Golden Gate Weather Services

The 8-Station Index Reaches 100% of Normal

2024-02-22T23:27:44Z

The 8-Station Index has reached 100% of normal for the first time this winter.

The 8SI Sierra Nevada Precipitation Index is arguably the single most important metric of California water supply. It’s a snapshot of the overall wetness that includes both snowpack and rainfall for the major watersheds of the upper Sacramento, Feather, Yuba, and American Rivers. These in turn feed into some of the largest of the California reservoirs (i.e., Shasta, Oroville, and Folsom).

As of February 21, 2024, the seasonal (i.e., July 1 to June 30) rainfall was 35.14”, compared to a normal of 35.12” for this date. [Normal for the entire July 1 to June 30 season is 52.81".]

Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Office: (650) 712-1876
Mobile: (510) 928-2824
Email: jnull@ggweather.com
Web: http://ggweather.com

El Niño Winter Forecasts - Past and Present

2023-09-28T14:38:41Z

This is a consolidation of the forecasts for last winter (2022-2023) and what eventually occurred as well as five of the forecasts for this upcoming winter (2023-2024). They are in two sets, one for the period of December-January-February (DJF) and then January, February-March (JFM). All of the forecasts from last year and this year were made in September. (In another post, I will look at how some of the forecasts evolved through subsequent months). I will leave it to the viewer to evaluate the veracity of last winter's forecasts.

Half Moon Bay Buoy Returns to Service with a Saildrone

2023-09-21T15:42:48Z

Since 1980, the Half Moon Bay Buoy (officially National Buoy Data Center #46012) has been monitoring weather, sea, and wave conditions off the coast. Besides being used by meteorologists for their forecasts, fishermen, boaters, surfers, and scientists rely on it to monitor conditions. Anchored about 24 miles west-southwest of Pillar Point, the buoy collects and transmits a wide array of meteorological and oceanographic parameters (i.e., wind speed, wind direction, wind gusts, air temperature, dew point temperature, sea temperature, sea-level pressure, significant wave height, average wave period and dominant wave period) that is archived by the National Buoy Data Center.

In February Buoy 46012 failed and was towed to port. Earlier this month, as an interim measure, the buoy was replaced with a Saildrone; an uncrewed data-collecting platform that will monitor the same parameters that the previous buoy did. Saildrones are made by an Alameda company, Saildrone Inc. They are bright red vessels, with a 23-foot-long double-kayak body topped by a sail containing an array of sensors and solar panels. In addition to taking stationary buoy measurements, there are literally fleets of Saildrones deployed around the world’s oceans collecting data for a wide array of scientific missions. See https://www.cnet.com/science/autonomous-saildrones-are-the-newest-weapon-in-fighting-climate-change/

The Half Moon Bay Saildrone will be active until at least June 2024. At that time it is to be decided by the National Weather Service if a buoy will be redeployed.

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

2022-2023 California Rainfall Season in Review

2023-06-30T04:44:49Z

Today marks the end of the very impressively wet 2022-2023 California rainfall season which began on July 1st. [See https://ggweather.posthaven.com/rainfall-season-vs-water-year for a discussion of why this differs from the Water Year traditionally used by hydrologists]. And while the rainfall totals are huge compared to recent years, they fell well short of being the all-time wettest. Additional links to some of this data can be found at: https://ggweather.com/ca2022rain.htm and https://ggweather.com/seasonal_rain.htm.

Background Info re Hot Car Child Deaths

2023-06-28T22:59:44Z

Background Info re Hot Car Child Deaths

With some warm to hot weather (finlly) on tap for the inland parts of SF Bay Area and interior California, the risk of hyperthermia and possibly heatstroke rises for children, pets, and the elderly. Below are a couple of fact sheets that I hope you will share. There is also a wealth of information available at https://www.noheatstroke.org/ that can be freely used and shared. And by just the right person seeing it, you might save a life.

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

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

Meteorologist's Links

2023-06-14T18:11:29Z

Spurred on by the NWS changing many of the URL's for a lot of their text products, I've updated and made some additions to my METEOROLOGIST'S LINKS page at:https://ggweather.com/home.html

Many on this email distribution are aware of this page which has been evolving for probably 20 years with handy links to products that I use almost daily. There are also links here to a number of the other resource pages that I hope are useful compilations in a single source. Enjoy.
T-Storm/Tornado Links: http://ggweather.com/tornado.htm
Hurricane Links: http://ggweather.com/hurricane.htm
Fire Weather Links: http://ggweather.com/firewx.htm
El Nino/La NIña Links: http://ggweather.com/enso.htm

Please let me know if you find any errors, broken links, or additional sites that may be of interest to meteorologists and the media.

Developing El Niño Comparisons

2023-06-05T16:25:34Z

The eastern tropical Pacific continues to warm toward a likely El Niño event later this summer that is then forecast to continue through the winter. For the first time in 3 years, the Oceanic Niño Index (ONI) has moved back into positive territory. (See https://ggweather.com/enso/oni.htm)

This warming is seen in all the Niño Regions with the most dramatic rise in Niño 1+2 off the South American coast where the anomalies are about +2.5 °C.

Comparing the current event to the two previous “very strong” El Niños in late May of 1997 and 2015 shows several differences. Currently, this year has not warmed as much in the west as prior years. It also shows 2015 as more of a Central Pacific event, with more similarity between 1997 and 2023.

It will be interesting to see how the current event develops over the next six months. Stay tuned.

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

Are California Coastal Water Temperatures Warmer During El Niño?

2023-05-24T15:48:36Z

Media reports of late, and during past El Niño events, have attributed the presence of warm water species of marine life along the California coast to El Niño. However, a look at the data doesn't support that conjecture. Contextually, the sea surface temperature (SST) warming associated with El Niño occurs in the tropical Pacific, approximately 3,000 miles away from California, plus there is no physical process where that equatorial water is transported to the California coast. And in the short-term, the current El Niño has not even officially formed yet, and most waters along the California coast are below normal.

Historically, during El Niño winters, there are just about equal chances of coastal water temperatures being above or below normal. The following analysis was done by looking at two separate areas along the California coast. In Northern/Central California the study area was a 2-degree square (36° to 38° N and 122° to 124° W) between about Point Reyes and Big Sur and about 100 miles offshore. In Southern California, the area was a 2-degree square (32° to 34° N and 117° to 119° W) between about Santa Barbara and San Diego and about 100 miles offshore,

During the 13 El Niño events since 1980, sorted by strength, the sea surface temperature anomalies (SSTAs) in the northern area were only warmer than normal in 6 of the 13 years.

And along the southern California coast, the El Niño year SSTAs were warmer than normal in 7 of the 13 years.

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

Updated El Niño Precipitation and Temperature Anomaly Maps

2023-05-16T19:07:51Z

I have updated the climatologies of previous El Niño precipitation and temperature anomaly maps, with all new graphics and now using "percent of normal" data. For example, below are the precipitation anomaly maps for the last two strong El Niño's; highlighting that even with a specific ENSO category there can be very large differences.
PRECIPITATION - https://ggweather.com/enso2023/us_elnino_precip.html
TEMPERATURE - https://ggweather.com/enso2023/us_elnino_temp.html
ENSO Resource Page - https://ggweather.com/enso.htm

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

When Will Tioga Pass Open in 2023?

2023-05-08T16:03:20Z

Due to this year's epic Central Sierra Nevada snowpack, current estimates from Yosemite National Park are that Tioga Pass will open later than usual this year; possibly not until July. To put this year into context, below is what has happened in previous years.

El Niño Resources for 2023

2023-04-24T13:29:09Z

Last week, the Climate Prediction Center issued an El Niño Watch, with the expectation that conditions in the tropical Pacific would transition into an El Niño pattern by late summer and continue into next winter. And immediately a number of headlines popped up, raising the specter of doom and gloom. The tone reminded me of the fall of 1997 and this cartoon from the Sacramento Bee:

Consequently, I have updated a number of El Niño and La Niña resources that may assist in keeping things in perspective. They are all available from the EL NIÑO / LA NIÑA RESOURCE PAGE

.

The Oceanic Nino Index is the defacto metric widely used to classify the strength of ENSO (El Niño - Southern Oscillation).events. See https://ggweather.com/enso/oni.htm for current and historic values.

I have also put together a page of misconceptions about ENSO Events. See http://ggweather.com/enso/enso_myths.htm

This is coupled with an ENSO Glossary with some of the more common terminology. See http://ggweather.com/enso/glossary.htm

And to put historical precipitation on the types and strengths of ENSO events, the following analyzed chronologies were updated for both the United States and California. See https://ggweather.com/enso2021/ for the US, then https://www.ggweather.com/ca_enso2021/ca_elnino.html and https://www.ggweather.com/ca_enso2021/ca_lanina.html for California.

Please let me know of any errors or omissions.

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

Historical Low Level Snow in the Bay Area

2023-02-21T16:23:18Z

The last widespread snowfall down to near sea level in the San Francisco Bay Area was 47 years ago, on February 5, 1976. Granted, there have been a handful of occasions since with small pockets of cold air allowing for snow to get close to sea level, but nothing widespread. And the odds against it happening later this week are small, but not impossible. The most likely scenario will be snow accumulations in areas around the bay above 1000 to 2000 feet.

Historically, there have only been 11 days when snow has been recorded near sea level in downtown San Francisco, Twice on February 5th; in 887 and again in 1976. (https://www.ggweather.com/sf/snow.htm).

The event on February 5, 1887, was the snowiest on record with over 3 inches in the downtown area of the City. This is well documented in Mark McLaughlin's wonderful "San Francisco Snowstorms" document (http://thestormking.com/Sierra_Stories/San_Francisco_Snowstorms/san_francisco_snowstorms.html)

The 1976 event was spectacularly captured by the SF Chronicle in this photo by Art Frisch.

The meteorology on Feb 5, 1976, showed a cold front having moved south over the state during the overnight hours and supported by a very cold 500 mb low (5280m) west of Pt. Reyes. The 1000-500 mb thickness was 5221 meters.

The hourly observations that morning showed snow falling at San Francisco International Airport, and it may have been the last snow observation recorded at SFO, since it is unlikely to have been picked up by current automated sensors. [I remember this quite vividly as I had worked a midnight shift as an observer at SFO some of those snowy observations and then drove home to the East Bay through a winter wonderland.]

The setup for later this week shows a similar strength upper low farther offshore than in 1976, with a 5210m minima on Friday morning. But will the moisture synch up with the coldest air and at the right time of day? The odds right now look better for low-level snow south of the Bay Area.

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

California Precipitation Rankings

2023-01-30T16:49:14Z

With clearing skies over California, the current rainfall totals for the month of January seem close to final.*

For historical context, the tables below rank the 20-wettest first seven months (July through January) of the rainfall season, and how those locations ended the season in June. The two biggest takeaways:
1. Despite the impressive parade of storms in December and the first half of January, only the Central and Southern Sierra Nevada Indices barely cracked the top 10 for each location's period of record.
2. All of these locations ended the season above normal for years that had similar amounts to where they are this year.

* Data for Los Angeles is current through 8 am January 30. A few showers still persist there, but it is doubtful that any additional rain will shift the ranking.

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

California Rainfall and Reservoir Updates

2022-11-16T15:41:18Z

Despite recent moderate precipitation amounts across the state (https://ggweather.com/seasonal_rain.htm), the rainfall and reservoir deficits continue to grow; well beyond the capability to make up the amounts in a single season. Even after the 1.79 inches that San Francisco has received to date, the total 4-season deficit is currently over 29 inches and will be over 50 inches by the end of the season, if no rain were to fall. (San Francisco normal 22.89", SF record 49.27 in 1861-1862.)

Likewise, the critical 8-Station Northern Sierra Precipitation Index (8SI) currently has a deficit of more than an entire season.

And these large rainfall deficits are evident in the current levels of the state's reservoirs which have steadily declined over the past 3= seasons and are at just 61% of their average mid-November storage.

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

Mini Review of Last year's CPC Winter (DJF) Outlook

2022-10-14T21:33:41Z

ABSTRACT
Comparison of last year's NOAA Climate Prediction Center (CPC) 90-day precipitation and temperature forecasts for the winter period of December-February (DJF) 2021-2022 with the actual observed conditions.

DATA SOURCES
The 90-day (DJF) outlooks were retrieved from the NOAA Climate Prediction Center (CPC) archives and the corresponding observed temperature and precipitation data were downloaded from NOAA ESRL Climate Division Data.

ANALYSIS
The CPC Winter Outlook DJF 2021-2022 did better than in several of the recent winters, partly because the overall pattern ended up close to a "typical" La Niña. However, it must be noted that the CPC outlooks are probabilistic versus deterministic, which makes them harder to judge as right or wrong.

Here is t subjective graphical grading used below. Overall if a forecast was in the right category (i.e., above normal was forecast and above normal was observed) it was graded as "good" and marked with a "+". Conversely, if it was the wrong category (i.e., above normal was forecast and below normal was observed then it was graded as "not good" with a "-". And if the forecast was off by a single category (i.e, above normal was predicted and it was normal) or there was a mixture of above and below in close proximity to one another then graded it as "mixed" and marked with a "0".

SUMMARY
Of the 41 precipitation regions compared, 14 (34%) regions rated as "good", 10 (24%) as "not good" and 17 (41%) as "mixed".
Of the 39 temperature regions compared, 20 (51%) regions were rated as "good", only 1 (3%) as "not good" and 18 (46%) as "mixed".

However, it is left to the individual reader to do their own comparisons and evaluate the relative usefulness of the forecasts to their particular activity.

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

A Mini-Analysis of Last year's Old Farmer's Almanac Winter Forecast

2022-10-12T14:19:19Z

See https://ggweather.com/farmers/2022/index.html

ABSTRACT
This review subjectively compares last year's 2022 Old Farmer's Almanac seasonal precipitation and temperature forecasts for the winter period of November-March (NDJFM) 2021-2022 with the observed temperature and precipitation anomalies for the same period.

DATA SOURCES
The Winter forecasts are reproduced from the 2022 Old Farmer's Almanac (Yankee Publishing, Dublin, NH) website and the corresponding observed temperature and precipitation data were downloaded from the Climate Diagnostics Center (CDC).

ANALYSIS
The subjective graphical grading is below. Overall if a forecast was in the right category (i.e., above normal was forecast and above normal was observed) it was graded as "good". Conversely, if it was the wrong category (i.e., above normal was forecast and below normal was observed then it was graded as "not good". And if the forecast was off by a single category (i.e, above normal was predicted and it was normal) or there was a mixture of above and below in close proximity to one another then I graded it as "mixed".

Of the 40 precipitation regions compared, 16 (40%) regions were rated as "good", 16 (40%) as "not good" and 8 (20%) as "mixed". Of the 33 temperature regions compared, only 2 (6%) regions rated as "good", 19 (58%) as "not good" and 12 (36%) as "mixed".

However, it is left to the individual reader to do their own comparisons and evaluate the relative usefulness of the forecasts to their particular activity.

See the past reviews at https://ggweather.com/links.html#ofa

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

La Niña and California Rainfall

2022-10-03T17:03:39Z

Most of the computer models are pointing toward the present moderate La Niña conditions persisting through the upcoming winter; for the third consecutive year. And given the past three years have seen below-normal rainfall across most of California, the immediate knee-jerk reaction has been that this will automatically be a fourth dry year, based on the misconception that La Niña always equals Dry for California. But a close inspection of past La Niñas since 1950, shows that this is not always the case. An updated detailed analysis can be found at https://www.ggweather.com/ca_enso2021/ca_lanina.html. (See the bottom of this email for other related links)

From that analysis:

To me, the important takeaways are to be wary of "average" or "typical" La Niña conditions and to look at the range of data from which those averages are derived. And most importantly, climatology is NOT a forecasting tool, but it does give context to any categorical proclamation about the prospects for the upcoming season.

El Niño - La Niña Resource page: https://ggweather.com/enso.htm
Current Oceanic Niño Index (ONI): https://ggweather.com/enso/oni.htm
La Niña and California Rainfall: https://www.ggweather.com/ca_enso2021/ca_lanina.html
El Niño and California Rainfall: https://www.ggweather.com/ca_enso2021/ca_elnino.html
ENSO-Related US Winter Precipitation: https://ggweather.com/enso2021/

As always, comments and suggestions are welcomed.

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

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The Hottest Week of the Year ... or Not

2022-07-25T14:41:52Z

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

But a few locations, especially along the immediate West Coast, have a delayed peak. For example, while on average, Sacramento has its warmest day of the year on July 20th, San Jose waits until August 29th and it's not until September 24th that San Francisco reaches its maximum. The largest moderating factor is the adjacent cool water of the eastern Pacific along with the weakening and southward shifting of the Pacific High.

Full-size versions of the California and United States maps (below) can be downloaded from https://ggweather.com/warmest_cal.jpg and https://ggweather.com/warmest_us.jpg. Tabular US Daily Normals are available at: https://ggweather.com/normals/daily91.htm.

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

Visualizing the California 3-year Rainfall Deficit

2022-04-25T17:34:36Z

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

ENSO-Related US Winter Precipitation Climatologies

2022-04-08T17:49:30Z

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

La Niña ... Not Fading Away

2022-04-07T14:36:09Z

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

3-Season California Rainfall

2022-04-01T14:13:27Z

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

2021-2022 Rainfall Season Updates

2022-02-01T18:47:44Z

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.

Tabular 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.

Drought Update - Still a Long Way to Go!

2022-01-06T20:11:52Z

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

California Precipitation Snapshot

2021-12-17T16:02:03Z

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

3rd Strongest Storm since 1950

2021-10-24T21:38:02Z

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

Increased Debris Flow Risks - Resources

2021-10-21T18:28:24Z

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

Updated Climate Normals Page (1991-2020)

2021-10-11T18:04:28Z

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

Shifting Climate - Warmer & Drier Later

2021-09-27T14:22:28Z

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

20 Years of Hot Cars and Tragedies

2021-07-25T02:38:03Z

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/