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:

     1998 – Golden 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

Dismal Beginning to SF Rainfall Season

 

Despite a rather dismal amount of rainfall in San Francisco thus far in December (0.15") this is only the 32nd driest beginning to the rainfall season (Jul 1 to June 30) going back to 1849-1850.  There has been 3.40" to date; thanks mostly to a nearly normal November. 

However, looking at similar years with between 2.90" and 3.90" (i.e., +/- 0.50" from the current 3.40") only 4 of those 22 years (18%) have finished above normal (23.65").
 

Dec 21st Rank

Season

thru Dec 21

Season Total

1

1958

-

1959

0.81

10.46

2

1917

-

1918

0.88

11.48

3

1936

-

1937

1.10

22.39

4

1862

-

1863

1.35

13.74

5

1939

-

1940

1.67

27.17

6

1956

-

1957

1.89

15.04

7

1868

-

1869

2.01

21.35

8

2013

-

2014

2.08

12.54

9

1959

-

1960

2.12

15.47

10

1911

-

1912

2.15

14.06

11

1850

-

1851

2.30

7.42

12

1890

-

1891

2.36

17.58

13

1980

-

1981

2.49

14.63

14

1905

-

1906

2.50

20.42

15

1878

-

1879

2.63

24.44

16

1930

-

1931

2.64

13.54

17

1887

-

1888

2.65

16.74

18

1943

-

1944

2.69

17.86

19

1978

-

1979

2.77

18.70

20

1990

-

1991

2.82

14.08

21

1976

-

1977

2.86

11.08

22

1986

-

1987

2.88

13.86

23

1910

-

1911

2.91

25.49

24

1872

-

1873

2.97

15.66

25

1923

-

1924

3.03

11.62

26

1854

-

1855

3.05

23.83

27

1929

-

1930

3.10

16.28

28

1953

-

1954

3.10

14.27

29

1974

-

1975

3.15

18.33

30

1932

-

1933

3.25

14.93

31

2011

-

2012

3.35

15.64

32

2017

-

2018

3.40

 

33

1991

-

1992

3.52

19.20

34

1989

-

1990

3.54

14.32

35

1975

-

1976

3.56

8.05

36

1933

-

1934

3.64

12.91

37

1863

-

1864

3.77

10.08

38

1967

-

1968

3.79

14.46

39

1908

-

1909

3.81

25.57

40

1883

-

1884

3.83

32.32

41

1907

-

1908

3.83

17.35

42

1870

-

1871

3.84

14.11

43

1938

-

1939

3.85

12.53

44

1891

-

1892

3.89

18.53

45

1935

-

1936

3.90

24.96

46

1948

-

1949

3.95

18.28

47

1921

-

1922

3.96

19.91

48

1898

-

1899

3.99

16.87

49

1876

-

1877

4.00

11.04

50

1877

-

1878

4.05

35.18

51

1897

-

1898

4.07

9.38

52

1895

-

1896

4.10

21.25

53

1949

-

1950

4.13

16.78

54

1925

-

1926

4.15

20.69

55

1919

-

1920

4.27

10.46

56

1999

-

2000

4.28

24.89

57

1886

-

1887

4.29

19.04

58

1869

-

1870

4.38

19.31

59

2000

-

2001

4.38

19.47

60

1860

-

1861

4.42

19.72

61

1971

-

1972

4.46

11.06

62

1856

-

1857

4.49

19.91

63

1855

-

1856

4.53

21.66

64

1946

-

1947

4.65

14.89

65

1993

-

1994

4.71

15.22

66

2008

-

2009

4.74

18.11

67

1865

-

1866

4.81

22.93

68

1912

-

1913

4.85

11.97

69

1853

-

1854

5.07

23.87

70

1851

-

1852

5.09

18.55

71

1902

-

1903

5.13

18.28

72

1977

-

1978

5.26

27.86

73

1947

-

1948

5.32

15.59

74

1968

-

1969

5.35

25.09

75

1881

-

1882

5.70

16.14

76

1916

-

1917

5.73

15.78

77

1963

-

1964

5.79

12.32

78

2007

-

2008

5.79

17.35

79

1901

-

1902

5.80

18.98

80

1965

-

1966

5.84

16.33

81

1992

-

1993

5.91

26.66

82

1893

-

1894

6.00

18.47

83

1903

-

1904

6.02

20.59

84

2009

-

2010

6.07

24.09

85

1960

-

1961

6.14

13.87

86

1988

-

1989

6.19

17.43

87

1942

-

1943

6.23

21.88

88

1914

-

1915

6.24

27.41

89

1931

-

1932

6.26

21.09

90

2015

-

2016

6.30

23.26

91

1979

-

1980

6.31

24.57

92

1937

-

1938

6.36

25.48

93

1934

-

1935

6.41

23.22

94

1998

-

1999

6.44

23.49

95

1906

-

1907

6.50

26.17

96

1940

-

1941

6.61

35.05

97

1941

-

1942

6.72

26.66

98

1928

-

1929

6.77

15.21

99

1927

-

1928

6.79

19.64

100

1961

-

1962

6.90

17.65

101

1900

-

1901

6.92

21.17

102

1884

-

1885

6.98

18.10

103

1995

-

1996

6.98

24.89

104

2003

-

2004

7.06

20.54

105

1857

-

1858

7.15

21.81

106

1858

-

1859

7.16

22.22

107

1915

-

1916

7.31

27.12

108

2004

-

2005

7.33

31.87

109

1861

-

1862

7.39

49.27

110

1859

-

1860

7.42

22.27

111

1964

-

1965

7.46

22.29

112

1985

-

1986

7.67

28.68

113

1892

-

1893

7.94

21.75

114

1954

-

1955

7.96

15.74

115

1987

-

1988

7.98

17.74

116

1882

-

1883

8.04

20.12

117

2016

-

2017

8.20

32.34

118

2005

-

2006

8.35

34.42

119

1913

-

1914

8.43

29.60

120

1909

-

1910

8.44

19.52

121

1969

-

1970

8.45

20.80

122

2006

-

2007

8.49

16.89

123

1873

-

1874

8.63

24.73

124

1896

-

1897

8.78

23.43

125

1955

-

1956

8.78

27.17

126

1867

-

1868

8.79

38.84

127

1879

-

1880

8.87

26.66

128

1904

-

1905

8.94

23.45

129

1966

-

1967

8.94

29.41

130

1888

-

1889

8.96

23.86

131

1880

-

1881

9.00

29.86

132

1875

-

1876

9.01

31.19

133

1944

-

1945

9.06

21.82

134

1962

-

1963

9.21

22.15

135

2010

-

2011

9.22

28.87

136

1951

-

1952

9.41

32.56

137

1874

-

1875

9.44

20.56

138

1945

-

1946

9.45

21.64

139

1899

-

1900

9.47

18.47

140

1920

-

1921

9.52

23.16

141

1957

-

1958

9.58

36.48

142

2012

-

2013

9.66

16.61

143

1952

-

1953

9.86

21.10

144

1926

-

1927

10.00

25.43

145

1981

-

1982

10.28

36.63

146

1871

-

1872

10.41

30.78

147

1982

-

1983

10.41

38.17

148

1924

-

1925

10.87

30.81

149

1918

-

1919

10.92

25.64

150

1894

-

1895

11.06

25.70

151

1997

-

1998

11.51

47.22

152

1996

-

1997

11.65

22.63

153

2002

-

2003

11.88

23.87

154

1922

-

1923

11.91

22.17

155

2001

-

2002

11.99

25.03

156

1970

-

1971

12.16

18.79

157

1983

-

1984

12.25

22.47

158

1973

-

1974

12.31

27.96

159

1984

-

1985

12.60

20.01

160

1994

-

1995

12.86

34.02

161

1852

-

1853

13.00

35.26

162

1864

-

1865

13.40

24.73

163

1950

-

1951

13.66

24.00

164

2014

-

2015

15.02

18.19

165

1866

-

1867

15.21

34.92

166

1972

-

1973

15.71

34.36

167

1885

-

1886

15.78

33.05

168

1849

-

1850

17.27

33.10

169

1889

-

1890

20.67

45.85


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

Burn Area Flooding Ecology


INCREASED FLOODING POTENTIAL IN BURN SCAR AREAS

The changed ecology of burned areas significantly increases the risk of flooding and flash flooding.

- Burned vegetation changes the water balance on denuded hillsides

- Burned organic matter on the soil increases water repellency

- Runoff is increased, carrying debris rapidly downslope



Additionally, runoff flows and debris combine with autumn leaves to clog drains for localized ponding and flooding on and around roadways.

See also https://www.weather.gov/riw/burn_scar_flooding

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

 

The Bigger Picture: October ENSO Pacific Climatology vs. Seasonal Precipitation

This Early October Comparative El Niño and La Niña Climatology is designed as a quick reference to allow users to see patterns, or non-patterns, between "similar" ENSO (El Niño Southern Oscillation) warm and cool Sea Surface Temperature (SST) events using the NASA JPL Sea Height Anomaly products. My initial takeaway is that by looking at the bigger picture and not just the equatorial Oceanic Niño Index (ONI) data, may give a better idea of the potential impacts from one season over another in terms of winter precipitation.

See http://ggweather.com/enso/october/. 



Comments, observations or suggestions gratefully welcomed.

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

Updated El Niño and La Niña Resourcces

With the recent trend of cooling in the tropical eastern Pacific and the increasing probabilities of at least a weak La Niña this coming Fall/Winter, I have updated many of the resources on EL NIÑO / LA NIÑA RESOURCE PAGE.  Some these are:

California La Niña Precipitation Climatology 
California El Niño Precipitation Climatology
US Winter Precipitation & Temperature Climatologies:  El Niño | La Niña
Oceanic Nino Index (ONI) (updated monthly)
Worldwide SST Historic Anomalies

Mega-Caveat: Please use these climatologies with great caution, primarily as a way of "book-ending" the range of possibilities, NOT as a forecasting tool. The two most recent events (i.e., Very Strong El Niño in 2015-16 and the Weak La Niña in 2016-17) were poster children for "All ENSO" events do not behave the same" and that there are lots of other global factors to consider.


 

Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
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 is a 500-year storm?

The ongoing catastrophic rainfall and flooding in Texas as the result of Hurricane Harvey have pushed often misunderstood and misused terms like “500-year storm” into the headlines. Probably the most important thing to keep in mind is that the time period (i.e., 100-year, 500-year, 1000-year) has nothing to do with the amount of time between events!

Instead, the terminology is the result of statistical calculations called “return period”, “return frequency” or “extreme period” analysis. These calculations estimate the probability of an event happening in any given year; and not the interval between similar events. For example, a 100-year storm has 1 chance in 100 of occurring, or one percent probability of happening in any given year.


It should also be noted that a 100-year rain event does not necessarily equate to a 100-year flood. Due to changes in a watershed, like the of filling in of channels or the paving over of permeable areas, the extent of flooding may change for the same amount of rainfall.


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

 

Posted

Above Normal July with Lots of Hot Days

Above Normal July with Lots of Hot Days

 

July 2017 saw most of the state's mean monthly maxima from 2 to 4 degrees above normal. The exceptions were Redding which was nearly 5 degrees above normal and Eureka 0.8 below normal and San Francisco at just 0.7 above normal.  See http://ggweather.com/calif/jul2017.htm.

Around the SF Bay Area, locales away from the coast saw quite a few days that equaled or topped the 90 degree mark:
Santa Rosa - 13 days (normal 5 days, record 21 days in 1931)
Livermore - 24 days (normal 14 days, record 26 days in 1950)
San Jose - 6 days (normal 4 days, record 12 days in 2006)
Gilroy - 10 days (normal 11 days, record 23 days in 1996)

Farther inland, 100 degree days were equally as popular (?):
Redding - 29 days (normal 13 days, previous record 25 days in 1961)
Sacramento Exec - 9 days (normal 5 days, record 17 days in 1988)
Fresno - 23 days (normal 10 days, record 26 days in 1985)



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

 

 

Posted

Warmer than Normal July for San Jose


In answer to numerous questions, yes it has been warmer than normal this July in the San Francisco Bay Area. But it is nowhere near record territory. As an intermediate point between the cool coast and hot interior valleys, San Jose works well as a single summertime temperature metric.

Through yesterday, San Jose's mean maximum temperature for the month was 84.3 degrees, or 2.4 degrees above the July normal of 81.9 degrees. It is interesting to note, that the last time San Jose had an above normal July was in 2006, a year when the average maximum was 85.2. The record was 1996 when the mean maxima was 87.2 degrees. Given forecast temperatures of a few degrees above normal for the remainder of the month, this year's numbers will edge up slightly.


Likewise, San Jose has had five days of 90 degrees or greater and will probably add a couple more days by the end month. The normal number of July 90 degree days is four. The record for 90 degree days is 12, set in 2006.  


Jan Null, CCM
Certified Consulting Meteorologist
Golden gate Weather Services
Phone: (408) 379-7500
Email: jan.null@sjsu.edu

 

 

Posted