tag:ggweather.posthaven.com,2013:/posts Golden Gate Weather Services 2022-04-25T17:36:29Z Jan Null tag:ggweather.posthaven.com,2013:Post/1823399 2022-04-25T17:34:36Z 2022-04-25T17:36:29Z Visualizing the California 3-year Rainfall Deficit

The following two graphs are an effort to visualize the rainfall deficits in California over the past three rainfall seasons. Even with abundant rain last October and December, this season will end up at about 80% of normal. And following the previous two dismally dry seasons, the total 3-season totals are only between 60% and 65% of normal at many locations; meaning we are over an entire year's rainfall behind normal.






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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1816506 2022-04-08T17:49:30Z 2022-04-08T17:50:24Z ENSO-Related US Winter Precipitation Climatologies

Totally revamped winter precipitation climatologies related to El Niño and La Niña through this winter's precip and with the new 1991-2020 normals. They really show the range of events that go into making an "average" El Niño or La Niña. See https://ggweather.com/enso2021/.



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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1815977 2022-04-07T14:36:09Z 2022-04-07T14:38:50Z La Niña ... Not Fading Away

The current La NIña in the eastern tropical Pacific remains stubbornly in place, with ONI essentially flat-lined on the border between "weak" and "moderate" categories. (https://ggweather.com/enso/oni.htm)



Since at least the first of the year, forecast models have shown warming into "neutral" territory, but to date, reality has not cooperated. (https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=enso-sst_table)



And significant upwelling of cool water in the ONI 3.4 region, points toward little change in the short term. (http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/wkxzteq.shtml)


One of the impacts of the ONI remaining in negative territory will be the potential for a more active than average hurricane season in the Atlantic Basin. This is reflected in the Seasonal Hurricane Forecast issued by Colorado State University earlier this morning. (https://tropical.colostate.edu/forecasting.html)

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

 

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1813678 2022-04-01T14:13:27Z 2022-04-01T14:14:48Z 3-Season California Rainfall


This is a summary of rainfall across California for the past three seasons (July 1, 2019 through March 31, 2022) and overall the amounts paint a picture of significant deficits statewide. In general, the northern half of the state has only received between about half and two-thirds of its normal rainfall, while the south half is close to three-quarters.




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


 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1790321 2022-02-01T18:47:44Z 2022-02-01T18:50:55Z 2021-2022 Rainfall Season Updates

The 2021-2022 California rainfall roller coaster of alternating wet and dry months continued through January, but unfortunately, the trend for February thus looks to break the pattern. Below are a number of metrics to give it all some context.

San Francisco's January rainfall was the 10th driest in its 173 year period of record. Note that there were three drier Janaurys within the last decade.

San Francisco's season to date rainfall of 16.89" ranks as the 38th driest. Looking at similar (16.89" +/- 1") past amounts, eight of them ended above normal (i.e, 22.89" and six below.  


July 2021 through December 2021 rainfall percent of normal. 

July 2021 through January  2022 rainfall percent of normal. 

T
abular Summary of December and January percent of normal.




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

 























Single Station rainfall versus normal for recent years.






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Jan Null
tag:ggweather.posthaven.com,2013:Post/1780081 2022-01-06T20:11:52Z 2022-01-06T20:12:56Z Drought Update - Still a Long Way to Go!

The latest Drought Monitor dropped this morning, and it shows a significant improvement over the past month. The area in the Exceptional Drought has fallen from 28% of the state to less than 1%, and the area in Extreme Drought is now at 16% compared to 52%. But over two-thirds of the state is still in at least Severe Drought or greater and the remaining areas of the state are still Abnormally Dry.
 
While, acknowledging that drought is much more than just precipitation (See “Defining Drought..It’s Not Just Rainfall), the following data will give some context to the extreme rainfall deficits over the past two-and-a-half rainfall seasons. In general, across the state, at least a full season’s normal rainfall would be needed, in the next six months, to balance the rainfall deficit that has accumulated.

The charts that follow are for the state as a whole, California’s 10 Hydrologic Regions, eight major cities, and the three Sierra Precipitation Indices.
 
Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather




 























 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1772331 2021-12-17T16:02:03Z 2021-12-17T16:56:41Z California Precipitation Snapshot

With a couple of days' break in the rain, here is an update of the current rainfall versus normal. While some of the numbers look downright gaudy, the storm door needs to remain open for several more months to overcome the rainfall deficits of the past two winters. Individual images are  available at: https://ggweather.com/water/



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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1751634 2021-10-24T21:38:02Z 2021-10-24T21:39:49Z 3rd Strongest Storm since 1950

Today's storm across the SF Bay Area, is tied as the 3rd strongest storm since 1950 on the Bay Area Storm Index (BASI), and the strongest in 26 years. BASI is based on the 24-hour rainfall at the official NWS site in Downtown San Francisco, the maximum sustained wind at San Francisco Internation Airport, and the highest wind gust at elevations below 1500 feet in the nine Bay Area Counties.

As of 2 pm, Downtown SF had 2.50" (for the maximum BASI value of 4), SFO had a sustained wind to 41 mph (for the max BASI value of 3), and the highest gust has been 86 mph at Wolf Back Ridge in the Marin headlands at 1120' for 2.7 points.. 

For info on BASI and past storms see https://ggweather.com/basi.htm 

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




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Jan Null
tag:ggweather.posthaven.com,2013:Post/1750454 2021-10-21T18:28:24Z 2021-10-21T18:30:55Z Increased Debris Flow Risks - Resources

With the strong likelihood of significant high-intensity rainfall over parts of North and Central California on Sunday and Monday comes the increased risk of debris flows (and flash flooding) in recently burned areas.

In the aftermath of a wildfire, there is a huge load of material deposited on the ground. Burned vegetation also changes the water balance of the denuded hillsides from wildfires by increasing the soil's water repellency. All of these factors combine for increased runoff of debris downslope.




There are lots of variables, like vegetation type, slope, and rain intensity that ultimately determine the likelihood and impact of debris flows in each individual burn scar.  The USGS produces very comprehensive analyses of these post-fire risks at https://landslides.usgs.gov/hazards/postfire_debrisflow/. However, the basic rules of thumb, mostly used operationally look at rainfall intensity and amount.


Other resources:
https://www.wrh.noaa.gov/lox/hydrology/files/DebrisFlowSurvivalGuide.pdf
https://www.weather.gov/riw/burn_scar_flooding

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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1746589 2021-10-11T18:04:28Z 2021-10-11T18:04:29Z Updated Climate Normals Page (1991-2020) Updated Climate Normals Page (1991-2020)

I have updated the US Climate Normals pages at Golden Gate Weather Services with the new 1991-2020 normals. These pages are designed to give quick, user-friendly access to both the monthly and daily normals for thousands of United States locations. (The normals for the previous periods of 1981-2010 and 1971-2000 are also available)


Please let me know of any comments or corrections.



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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1740984 2021-09-27T14:22:28Z 2021-09-28T18:47:55Z Shifting Climate - Warmer & Drier Later

For San Francisco, the new climate normal period of 1991-2020 is both drier and warmer than previously (1981-2010). The hottest day of the year was 70.4° on September 24th, and it is now 70.6° and a week later on October 1st.
 

And San Francisco's rainfall season is now slightly (3%) less and delayed by about a week. The new normal date for the first 2" of rain for the season is now November 14th, compared to November 8th.


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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1717129 2021-07-25T02:38:03Z 2021-07-25T02:42:52Z 20 Years of Hot Cars and Tragedies

Today, July 24th, marks the bittersweet 20th anniversary of my involvement with Pediatric Vehicular Heatstroke (PVH).  On that sunny 86° summer afternoon in 2001, I got a call from a reporter telling me about the death of a 5-month-old boy inside a hot car in San Jose and asking, “How hot could it have gotten in that car?”.  And so began my 20-year journey of measuring how hot cars get and the tracking of the tragic deaths of children in hot vehicles.

In trying to find the answer to the reporter’s query, I found only a single article and it was for a single 93-degree day in Louisiana. But my scientific curiosity was piqued and during that summer I started tracking temperatures inside vehicles. I was startled at not only how hot it could get but also how rapidly the temperature rose in the car.

The following summer, I did a controlled study where I sampled temperatures in cars over 16 days that ranged in temperature from 72° to 96°.  I was also working on another project with the Stanford University Hospital Emergency Medicine Department and became acquainted with Dr. Catherine McLaren and Dr. James Quinn. They became my co-authors for the article “Heat Stress from Enclosed Vehicles: Moderate Ambient Temperatures Cause Significant Temperature Rise in Enclosed Vehicles”.  This article was published by the American Academy of Pediatrics in 2005 and became the “go-to” article on the topic and has been referenced worldwide.

The article also led to my working with numerous child car safety groups and other organizations, and ultimately to my tracking the instances and circumstances that led to the deaths of children in hot cars. A dedicated website, NoHeatstroke.org was created to give easy access to this research and timely updates when there were PVH tragedies. Through the years, I have spoken at dozens of national conferences, given countless webinars and literally hundreds of interviews to increase awareness and share ideas on
preventing deaths of children in hot cars.

This 20-year milestone is important to acknowledge the children that have died and to continue to raise awareness about children dying in hot cars. If even one child is saved from being left in a hot car, it is more than worth the years of researching these tragic and unnecessary deaths.

 

Sincerely,
Jan


Jan Null, CCM
Adjunct Professor of Meteorology
San Jose State University
Email: jan.null@sjsu.edu  
Web: https://noheatstroke.org 
Twitter: https://twitter.com/ggweather
Facebook: https://www.facebook.com/noheatstroke/

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1716587 2021-07-23T17:42:43Z 2021-07-23T17:45:01Z Updated Fire Weather Resource Page

With the early start to what may prove to be a long California fire season, I have updated the Fire Weather Resource Guide.(https://ggweather.com/firewx.htm) to be a one-stop location for most things related to Fire Weather. 



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


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Jan Null
tag:ggweather.posthaven.com,2013:Post/1711257 2021-07-07T14:57:01Z 2021-07-08T14:47:17Z Driest California Average Rainfall on Record

  

The just ended California rainfall season has ended with the driest average statewide rainfall in the 126 seasons on record going back to 1895. And the 2-season average is the second driest with just 60% of normal. Similarly, half of California's 10 hydrologic regions saw their driest on record for the 2020-2021 season. The two-season numbers were only slightly better, primarily in the southern half of the state. [Data Source: Western Region Climate Center (https://wrcc.dri.edu/)]





 






Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Phone: (650) 712-1876
Email: jnull@ggweather.com
Web: http://ggweather.com
Twitter: @ggweather
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Jan Null
tag:ggweather.posthaven.com,2013:Post/1708230 2021-06-28T15:42:49Z 2021-06-28T15:46:54Z 2020-2021 Rainfall Season Recap and Historical Context

 

Wednesday will mark the end of what has been a dismally dry 2020-2021 rainfall season across California with many stations logging one of their top ten driest seasons on record. And even more significant are some of the two-season totals which are also among the driest, especially in the critical watersheds represented by the Sierra Nevada Indices. And most troubling in terms of the Sierra Nevada are extremely dry three and four-year totals.


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








 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1690020 2021-05-12T14:31:25Z 2021-05-12T14:43:58Z 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

 

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1675134 2021-04-06T04:40:09Z 2021-04-06T13:56:50Z 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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1673205 2021-04-01T15:13:25Z 2021-04-01T15:15:28Z 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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1661407 2021-03-04T18:50:49Z 2021-03-04T19:34:35Z 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


 






 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1648754 2021-02-02T18:48:16Z 2021-02-02T19:03:14Z 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/

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1648655 2021-02-02T15:08:59Z 2021-02-02T15:11:02Z 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/

 
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Jan Null
tag:ggweather.posthaven.com,2013:Post/1629253 2020-12-18T14:53:29Z 2020-12-18T15:19:21Z "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
 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1626787 2020-12-11T15:20:30Z 2020-12-11T15:26:01Z 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

 


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Jan Null
tag:ggweather.posthaven.com,2013:Post/1620763 2020-11-24T16:29:31Z 2020-11-24T16:30:42Z 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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Jan Null
tag:ggweather.posthaven.com,2013:Post/1619421 2020-11-20T18:04:18Z 2020-11-20T18:18:02Z 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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1618295 2020-11-17T19:01:36Z 2020-11-17T19:06:07Z Updated Oceanic Niño Index Graphics

With renewed interest in La NIña I have updated the graphics depicting the Oceanic Niño Index (ONI). Most notably and to make the data more readable, separate time-series graphs for the periods of 1950-1989 and 1990-present have been added. This is in addition to the previous 1950-present time-series. See https://ggweather.com/enso/oni.htm.






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

 

 

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1592965 2020-09-10T16:27:28Z 2020-09-10T16:28:28Z La Niña 2020 - No Sure Thing

The NOAA Climate Prediction Center (CPC) announced this morning that we have entered into a weak La Niña pattern that is expected to last through the winter. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml



But, what does that mean as far as this winter's rainfall across California and the United States? Given past climatology, it can mean almost anything!  This is dramatically illustrated by the past two La Niñas, both weak, which occurred in the winters of 2016-2017 and 2017-18. Their rainfall patterns looked dramatically different, especially in the West and California. See https://www.ggweather.com/ca_enso/ca_lanina.html and https://ggweather.com/enso2016/us_lanina.html 

For comparison in California, below are the seasonal percentage of normal rainfall for the 11 La Niña events since 1950:


 

And likewise, the precipitation anomalies for the United States.


The bottom line is that with most ENSO (El Niño Southern Oscillation) events, and especially with weak La Niñas, there is no clear signal that can be used as a predictor. What is often forgotten, is that while ENSO events have a strong influence on a given year's weather, they are not the only game in town and the impact of ENSO is influenced by a myriad of other interacting factors like the North Atlantic Oscillation (NAO), Pacific North America (PNA) pattern, Arctic Oscillation (AO), Pacific Decadel Oscillation (PDO), Madden-Julian Oscillation (MJO), etc. STAY TUNED!

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

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1586505 2020-08-24T15:29:14Z 2020-08-24T15:31:23Z California Rain and Fire Climatology

The recent spate of large fires has pushed 2020 in the unenviable position of already having the 3rd most acreage burned. And there are are still over four months of the year left, and the dry Fall months with offshore winds are often when things get worse. To date, 2020 has seen approximately 1.35 million acres burned, behind only 2018 which had 1.85M acres burned and 2008 with 1.38M acres.



The potential for a bad year has been exacerbated by the exceptionally dry 2019-2020 rainfall season, that statewide averaged just 73% of normal (21.78").



And looking at the combination of the two shows a real bias toward drier years having more acreage burned across Califonia. 

However, there are almost as many caveats as there are datapoints. First, the impacts on the state are more than just the number of acres, but where they are and do they include inhabited areas. And, the rainfall dataset is for a single statewide average and does not take into account if the rain fell more in areas that saw more acres burned.  But the pattern is compelling and should be a cautionary tale for dry years.

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

 

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1584637 2020-08-18T18:55:23Z 2020-08-18T18:59:16Z Comparing 2006 and 2020 California Heat Waves

How does the current heatwave compare to the July 2006 event? A quick analysis shows them to be quite similar. Both show the West being dominated by large 500 millibar highs centered over the Great Basin. For the dates chosen, in the approximate middle of the hottest 7-day periods, the current high is only slightly stronger. 



There are many metrics that can be used to compare, but here I have looked at the warmest 7-day period, based on daily maximum and forecast temperatures for July 2006 and August 2020. In most of the nine stations examined, the values are comparable. The largest outliers were in Redding and Livermore which were 5 degrees hotter in 2006, and Fresno which was 4 degrees hotter. 
 

There are many caveats to be applied to such a simple analysis, including the influence of nighttime minimums, the humidity given the recent influx of subtropical air, changes in population, etc.


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

 

 

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Jan Null
tag:ggweather.posthaven.com,2013:Post/1579216 2020-07-30T14:59:50Z 2020-07-30T15:02:25Z Hottest Week of the Year?

For many locales across the United States, the last week of July is the hottest time of the year. And given the prolonged heat over much of the country this summer, just the idea that there is cooler weather ahead may be reason to rejoice.

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 degrees until September 24th. Yet, just 40 miles away, San Jose has one of the earlier hottest days on average, peaking out at 83.8 degrees on July 10th. 

US Daily Normals can be found at:  https://ggweather.com/normals/daily.htm

  



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

 

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Jan Null