A Drier California Seen in New Normals


 

The differences in the new (1991-2020) rainfall normals in California show a noticeably drier state when compared to the previous period (1981-2010). On average, precipitation for stations in Northern California decreased by 8%, while Central and Southern California stations decreased by 6% and 12% respectively. On a slightly brighter note, in the Northern Sierra Nevada, there was essentially no change, but the Central and Southern Sierra normals fell by 3% and 5%.

 



11111

 

 

Posted

The (Not So) Elusive Green Flash

 

As a meteorologist, I have long been aware of the Green Flash and would always try see it when I watched the sunset over the ocean. But I never did; and most of the colleagues and friends that I speak to haven’t either! That has all changed since moving to the coast about a year ago. Now that I frequently photograph sunsets, I probably capture it at least 50% of the time! So, what has changed?   

The biggest difference is that I switched from trying to “see” the Green Flash to photographing it! When most people are trying to see it, they are staring into a bright yellow-orange-red ball, and in doing so their irises dilate down to the size of pinheads and their color vision is degraded; making it almost impossible to ever see the green flash with the naked eye.

There are actually two different basic types of Green Flash.  The first occurs as a relatively bright flash of an emerald-green color right after the upper disk of the sun has dipped below the horizon. This “classic” type is the one most often seen when a person has not been watching the bright sun during the setting process. It’s the result of warm air overlying the colder ocean and the effects of an inferior-mirage display of the sun and the actual disk of the sun interacting. (For a great technical explanation see https://www.atoptics.co.uk/atoptics/gfimform.htm).



The second variety of Green Flash appears as a small detached element of green light above the disk of the sun. During the course of the sun setting, there are often multiple occurrences of these “green wiggles” of light. This type of flash happens when there is a temperature inversion (i.e., cooler air near the surface and warmer aloft) resulting in a mock-mirage. (See https://www.atoptics.co.uk/atoptics/gfmmform.htm)
 


And as I found out recently, bright light from the full moon can also be the source of a Lunar Green Flash! The image below was taken November 2020 as the full moon set next to Pigeon Point Lighthouse on the San Mateo County, CA, coast. And it wasn’t until I got home and looked at the image on a monitor that I noticed the tiny wiggle of a rare Lunar Green Flash.
 

For a deeper dive into the topic check out what I consider the two definitive resources that I have found on the topic. The first is Les Cowley’s Atmospheric Optics pages (https://www.atoptics.co.uk/), which is a great go-to source for not only the Green Flash, but also Rainbows, Halos, Rays and dozens of other visual phenomena. The second is Andrew Young’s Green Flash pages (https://aty.sdsu.edu/). Enjoy and happy Green Flash hunting.

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

 

Posted

California Rainfall Update

 

The rainfall for the bulk of the last two seasons is now the second driest in 170 years of record for San Francisco. The 21-month total rainfall for the period from July 1, 2019 through March 31, 2021 is just  20.46". This is 45% of the normal rainfall for that period; a deficit of 24.52", which is more than one full rainfall season's total of 23.65".  The only drier period was 1975-77 with a total of 18.53".




California Percent of Normal Rainfall (July 1 to March 31, 2021)


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

 

Posted

California Drought Update and Comparison


With more and more questions along the lines of "Are we in a drought", below are several images from the Drought Monitor, today and historically. The first map is the latest issuance. followed by the map from the first week of January, The only significant difference is across a swath from the Big Sur Coast to Lake Tahoe which shifted down a category as a result of the Atmospheric River the last week of January.

More significant is the difference between today's Drought Monitor, after 2 dry years, and that from March 2013, in the 2nd year of what was to be a 4-year drought. In 2013, much of California was still "abnormally dry" (~50%) while today in 2021 it's less than 10%, with the remainder defined as drought. 

But for context, it's important to recognize that drought is more than just the amount of rainfall; and that it impacts different segments of the state's population and economy differently.  See Defining Drought...It's Not Just the Rainfall.

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


 






 

Posted

New California Rainfall Normals Show a Downward Trend

 

Every decade, the 30-year normals that are the de facto climatological standard, are recalculated. Sometime within the next six months, an update from the 1981-2010 normals to the 1991-2020 normals will be published by NOAA and other agencies around the world. [See https://ggweather.posthaven.com/what-do-meteorologists-mean-by-normal]
 
Until that date, below are close approximations of what those values will look like for a number of key stations around California, along with their historical normals through each station’s period of record.  It is interesting to note that over the past decade, all the California stations, except Eureka, shows a drop in their 30-year normals, averaging approximately 5%.
 
This shift was largely the result of the drought years across much of the state from 2011 to 2015 that pushed values downward. For example, the San Francisco average rainfall for the last decade (2011-2020) was 20.22”, replacing the average for 1981-1990 which had been 22.39”. The intervening decades of 1991-2000 and 2001-2010 had averages of 25.25” and 23.16” respectively.

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

 

Posted

Groundhog Day: More than a Furry Rodent or Repetitious Movie


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

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 also 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 it with them to the area that would later become Germany. Eventually, when German immigrants came to North America they 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.

NOAA's National Center for Environmental Information has summarized this tradition and its associated climatology at: https://www.ncei.noaa.gov/news/groundhog-day-forecasts-and-climate-history.
Additional information can be found at http://www.groundhog.org/.


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

 
Posted

"Camelot" Climate Index


What's your perfect climate? Lots of sunshine and hot temperatures? Four distinct seasons? Lots of snow for skiing or tornadoes for storm-chasing? Or maybe that decreed by King Arthur in the Broadway musical "Camelot".


In reality, it's totally subjective with no one-size-fits-all solution. With that caveat, the Camelot Climate Index (CCI), as portrayed below, was designed (as a grad school project) to be a "pleasant" climate with mild temperatures and minimal precipitation. In its latest iteration, the primary data used are from the NCDC 30-year normals for the period 1981-2010. A complete description of the methodology can be found here. Enjoy.


Camelot Climate Index

City

State

INDEX

San Diego

 CA

89

San Francisco City

 CA

87

Los Angeles City

 CA

86

Sacramento

 CA

80

Eureka

 CA.

79

Las Vegas

 NV

78

Fresno

 CA

78

Redding

 CA

76

Galveston

 TX

76

Key West

 FL

76

Tucson

 AZ

76

El Paso

 TX

76

Yuma

 AZ

75

Honolulu

 HI

75

Kahului

 HI

75

Phoenix

 AZ

75

Seattle SeaTac Ap

 WA

74

Apalachicola

 FL

73

Cape Hatteras

 NC

73

Lihue

 HI

73

Portland

 OR

72

Albuquerque

 NM

72

Tampa

 FL

71

Midland-Odessa

 TX

71

Norfolk

 VA

70

Atlanta

 GA

70

Miami

 FL

70

Roswell

 NM

70

Charleston Ap

 SC

70

Jacksonville

 FL

70

Abilene

 TX

69

Lake Charles

 LA

69

Reno

 NV

69

Savannah

 GA

69

Wilmington

 NC

69

Charlotte

 NC

69

Boise

 ID

69

New York C.Park

 NY

68

Grand Junction

 CO

68

Pensacola

 FL

68

Lubbock

 TX

68

Greensboro-Winston-Salem Ap

 NC

68

Amarillo

 TX

68

Oklahoma City

 OK

68

Washington Nat'l Ap

 DC

68

Boston

 MA

68

Macon

 GA

68

Asheville

 NC

68

Greenville-Spartanburg Ap

 SC

68

Salt Lake City

 UT

67

Philadelphia

 PA

67

Cheyenne

 WY

67

Richmond

 VA

67

Spokane

 WA

67

Columbia

 SC

67

Denver

 CO

67

Lynchburg

 VA

67

Raleigh

 NC

67

Knoxville

 TN

66

Dallas-Fort Worth

 TX

66

Louisville

 KY

66

Atlantic City Ap

 NJ

66

Pueblo

 CO

66

Austin/City

 TX

66

Flagstaff

 AZ

66

Memphis

 TN

66

Billings

 MT

66

Harrisburg

 PA

66

Brownsville

 TX

66

Great Falls

 MT

66

Shreveport

 LA

65

Corpus Christi

 TX

65

Providence

 RI

65

Dodge City

 KS

65

Ely

 NV

65

Birmingham Ap

 AL

65

Concordia

 KS

65

Lander

 WY

65

Nashville

 TN

65

New Orleans

 LA

65

Fort Wayne

 IN

65

Wichita

 KS

65

Paducah

 KY

65

Baltimore

 MD

65

St. Louis

 MO

65

Pocatello

 ID

65

Chattanooga

 TN

65

Port Arthur

 TX

65

Springfield

 IL

64

Omaha (North)

 NE

64

Helena

 MT

64

Dayton

 OH

64

Little Rock

 AR

64

Montgomery

 AL

64

Sioux City

 IA

64

Evansville

 IN

64

Kansas City

 MO

64

Indianapolis

 IN

64

San Antonio

 TX

64

Milwaukee

 WI

64

Springfield

 MO

64

Detroit

 MI

64

Minneapolis-St.Paul

 MN

64

Tupelo

 MS

64

Peoria

 IL

64

Lincoln

 NE

63

Des Moines

 IA

63

Cleveland

 OH

63

Chicago

 IL

63

Jackson

 MS

63

Fort Smith

 AR

63

Avoca

 PA

63

Columbus

 OH

63

Tulsa

 OK

63

Toledo

 OH

63

Topeka

 KS

63

Portland

 ME

63

Rapid City

 SD

63

Greater Cincinnati Ap

OH

63

Green Bay

 WI

63

Houston

 TX

63

Albany

 NY

63

Buffalo

 NY

63

Columbia

 MO

63

Winnemucca

 NV

63

Rochester

 NY

62

North Platte

 NE

62

Allentown

 PA

62

Hartford

 CT

62

Pittsburgh

 PA

62

Lansing

 MI

62

Moline

 IL

62

Huron

 SD

62

Valentine

 NE

62

Binghamton

 NY

62

Sheridan

 WY

62

Blue Hill

 MA

61

Madison

 WI

61

Fargo

 ND

61

Missoula

 MT

61

Williston

 ND

61

Bismarck

 ND

61

Grand Rapids

 MI

61

Burlington

 VT

60

Alpena

 MI

60

Duluth

 MN

60

Concord

 NH

59

Syracuse

 NY

59

Quillayute

 WA

59

Sault Ste. Marie

 MI

58

Anchorage

 AK

57

Elkins

 WV

56

Hilo

 HI

54

Nome

 AK

53

Juneau

 AK

51

Mt. Washington

 NH

36


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

Posted

25th Anniversary of Dec 1995 West Coast Mega Storm

See: https://ggweather.com/dec1995/

Today and tomorrow (Dec 11-12) mark the 25th anniversary of what is arguably the strongest storm to hit the San Francisco Bay Area and the West Coast in the past 70 years. It is the only time in that period that saw SF Bay Area winds in excess of 100 mph at sea level and over 130 mph on Mount Diablo. And at the same time, San Francisco recorded over 5 inches of rain in a 30-hour period while Kentfield had in excess of 11 inches. It is the strongest storm, and benchmark of the Bay Area Storm Index (BASI) with a rating of 10.0.

Dr. John Monteverdi (Emeritus Professor of Meteorology at San Francisco State University) and I have put together a webpage with some of the highlights from this remarkable event.  See https://ggweather.com/dec1995/





Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (650) 712-1876
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather

 


Posted

A Climatological Look at Dry Autumns

A Climatological Look at Dry Autumns

  

With a very dry start to the 2020-2021 California rainfall season, and no rain in the forecast through the end of the month, this is a look at what has happened in similar seasons. San Francisco, with the longest continuous rainfall record in the state back to 1849, is used for comparison.

To date, San Francisco has only had a paltry 0.54", which is just 12% of the normal July through November average of 4.55".

Below is a breakdown of the 16 seasons that had less than one-inch to begin the season. Of the previous 15 seasons, 5 of them finished the season above normal rainfall, and 10 finished below normal. Likewise, for seasons with a moderate La Niña, there was one season (1995) with above normal SF seasonal rainfall and two that ended below normal.

But caveat emptor, this data is climatology and NOT a forecast. 




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






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Posted

21st Century La Niñas and California Precipitation



Below is a graphical catalog of the eight La Niña Sea Surface Temperature Anomalies (SSTA) that have occurred since the turn of the century; along with the corresponding California precipitation anomaly, and the previous year's ENSO category.

In broad strokes, over the seven previous La Niñas, four were DRY (2007-8, 2008-0, 2011-12, 2017-18) and three were WET (2005-06, 2010-11, 2016-17) across most of California. And it is interesting to note that all three of the wet years followed El Niño years, while the four dry years followed La Niñas.

The latest forecast from CPC and IRI are pushing this winter into the Moderate La Niña category, and briefly into the Strong range. Last year there was a weak El Niño.



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

 

Posted