Dolores from a tropical depression on July 11 into a Category 4 hurricane July 15. Anomalously warm SSTs in the tropical and sub-tropical Eastern Pacific also played a role, helping to maintain the strength of Dolores and increasing the amount of water vapor entrained by the system and transported into Southern California.

Many stations set new records, not only for the date, but for any day in July. Downtown Los Angeles (USC) set rainfall records for the date on Saturday and Sunday and tied Monday's record. Downtown Los Angeles recorded 0.36 inch of rain Saturday. This is more rain than any day in any July since recordkeeping began in 1877. That one day of rainfall even broke the monthly record for July in Los Angeles! Prior to this event the wettest July on record was in 1886, when 0.24 inch was recorded.

There was very heavy rain in the mountains on Sunday, with rain rates exceeding an inch a hour. From 5:15 p.m. to 5:25 p.m. a CBS Radio weather station on Mt. Wilson recorded a half-inch of rain in just 10 minutes!

Though the rain created its own problems -- including flash floods, debris flows and rock slides -- the soaking rains helped quell the Pines Fire near Wrightwood and the North Fire near Cajon Pass. Over the three day period from Saturday to Monday the Big Pines Remote Automated Weather Station (RAWS), near the Pines Fire, recorded 3.12 inches of rain. Several stations in the San Gabriels recorded more than three inches of rain, including Clear Creek and Opids Camp. Here's a NWS compilation of some rainfall totals in the Los Angeles forecast area and the San Diego forecast area.

After dawdling around for several months our on again, off again El Nino is finally firing on all cyclinders and could reach ONI and MEI levels not seen since 1997-98 and 1982-83. The Multivariate ENSO Index (MEI) for May-June was 2.06. This was the third highest value for the season, exceeded only in 1983 (2.2) and 1997 (2.3). It is the second highest for the season during the development phase of an El Nino event. The 2015 April-May-June Oceanic Nino Index (ONI) value of 0.9 was higher than than in 1982 (0.6) and 1997 (0.6). Several dynamical models in the IRI/CPC ENSO Predictions Plume of forecast Nino 3.4 SST anomaly, released July 16, project Nino 3.4 SST anomalies in excess of 2.5°C this fall.

Analysis of correlations of CMAP Precipitation with globally integrated atmospheric angular momentum using ESRL/PSD's Linear Correlations in Atmospheric Seasonal/Monthly Averages tool suggests that precipitation in the southern half of California is more strongly correlated with atmospheric angular momentum (AAM) than with Nino 3.4 SST. For example, compare the correlation of CMAP Precipitation to AAM and to Nino 3.4 SST for Dec-Jan-Feb 1980-2012. Cyclical increases in relative atmospheric angular momentum are often associated with El Ninos. This can be seen in the plots of the Global Wind Oscillation in my El Nino Comparison Chart.

After being negative for 3 1/2 years, the PDO Index has been positive since January 2014. December's PDO value of 2.51 was the highest for that month on record since 1900. June's value of 1.54 was the 13th highest since 1900.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

 

Tuesday, 28 July 2015 08:07:55 (Pacific Daylight Time, UTC-07:00)  #    Disclaimer  |   | 
# Monday, 06 July 2015

Following is a chart comparing 2014-15 to warm ENSO episodes that have occurred since 1950. The warm episodes are based on the revised Oceanic Niño Index (ONI) which is calculated using the three month running mean of ERSST.v4 SST anomalies in the Niño 3.4 region with multiple-centered 30 year base periods. Unless noted the warm episodes are those specified in the CPC's tabulation of Cold & Warm Episodes by Season. A description of the parameters follows the chart. With the exception of years prior to 1957, a GWO phase space plot is included for each warm episode.

Year Jul-Sep
AAM
Nov-Mar
AAM
Peak MEI Peak MEI Season Peak
ONI
Peak ONI Season L.A. Rain GWO
Phase Plot
1951-521 -- -- 0.847 JULAUG 0.9 SON 26.21 --
1952-532 -- -- 0.788 APRMAY 0.7 FMA-AMJ 9.46 --
1953-542 -- -- 0.520 AUGSEP 0.8 ASO, SON, OND 11.99 --
1957-583 -- 0.773 1.472 DECJAN, JANFEB 1.7 DJF 21.13 Click for Nov-Mar GWO Phase Space Plot
1958-59 -0.919 -0.206 0.807 JANFEB 0.6 NDJ, DJF, JFM 5.58 Click for Nov-Mar GWO Phase Space Plot
1963-64 0.005 0.046 0.859 OCTNOV, DECJAN 1.2 SON, OND 7.93 Click for Nov-Mar GWO Phase Space Plot
1965-66 -0.826 -0.748 1.477 JULAUG 1.8 OND 20.44 Click for Nov-Mar GWO Phase Space Plot
1968-69 0.130 0.513 0.867 JANFEB 1.0 JFM 27.47 Click for Nov-Mar GWO Phase Space Plot
1969-70 0.358 0.413 0.653 OCTNOV 0.8 ASO, SON, OND 7.77  
1972-73 -0.096 -0.239 1.896 JUNJUL, JULAUG 2.0 OND 21.26 Click for Nov-Mar GWO Phase Space Plot
1976-77 0.284 -0.828 1.024 AUGSEP 0.8 OND,NDJ 12.31 Click for Nov-Mar GWO Phase Space Plot
1977-78 -0.646 1.008 1.006 SEPOCT, OCTNOV 0.8 OND, NDJ 33.44 Click for Nov-Mar GWO Phase Space Plot
1979-804 0.496 -0.013 1.016 NOVDEC 0.6 NDJ, DJF 26.98 Click for Nov-Mar GWO Phase Space Plot
1982-83 0.938 2.337 3.024 FEBMAR 2.1 OND,NDJ, DJF 31.25 Click for Nov-Mar GWO Phase Space Plot
1986-875 0.232 0.019 2.140 APRMAY 1.2 JFM 7.66 Click for Nov-Mar GWO Phase Space Plot
1987-885 1.153 1.000 1.956 JULAUG 1.6 JAS, ASO 12.48 Click for Nov-Mar GWO Phase Space Plot
1991-92 -0.008 0.808 2.269 MARAPR 1.6 DJF 21.00 Click for Nov-Mar GWO Phase Space Plot
1994-95 -0.422 0.764 1.434 SEPOCT 1.0 NDJ 24.35 Click for Nov-Mar GWO Phase Space Plot
1997-98 1.811 1.481 3.005 JULAUG,AUGSEP 2.3 OND, NDJ 31.01 Click for Nov-Mar GWO Phase Space Plot
2002-03 0.047 0.324 1.185 DECJAN 1.3 OND 16.49 Click for Nov-Mar GWO Phase Space Plot
2004-05 -0.020 0.747 1.032 FEBMAR 0.7 JAS-NDJ 37.25 Click for Nov-Mar GWO Phase Space Plot
2006-07 0.143 -0.322 1.299 OCTNOV 1.0 NDJ 3.21 Click for Nov-Mar GWO Phase Space Plot
2009-10 -0.103 0.303 1.524 JANFEB 1.3 NDJ,DJF 16.36 Click for Nov-Mar GWO Phase Space Plot
2014-156 -0.526 -0.297 0.967, 1,567 APRMAY14, APRMAY15 0.6 OND, NDJ 8.52 Click for Nov-Mar GWO Phase Space Plot

1. AAM and AAM tendency anomaly data for 1951-52 not available.
2. Continuous warm episode from DJF 1952/53 to DJF 1954.
3. AAM anomaly is average for Jan-Mar 1958.
4. Warm episode per ERSST.v4, but not ERSST.v3b.
5. Continuous warm episode from ASO 1986 to JFM 1988.
6. Warm episode per ERSST.v3b, but not ERSST.v4.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric angular momentum anomaly for the periods July 1 to September 30 amd November 1 to March 31 of the following year. Data is from the GWO phase space data file linked on the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Peak MEI: The peak seasonal value of the Multivariate ENSO Index (MEI). Reference Wolter and Timlin, 1993, 1998. MEI values are normalized and may shift as new data is added.

Peak MEI Season: The peak bi-monthly season(s) for which the MEI is computed.

Peak ONI: The peak Oceanic Niño Index (ONI) based on SST anomalies in the Niño 3.4 region. Reference Climate Prediction Center Cold & Warm Episodes by Season (Multiple centered 30-year base periods.)

Peak ONI Season: The peak tri-monthly season(s) for which the ONI is computed.

L.A. Rain: The July-June rainfall year precipitation total in inches for Downtown Los Angeles (USC). Reference WRCC LOS ANGELES DWTN USC CAMPUS, CA.

GWO Phase Space Plot: Plot of global relative atmospheric angular momentum anomaly vs. global relative atmospheric angular momentum tendency anomaly for the period November 1 to March 31 of the following year. Data is from the GWO phase space data file linked on the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Monday, 06 July 2015 10:56:10 (Pacific Daylight Time, UTC-07:00)  #    Disclaimer  |   | 
# Tuesday, 20 January 2015

Southwestern U.S. Current Departure from Normal Precipitation Since October 1 as of 1/19/2015 12:00 UTC. Click
Current Departure from Normal Precipitation Since October 1
AHPS Precpitation Analysis as of 1/19/2015 12:00 UTC.

After being negative for 3 1/2 years, the PDO Index has been positive since January 2014. December's PDO value of 2.51 is the highest for that month on record (since 1900), exceeding December 2002's value of 2.10 and December 1940's value of 1.96.

Even so, the highly anticipated 2014-15 El Nino continues to dawdle with little ocean-atmosphere coupling and an emphasis on an higher amplitude meridional flows. Due in part to the upwelling phase of a series of oceanic Kelvin waves, equatorial Pacific heat content and SST anomalies have diminished. After having been at or above 0.5 °C for the past twelve weeks OISST.v2 Nino 3.4 SST Anomalies dropped to 0.4 °C for the week centered on January 7, 2015 and as of the week of January 14 was at 0.5 °C.

The Multivariate ENSO Index (MEI) for NOV/DEC has decreased 0.13 SD to +0.58, but has maintained its historic rank (since 1950) at 47. A rank of 46 is the threshold for weak El Nino conditions in the context of the MEI. The FNL Global Wind Oscillation for the past 90 days continues to reflect the lack of definitive atmospheric coupling.

So far this rain season Northern California and the coastal areas of Central and Southern California have fared much better in terms of precipitation than last year. As of today Downtown Los Angeles (USC) precipitation for the water year (beginning July 1) is at 90% of normal and Downtown San Francisco is at 127%.

As this AHPS plot of precipitation since October 1 shows, many areas of California have recorded at least 75% of normal precipitation. Unfortunately the Sierra Nevada is not one of them. While better than last year's dismal 14% of normal on this date, this year's snowpack is currently well below average, and was last reported at 36%. Here is an AHPS plot of precipitation departure since October 1 that shows the deficits in the Sierra Nevada.

At the moment it doesn't look like the snowpack will get much help in the short term. After fending off a little shortwave the blocking ridge is forecast to rebuild to new heights, bringing unseasonably mild weather to much of the West Coast. There does appear to be the possibility of a wildcard low latitude low developing under the block and that could result in some precipitation in Southern California next week. If such a system develops, given the warm state of the Eastern Pacific, it could be wetter than expected. We'll see!

In the early morning hours of Friday, December 12, 2014, a very strong cold front, enhanced with moisture from an atmospheric river, produced a line of strong storms that produced rain rates in the Springs Fire burn area as high as 2 inches per hour. This resulted in widespread flash floods and debris flows in the burn area, much of which is in Pt. Mugu State Park. Mud and debris flows originating from the burn area inundated homes below Conejo Mountain and closed Pacific Coast Highway. This slideshow includes photos of the aftermath of the flash floods and debris flows in Blue Canyon, Sycamore Canyon and Upper Sycamore. The photos were taken on a trail run on December 14, 2014. Also included are some NWS Los Angeles/Oxnard tweets and some additional meteorological images and info.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

 

Tuesday, 20 January 2015 08:44:31 (Pacific Standard Time, UTC-08:00)  #    Disclaimer  |   | 
# Sunday, 07 December 2014

CNRFC 96 Hr Gridded Precipitation Totals for the Four-Day Period Ending 12/04/2014 4:00 am Click
CNRFC 96 Hr Gridded Precipitation Totals
For the Four-Day Period Ending 12/04/2014 4:00 am.

After being negative for 3 1/2 years, the PDO Index has been positive since January 2014. October's PDO value of 1.49 is the 6th highest for that month since 1900 and comparable to PDO Index values in October 1997, 1957, 1993, and 1987.

PDO/AMO-based Precipitation composites suggest a warm Pacific generally produces more Winter precipitation in California than a cold Pacific. This makes sense. Among other effects a warm Pacific increases evaporation, air temperature, and the amount of water vapor transferred to the atmosphere. This in turn can increase precipitation. Here is a comparison of Pacific SST anomalies at the beginning of December 2014 and December 2013. Mouse over the image to switch to the December 1, 2013 image.

A warm Pacific may have contributed to the amount of precipitation produced in California by a large Pacific upper level low this past week. Two periods of rain were observed in Southern California -- one on Sunday and the other on Tuesday and Wednesday.

Sunday an embedded short wave in the moist southerly flow produced more rain than expected in many areas of Los Angeles. Surprisingly high rain rates and amounts in the Santa Monica Mountains, resulted in debris flows in the Springs Fire burn area that closed PCH. Here's a NWS compilation of some rainfall totals in the forecast area.

Even with the parent low lifting to the north on Tuesday and the 570 mb contour near Santa Barbara, the very moist southerly flow orographic lift and sufficient dynamics produced widespread precipitation in Southern California with some impressive precipitation totals. Tuesday record rainfall for the date occurred at both Downtown Los Angeles and Downtown San Francisco. Yucaipa Ridge in the San Bernardino Mountains recorded a whopping three-day rainfall total of 14.6 inches. Following are three-day rainfall compilations from the NWS Los Angeles/Oxnard and NWS San Diego.

Here are graphics from the CNRFC with gridded precipitation totals for the four day period from early Sunday morning to early Thursday morning for Southern California, the Sierra Nevada and the San Francisco Bay Area. Some preliminary precipitation totals of 5 inches or more are noted.

Equatorial Pacific SSTs continue to rebound with OISST.v2 Nino 3.4 SST Anomalies above 0.5 °C for the past seven weeks and now stand at 1.0 °C for the week centered on November 26, 2014. The Multivariate ENSO Index (MEI) for OCT/NOV has increased 0.35 SD to 0.71, increasing its historic rank (since 1950) from 42 to 47, just within the MEI's weak El Nino threshold. However as noted by the CPC in their December 4, 2014 ENSO Diagnostic Discussion, "the overall atmospheric circulation has yet to show a clear coupling to the anomalously warm waters." The FNL Global Wind Oscillation for the past 90 days continues to reflect the lack of definitive atmospheric coupling

For now the Pacific storm door appears to be open. Most medium-range guidance is suggesting another significant system will be affecting California in the Thursday-Friday timeframe. We'll see!

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

 

Sunday, 07 December 2014 13:33:07 (Pacific Standard Time, UTC-08:00)  #    Disclaimer  |   | 
# Friday, 07 November 2014

SST NINO Region Anomalies from the CPC ENSO Diagnostic Discussion 11/6/2014. Click
SST NINO Region Anomalies
From the CPC ENSO Diagnostic Discussion 11/6/2014.

One thing is very clear; we have a lot to learn about the atmosphere's response to anomalously warm equatorial Pacific SSTs. It's difficult to imagine a better scenario for El Niño development than the conditions seen in the equatorial Pacific earlier this year.

After being negative for 42 out of the previous 43 months, the Pacific Decadal Oscillation (PDO) index turned positive in January 2014 and has remained positive through the summer. Beginning in January and ending in late June the downwelling phase of a very strong Kelvin wave propagated across the Pacific, with upper ocean area-averaged heat content anomaly between 180 and 100W peaking at the end of March. Since January there have been westerly wind bursts and periods of increased low-level westerly zonal wind anomalies of variable duration and extent.

The Oceanic Niño Index (ONI) jumped from -0.5 in the FMA season to -0.1 in MAM, and then to +0.1 in AMJ. During that same period the Multivariate ENSO Index (MEI) jumped from a rank of 35 in MARAPR to 59 in APRMAY -- a value that put it on the doorstep of a strong El Nino ranking. Which all looked supportive of at least a moderate El Nino developing.

But it didn't. After climbing up to 0.6 °C in late May, Nino 3.4 region SST anomalies dropped to below 0.0 °C in late July. Since then a more modest downwelling Kelvin wave has restored some of the basin heat content and Nino 3.4 anomalies have rebounded back to 0.6 °C.

So what's next? While El Nino development still appears to be possible this Winter, it would be one of the two latest developing El Ninos in the record from 1950 to the present -- the other being 1952-53. One possibility is that this year's vacillations are the precursor to the EARLY development of an El Nino event next year.

One worrisome detail is that the Global Wind Oscillation (GWO) has been behaving similarly to the failed El Nino of 2012. Compare this plot of the GWO from June 1 to October 31 of this year to the plot of the GWO from June 1 to October 31, 2012. In both 2014 and 2012 the GWO has shown a neutral or weak La Nina-like response. The GWO for the period June 1 to October 31, 1997 is an example of a definitive atmospheric response to strong El Nino conditions.

On a more positive note, a relatively strong, but fast-moving Pacific cold front and trough resulted in rain and snow in California over Halloween. In the Los Angeles area rainfall amounts generally varied from around 0.3 inch to 0.75 inch or so with isolated amounts as high as about 2.0 inches in the mountains. Here are some tabulated rainfall amounts from around the area from the NWS Los Angeles/Oxnard and NWS San Diego.

The 1981-2010 climate normal average rainfall for Downtown Los Angeles in November is 1.04 inches. Month to date we're about average for the date, and water year to date we're ahead of last year, but about 0.6 inch below normal.

Based on the current GFS and ECMWF forecasts those deficits are probably going to increase over the next two weeks, but it is way too early in the rain season to attribute the dry weather to a continued dry pattern. El Niño or not; dry November or not; the switch from a cold Pacific to a warm Pacific is a significant change and one that some guidance suggests should increase our rainfall. We'll see!

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

 

Friday, 07 November 2014 14:18:36 (Pacific Standard Time, UTC-08:00)  #    Disclaimer  |   | 
# Thursday, 03 July 2014

Percentage of Normal Precipitation for July 1, 2012 to June 30, 2014 (WRCC) Click
Two-Year Percentage of Normal Precipitation
July 1, 2012 to June 30, 2014 (WRCC).

Downtown Los Angeles (USC) finished the water year (July 1 to June 30) with 6.08 inches of recorded rainfall. This is about 41% of the 1981-2010 normal of 14.93 inches. It was the seventh driest water year since recordkeeping began in 1877. When combined with last year's water year total of 5.85 inches, the back-to-back water years from July 1, 2012 to June 30, 2014 are the driest on record for Los Angeles. The total rainfall deficit over the two year period was about 18 inches.

El Nino has been knocking on the door, but until very recently the atmosphere has only been responding in spits and sputters.

The weekly OISST.v2 Nino 3.4 SST temperature anomaly has been vacillating in the range 0.4 to 0.6 beginning with the week centered on April 23, 2014 and now stands at 0.5. Nino 1+2 and Nino 3 anomalies have generally been increasing and as of the week centered on June 25 are at 1.6 and 1.0 respectively. Here is a plot of the Nino regions SST anomalies from the CPC. Following a period of strengthened tradewinds, another westerly wind burst has developed in the Western Pacific. There have been several WWB this year and the most recent WWB could lead to additional warming of equatorial SSTs.

In response to the upwelling phase of an oceanic Kelvin wave there has been a decrease in subsurface Pacific equatorial heat content and some associated cooling at depth.

The Global Wind Oscillation (GWO) can be a useful tool for evaluating the degree to which the atmosphere is responding to El Nino or La Nina conditions. As this plot of the GWO for the period March 1 to July 31, 1997 shows, during the spring and summer of 1997 El Nino conditions were already resulting in a definitive atmospheric response. Here is a plot of the GWO from March 1 to July 1 of this year. Over most of this period the GWO has shown a neutral or weak La Nina-like response. Recently the GWO has exhibited a positive shift in AAM anomaly that, if sustained, could be indicative of a coupled ocean-atmosphere response.

The Plume-based and Consensus Forecasts in the June 19 IRI/CPC ENSO Quick Look (PDF) show an increasing chance of El Nino conditions developing over the NH summer, with an approximately 80% chance of El Nino conditions being established by the OND season. A July 2 run of the CFSv2 forecasts Nino 3.4 anomalies to briefly decline, then increase substantially from July into October. We'll see!

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

 

Thursday, 03 July 2014 13:48:36 (Pacific Daylight Time, UTC-07:00)  #    Disclaimer  |   | 
# Wednesday, 01 January 2014

Downtown Los Angeles Rainfall for the Driest Calendar Years from 1878-2013. Click
Downtown Los Angeles Rainfall
Driest Calendar Years 1878-2013.

Since January 1 Downtown Los Angeles has recorded only 3.60 inches of rain, making it the driest calendar year since recordkeeping began in July of 1877. The previous record of 4.08 inches was set in 1953 and 1947. Downtown Los Angeles averages about 15 inches of rain in a calendar year.

Precipitation composites for years with comparable PD0-AMO indices constructed by Dr. Klaus Wolter of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado appears to have anticipated this year's drought in Southern California. While Oct-Dec anomalies for Southern California were -0.5 to -0.7 SD below the 1895-2000 Longterm Average, Jan-Mar anomalies were -0.1 to -0.3 SD below average. Assuming the anomaly maps to be correlative the drought's stranglehold on Southern California may weaken somewhat over the next three months.

To get an idea of how the precipitation anomaly might vary over the next three months, the US Climate Division Dataset Mapping Page was used to recreate the standardized Oct-Dec precipitation anomaly and Jan-Mar precipitation anomaly maps using the same years as Dr. Wolter's composites. Then standardized composite precipitation anomaly maps were constructed for the months of January, February, and March. Based on these composites some lessening of the severity of the drought in Southern California is suggested throughout the period Jan-Mar with the biggest improvement indicated in March -- except for coastal Southern California. A map showing the composite precipitation anomaly in inches for the period October to March was also generated.

While today's medium range forecasts and 6-10 day and 8-14 day precipitation outlooks aren't particularly encouraging there are some straws to grasp. The AO Index, which has been positive for most of the rainy season is now negative and the Global Wind Oscillation (GWO) is in its first full orbit into positive AAM territory in several months. Whether these changes eventually result in rain for Southern California we'll just have to see.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

 

Wednesday, 01 January 2014 13:44:12 (Pacific Standard Time, UTC-08:00)  #    Disclaimer  |   | 
# Sunday, 20 October 2013

CPC Dec-Jan-Feb Precipitation Outlook Click
CPC Dec-Jan-Feb Precipitation Outlook
Released October 17, 2013.

Updated November 5, 2013. My mistake -- a spreadsheet range error -- thanks for the heads up Reg! The driest January 1 to November 1 for Downtown Los Angeles was in 1972 with 0.92 inch. Here are the driest ten years for that period:

1. 1972 0.92
2. 2002 1.62
3. 1984 1.93
4. 1961 2.37
5. 1971 2.39
6. 1947 2.45
7. 2013 2.78
8. 1894 2.89
9. 1953 2.89
10. 2007 3.37

An energetic upper level low brought the first widespread precipitation of the rain season to Southern California October 9, with rain at the lower elevations and some snow in the local mountains. Rainfall amounts varied widely, ranging from a trace in some areas to over an inch in the mountains.

Downtown Los Angeles (USC) recorded only 0.04 inch for the storm, bringing the water year rainfall total to 0.13 inch, which is 0.31 inch below normal. Downtown Los Angeles has recorded only 2.76 inches of rain since January 1. This is one of the driest January 1 - October 20 in Los Angeles over the past 135 years! To get out of the bottom ten for calendar year rainfall Los Angeles needs about 3.5 inches of rain by December 31. Normal rainfall for November is 1.04 inches and for December is 2.33 inches.

For months I've been monitoring climate data and forecasts looking for something on which to base a 2013-14 Winter precipitation Outlook. Historically ENSO has played the major role in Southern California rain season weather, with El Nino conditions generally producing wetter weather and La Nina conditions generally drier. But ENSO conditions are currently Neutral and are expected to remain so through the end of the year.

Most climate models forecast slow warming of SSTs in the equatorial Pacific (NINO 3.4 region) over the next several months, but at this time of the year it would be very unusual to have substantial warming. The CPC/IRI ENSO Forecasts from IRI's October Quick Look indicate the probability of an El Nino developing before the end of the year is less than 20% -- and 20% seems high.

One computer model that at times has been forecasting above average precipitation in Southern California this Winter is the Climate Forecast System version 2 (CFSv2). The CFSv2 is fully coupled ocean-atmosphere-land-sea ice model used to forecast parameters such as sea surface temperature, temperature and precipitation rate. While skillful at predicting tropical SSTs, the CFSv2 generally performs very poorly when forecasting precipitation over land, so forecasts such as this earlier one for Dec-Jan-Feb must be viewed somewhat skeptically.

Another glass half-full observation is that the Madden-Julian Oscillation (MJO) has been relatively active this year and if this activity continues it provides recurring opportunities for enhanced U.S. West Coast precipitation. The downside is that it can result in periods of dry weather as well.

With the ocean and atmosphere neutral there's just not much on which to base a rain season forecast. As a result of the government shutdown the release of the official NOAA 2013-14 Winter Outlook has been delayed until November. The October CPC outlook is usually the basis of the initial official NOAA U.S. Winter Outlook. The U.S. Dec-Jan-Feb Precipitation Outlook, released October 17, calls for an equal chance of below average, average, or above average precipitation for all of California. We'll see!

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Sunday, 20 October 2013 15:31:26 (Pacific Daylight Time, UTC-07:00)  #    Disclaimer  |   | 
# Saturday, 08 December 2012

MIRS Integrated Water Vapor, December 2, 2012 1800 UTC for the preceeding 12 hours. Click
MIRS IWV All Satellites
December 2, 2012 1800 UTC Preceding 12 hours.

If you were to only look at the Global Wind Oscillation (GWO) for November you might think our 2012-2013 El Nino hadn't flopped. The relative AAM anomaly peaked at about 1.4 around November 20, which is the highest it's been since the El Nino of 2009-2010.

Most of the AAM was added in the NH between 15°N and 30°N. This led to the development of a high amplitude mid-Pacific ridge, and undercutting of the ridge by the westerlies. This enabled a low near the dateline to tap tropical moisture and relay it into the circulation of a large eastern Pacific low. This linkage provided the moisture necessary to create the atmospheric rivers that produced excessive precipitation in Northern and Central California last week.

Over the 5-day period ending Monday morning (December 3) Northern and Central California recorded double-digit precipitation totals with several stations recording rainfall amounts in excess of 15 inches. Here are archived Public Information Statements issued by NWS San Francisco Bay Area/Monterey and NWS Eureka with some of the phenomenal precipitation totals recorded in those areas. This AHPS Precipitation Analysis shows the observed precipitation in the western U.S. for the 7-day period ending Monday morning.

New forecast methods developed by NOAA's ESRL PSD using satellite-derived and GFS medium range forecast data indicated high levels of water vapor transport early Friday and early Sunday. This typically characterizes AR events. This Evaluation of GFS Forecast Fields (PDF) shows the observed Integrated Water Vapor (IWV) for December 2, the corresponding analysis, and the 1-day to 5-day forecasts.

System dynamics were much weaker in Southern California, and the IWV content of the atmospheric rivers was less. (Friday IPW and Sunday IPW). Even so orographically favored areas were still able to wring several inches of rain from the moist flow. From Tuesday night to Monday morning Opids Camp recorded 3.02 inches, White Ledge Peak 4.09 inches, Refugio Pass 4.61 inches, and Rocky Butte 8.51 inches.

Over the same period Downtown Los Angeles (USC) recorded 1.03 inches, bringing the water year total to 1.36 inches. As of today that's 1.08 inch less than normal. Here's an archived copy of a NWS compilation of preliminary rainfall totals in our area.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Saturday, 08 December 2012 17:30:17 (Pacific Standard Time, UTC-08:00)  #    Disclaimer  |   | 
# Saturday, 29 September 2012

In a post last June I mentioned that the atmosphere wasn't responding to warming Pacific equatorial SSTs. At that time normalized relative AAM values had dropped to around -2 sigma. Although El Nino-like SST conditions developed in the equatorial Pacific in July and persisted in August, the atmospheric component (AAM) did not follow suit. The average AAM for the period July-September was less than any other El Nino year going back to 1950. (See chart below.)

Following a relative rapid 2 sigma increase over a period of six months, the July/August value of the Multivariate ENSO Index (MEI) dropped from 1.139 to 0.579, and its rank for the season dropped from just below a 'strong' El Nino to just below a 'weak' El Nino. Over the last month SST Anomaly in Nino Region 3.4 has dropped 0.6°C. A review of the ONI record reveals that a drop in the index, which is based on a 3 month running mean of Nino 3.4 anomaly, has not occurred before the Sep-Oct-Nov season during a warm episode.

As of mid September most models were still forecasting development of weak El Nino conditions. The IRI/CPC Plume-based ENSO Forecast puts the probability of El Nino conditions in the Sep-Oct-Nov season at a little over 80%! The probability of Neutral conditions is pegged at a little under 20%. The chance of returning to La Nina conditions is considered virtually nil. Going back to 1950, year two La Nina conditions almost always transition either back to La Nina conditions or to El Nino conditions. Depending on the climatology used there is either one (1985-86) or no cases of a transition to Neutral conditions from a second year La Nina.

Many dynamical model MJO forecasts are predicting a developing MJO signal in the Western Pacific, and that appears to be occurring. Velocity potential loops and Pacific Basin stitched satellite imagery show enhanced convection west of the date line, and today's MJO phase space plot from CAWCR/BOM shows a signal beginning to emerge. On the wind side, Mountain torques are over +4 sigma and Coriolis torque is at -2 sigma. Whether the (apparently) emerging MJO will help reboot our fading El Nino remains to be seen.

Update Friday, October 5, 2012. Eastward-propagating MJO-like signal didn't evolve as forecast by GFS (and several other models). Here's today's MJO phase space plot from CAWCR/BOM. Large swings in the magnitude of Mountain and Coriolis torques have continued. Relative AAM remains at about -1 sigma. The Early October CPC/IRI Consensus Probabilistic ENSO Forecast indicates an increasing chance of Neutral conditions developing over the next several months, but still gives an edge to El Nino conditions developing before the end of 2012.

Following is a chart comparing 2012-13 to warm ENSO episodes that have occurred since 1950. The warm episodes are based on the revised Oceanic Niño Index (ONI) based on multiple-centered 30 year base periods and are those specified in the CPC's tabulation of Cold & Warm Episodes by Season. A description of the parameters follows the chart. With the exception of years prior to 1957, a GWO phase space plot is included for each warm episode.

Year Jul-Sep
AAM
Nov-Mar
AAM
Peak MEI Peak MEI Season Peak
ONI
Peak ONI Season L.A. Rain GWO
Phase Plot
1951-521 -- -- 0.853 JULAUG 1.2 SON 26.21 --
1952-533 -- -- 0.840 APRMAY 0.7 MAM 9.46 --
1953-543 -- -- 0.522 AUGSEP 0.8 ASO,SON,OND 11.99 --
1957-58 -- 0.773 1.473 DECJAN, JANFEB 1.8 NDJ, DJF 21.13 Click for Nov-Mar GWO Phase Space Plot
1958-592 -0.919 -0.206 0.803 JANFEB 0.6 NDJ, DJF,JFM 5.58 Click for Nov-Mar GWO Phase Space Plot
1963-64 0.005 0.046 0.857 OCTNOV, DECJAN 1.4 OND 7.93 Click for Nov-Mar GWO Phase Space Plot
1965-66 -0.826 -0.748 1.483 JULAUG 1.9 SON,OND 20.44 Click for Nov-Mar GWO Phase Space Plot
1968-694 0.130 0.513 0.868 JANFEB 1.1 DJF, JFM 27.47 Click for Nov-Mar GWO Phase Space Plot
1969-704 0.358 0.413 0.644 OCTNOV 0.9 SON,OND 7.77  
1972-73 -0.096 -0.239 1.886 JUNJUL, JULAUG 2.1 OND,NDJ 21.26 Click for Nov-Mar GWO Phase Space Plot
1976-77 0.284 -0.828 1.027 AUGSEP 0.8 OND,NDJ 12.31 Click for Nov-Mar GWO Phase Space Plot
1977-78 -0.646 1.008 1.007 SEPOCT, OCTNOV 0.8 OND, NDJ 33.44 Click for Nov-Mar GWO Phase Space Plot
1982-83 0.938 2.337 3.037 FEBMAR 2.2 NDJ, DJF 31.25 Click for Nov-Mar GWO Phase Space Plot
1986-875 0.232 0.019 2.122 APRMAY 1.3 JFM 7.66 Click for Nov-Mar GWO Phase Space Plot
1987-885 1.153 1.000 1.951 JULAUG 1.6 JAS, ASO 12.48 Click for Nov-Mar GWO Phase Space Plot
1991-92 -0.008 0.808 2.271 MARAPR 1.6 DJF 21.00 Click for Nov-Mar GWO Phase Space Plot
1994-95 -0.422 0.764 1.434 SEPOCT 1.2 NDJ 24.35 Click for Nov-Mar GWO Phase Space Plot
1997-98 1.811 1.481 3.001 JULAUG,AUGSEP 2.4 OND 31.01 Click for Nov-Mar GWO Phase Space Plot
2002-03 0.047 0.324 1.184 DECJAN 1.3 OND,NDJ 16.49 Click for Nov-Mar GWO Phase Space Plot
2004-05 -0.020 0.747 1.018 FEBMAR 0.7 JAS-NDJ 37.96 Click for Nov-Mar GWO Phase Space Plot
2006-07 0.143 -0.322 1.289 OCTNOV 1 OND, NDJ 3.21 Click for Nov-Mar GWO Phase Space Plot
2009-10 -0.103 0.303 1.520 JANFEB 1.6 NDJ,DJF 16.36 Click for Nov-Mar GWO Phase Space Plot
2012-136 -0.951 0.296 1.139 JUNJUL 0.6 SON 5.85 Click for Nov-Mar GWO Phase Space Plot

1. AAM and AAM tendency anomaly data for 1951-52 not available.
2. AAM anomaly is average for Jan-Mar 1958.
3. Continuous warm episode from DJF 1952/53 to JFM 1954.
4. Continuous warm episode from JAS 1968 to DJF 1969/70.
5. Continuous warm episode from JAS 1986 to JFM 1988.
6. Data as of May 8, 2013.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric angular momentum anomaly for the periods July 1 to September 30 amd November 1 to March 31 of the following year. Data is from the GWO phase space data file linked on the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Peak MEI: The peak seasonal value of the Multivariate ENSO Index (MEI). Reference Wolter and Timlin, 1993, 1998. MEI values are normalized and may change as new data is added.

Peak MEI Season: The peak bi-monthly season(s) for which the MEI is computed.

Peak ONI: The peak Oceanic Niño Index (ONI) based on SST anomalies in the Niño 3.4 region. Reference Climate Prediction Center Cold & Warm Episodes by Season (Multiple centered 30-year base periods.)

Peak ONI Season: The peak tri-monthly season(s) for which the ONI is computed.

L.A. Rain: The water year precipitation total in inches for Downtown Los Angeles (USC). Reference NWS Los Angeles/Oxnard Downtown Los Angeles Climate Page, 1921-2006 Water Year Rainfall.

GWO Phase Space Plot: Plot of global relative atmospheric angular momentum anomaly vs. global relative atmospheric angular momentum tendency anomaly for the period November 1 to March 31 of the following year. Data is from the GWO phase space data file linked on the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Saturday, 29 September 2012 15:15:07 (Pacific Daylight Time, UTC-07:00)  #    Disclaimer  |   |