El Niño Resources for 2023


 

Last week, the Climate Prediction Center issued an El Niño Watch, with the expectation that conditions in the tropical Pacific would transition into an El Niño pattern by late summer and continue into next winter. And immediately a number of headlines popped up, raising the specter of doom and gloom. The tone reminded me of the fall of 1997 and this cartoon from the Sacramento Bee:


Consequently, I have updated a number of El Niño and La Niña resources that may assist in keeping things in perspective. They are all available from the EL NIÑO / LA NIÑA RESOURCE PAGE 

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The Oceanic Nino Index is the defacto metric widely used to classify the strength of ENSO (El Niño - Southern Oscillation).events. See https://ggweather.com/enso/oni.htm for current and historic values.


I have also put together a page of misconceptions about ENSO Events. See http://ggweather.com/enso/enso_myths.htm



This is coupled with an ENSO Glossary with some of the more common terminology. See http://ggweather.com/enso/glossary.htm



And to put historical precipitation on the types and strengths of ENSO events, the following analyzed chronologies were updated for both the United States and California. See https://ggweather.com/enso2021/  for the US, then https://www.ggweather.com/ca_enso2021/ca_elnino.html and https://www.ggweather.com/ca_enso2021/ca_lanina.html for California.




Please let me know of any errors or omissions.

Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather

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Historical Low Level Snow in the Bay Area


 

The last widespread snowfall down to near sea level in the San Francisco Bay Area was 47 years ago, on February 5, 1976. Granted, there have been a handful of occasions since with small pockets of cold air allowing for snow to get close to sea level, but nothing widespread. And the odds against it happening later this week are small, but not impossible. The most likely scenario will be snow accumulations in areas around the bay above 1000 to 2000 feet. 

Historically, there have only been 11 days when snow has been recorded near sea level in downtown  San Francisco, Twice on February 5th; in 887 and again in 1976. (https://www.ggweather.com/sf/snow.htm). 


The event on February 5, 1887, was the snowiest on record with over 3 inches in the downtown area of the City.  This is well documented in Mark McLaughlin's wonderful  "San Francisco Snowstorms" document (http://thestormking.com/Sierra_Stories/San_Francisco_Snowstorms/san_francisco_snowstorms.html)


The 1976 event was spectacularly captured by the SF Chronicle in this photo by Art Frisch.
 
The meteorology on Feb 5, 1976, showed a cold front having moved south over the state during the overnight hours and supported by a very cold 500 mb low (5280m) west of Pt. Reyes. The 1000-500 mb thickness was 5221 meters.






The hourly observations that morning showed snow falling at San Francisco International Airport, and it may have been the last snow observation recorded at SFO, since it is unlikely to have been picked up by current automated sensors. [I remember this quite vividly as I had worked a midnight shift as an observer at SFO some of those snowy observations and then drove home to the East Bay through a winter wonderland.]




The setup for later this week shows a similar strength upper low farther offshore than in 1976, with a 5210m minima on Friday morning. But will the moisture synch up with the coldest air and at the right time of day? The odds right now look better for low-level snow south of the Bay Area.



Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather

 

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California Precipitation Rankings


With clearing skies over California, the current rainfall totals for the month of January seem close to final.*

For historical context, the tables below rank the 20-wettest first seven months (July through January) of the rainfall season, and how those locations ended the season in June. The two biggest takeaways:
1. Despite the impressive parade of storms in December and the first half of January, only the Central and Southern Sierra Nevada Indices barely cracked the top 10 for each location's period of record.
2.  All of these locations ended the season above normal for years that had similar amounts to where they are this year.

* Data for Los Angeles is current through 8 am January 30. A few showers still persist there, but it is doubtful that any additional rain will shift the ranking.











Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather






 

 

Posted

California Rainfall and Reservoir Updates

 

Despite recent moderate precipitation amounts across the state (https://ggweather.com/seasonal_rain.htm), the rainfall and reservoir deficits continue to grow; well beyond the capability to make up the amounts in a single season. Even after the 1.79 inches that San Francisco has received to date, the total 4-season deficit is currently over 29 inches and will be over 50 inches by the end of the season, if no rain were to fall. (San Francisco normal 22.89", SF record 49.27 in 1861-1862.)

Likewise, the critical 8-Station Northern Sierra Precipitation Index (8SI) currently has a deficit of more than an entire season. 

And these large rainfall deficits are evident in the current levels of the state's reservoirs which have steadily declined over the past 3= seasons and are at just 61% of their average mid-November storage.

Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather

 

 

Posted

Mini Review of Last year's CPC Winter (DJF) Outlook

ABSTRACT
Comparison of last year's NOAA Climate Prediction Center (CPC) 90-day precipitation and temperature forecasts for the winter period of December-February (DJF) 2021-2022 with the actual observed conditions.

DATA SOURCES
The 90-day (DJF) outlooks were retrieved from the NOAA Climate Prediction Center (CPC) archives and the corresponding observed temperature and precipitation data were downloaded from NOAA ESRL Climate Division Data.

ANALYSIS
The CPC Winter Outlook DJF 2021-2022 did better than in several of the recent winters, partly because the overall pattern ended up close to a "typical" La Niña.  However, it must be noted that the CPC outlooks are probabilistic versus deterministic, which makes them harder to judge as right or wrong.

Here is t subjective graphical grading used below. Overall if a forecast was in the right category (i.e., above normal was forecast and above normal was observed) it was graded as "good" and marked with a "+". Conversely, if it was the wrong category (i.e., above normal was forecast and below normal was observed then it was graded as "not good" with a "-". And if the forecast was off by a single category (i.e, above normal was predicted and it was normal) or there was a mixture of above and below in close proximity to one another then graded it as "mixed" and marked with a "0".  

SUMMARY
Of the 41 precipitation regions compared, 14 (34%) regions rated as "good", 10 (24%) as "not good" and 17 (41%) as "mixed".
Of the 39 temperature regions compared, 20 (51%) regions were rated as "good", only 1 (3%) as "not good" and 18 (46%) as "mixed".

However, it is left to the individual reader to do their own comparisons and evaluate the relative usefulness of the forecasts to their particular activity.



Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather

Posted

A Mini-Analysis of Last year's Old Farmer's Almanac Winter Forecast

See https://ggweather.com/farmers/2022/index.html

ABSTRACT
This review subjectively compares last year's 2022 Old Farmer's Almanac seasonal precipitation and temperature forecasts for the winter period of November-March (NDJFM) 2021-2022 with the observed temperature and precipitation anomalies for the same period.


DATA SOURCES
The Winter forecasts are reproduced from the 2022 Old Farmer's Almanac (Yankee Publishing, Dublin, NH) website and the corresponding observed temperature and precipitation data were downloaded from the Climate Diagnostics Center (CDC).

ANALYSIS
The subjective graphical grading is below.  Overall if a forecast was in the right category (i.e., above normal was forecast and above normal was observed) it was graded as "good". Conversely, if it was the wrong category (i.e., above normal was forecast and below normal was observed then it was graded as "not good". And if the forecast was off by a single category (i.e, above normal was predicted and it was normal) or there was a mixture of above and below in close proximity to one another then I graded it as "mixed".  

Of the 40 precipitation regions compared, 16 (40%) regions were rated as "good", 16 (40%) as "not good" and 8 (20%) as "mixed". Of the 33 temperature regions compared, only 2 (6%) regions rated as "good", 19 (58%) as "not good" and 12 (36%) as "mixed".

However, it is left to the individual reader to do their own comparisons and evaluate the relative usefulness of the forecasts to their particular activity.


See the past reviews at https://ggweather.com/links.html#ofa


Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather

 

 

Posted

La Niña and California Rainfall


Most of the computer models are pointing toward the present moderate La Niña conditions persisting through the upcoming winter; for the third consecutive year. And given the past three years have seen below-normal rainfall across most of California, the immediate knee-jerk reaction has been that this will automatically be a fourth dry year, based on the misconception that La Niña always equals Dry for California. But a close inspection of past La Niñas since 1950, shows that this is not always the case.  An updated detailed analysis can be found at https://www.ggweather.com/ca_enso2021/ca_lanina.html. (See the bottom of this email for other related links)

From that analysis:




To me, the important takeaways are to be wary of "average" or "typical" La Niña conditions and to look at the range of data from which those averages are derived. And most importantly, climatology is NOT a forecasting tool, but it does give context to any categorical proclamation about the prospects for the upcoming season.

El Niño - La Niña Resource page: https://ggweather.com/enso.htm
Current Oceanic Niño Index (ONI): https://ggweather.com/enso/oni.htm
La Niña and California Rainfall: https://www.ggweather.com/ca_enso2021/ca_lanina.html
El Niño and California Rainfall: https://www.ggweather.com/ca_enso2021/ca_elnino.html
ENSO-Related US Winter Precipitation: https://ggweather.com/enso2021/

As always, comments and suggestions are welcomed.

Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather



 

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Posted

The Hottest Week of the Year ... or Not



For many locales across the United States, the last week of July is the hottest time of the year (i.e., the highest normal maximum temperature). And given the prolonged heat over much of the country this summer, just the idea that there is cooler weather ahead may be a reason to rejoice.

But a few locations, especially along the immediate West Coast, have a delayed peak. For example, while on average, Sacramento has its warmest day of the year on July 20th, San Jose waits until August 29th and it's not until September 24th that San Francisco reaches its maximum. The largest moderating factor is the adjacent cool water of the eastern Pacific along with the weakening and southward shifting of the Pacific High.

Full-size versions of the California and United States maps (below) can be downloaded from https://ggweather.com/warmest_cal.jpg and https://ggweather.com/warmest_us.jpg. Tabular US Daily Normals are available at: https://ggweather.com/normals/daily91.htm.






Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather


Posted

Visualizing the California 3-year Rainfall Deficit


The following two graphs are an effort to visualize the rainfall deficits in California over the past three rainfall seasons. Even with abundant rain last October and December, this season will end up at about 80% of normal. And following the previous two dismally dry seasons, the total 3-season totals are only between 60% and 65% of normal at many locations; meaning we are over an entire year's rainfall behind normal.






Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather

 

Posted