A powerful west to northwest swell impacted the central coast from Dec 16th to Dec 20th prompting a High Surf Warning and a High Surf Advisory along the coast. This was also accompanied by an upper level low that produced gusty winds and heavy rainfall.
Every event with a place to put it; 7 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS MTR wrote it up.
A powerful west to northwest swell impacted the central coast from Dec 16th to Dec 20th prompting a High Surf Warning and a High Surf Advisory along the coast. This was also accompanied by an upper level low that produced gusty winds and heavy rainfall. This led to large breaking waves up to 50 feet at Mavericks and caused damage to a bay front restaurant. There were also multiple water rescues during this surf event.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS San Francisco Bay Area, CA wrote its last area forecast discussion before the first event at Dec 16, 4:18 PM PST, 3 hours 12 minutes earlier.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
418 PM PST Sun Dec 16 2018
.SYNOPSIS...A potent system will push through a cold front and a
band of moderate to heavy rainfall this afternoon and evening.
Expect strong gusty winds out of the south ahead of frontal
passage. Showers and a few thunderstorms will be possible in the
wake of the front, followed by clearing and drying conditions on
Monday. Large waves will be impacting the coastline late Sunday
through Tuesday. A weak system may skirt the northern portions of
the area on Tuesday, but conditions will largely dry out through
the middle of next week.
&&
.DISCUSSION...as of 01:14 PM PST Sunday...A broad and deep upper
level trough continues to move towards the coast, with gusty winds
continuing and a round of moderate to heavy rainfall set to move
through late this afternoon and evening. Light to moderate rain
has fallen across the North Bay since last night, where rainfall
totals have ranged from 1-2 inches in the mountains and generally
less than half an inch in the valleys. There has been a strong
north to south gradient in terms of rainfall totals observed across
Sonoma County, with northern portions receiving the most rain
while the southern third has only picked up a few hundredths in
the valleys.
A band of moderate to heavy rain will move through from northwest
to southeast this afternoon and evening along and ahead of a cold
front, with scattered showers ahead of this band. The band should
reach the greater Bay Area by mid afternoon and push southeast to
Monterey Bay by early this evening. Overall the heavier rain
should be short-lived but ponding of water on roadways is possible
late this afternoon through this evening. Showers will decrease
behind the front, ending near SF Bay by about midnight and moving
out of the Central Coast early Monday morning. Expected rainfall
totals haven't changed much from the previous forecast, with 0.5
to 1.25 inches in the urban areas from the Golden Gate south and
1-3 inches in the higher terrain. The North Bay will see an
additional 0.5 to 1.5 inches on top of what has already fallen,
with locally higher amounts in the mountains.
South to southeast winds this afternoon ahead of the cold front
are gusty at the coast and in the hills with gusts in the 30-40
mph range, locally up to 50 mph in the highest terrain, and breezy
elsewhere with gusts 20-30 mph. Winds will veer to the west and
decrease rapidly after the frontal passage. Left isolated
thunderstorms in the forecast as there remains some weak
instability this evening along and behind the cold front. The
potential for thunder is not high but some isolated locations
could hear a rumble of thunder. Additionally, as has been
advertised high surf will continue through Monday evening with
large breaking waves and very dangerous conditions on the beach.
See the BEACHES section below for more information on the hazards.
All areas should be dry by Monday morning as the trough departs to
the east and a shortwave ridge moves overhead. A disturbance will
ride over the top of the ridge on Tuesday, producing significant
rainfall well to our north, but leaving our area mostly dry. Areas
to the north of the Golden Gate may see some light showers on
Tuesday and Tuesday night, but likely amounting to no more than a
few hundredths of measurable precip.
The ridge will then amplify Wednesday through Thursday, keeping
conditions dry and allowing temperatures to warm several degrees.
Some of our southern inland locations could be approaching 70
degrees these days. Another weak system is expected to move
through the area Thursday night but largely fall apart.
Temperatures will cool a few degrees heading into next weekend.
The long range pattern appears to remain fairly active, with
periodic chances of rain late next weekend into early next week.
&&
.AVIATION....as of 04:15 PM PST Sunday...A cold frontal boundary
is moving across the San Francisco and Monterey Bay areas this
afternoon and will continue to do so through the remainder of the
day. Breezy prefrontal winds, post frontal wind shifts, moderate
to brief heavy rainfall, temporary reductions in visibility down
to the 2-4 sm range, and ceilings down to 2500-3500 feet
(generally) are all expected as this occurs. Gradually improving
conditions overnight with widespread VFR expected by no later than mid
morning tomorrow.
Vicinity of KSFO...Deteriorating conditions as frontal boundary
approaches over the next few hours, then gradually improving
conditions overnight into Monday morning. Generally MVFR today
with periods of IFR visibility during heaviest rain. Breezy south
to southwest winds with a seldom gust into the mid 20s ahead of
the front.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...Light rain has begun to move into the
area ahead of the main front. Expect gradually lowering ceilings
and an increase in rain intensity through the remainder of the
daylight hours. Improving conditions overnight into Monday
morning.
&&
.BEACHES...as of 09:45 AM PST Sunday...Dangerous conditions are
expected today and Monday as very large surf impacts the
coastline. Long period forerunners will arrive this morning
increasing the risk for sneaker waves and rip currents. The period
will diminish as the swell height increase through the day today
before peaking this evening through early Monday. Peak swells of
17 to 21 ft at 19 to 21 seconds will be possible. Buoy 006 SE Papa
is currently showing the swell train moving through - swell 30 ft
at 19 secs. JASON Satellite waveheight data shows wave heights of
36-38 feet. Large breaking waves of 25 to 40 ft will be possible
at west and northwest facing locations, with breakers up to or
exceeding 50 ft at favored break points along the coast today. A
High Surf Warning remains in effect through 9 PM Monday along the
entire coastline.
&&
.MARINE...as of 09:45 AM PST Sunday...Strong and gusty southerly
winds will persist through the morning ahead of an approaching
frontal system leading to steep fresh swell and hazardous sea
conditions. A very large, long period WNW swell will begin to move
into the coastal waters this morning, with significantly building
seas by this evening through Monday morning. The swell will taper
off late Monday into Tuesday, however, a different large
northwest swell train builds Wednesday into Thursday.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...High Surf Warning...Entire coastline
SCA...Mry Bay
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
SCA...Rough Bar Advisory for SF Bar
SCA...SF Bay until 6 PM
&&
PUBLIC FORECAST: ST
AVIATION: DRP
MARINE: RGass
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www.youtube.com/nwsbayareaThe national radar mosaic for the moment the first event began.
6 high surf, 1 flood, 1 rip current. Local standard time, as filed.
Dangerously high surf prompts cancellation of World Surf League event at Mavericks https://www.nbcnews.com/news/us-news/storms-shatter-records-east-create-massive-waves-west-n948646.
San Francisco Buoy reported wave heights of at least 13 feet and peaking at 20 feet.
Monterey Bay Buoy recorded wave heights between 17 and 26 feet.
Roadway flooding on southbound I-280 at Saratoga off ramp. Hydroplaning of cars have resulted in accidents.
Large waves crash into a window at a restaurant in Pacifica shattering the glass and flooding a room https://abc7news.com/weather/massive-waves-hit-bay-area-beaches/4915867/.
Surfer at Mavericks wipes out in large wave and needs to be rescued https://abc7news.com/sports/what-its-like-to-wipe-out-on-a-50-foot-wave/4918957/. Time is estimated.
State parks lifeguard responds to swimmer in distress at Carmel Beach. The swimmer was rescued with no injuries https://www.kion546.com/news/state-parks-lifeguard-saves-swimmer-at-carmel-beach/938070425.
Monterey Bay buoy reported wave heights of over 25 feet.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2018Every state in 2018This day in weather historyWarnings in California, December 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 791930, 792066, 792063, 791932, 791927, 791929, 791928, 791933.