tag:ggweather.posthaven.com,2013:/posts Golden Gate Weather Services 2018-01-02T17:09:33Z Jan Null tag:ggweather.posthaven.com,2013:Post/1225227 2018-01-02T17:07:52Z 2018-01-02T17:09:33Z 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/
 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1223623 2017-12-29T15:19:45Z 2017-12-29T15:22:59Z 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/

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1219934 2017-12-21T17:50:54Z 2017-12-21T17:52:32Z 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/

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1205514 2017-11-15T16:49:56Z 2017-11-15T18:17:39Z 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/

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1199005 2017-10-17T21:21:00Z 2017-10-17T21:23:05Z 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/

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1192155 2017-09-19T00:48:47Z 2017-09-19T00:48:47Z 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/

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1187069 2017-08-28T14:11:19Z 2017-08-28T14:12:59Z 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/

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1179277 2017-08-01T12:30:48Z 2017-08-01T12:30:49Z 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

 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1177848 2017-07-27T21:25:19Z 2017-07-27T21:26:58Z 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

 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1168520 2017-06-28T16:13:48Z 2017-06-28T16:16:34Z Summary of 2016-17 California Rainfall Season

httpsgallerymailchimpcom204b7b5836feabf8f536d0226images2614bb99-66e8-4dcb-b0e6-62fec44ffdfejpg


This Friday, June 30th, marks the end of a rather remarkable California rainfall season. Here are some of the numbers highlighting the past very wet 12 months.

httpsgallerymailchimpcom204b7b5836feabf8f536d0226imagesad83ef67-2969-4661-9b8f-6303dd954ec9jpg

 

httpsgallerymailchimpcom204b7b5836feabf8f536d0226imagese1bb3ee5-d2eb-4aeb-9fba-249e0de988f0jpg


httpsgallerymailchimpcom204b7b5836feabf8f536d0226images1f671fce-d23c-45e3-adf4-29122166e138jpg


Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com
@ggweather

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1166616 2017-06-22T20:32:15Z 2017-06-22T20:33:22Z Too Hot for Dogs Too!

DO NOT walk your dog in the heat! Besides possible heatstroke, just like humans, your dog could likely be scorching the pads on his paws. Veterinarians say that burns can occur when the surface exceeds 125 degrees. To illustrate, I took some measurements of some surface temperatures today at 10:30 am and again at 12:30 pm. And these are still not the hottest time of day! As a rule of thumb (or paw), if you can't stand on it barefoot then don't let your dog walk on it! 

Jan Null, CCM
Golden Gate Weather Services
jnull@ggweather.com

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1165414 2017-06-19T14:23:37Z 2017-06-19T14:26:49Z Don't Trust Your Car's (or Bank's) Thermometer

With the warm weather I’ve been hearing about LOTS of really hot outlier temperatures being reported from car thermometers; and their owners wondering why they’re so different from official temperature reports. To clarify, let’s look first at how the official temperatures are measured.

There are four general guidelines for accurately measuring air temperatures.
- The thermometer must be outside of direct sunlight., otherwise you are measuring the sun’s intense shortwave energy and not the air temperature.
- It should also be in a well ventilated environment that’s representative of surrounding air, not in an enclosed area.
- Official temperatures are taken at about 5 feet above a natural surface and not a heat-retaining surface like concrete or asphalt. There can be as much as a 25 degree difference between air right above the ground and that at 5 feet.

- And measurements should also be far enough away from other heat emitting sources like walls and vehicles as to not be biased.

Conversely, the thermometers on most cars violate just about every one of the above guidelines. They are usually located under the front grillwork or adjacent body panel, only a foot or two above the highway or parking lot. Especially when a car has been sitting it is measuring the air heated by the parking surface plus any residual heat being given off by the vehicle itself. Even when a car is moving the temperature readings are upwardly biased by the heat given off by the roadway and the vehicle. It’s been my experience that car outside temperatures at startup on a warm day can be more than 10 degrees to toasty, and even while they seem generally to be at least 5 degrees too warm.


Similarly, the readings from locations like bank thermometers and some backyard thermometers don’t do a good job of accurately capturing the air temperature for some of the same reasons.

So when you next start up your car and see a dashboard outside temperature reading of 120° you can take solace in the fact that it’s probably only 105°!

Jan Null, CCM
Golden Gate Weather Services

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1150762 2017-05-01T15:55:52Z 2017-05-01T15:58:12Z California April Weather and Rainfall Season Summary

April was generally wetter than normal across California, except south of the Tehachapi's; while there were above normal temps near the coast and cooler readings inland.  See California Key City Climatology.

The seasonal rainfall continues to be mostly well above normal through the end of April, especially in the important Northern and Central Sierra Nevada watersheds. See California Rainfall Season to Date  and


The California Precipitation Snapshot has also been updated. 

Jan Null, CCM
Golden Gate Weather Services
jnull@ggweather.com

 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1149863 2017-04-27T15:57:16Z 2017-04-27T15:58:55Z NOT the end of the rain for the season

No, it's NOT yet the End of the Rainfall Season!!

Despite proclamations by several individuals, the most recent rainfall does NOT mark the end of California's rainfall season. Yes, the amounts drop off significantly as we transition into late spring and summer, but climatologically it would be quite unusual not to have rain in May and June. For example, the last time that San Francisco had zero rain for the months of May and June was in 1978!

Below are the normal rainfall amounts and the normal number of days of rain across California for May and June.


Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com
jnull@ggweather.com

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1137304 2017-03-09T17:17:16Z 2017-03-09T17:19:19Z A Look Back at the CPC 2016-17 Winter Outlooks


It's time to take a quick look back at the good, the bad and the ugly of the CPC Winter Precipitation and Temperature Outlooks from this past winter. Because of the probabilistic nature of this outlooks this review, like previous reviews, is very subjective. But at least in the West, when their sub-headline for the just finished winter was "Drought expected to persist in California" followed the previous winter's busted above normal El Niño forecast, the efficacy of the product certainly needed scrutiny. See or details CPC Winter 2016-17 Seasonal and Monthly Precipitation and Temperature Outlooks in Review:




Jan Null, CCM
Golden Gate Weather Services
jnull@ggweather.com

  

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1136987 2017-03-08T19:13:50Z 2017-03-08T19:14:54Z California 2nd Rainiest Jul-Feb

 

Statewide, the first eight months of the current rainfall season were the 2nd wettest on record in California going back to 1895-96. This season's 28.03" statewide was just short of the 1968-69 record of 28.30". Looking at the individual climate divisions, the Sacramento drainage (Clim Div 2) and the Northeast Interior (Clim Div 3) had their wettest ever, while the San Joaquin drainage (Clim Div 5) had their 3rd wettest. Neither of the Southern California climate divisions (i.e., Clim Div 6 and 7) were in the top 10.    



Jan Null, CCM
Golden Gate Weather Services
jnull@ggweather.com

 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1135788 2017-03-03T17:23:19Z 2017-03-03T17:25:48Z California Rainfall Data Archive


In response to many many requests for how this rainfall season compares to previous wet years I have put together an archive of monthly rainfall for data for about 50 California locations. The data is cobbled together from a variety of NOAA and NWS sources. The data is for each location's entire period of record, but beware some locales have missing data. My plan is to update this at the end of the rainfall season (i.e., June 30). Please let me know of any comments, errate of suggestions. See http://ggweather.com/monthly/ . Enjoy.



Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com
jnull@ggweather.com

 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1135283 2017-03-01T23:16:26Z 2017-03-01T23:18:16Z Ranked SF Bay Area and Sierra February and Jul-Feb Rainfall

 





 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1130250 2017-02-10T18:21:18Z 2017-02-10T18:38:53Z Rainfall Season vs. Water Year

 

Unlike most parts of the United States, California’s Mediterranean climate is defined by its “summer drought” given that there is a natural break between one rainy season and the next.  This was recognized by settlers as far back as the Gold Rush and since that time the most common metric to quantify California (and other western states’) rainfall has been a July 1 to June 30 “rainfall season”. Consequently, thousands of reports, studies and analyses related to California rainfall have been based on the rainfall season, including the following from is some of the earliest chronicling of California weather.
 

Conversely, because there is lag of several months to when streamflows in the state’s rivers are at their lowest, hydrologists have historically (and logically for their purposes) used a Water Year (WY) metric from October 1 to September.

However, about two years ago, for reasons that have never been adequately explained, the National Weather Service (NWS) Western Region decided, without the opportunity for comment from the rest of the meteorological community or the public, to start calculating their rainfall products (i.e., Climate Station Precipitation Summary , and others) in regards to the hydrologist’s Water Year. (The remainder of the NWS, by the way uses the calendar year for summarizing rain data, as they do not have a natural summer break in rainfall.)  While this might be nice for consistency with the hydrologic community it puts them out of step with the vast wealth of historic data and others in the rest of the meteorological community.  This was even highlighted by a recent article in the LA Times, “Ideologies clash as weather service realigns rainfall calendar

The numerical differences between rainfall season and water year are slight (i.e., typically only about 3% of the annual amount) given the small amount of rain that typically falls in the months of July, August and September. And that rain is not lost, it is either counted at the end of one methodology’s season or the beginning of the other’s.

As stated about, the problem comes about when trying to compare data published by the NWS in terms of the hydrologist’s WY, with data from past events which have been characterized by meteorologists’ rainfall season.  [To their credit, NWS San Francisco Bay Area automatically generates a table which has both the rainfall season and water year, and it is my understanding the software used was made available, but unfortunately not adopted, by other NWS offices.]

An effort has been made, outside the NWS, to make available to the public and meteorological community data showing rainfall in terms of the July 1 to June 30 rainfall season with products like California Rainfall Season Totals. But this does not address the amount of unnecessary effort expended by everyone, but a very small group, to keep the data consistent and meteorologically logical.
 
Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com
jnull@ggweather.com

 


 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1127654 2017-01-31T18:41:22Z 2017-01-31T18:42:52Z Not the Wettest January or Season to Date


Yes, January and the Rainfall Season to date (July 1 to January 31) have been wetter than normal, but they are far from "the wettest" or record-setting. Only the 5-station Central Sierra Index had their wettest January on record, but that period of record goes back to only 1913, more than 60 years shorter than most of the other records. Of the individual stations with long periods of record extending back to the mid-19th century, San Francisco's 9.42" was only the 16th rainiest and Redding's 11.45" was their 23rd wettest.

Likewise, the season-to-date number have been impressive, but most have not even been in the top 10 wettest. 


The following are the Top 10 Wettest Januarys.


The following are the Top 10 Wettest July through January.


Jan Null, CCM
Golden Gate Weather Services
jnull@ggweather.com

 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1125356 2017-01-23T17:13:24Z 2017-01-23T17:13:24Z California Precipitation Snapshot California Precipitation Snapshot

 

California continues to rack up impressive rainfall totals. All 3 of the Sierra indices are within a storm of normal for entire season (Jul 1 - Jun 30)!  Sacramento has already exceeded a full season. See http://ggweather.com/water/


Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com
jnull@ggweather.com

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1125354 2017-01-23T17:12:01Z 2017-01-23T17:12:01Z California Precipitation Snapshot California Precipitation Snapshot

 

California continues to rack up impressive rainfall totals. All 3 of the Sierra indices are within a storm of normal for entire season (Jul 1 - Jun 30)!  Sacramento has already exceeded a full season. See http://ggweather.com/water/


Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com
jnull@ggweather.com

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1125352 2017-01-23T17:08:51Z 2017-01-23T17:11:38Z California Precipitation Snapshot California Precipitation Snapshot

 

California continues to rack up impressive rainfall totals. All 3 of the Sierra indices are within a storm of normal for entire season (Jul 1 - Jun 30)!  Sacramento has already exceeded a full season. See http://ggweather.com/water/


Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com
jnull@ggweather.com

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1121766 2017-01-09T17:37:23Z 2017-01-09T17:40:43Z California Precipitation Snapshot; Bay Area Storm Index

The California precipitation picture got a lot prettier over the weekend; especially in Sierra Nevada which saw huge gains. For example the the southern Sierra Nevada (i.e., Tulare Basin) jumped from 103% of normal on January 1 to 165% through yesterday (January 8), while the northern and central Sierra increased to 173% and 172% respectively. See  http://ggweather.com/water/



In the San Francisco Bay Area the Sunday storm ranked as an 8.5 on the Bay Area Storm Index (BASI).  This was based on a 24-hour downtown San Francisco rainfall total of 1.62", a maximum sustained wind at SFO of 44 mph and a peak (below 1500' elevation) wind gust of 75 mph at Spring Valley in San Mateo County above Crystal Springs. This is the highest ranked storm since October 2009 (see archive).  

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

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1119893 2017-01-02T13:33:18Z 2017-01-02T13:37:38Z December Summary; Seasonal Precipitation Snapshot; La Niña; AMS in Seattle December Summary; Seasonal Precipitation Snapshot; La Niña; AMS in Seattle


December rainfall in California was pretty much upside down compared to recent months, with near normal rainfall in the north and above normal in the south. San Diego totaled 4.22 inches (276% of their December normal) while Los Angeles had 4.55" (195%). The northern third of the state was close to normal with just rain-shadowed San Jose lagging behind at 58%. [http://ggweather.com/calif/dec2016.htm]

Despite a couple colder than normal periods, only Eureka and Sacramento had monthly average minima of more than 2 degrees below normal. At the same time, LA and San Diego average monthly minima were more than 2 degrees above normal.
[http://ggweather.com/calif/dec2016.htm]

~~~~~~~~~~~~~~~~~~~
A snapshot of the first six months of the rainfall season (July 1 to June 30) shows totals well above normal at most locations, with the biggest gains against normal in the south, where Los Angeles and San Diego pushed to 138% and 158% of normal respectively. http://ggweather.com/water/

See also http://ggweather.com/seasonal_rain.htm which is updated daily, in the early evening.

With the potential for extensive rains in the next 10 days, I have updated the Rainfall, River and QPF Page .

~~~~~~~~~~~~~~~~~~~

La Niña's cooling in the tropical eastern Pacific may have bottomed and the weekly Sea Surface Temperature Anomalies (SSTAs) for the past month have averaged just -0.4.

~~~~~~~~~~~~~~~~~~~

Finally, I am headed for the 97th AMS Annual Meeting in Seattle later this month to present a paper of Heatstroke Deaths of Children in Vehicles. If you are also going to be in attendance, drop me an email and we can try to connect.
~~~~~~~~~~~~~~~~~~~

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

 

 


 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1116726 2016-12-19T17:27:45Z 2016-12-19T17:28:50Z California Precipitation Snapshot

I've created a new web page, California Precipitation Snapshot, that graphically summarizes the current rainfall season at 8 major city locations (San Francisco, San Jose, Sacramento, Eureka, Redding, Fresno, Los Angeles and San Diego) plus the three Sierra Nevada Precipitation Indices.  See http://ggweather.com/water/



Happy holidays.

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com

 

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1112215 2016-12-01T17:04:40Z 2016-12-01T17:07:07Z California Rainfall at the Beginning of Winter

Today, December 1st, begins meteorological winter; the three coldest months in the Northern Hemisphere. And for most locations in California it corresponds to the three wettest months.

After a much wetter than normal October (http://ggweather.com/calif/oct2016.htm) for Northern and Central California the November totals (http://ggweather.com/calif/nov2016.htm) were more of mixed bag, but still concentrated in the north.  Consequently the totals for the first five months of the rainfall season (July 1 to November 30) have the northern half of California above normal (http://ggweather.com/seasonal_rain.htm).  

Given the rainfall bias in the north the Drought Monitor is showing relief there but still 43% of Calif in Extreme or Exceptional Drought.



Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1106848 2016-11-09T18:35:18Z 2016-11-09T18:35:18Z A Different Flavor of La Niña?

Unlike those picture puzzles where you are asked to find subtle differences between images, a look at the NASA sea surface height anomaly images for the past three weak La Niñas (1995, 2000, 2011) plus this year (2016), leaves little doubt that what's going on in the eastern Pacific is not subtle at all.  The most striking difference is the anomalous warm water from the equator north to about 25 degrees north. This area warmed in conjunction with last year's very strong El Niño and may have contributed to the atypical winter along the west Coast of North America (see "Differences Between 2015-16 El Niño and Previous Strong and Very Strong Events").




With the current Oceanic Niño Index (ONI) already at weak La Niña levels, tomorrow's updated CPC ENSO Advisory is likely to up the odds for a La Niña this fall and winter. But can we still use the standard "La Niña playbook" of looking at past events as an indicator of broad-scale for West Coast precipitation patterns for this winter?  Last winter the conventional wisdom for the impacts of a very strong El Niño did not work out per previous events. Consequently, it looks like extreme caution should be exercised in looking for patterns based upon the climatological past related to the prospects for current La Niña. 

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com


Miscellaneous La Niña Resources (use with caution):
La Niña Winter Precipitation & Temperature Climatology  
California Climatology of La Niña Events and Precipitation  
California Precipitation Climatology for Cool Neutral and Weak La Niña Events  

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1104626 2016-11-01T17:27:23Z 2016-11-01T17:30:24Z October Rain Only "A Good Start"

 

October 2016 was a wet month in the northern two-thirds of the state but the south continued to be pretty dry.  (See: summary)  Monthly rainfall ranged from over 450% of normal at Eureka and Sacramento, while Los Angeles and San Diego only had 79% and 12% of their normal October rain respectively. But these numbers need to be put into context as October normals are relatively small and there is not a statistically significant relationship between October rainfall and how the rest of the rainfall season (July 1 to June 30) ultimately ends up.

San Francisco’s 2.43 inches for the month is 217% of normal (1.12”), but this ranks as only the 23rd wettest October going back to 1849. The wettest was 7.28” in 1889 (below).  One factor affecting the perception of it being a very rainy month were the number of days of rain. This year there were 12 days of measurable rain in San Francisco, the second highest number on record.  The most was 13 days in that very wet October of 1889.

Looking at the 25 wettest Octobers (below) there is not a correlation to how the seasons ultimately ended up; other than being a “good start” by saturating the soil to enhance future runoff and significantly reducing the fire danger. Eleven of those 25 wettest Octobers actually ended up below the 168-year average of 21.57”. This including the 2nd driest season on record; 1975-1976 when the season ended with a paltry 8.05”.



Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com


 
]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1087541 2016-09-07T15:53:52Z 2016-09-07T16:44:36Z When is the Hottest Day of the Year?

 

As we head toward the Autumnal Equinox (Sept. 22 @ 7:21 am pdt) most cities around California and the nation are well past their normal hottest day of the year, which typically occurs about a month after the Summer Solstice. But a few locations, especially along the West Coast, wait until August and even September to peak. And San Francisco is certainly the latest of any major United States city by not reaching its normal highest maximum temperature of 70.4 until September 24th.

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com




]]>
Jan Null