tag:ggweather.posthaven.com,2013:/posts Golden Gate Weather Services 2018-06-29T13:54:35Z Jan Null tag:ggweather.posthaven.com,2013:Post/1298095 2018-06-29T13:53:20Z 2018-06-29T13:54:35Z Summary of California 2017-2018 Rainfall Season Ending Tomorrow

The California 2017-2018 rainfall season ends tomorrow with totals across the state below normal and on the order of half of the totals recorded in 2016-17. See http://ggweather.com/ca2017rain.htm and http://ggweather.com/ca2016rain.htm.



See also the Precipitation Snapshot at http://ggweather.com/water/



Also the Western Region Climate Center's Precipitation Anomaly maps from https://wrcc.dri.edu/anom/cal_anom.html



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

 
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Jan Null
tag:ggweather.posthaven.com,2013:Post/1284918 2018-05-18T17:10:56Z 2018-05-18T17:13:01Z Updated Resource Pages; Tioga Pass by the Nummbers


I have updated the following Weather Resource pages for 2018. But please let me know of any errata, suggestions or additions. Enjoy.

2018 Thunderstorm and Tornado Resource Guide

2018 Hurricane Resource Guide

2018 Fire Weather Resource Guide


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

With Tioga Pass due to open Monday (5/21/2018) here are some historical records going back to 1980.



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/


 
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Jan Null
tag:ggweather.posthaven.com,2013:Post/1269640 2018-04-06T18:09:13Z 2018-04-06T18:10:48Z Beware Daily Weather Records!!

 

During big rain events, a particular rainfall amount may be touted as record rainfall for the date, just as during hot weather the temperature may be proclaimed a daily maximum record. Ideally, meteorological data should be based on where we are in our orbit around the sun and not a particular calendar day. This is because our calendar is slightly flawed when it comes to specific days as it takes 365.25 days to circle the sun giving us a leap day every four years.

Consequently, the dates in a leap year after February 29th, are all displaced by one day. That is, April 6th in 2017, 2018 and 2019 is the 96th day of the year, while April 6th in a leap year (i.e., 2016, 2020) is the 97th day. So, if a record event for a particular date happened in a leap year versus a non-leap year we are actually comparing different days based upon of position relative to the "solar year".

For example, the largest rainfall amount for San Francisco for April 21st is 1.39” in 1880, a leap year so it was the 112th day of that year. But the record for April 22nd, is 0.43” in 2007, not a leap year so it is also the 112th day of the year!
Which is correct?  The bottom line is that neither is really right all of the time!
 

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/

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1268998 2018-04-04T23:19:27Z 2018-04-04T23:21:02Z 1 & 2-Day SF Bay Area April Rainfall Records

  

1 and 2 Day SF Bay Area April Rainfall Records

 

One Day Record

Two Day Record

 

 Name

Rain (in.)

Date

Rain (in.)

Date

Since

ALAMEDA COUNTY

 BERKELEY

2.49

 1896-04-24 

4.04

 1958-04-02 

1893

 FREMONT

0.96

 2003-04-13 

1.62

 2003-04-13 

1996

 HAYWARD AIR TERMINAL

0.98

 2012-04-10 

1.65

 2003-04-13 

1998

 LIVERMORE

1.80

 1958-04-03 

2.10

 1958-04-04 

1903

 LIVERMORE MUNICIPAL AP

1.14

 2003-04-12 

1.79

 2003-04-13 

1998

 NEWARK

1.41

 2003-04-13 

1.46

 2003-04-14 

1906

 OAKLAND INTL AP

2.03

 1974-04-01 

2.24

 2012-04-13 

1948

 OAKLAND MUSEUM

2.07

 1974-04-01 

2.10

 1974-04-02 

1970

 TRACY PUMPING PLANT

1.10

 1983-04-28 

1.70

 1983-04-28 

1955

 UPPER SAN LEANDRO FILTERS

2.20

 1974-04-02 

3.12

 1974-04-02 

1948

CONTRA COSTA COUNTY

 CONCORD BUCHANAN FIELD

0.97

 2012-04-12 

1.54

 2017-04-07 

1999

 CONCORD WASTEWATER PLANT

1.20

 2017-04-07 

1.91

 2017-04-08 

1991

 MARTINEZ WATER PLANT

1.50

 2003-04-13 

1.81

 2017-04-08 

1970

 MOUNT DIABLO JUNCTION

2.35

 1958-04-03 

2.90

 1958-04-04+

1952

 RICHMOND

2.32

 1953-04-27 

2.48

 1982-04-11 

1950

MARIN COUNTY

 KENTFIELD

4.95

 1935-04-07 

5.31

 1935-04-08 

1902

 SAN RAFAEL-CIVIC CENTER

4.39

 1896-04-25 

5.24

 1958-04-02 

1894

MONTEREY COUNTY

 BIG SUR STATION

4.50

 1982-04-11 

6.37

 1982-04-11 

1915

 CARMEL VALLEY

1.60

 2006-04-05 

2.27

 2006-04-05 

1959

 KING CITY

1.58

 1982-04-10 

2.25

 1912-04-10 

1902

 MONTEREY

2.11

 1974-04-01 

2.36

 1912-04-11 

1906

 MONTEREY PENINSUL AP

1.23

 1969-04-05 

1.47

 1969-04-06 

1968

 MONTEREY WFO

1.45

 2006-04-04 

1.68

 2006-04-04 

1995

 SALINAS AP

2.15

 1974-04-01 

2.15

 1974-04-02 

1930

 SALINAS NO. 2

2.09

 1974-04-01 

2.58

 1974-04-02 

1958

NAPA COUNTY

 ANGWIN PACIFIC UNION COL

3.08

 1982-04-11 

3.82

 1982-04-11+

1940

 CALISTOGA

2.65

 1911-04-05 

5.26

 1996-04-02 

1906

 MARKLEY COVE

2.64

 1982-04-11 

2.94

 1982-04-12 

1970

 NAPA COUNTY AIRPORT

1.07

 2017-04-06 

1.85

 2017-04-07 

1998

 NAPA STATE HOSPITAL

2.66

 1996-04-01 

3.23

 1958-04-03 

1893

 SAINT HELENA

3.52

 1927-04-01 

5.64

 1926-04-05 

1907

 SAINT HELENA 4 WSW

2.20

 2010-04-12 

2.88

 2017-04-08+

1948

SAN BENITO COUNTY

 HOLLISTER 2

1.43

 1981-04-19 

1.63

 1981-04-20 

1948

 PANOCHE 2 W

1.14

 1958-04-03 

1.24

 1957-04-18 

1949

 PINNACLES NM

2.17

 1958-04-03 

2.39

 1958-04-04 

1937

SAN FRANCISCO COUNTY

 SAN FRANCISCO DOWNTOWN

3.45

 1853-04-16 

3.59

 1853-04-17 

1849

 SAN FRANCISCO OCEANSIDE

1.45

 1978-04-15 

1.50

 1978-04-16 

1948

SAN MATEO COUNTY

 HALF MOON BAY

2.36

 1941-04-04 

2.54

 1953-04-27 

1939

 REDWOOD CITY

2.54

 1958-04-02 

3.90

 1958-04-02 

1906

 SAN FRANCISCO INTL AP

2.30

 1958-04-02 

3.21

 1958-04-02 

1945

 SKYLINE RIDGE PRESERVE

2.75

 2003-04-13 

2.96

 2003-04-13 

1995

SANTA CLARA COUNTY

 GILROY

3.65

 1958-04-03 

4.07

 1958-04-04 

1906

 LOS GATOS

3.70

 1901-04-29 

5.89

 1958-04-02 

1893

 MOFFETT FEDERAL AIRFIELD

1.17

 1958-04-02 

1.73

 1983-04-28 

1945

 MOUNT HAMILTON

1.87

 1965-04-09 

3.38

 1965-04-10 

1948

 SAN JOSE

1.46

 1983-04-28 

2.06

 2006-04-04 

1893

 BEN LOMOND NO. 4

5.35

 1941-04-04 

7.15

 1958-04-02 

1937

 SANTA CRUZ

3.75

 1923-04-04 

4.05

 1923-04-05 

1893

 WATSONVILLE MUNICIPAL AP

1.51

 2006-04-04 

2.24

 2012-04-13 

1945

 WATSONVILLE WATERWORKS

2.85

 1983-04-28 

3.15

 1983-04-29 

1908

SONOMA COUNTY

 BODEGA 6 WSW

2.28

 2010-04-11 

2.42

 2010-04-12 

2008

 CLOVERDALE

2.80

 1982-04-11 

4.20

 2010-04-12 

1950

 FORT ROSS

4.23

 1953-04-27 

5.36

 1953-04-27 

1895

 GRATON

4.00

 1953-04-27 

4.61

 1926-04-05 

1926

 HEALDSBURG

3.25

 1953-04-27 

4.57

 1927-04-02 

1893

 OCCIDENTAL

5.20

 1953-04-27 

5.49

 1953-04-28 

1943

 PETALUMA AIRPORT

2.45

 1941-04-04 

4.40

 1926-04-05 

1893

 SANTA ROSA

3.06

 1926-04-04 

5.99

 1926-04-05 

1902

 SANTA ROSA SONOMA CO AP

2.36

 2017-04-06 

2.77

 2017-04-07 

1998

 VENADO

4.68

 2006-04-12 

5.29

 2017-04-08 

1948



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/1267808 2018-04-01T20:47:30Z 2018-04-01T20:48:43Z California April 1st Precipitation Update

 

March rainfall and snowfall across California saw the most significant gains in the Sierra Nevada Precipitation Indices where the average percentage of normal jumped from 41% of normal-to-date to 69% of normal. See http://ggweather.com/water/



Also http://ggweather.com/seasonal_rain.htm and 


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/



 
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Jan Null
tag:ggweather.posthaven.com,2013:Post/1264166 2018-03-22T19:01:54Z 2018-03-22T19:03:43Z California March Rainfall Summary - No Miracle 


As rainfall begins to taper off in many parts of the state, the historical context is that this is more of a Mediocre March than a Miracle March!  Rainfall today and a few showers over the weekend will add a little bit to the numbers below but in general the models have a pattern shift to high pressure and dry weather for next week. The bottom line is that while there have been good gains in rainfall statewide this month, most of California has a near zero chance of reaching normal for the season. 


The March 2018 values above are through midnight March 21.

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/

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1262080 2018-03-16T17:14:37Z 2018-03-16T17:19:42Z 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/

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1257225 2018-03-05T17:10:38Z 2018-03-05T17:11:39Z 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/

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1254678 2018-03-01T15:31:01Z 2018-03-01T15:34:04Z 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/

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1250922 2018-02-21T20:58:14Z 2018-02-21T20:59:59Z 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/

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1244536 2018-02-08T17:17:30Z 2018-02-08T17:19:21Z 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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1243992 2018-02-07T16:51:59Z 2018-02-07T16:55:50Z 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

 

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1241881 2018-02-02T14:03:45Z 2018-02-02T14:05:11Z 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/

]]>
Jan Null
tag:ggweather.posthaven.com,2013:Post/1240510 2018-01-30T23:50:17Z 2018-02-05T23:59:24Z 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/

 

]]>
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/

 

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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/

 

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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

 

 

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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

 

 

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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

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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.

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


httpsgallerymailchimpcom204b7b5836feabf8f536d0226images1f671fce-d23c-45e3-adf4-29122166e138jpg


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

 

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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

 

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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

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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

 

 

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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

 

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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

  

 

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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

 

 

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Jan Null