El Niño 2015-16 becoming Poster Child for "All El Niños are not the same!"

El Niño 2015-16 becoming Poster Child for "All El Niños are not the same!"

 

Among the mantras from the past year by myself, SF State Professor Dr. John Monteverdi and many other responsible meteorologists, are that 1) each El Niño is unique, 2) the number of past events is statistically very small for comparison, and 3) that there are "no guarantees". To date many of the blogs, webpages and associated articles have look at the similarities to previous strong and very strong El Niño events.

However, as the El Niño 2015-2016 and its impacts continue to unfold, Dr. Monteverdi and I felt it's important to look at how this year is dissimilar in many ways to previous events.  To that end we have co-authored the following page: Differences Between 2015-16 El Niño and Previous Strong and Very Strong  Events.   

Below is one of the figures from that page, which breaks down the Sea Surface Temperature Anomalies (SSTAs) for each of the strong and very strong El Niños for all four of the Niño sampling regions in the tropical Pacific. Other data includes how the circulation patterns are different along with how the November through January precipitation and temperature patterns don't match very well with previous events, 



Coming soon, will be a separate page with how the second half of the winter during these events has looked.

Jan Null, CCM
Golden Gate Weather Services

Dr. John Monterverdi, CCM
San Francisco State University

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January 2016 Wet and Mild Across California

In the major cities across California the January 2016 rainfall ranged from "just" 102% of normal in Los Angeles to over 200% of normal at Redding (213%) and Fresno (202%). Rain in the critical Sierra Nevada watersheds ranged from 175% of normal in the Northern Sierra 8-Station Index  to 119% of normal in the Tulare Basin 6-Station Index. (See http://ggweather.com/calif/jan2016.htm)

 

The rainfall season- (July 1 to June 30) to-date totals and percentages of normal for 46 California stations are available at: http://ggweather.com/seasonal_rain.htm.

Monthly temperatures were generally warmer than normal though maxima in Redding and LA slipped in as cooler than normal.  (See http://ggweather.com/calif/jan2016.htm)

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

 

 

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What's Different with El Niño 2015-16?


 

As we turn the corner into the second half of the rainfall season, it is becoming increasing apparent that the ongoing El Niño is becoming the poster child for "all El Niños are not alike!". While it is still way too early to know what this will ultimately mean for California's rainfall season, it is noteworthy to look at some of the differences.

While most attention has been focused on the Niño 3.4 region (see map) which has been very similar to the very strong El Niño event of 1997-1998, there have been some significant differences in the adjacent regions. The Niño 4 region to the west alongthe equator has been warmer than 1997-98, while Niño 3 and Niño 1+2 regions have been cooler.



There have also been significant differences in the monthly rainfall patterns compared to previous strong and very strong events.  The following sample is for the San Francisco, Los Angeles, the Northern Sierra Nevada (8-station index) and the Central Sierra (5-station index), with monthly totals for November and December and for January through the 26th.



Please insert the usual caveats, that it's still only the midpoint in the rainfall season and we don't know how these differences will impact the remainder of the rainy months. But it is different, so stay tuned.

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

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Comparative Monthly Rainfall Climatology of Strong and Very Strong* El Niño Events

Comparative Monthly Rainfall Climatology ofStrong and Very Strong* El Niño Events

 

As the current very strong El Niño continues, it's time to examine how the current event looks in comparison to past similar strength events.  The following is breakdown of the precipitation anomalies on a month-to-month basis for the previous strong (1957-58, 1965-66, 1972-73) and very strong (1982-83, 1997-98) El Niños. 

- December 2015 across the Pacific Coast states was almost a reverse image of the 1997 and there are really no good analog event for the West Coast. 

- Recent discussions have centered on Southern California being "left out" of the January mid-latitude storm track, but an examination shows that only in January 1983 was Southern California above normal.


The full analysis can be found at http://ggweather.com/enso/strong/.

This page will be updated monthly through March as the each month's data becomes available.  Send comments and questions to jnull@ggweather.com.

 

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Maybe Not So Super Super-Bowl Weather 

 

Maybe More Soupy Than Super

The first week of February 2016 will see the eyes of the world focused on the San Francisco Bay Area for Super Bowl 50 on February 7, 2016.  If past Februarys, and the recent impacts of El Niño, are any indication, the odds are pretty high of that some of the outside activities will be wet.

During the first week of February, over the past 49 years, it has rained on average two days with an average rainfall amount of 0.81 inches at San Jose Airport, just 3 miles away from Levi Stadium in Santa Clara, CA. That rained occurred on 37 of the 49 weeks, or 76% of the time.  It is also interesting to note that the two wettest Super Bowl Weeks were during the strong El Nino events of 1997-98 (6.76") and 1972-73 (2.23").

Over the past 49 February 7ths it has rained 20 times, or 41% of the time.  And on those occasions the average rainfall has been 0.22 inches. 

The last time the Super Bowl was played in the San Francisco Bay Area was Super Bowl 19 on January 20, 1985.  That day was clear, cool and crisp with a high temperatures of only 52 degrees.  And the San Francisco 49ers beat the Miami Dolphins,  38-16.

The average high temperature during the 1st week of February is 61 degrees and the average low is 43.


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

 

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How Much Rain Is Needed to End the California Drought? 

How Much Rain Do We Need to End the California Drought? 

 

First, drought, like beauty, is in the eye of the beholder. Each different user group has their own metric for how much is enough for them to breathe easier.  For some activities just a normal rainfall year in their local area might be enough, while much of the state needs at least 150% of normal and some users may need on the order of 200% of normal.  Of course all of these solutions are complicated by California’s complex water delivery system which means that where the rainfall is measured is not necessarily where it is used! [The Drought Monitor and Drought Termination and Amelioration pages give some insight, though both are biased by factors related to agricultural drought.]

A simplistic way to look at the water shortage in California is to look at the rainfall deficits around the state from the past four seasons, and then add in the current rainfall season. In doing so (see table below) the deficits range from almost two times normal to about three-and a half time normal.

Or to look at it another way, all but Salinas would need an all-time record rainfall year to erase the 5-year deficit.



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

 

 

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Seasonal Rainfall Page

Seasonal Rainfall Page

 

I have begun producing an (almost) daily update of California Rainfall Summary, based on the long-established rainfall season of July 1st to June 30th. The data is based on the raw summary put out by the CNRFC, which unfortunately and unexplicitly changed to the October 1st water year (WY), but with the more climatologically sound July to September period added in. An example of the product is below, and the link to the actual daily summary is:  http://ggweather.com/seasonal_rain.htm

Also included on the page is a link to the Excel spreadsheet (with instructions) that you can use to create the seasonal summary yourself if I am unable and/or you are impatient. Enjoy!


Questions and comments welcome.

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

 

 

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Why This Isn't Really the First El Niño Storm of the Season

Why This Isn't Really the First El Niño Storm of the Season

 

Many headlines in recent days have been touting the current and upcoming rain as the first El Niño storm(s) of the year.  In reality, every weather system we have seen in California, and elsewhere, have been influenced by El Niño; going back to its strengthening in the eastern tropical Pacific last fall. And every storm will continue to have to some "El Niño DNA" in them, well into spring.

The pattern that we saw in December, with a series of colder storms from the Gulf of Alaska, were not as characteristic of El Niño, but they were certainly related as distant cousins.

The current pattern, with a series of storms moving almost directly west to east (i.e., zonal flow) across the Pacific in the middle latitudes, is what is more commonly thought of as a "typical" El Niño pattern.



This pattern is more closely related to the impact of El Niño on the jetstream pattern in the Pacific; and to extend the familial metaphor are more like brothers and sisters.  This is very reminiscent to what we saw in January through March of 1998.  It should be noted that during those months in 1998 that while there were lots of rainy days, most of the daily amounts were in the moderate category and not heavy rain days.

Jan Null, CCM
Golden Gate Weather Services

 

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December California Summary and Wet Weather Forecast Tools

December Summary and Forecast Tools

 

The December California Summary was highlighted by some stark contrasts in rainfall around the state while temperatures were pretty close to normal. In the SF Bay Area, downtown San Francisco rainfall was 14% above normal while San Jose was 15% below normal. (So the average of the two would be normal?)  Elsewhere north of the Tehachapis, rainfall was generally well above normal, with 180% of normal at Eureka, 168% at Fresno and 131% at Redding; but Sacramento was the outlier with only 50%of normal. 
 


I have put together a simple map interface to access the "sampled" GFS for locations around California. See http://ggweather.com/gfs.htm.  

While the GFS is not always the best model,especially out past about 5 days, the sampled data gives a good quick "first guess".  For example the "Total Precip" column is an easy way to see the timing of an approaching system. And if any of the values on the page are underlined, you can click through to see the associated charts. Previous QPF amounts can also be compared at http://wxweb.meteostar.com/sample/compare_qpf.shtml?text=KOAK.
 


The QPF page has been updated and hopefully all the links are working. Lots of rainfall and river resources to be aware of and hopefully used often in the coming months.
 



Happy New Year.

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

Posted

Northern California Mid-Winter Dry Spells

Northern California Mid-Winter Dry Spells

 

On almost as regular basis as the swallows returning to San Juan Capistrano an extended period of dry weather likes to return to Northern and Central California in the middle of winter.

Based on San Francisco's daily rainfall, over the past 65 rainfall seasons (i.e., July 1 to June 30) there has been a "dry" period in December or January averaging 20 days. For practical purposes a "dry period" is defined here as consecutive dry days with no rain, or consecutive days broken by no more than two non-consecutive intervening days of very light (* i.e., ≤ 0.08 inches) rain].  The average dry period during seasons with an El Niño was 17 days, while the average rose to 19 days during "ENSO neutral" years and 21 days during La Niña.

The shortest dry spell was 8 days which occurred twice, in 1957-58 and again in 1994-95.  Both of these seasons were during El Niño events.  The longest dry spell was 56 days in 2014-2015, when there was 18.19 inches.  All of these dry periods began in December or January with the exception of the 1964-65 period which was 19 days but did not begin until February 6th.

Even the very wet El Niño seasons of 1982-83 and 1997-98 had intervening dry spells and 22 and 17 days respectively.

The bottom line is that an extended period of dry weather is the rule and not the exception in the middle of almost every winter as the atmosphere settles into a two to three week period of equilibrium dominated by high pressure.

Also posted at:  http://ggweather.com/enso/winter_dry_spells.htm
 

Season

Consecutive *Dry Days

Begin Date

*Intervening Days/Amount

San Francisco % of Average

ENSO Type

1950-51

13

17-Dec

 

111%

Weak La Niña

1951-52

12

6-Dec

1/.08

150%

Weak El Niño

1952-53

13

21-Jan

 

97%

Weak El Niño

1953-54

13

21-Dec

1/.01

66%

Weak El Niño

1954-55

16

14-Dec

 

73%

Weak La Niña

1955-56

20

28-Jan

 

126%

Moderate La Niña

1956-57

33

6-Dec

2/.03

69%

 

1957-58

8

6-Dec

 

169%

Strong El Niño

1958-59

12

12-Jan

 

48%

Weak El Niño

1959-60

13

15-Dec

 

71%

 

1960-61

36

19-Dec

1/.02

64%

 

1961-62

21

22-Dec

 

82%

 

1962-63

42

18-Dec

 

102%

 

1963-64

19

25-Dec

2/.08

57%

Moderate El Niño

1964-65

19

6-Feb

 

103%

Weak La Niña

1965-66

21

7-Jan

1/.02

75%

Strong El Niño

1966-67

30

11-Dec

1/.01

136%

 

1967-68

23

19-Jan

 

67%

Weak La Niña

1968-69

13

24-Dec

 

116%

Weak El Niño

1969-70

12

26-Dec

 

96%

Weak El Niño

1970-71

29

17-Jan

 

87%

Moderate La Niña

1971-72

21

30-Dec

 

51%

Weak La Niña

1972-73

15

24-Dec

 

159%

Strong El Niño

1973-74

11

20-Jan

 

128%

Strong La Niña

1974-75

22

5-Dec

2/.04

84%

Weak La Niña

1975-76

25

10-Jan

 

37%

Strong La Niña

1976-77

26

13-Jan

 

51%

Weak El Niño

1977-78

16

20-Jan

1/.02

124%

Weak El Niño

1978-79

15

19-Dec

 

87%

 

1979-80

26

18-Jan

 

113%

Weak El Niño

1980-81

16

5-Dec

 

71%

 

1981-82

12

6-Jan

 

171%

 

1982-83

22

24-Dec

 

176%

Very Strong El Niño

1983-84

15

31-Dec

 

104%

Weak La Niña

1984-85

11

27-Dec

 

92%

Weak La Niña

1985-86

21

8-Dec

 

132%

 

1986-87

15

7-Jan

 

64%

Moderate El Niño

1987-88

28

30-Jan

 

82%

Moderate El Niño

1988-89

11

11-Jan

 

81%

Strong La Niña

1989-90

36

26-Nov

 

66%

 

1990-91

17

20-Dec

 

65%

 

1991-92

17

8-Jan

1/.04

89%

Moderate El Niño

1992-93

14

22-Jan

 

123%

 

1993-94

20

15-Dec

1/.03

70%

 

1994-95

8

31-Jan

 

157%

Weak El Niño

1995-96

15

31-Dec

1/.02

115%

Weak La Niña

1996-97

20

27-Jan

2/.07

105%

 

1997-98

17

15-Dec

2/.03

218%

Very Strong El Niño

1998-99

21

21-Dec

2/.02

109%

Moderate La Niña

1999-00

27

14-Dec

1/.03

115%

Moderate La Niña

2000-01

22

16-Dec

1/.03

90%

Weak La Niña

2001-02

18

3-Jan

1/.02

116%

 

2002-03

19

24-Jan

 

110%

Moderate El Niño

2003-04

11

10-Dec

1/.04

95%

 

2004-05

17

9-Dec

 

147%

Weak El Niño

2005-06

14

3-Dec

1/.03

159%

 

2006-07

12

5-Jan

 

78%

Weak El Niño

2007-08

10

11-Jan

 

81%

Moderate La Niña

2008-09

18

3-Jan

 

84%

 

2009-10

12

31-Dec

1/.05

111%

Moderate El Niño

2010-11

14

31-Dec

 

133%

Moderate La Niña

2011-12

49

1-Dec

 

72%

Weak La Niña

2012-13

16

7-Jan

1/.01

77%

 

2013-14

36

12-Dec

2/.08

58%

 

2014-15

56

21-Dec

1/.07

84%

 



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

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