Cool May Gray

Coastal areas of California had a cool gray May while statewide rainfall for the month ranged from to zero to over 12 times normal.


A saggy trough of low pressure aloft made the marine layer a nearly permanent fixture for the month. Consequently cities near the coast were mostly 2 to nearly 6 degrees below normal, though San Diego managed to be just 0.6 below normal.  Inland it was also cooler than normal in most areas, though Redding in the northern Sacramento Valley was three degrees above normal while Sacramento, only  150 miles to the south, felt the persistent marine layer and was 3.2 degrees below normal.


In San Jose, after an 84 degree max on May 1st not a single day exceeded normal. For the month San Jose's average May 2015 maxima of 68.6 degrees was 5.7 cooler than its normal of 74.3 degrees, the coolest May since 67.97 degrees in 1977. (Their record coolest May is 66.81 inches in 1915.) It was also the first month below normal in San Jose since last September.


San Francisco was similarly cool, with only May 1st topping 64 degrees all month. And it was the 1st time since September 2013 that the average monthly maxima was below normal!


The persistent trough also produced several significant rain events on the South Coast, with San Diego's 2.39" for the month was their wettest May since 2.54 in 1921, and 1292% of normal. Elsewhere rainfall was hit or miss and highly variable with generally drier amounts north.





Jan Null, CCM

Golden Gate Weather Services


Updated El Niño Climatologies and Forecasts

Updated El Niño Climatologies

With many of the May versions of the SST ONI forecasts beginning to show El Niño strengthening well into the strong category (see below) I have updated a number of El Niño climatologies to add a "very strong" category. Each of the previous categories (Weak, Moderate, Strong) spanned a half degree anomaly on the ONI and it seemed logical to add a category for the next step of greater than or equal to an ONI of +2.0.  See El Niño and La Niña Years and Intensities (ONI).

This moved two years (1982-83 and 1997-98) from the strong category to "very strong" and an examination of these two years understandably shows the most definitive signature for rainfall for California.  [The 1972-73 season fell just shy of the meeting the "very strong" criteria, but certainly exhibited a similar very wet California outcome.] See El Niño and La Niña Winter Historic Precipitation and Temperatures and Climatology of El Niño Events and California Precipitation.

Important Caveat:  These are climatologies of past events and are made up of a broad range of events from a small sample that are averaged together.  Consequently, like all averages, this type of data should not be used as a forecast! Or as your stock broker says "Past performance is no guarantee of future result." 


Updated El Niño Forecasts

The new mid-May plume of forecasts come out from IRI/CPC on Thursday (5/21) but many of the individual elements are already available and showing significant warming in future months across the eastern equatorial Pacific.
NOAA Ensemble Mean 
ECMWF Nino Plumes
Australian BOM Nino3.4 Outlook 

Jan Null, CCM
Golden Gate Weather Services


El Niño Forecasts - Past and Present

El Niño Forecasts - Past and Present


Following yesterday's latest NOAA El Niño Advisory there is, similar to last spring, already talk about the upcoming "strong El Nino".  However, a look at the actual model data from April 2014 and April 2015 does not support this. [Neither did the forecast from last year]

The most robust 2015 model is the NCEP CVSv2, but it was also one of the strongest last year and we know how that came out! 

Yes, we are starting off warmer (i.e., a higher Oceanic Niño Index) than last year and this certainly portends the current event persisting and being stronger than last year. But from what the models are actually saying it's still early to say if or when it will reach the strong threshold.

And then there are the comparisons to the very strong event of the winter of 1997-98! From what I am seeing so far, it is WAY too early to compare the two. The current (FMA) ONI is at +0.6, while the ONI for FMA 1997 was already at 1.4. Likewise, the water temperatures of the upper 300 meter along the equator is +1.4 anomaly, while back in 1997 it was +1.9.  There are lots of other comparative metrics to look at and a significant Kelvin wave is bringing warmer subsurface water into the eastern tropical Pacific; but this also happened last year about this time.

Bottom line: too early to tell.

Jan Null, CCM
Golden Gate Weather Services


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Heatstroke Deaths of Children in Cars

Even as temperatures are just beginning to rise this Spring there has already been the first 2015 juvenile heatstroke death when a 2-1/2 year old boy died last week in a hot car in Phoenix.  But it doesn't even need to be a blazing hot day in a southern state for these tragedies to occur as evidenced by deaths last year in places like Oregon and Michigan on relatively mild days.


Most people may have seen media reports about an isolated incident or two of a child dying in a hot car, but when put into a nationwide context there is an epidemic. On average 37 young lives are lost every year in the United States.  Since 1998 over 636 infants and  children have died horrible deaths due to heatstroke inside hot vehicles.


These incidents cross every socio-economic classes, from professionals like attorneys, professors and dentists to white collar engineers to blue collar workers to the unemployed. Over half (53%) of juvenile vehicular heatstroke fatalities occur when a caregiver is somehow distracted and accidentally leaves a child in a vehicle, most often when the child was supposed to be dropped off at either childcare or preschool.


Another 29% of the heatstroke deaths occur when children playing in vehicles are overcome by the heat.  And the saddest group is comprised of the remaining 17% of the children who died in hot cars after being intentionally left in vehicles by a caregiver who chose to run an errand, get their hair done, go to bar or the casino, etcetera.


Heatstroke (aka extreme hyperthermia) describes heat-related illnesses when a body’s temperature exceeds its normal range and loses its ability to cool itself. This is exacerbated in infants and children whose body’s heat up three to five times faster than adult.  When a person’s body temperature reaches 104 degrees (the clinical definition for heat stroke) their cooling system is overwhelmed to the point it begins to shut down.  A person with heatstroke may experience symptoms that include confusion, faintness, strong and rapid pulse, and possible delirium, hot dry skin or even unconsciousness.  Continued exposure to very high temperatures can produce brain damage and other organ failure.  At 107 degrees, cells within the body start to die and organs begin to shut down, quickly leading to death.


A car, truck, SUV or van heats up rapidly to lethal temperatures in a very short period of time.  This author began research on the topic in 2002 that was subsequently published in Pediatrics and is continuing and kept up-to-date online at  The research found that temperature readings inside a closed vehicle peak at between 40 and 50 degrees above the outside air temperatures with about two-thirds of the rise in the first 20 minutes.  Consequently, even on a mild 70 degree day temperatures can reach readings that can be fatal to an infant or small child.  The research also found that “cracking” the windows had a negligible effect on the temperature.


This research has become a “go to” source  on the topic and is used worldwide.  It is hope that interest in this sad topic will raise the level of interest and awareness and ultimately to save some innocent lives.  The bottom line is that each and every one of these deaths

is 100% preventable.  Infants and children are the most precious cargo that is ever transported in a vehicle and we should always be cognizant of the potential dangers to a child left alone in a car.


Please take a moment to share this information either personally or via social media with your family, friends and colleagues. It might save a life.


Jan Null, CCM

San Jose State University

Baseball Weather

It's only the second week of the baseball season and already radio and television announcers are bobbling what should be easy weather ground-balls. The most egregious errors are usually misstatements about the humidity and why the ball doesn't go as far.  NOT!

The difference in the distance a 375 foot homerun travels when the humidity is 20% and when it is 60% is less than a foot.  And the difference in the amount that a 90 mph curveball breaks is only a tenth of an inch. (There may be some absorption of moisture by a baseball on a particularly muggy day, but those amounts have been found to also be negligible).

The temperature (and thus the air density) has a slightly greater impact with the difference in the distance of a home run on a 50 degree day being about 16 feet less than on a 90 degree day.  The altitude above sea level and corresponding air lower density difference means a 375 foot homer at sea level would travel about 405 feet at Coors Field in Denver.

But the meteorological element with the greatest impact is the wind.  Just a 5 mph tailwind will carry that 375 foot home run to 415 feet and a 10 mph wind will translate to an epic 455 foot blast.

The bottom line is that if you want to see really long homeruns go to Denver on a hot dry day with the wind blowing out!

A more detailed treatment of the topic can be found in last year’s Jan/Feb issue of Weatherwise Magazine ( )

Play ball.
Jan Null, CCM
Golden Gate Weather Service


El Niño Just Keeps Hanging On

Meteorologists are singing the Supreme's 1967 song "You Keep Me Hangin' On" as the current weak El Niño just won't go away.

The latest Oceanic Niño Index (ONI) checked in at the minimal 0.5 level for JFM to remain barely in the weak El Nino category. This is now the 5th consecutive 3-month period at or above that threshold making this now an "official" El Nino event.

The latest CPC El Nino Advisory keeps a 70% chance of at least a minimal El Niño continuing through the summer and a 60% chance through next autumn. And the IRI/CPC ENSO Predictions Plume  actually shows a slight warming of the ONI through the next 6 months.

It is relatively rare that a warm ENSO event persists from one winter through the summer months into the following winter. Since 1950 the only three previous instances were the weak 1953-54 El Niño that lasted into the 1954-55 winter and then the moderate 1968-69 and 1986-87 events that also persisted into the following winter. (

Jan Null, CCM
Golden Gate Weather

4-Year Rainfall Deficits Look Daunting

The recent rains have prompted questions about "what does this mean for the drought" in California. The short answer is that while every inch of rain helps, the deficits over the past 4 years will not be easily mitigated.

The total 4-year deficits from normal, range from about 1 to 1.5 seasons worth over Northern California, to between a 1.5 and 2.0 season deficit in the central interior, while generally south of the Tehachapis there is a 2 season deficit. This means that for a location with a 1.5 season deficit to erased next year, that location would need 250% of normal rainfall.

Note: The 2014-15 totals above only reflect rainfall through April 5th and any additonal rainfall between now and the end of June would go toward reducing the deficit.

An even more important caveat to the above is that this table is based only on rainfall deficits while drought mitigation for California is further complicated by a host of other factors including reservoir levels, groundwater levels and water usage.

Jan Null, CCM
Golden Gate Weather Services



It's More than Just the Snowpack

The latest snowpack numbers are in and they continue to be dismal; BUT the total amount of water in the major reservoirs around the state is actually 5% higher than July 1, 2014 (i.e., after most of last years snow had melted).

This is dichotomy is largely due to the high water content of the relatively warm December and early February storms and the runoff reaching the reservoirs sooner rather than later. It was further enhanced by the focus of the storms being over Northern California where there are the largest reservoirs. The three largest California reservoirs, Shasta, Oroville and Trinity, saw the greatest increases with +18%, +8% and +6% respectively.

There are a number of caveats to consider in putting this into the larger context of the ongoing California Drought. First, there will be some useage between now and July 1st so the differential will shrink if comparing July 1st to July 1st. Second, and most important, the quantifying of drought is more than just snowpack or reservoir storage; it also includes groundwater supplies and useage.

Jan Null, CCM
Golden Gate Weather Services


Record Warmth and Dismally Dry Across California in March

March 2015 was dismally dry and way too warm across California. Most stations' rainfall was in the bottom 10 years for their period of record and temperatures smashed average monthly maximum records.

City stations in the middle part of the state had March percent of normal (PON) readings in single digits; from 3% in Fresno to 7% in San Jose and Sacramento. It was marginally better to the north and south with PON's that ranged from 24% at Redding to 61% at Eureka, while LA and San Diego had 36% and 51% respectively. (

This also meant that the seasonal rainfall picture continued to slip with season-to-date PON's ( generally in the 70% to 90% range, though Fresno trails far behind at only 49% of normal. Many of these number are however better than even the end of last season values ( due in large part to an exceptionally wet December.

It is also important to note that despite the dire single digit snowpack numbers, the amount water that got into the reservoirs from the warm December rains probably resulted in more acre-feet of storage into the reservoirs than if those same storms had been colder with more snow.

The March temperatures were beyond toasty, with six of the eight key cities having all-time March monthly maximum temperatures (and also some monthly average temperature records). The monthly anomalies ranged from only 1.7 degrees above normal at Eureka to "just" 5.6 above normal for San Francisco to blazing 10.1 degrees above normal at both Redding and Sacramento. (

March 2015 Average Maximum Temperature Records
- Redding 74.6 (previous record 74.3 in 2004)
- Sacramento 74.9 (previous record 72.6 in 2004)
- Fresno 77.7 (previous record 72.2 in 1972)
- Los Angeles 79.1 (previous record 75.4 in 1988)
- San Diego 74.2 (previous record 72.1 in 1959)

Jan Null, CCM
Golden Gate Weather Services