March 15th California Rainfall Deficits

 

The table below shows the current rainfall to date, the amount of rain (i.e., deficit) to reach the June 30 normal, and what the amount of "normal" rainfall is between now and June 30. For example, San Francisco is 11.22", which means we would need another 12.43" between now and June 30, BUT normal between now and then is just another 3.76"; so we would need over 3.3 times normal!
 

 

CALIFORNIA RAINFALL DEFICITS

Northern California

Rain thru

Deficit to End of

Normal

15-Mar

Season Normal

Mar 16-Jun 30

Crescent City

35.62

28.41

14.19

Eureka

27.27

13.06

8.43

Ukiah

16.23

21.12

6.79

Montague/Siskiyou

4.84

13.63

4.82

Alturas

6.81

7.36

4.64

Mount Shasta City

14.72

28.49

8.83

Redding

13.89

20.73

6.82

Sacramento Exec AP

11.18

7.34

3.22

Sacramento - CSUS

11.68

8.59

3.55

Blue Canyon

34.78

29.84

13.80

Santa Rosa

17.63

18.65

5.71

San Francisco Downtown

11.22

12.43

3.76

SFO Airport

10.28

10.37

3.16

Oakland Airport

10.18

10.63

3.61

Livermore

7.83

7.88

2.61

Mountain View - Moffett

6.64

8.04

2.56

San Jose

6.49

9.33

2.92

Nrn Sierra Index - 8SI

28.94

25.58

11.78

Central California...

Rain thru

Deficit to End of

Normal

15-Mar

Season Normal

Mar 16-Jun 30

Stockton

6.27

7.79

2.57

Modesto

4.84

8.27

2.62

Merced

4.18

8.32

2.53

Madera

3.69

8.33

2.29

Fresno

3.53

7.97

2.54

Hanford

3.05

7.05

2.01

Bakersfield

2.75

3.72

1.35

Bishop

0.22

4.96

0.87

Salinas

3.74

9.09

2.40

Paso Robles

4.94

7.84

2.00

Santa Maria

3.64

10.31

2.49

Cntrl Sierra Index - 5SI

18.66

23.91

9.66

Srn Sierra Index - 6SI

10.17

20.33

6.72

Southern California

Rain thru

Deficit to End of

Normal

15-Mar

Season Normal

Mar 16-Jun 30

Sandberg

5.60

6.73

1.81

Palmdale

1.55

6.75

1.21

Lancaster

1.85

5.53

0.95

Santa Barbara

5.52

12.24

2.77

Camarillo

3.04

12.18

1.81

Burbank - Bob Hope

4.80

12.51

2.72

LAX Airport

2.90

9.92

1.72

Los Angeles Downtown

3.37

11.56

2.22

Long Beach

2.94

9.32

1.61

Fullerton

2.72

11.16

1.77

Irvine - John Wayne

1.43

11.90

1.68

Oceanside

3.89

9.77

1.96

Ramona

5.44

10.60

2.78

San Diego - Lindbergh

2.99

7.35

1.74

Ontario

3.00

12.04

2.07

Riverside

4.12

8.28

1.69

Palm Springs

3.66

2.08

0.42

Thermal

1.76

1.44

0.22

Campo

4.23

11.50

2.37

Barstow-Daggett

1.13

2.93

0.48

Needles

1.24

3.38

0.57


Season to date percent of normal rainfall.


Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com  
Web: http://ggweather.com
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/

 

Posted

Sierra Snow: Great for Skiers, Less so for Water Supply

Despite impressive snow depths of the past week's storms, the more important metric in terms of California's water supply is the amount of water equivalent. And here, all that fluffy powder fell short with its ratios of between 16 and 25 inches of snow to an inches of water. consequently the important Sierra Indices (below) only showed modest increases.  




Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com  
Web: http://ggweather.com
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/

Posted

Don't Count on a Miracle March (or April) to Save the Day

  

Despite this morning's soggy San Francisco beginning to the month of March, the historic odds of even getting close to normal are near zero; even with an above normal March AND April.

After late evening rain on February 28th, San Francisco doubled their monthly total from 0.21" to 0.42". This pushed them down (up?) to the 16th driest out of 169 years in SF February rainfall records. It also pushed the 8-month total for the rainfall season to date (i.e., July 1 to Feb. 28) to 9.03", the 17th lowest on record.

A look at San Francisco's rainfall seasons following such a dry first eight months shows that it has never recovered, even with substantial March and April rains, to even close to normal. Of all the years that saw less than 11 inches of rain in this period, only one (1898-99) made it to 71% of normal by the end of the season with 16.87".

For seasons with only between 8" and 10" of rain on March 1st, the average March-April totals have been just 3.08", or 65% of normal for the two-month period.  



Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com  
Web: http://ggweather.com
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/

 

Posted

San Francisco's Dismally Dry Days Continue

  

Today (Wed, 2/21) marks the 27th consecutive winter day that San Francisco has NOT had measurable rainfall this season. (The last day of rain in the City was January 25th.) This makes it the 13th longest winter dry spell beginning in December, January or February over San Francisco's 169 season history.

Probably the first real "chance" of rain is next Monday, which would make the streak 31 days and tied for the 5th longest. 


Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com  
Web: http://ggweather.com
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/

 

Posted

San Francisco Winter Dry Spells


As of today, February 8, there has been no measurable rainfall (i.e., 0.01" or greater) in San Francisco for 14 days and no rain in the forecast for at least another week. Mid-winter dry spells are NOT unusual (see http://ggweather.com/enso/winter_dry_spells.htm ), but how far would we need to go extend the current dry streak to make it into record territory? Actually a lot farther!

If we had no rain in the next two weeks, that would bring the total number of consecutive dry days to 28, the 9th longest streak in SF's 169 year period of record. And if extended through the end of the month that would bring the total to 34 days or 4th longest.

Note in the table below that the winter of 2014-2015 had two of the top six dry spells with a 43 day period from late December into February (43 days), almost immediately followed by a 30 day dry spell into early March! 



Jan Null, CCM
Adjunct Professor of Meteorology
San Jose State University
Phone: (408) 379-7500
Email: jan.null@sjsu.edu

 

Posted

Defining Drought ... It's Not Just Rainfall


Defining Drought … It’s Not Just the Rainfall

With the fading odds of having even a normal rainfall season across most of California (http://ggweather.posthaven.com/poor-odds-of-reaching-normal-after-dry-first-7-months-of-the-rainfall-season) the “D” word is being once more making its way into many conversations. But, what exactly is constitutes a “drought”. There is no simple answer and it certainly depends on who ask and where they live.

The American Meteorological Society defines drought as “A period of abnormally dry weather sufficiently long enough to cause a serious hydrological imbalance”. The important takeaway from this broad brush definition is the use of term “hydrological imbalance” and not rainfall deficit. This is especially true in California where the State’s diverse infrastructure means water falling in the northern half of the state strongly impacts hydrologic imbalances many hundreds of miles away in the south.

Broadly, drought can be subdivided into four categories: meteorological drought, hydrological drought, agricultural drought, and socioeconomic drought.

Meteorological drought is a measure of the “degree of dryness” resulting from rainfall and snowfall deficits. There is additionally a very important temporal aspect which impacts the other types of drought by its dependence on not only the degree of deficit but also its longevity. These deficits can be measured as the number of days without rain or the percent of an average amounts of precipitation over days, months, years of even decades.

Hydrological drought is a measure of water supply available from rivers, reservoirs and groundwaters; and the infrastructure to distribute that water. The temporal aspect is even more important with hydrological drought as there can be significant time lags between when precipitation occurs and it impacts surface or subsurface supplies. [This is one of the reasons that meteorologists in California and the West use July 1 to June 30 rainfall season as opposed to the hydrologist’s October 1 to September 30 water year (http://ggweather.posthaven.com/rainfall-season-vs-water-year)]  

Agricultural droughts operate on a short time scale as a precipitation deficit during even a short growing season can have significant impacts. These impacts are exacerbated (or mitigated) by crop type, the availability of stored water (i.e., hydrologic drought) plus soil type and moisture.

Socioeconomic drought is the impact on human activities and the related economies and is a function of all the previous three types of drought as well as metrics like population change and water usage patterns.

A variety of indices and other metrics have been developed to attempt to quantify drought, though one that is good for agricultural drought may not be as adept at capturing socioeconomic impacts.

The bottom line is that drought has many intersecting layers and the effects of any or all of these drought types is dependent upon the user and his location. Drought is complicated!

Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com 
Web: http://ggweather.com
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/


Additional Resources:
American Meteorological Society (AMS) https://www.ametsoc.org/ams/index.cfm/about-ams/ams-statements/archive-statements-of-the-ams/meteorological-drought/
National Drought Mitigation Center (NDMC)
http://drought.unl.edu/DroughtBasics/TypesofDrought.aspx
National Center for Environmental Information (NCEI)
https://www.ncdc.noaa.gov/monitoring-references/dyk/drought-definition
Western Region Climate Center (WRCC)
https://wrcc.dri.edu/Water/drought.php

 

Posted

Groundhog Day: More than a Furry Forecast and a Movie

This morning it has been reported that Punxsutawney Phil did see his shadow and thus forecast six more weeks of winter for 2018.

Groundhog Day has its roots in an ancient Celtic celebration called Imbolog. This date is the midpoint between the winter solstice and the spring equinox. In an agrarian society that was very dependent on the weather, this was a time to celebrate having made it halfway through winter. The superstition arose that if the weather was fair on Imbolog, the second half of the winter would be cold and stormy, but if the weather was cold and overcast or stormy, the second half of the winter would be mild.

In Christian times, February 2nd was celebrated as Candlemas, but the earlier Imbolog superstition continued. In Scotland they said, ``If Candlemas be bright and clear, there'll be two winters in the year'' and in England, they said, ``If Candlemas be sunny and warm, ye may mend your mittens and look for a storm.''

The Romans learned of this tradition from the Celts, and eventually brought them to the area that would become Germany. Eventually German immigrants brought these beliefs to Pennsylvania. Their tradition of predicting the weather became centered on the woodchuck, or groundhog, and if he could see his shadow, there would be six more weeks of winter.

A newspaper in Punxsutawney, PA helped keep the tradition alive and in 1887 declared Phil as America’s official forecasting groundhog. As the story became embellished each year the other newspapers picked it up and the rest as they say is history. Regionally there have been a number of other furry rodent contenders such as General Beauregard Lee of Atlanta, Sir Walter Wally in Raleigh, NC and Jimmy of Sun Prairie, WI.  And in 1993 the motion picture "Groundhog Day" popularized the event even further.

For NOAA's National Climatic Data Center's look at this tradition and its associated climatology see https://www.ncdc.noaa.gov/customer-support/education-resources/groundhog-day.
Other resources can be found at http://www.groundhog.org/.

But, most importantly:


Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com
  
Web: http://ggweather.com
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/

Posted

Poor Odds of reaching Normal after dry first 7 months of the Rainfall Season 


Statewide rainfall percentages of normal through the first seven months of the rainfall season range from dry in the normal to very dry in the south. See http://ggweather.com/seasonal_rain.htm. And an analysis of previous seasons for key locations around the state with low totals for the first seven months does NOT bode well for the likelihood of at least normal rainfall for the 2017-2018 season.

Summarizing the tables below:

San Francisco: This is the 47th driest season through January. Only 2 seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
San Jose: This is the 32nd driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
Santa Rosa: This is the 37th driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
San Jose: This is the 32nd driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
Eureka: This is the 50th driest season through January. Only 3 seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
Redding: This is the 16th driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
8 Station Northern Sierra Index: This is the 29th driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
Sacramento: This is the 47th driest season through January. Only 1 season that has been this dry or drier have ended the full season with at least normal rainfall. 
Fresno: This is the 8th driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
5 Station Central Sierra Index: This is the 4th driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
6 Station Southern Central Sierra Index: This is the 4tht driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
Los Angeles: This is the 11th driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 
San Diego: This is the 16th driest season through January. No seasons that have been this dry or drier have ended the full season with at least normal rainfall. 

BIG CAVEAT: Please keep in mind that a below normal rainfall season does NOT necessarily equal drought. In addition to the rainfall, drought in a particular region of the state is also a function of stored surface and ground water, as well as the infrastructure to import water from other parts of the state. It can also vary by usage as the needs of a rancher needing water to grow grass to feed his cattle is very different than a water manager in an urban area.



Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com  
Web: http://ggweather.com
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/

 

Golden Gate Weather Services 20th Anniversary




January 2, 2017

Today marks the 20th anniversary of the founding Golden Gate Weather Services. After almost 24 good years with the National Weather Service I ventured out on my own for what has been 20 great years. Here are some of the things I have been privileged to do in that time:

     1998Golden Gate Weather Services founded by Jan Null, CCM 
     200+ - Television interviews
     1000+ - Radio and newspaper interviews
     146 - “Weather Corner” columns in the San Jose Mercury News
     150 - Golden Gate Weather Blog posts
     500+ - Cases retained in as a forensic meteorologist
     35+ - Trials testified in as a forensic meteorologist
     100+ - Depositions testified in as a forensic meteorologist
     742+ - Pediatric Vehicular Heatstroke Deaths tracked on NoHeatstroke.org 
     18 - Presentations to national groups about Pediatric Vehicular Heatstroke
     2 - National Public Service Awards re: heatstroke from NHTSA & NWA
     1 - Presentation to US House Science Committee about El Niño
     30 - Years as Adjunct Professor/Lecturer at SFSU and SJSU
     800+ - Intro and Severe Weather classes taught at SFSU and SJSU
     14 - Articles written for Weatherwise magazine
     6 - Years as part-time contract meteorologist at PG&E
     2 - Years as Director of Meteorology at PlanetWeather.com

Thanks for all of your support and friendship over the years.

Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com  
Web: http://ggweather.com 
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/
 

 

Posted

What Do Meteorologists mean by “Normal”?

Is it:
a.  conforming to a standard; usual, typical, or expected?.
b.  a line, ray, or other linear feature intersecting a surface at right angles?
c.  a town in Illinois?
d.  none of the above?

Meteorologically it is indeed “none of the above”. Recently, I have been asked several times about what meteorologists and climatologists mean by “normal”.  (I optimistically hope that the questions are in the context of the weather, and not whether meteorologists themselves are “normal”!)

Most users get that “normal” is some kind of average, but climatologically it is a very specific average. “Normal” is defined by the World Meteorological Organization (WMO) and its member nations, including the United States, as a 30-year average of a weather element (i.e., temperature, rainfall, wind, etc.) that is recalculated every decade (http://www.wmo.int/pages/prog/wcp/wcdmp/GCDS_1.php). The current “normal period” is the 30-year period from 1981 through 2010 and next one won’t be until data is in for the 1991-2020 period. A 30-year period was chosen as long enough to dampen out extreme short-term variations, but also not so long as to disguise changes over time.

The use of a standardized climatological normal gives a common benchmark against which conditions can be compared. This is not only in the context of whether a given day or event is “normal” but also whether there are shifts in conditions from one climate normal period to another.
Certainly, other metrics like the average over a locations entire period of record (POR) or the average of the most recent 20 years can and are used. But the standardized “normal” period give a common point of reference.  And it does make a difference!

For example, looking at the historical rainfall record for San Francisco, it can indeed be seen that there have been some decided differences in our point of reference.  The current normal (1981-2010) annual rainfall in San Francisco is 23.65 inches.  Even compared to the previous normal period (1971-2000) there was a significant difference; with a 6% increase from previous normal of 22.28”.

The table below shows the variation in San Francisco’s 30-year averages, with the normal years highlighted in red. The highest 30-year average was 24.81” for the 1860-1889 period, and the lowest was 19.51” in the 1942-1971 period.
 
A snapshot of California key city precipitation and temperature normals can be found at http://ggweather.com/normal/ with data for over 9800 United States locations at http://ggweather.com/normals/. For more complete normals see https://www.ncdc.noaa.gov/cdo-web/datatools/normals.
 
Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (408) 379-7500
Email: jnull@ggweather.com   
Web: http://ggweather.com
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/Golden-Gate-Weather-Services-151100414926621/

 

Posted