Alert archive / California / High Surf Warnings in 2021
High Surf Warning 1, NWS San Francisco Bay Area, CA
NWS San Francisco Bay Area, CA issued this high surf warning at Jan 9, 2021, 8:18 AM PST for 6 counties in California. It took effect at Jan 10, 2021, 7:00 AM PST. It was in force for 14 hr. No storm report in the archive falls inside the area while it was in force.
The area
The counties it named.
The facts
- Issued
- Jan 9, 2021, 8:18 AM PST (16:18 UTC)
- In effect from
- Jan 10, 2021, 7:00 AM PST
- Expired
- Jan 10, 2021, 9:00 PM PST
- In force
- 14 hr
- Issued by
- NWS San Francisco Bay Area, CA
Counties City and County of San Francisco, CA, Marin County, CA, Monterey County, CA, San Mateo County, CA, Santa Cruz County, CA, Sonoma County, CA
The radar
The San Francisco radar (KMUX), 53 km from the middle of the area, began a volume at 16:19 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Oakland, CA (KOAK), launched 12:00Z, 4.3 hours before the alert went out and 26 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1228 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- -22 m²/s²
- 0-3 km storm-relative helicity
- 25 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
173 WHUS46 KMTR 091618 CFWMTR Coastal Hazard Message National Weather Service San Francisco CA 818 AM PST Sat Jan 9 2021 CAZ006-505-509-529-530-100500- /O.NEW.KMTR.SU.W.0001.210110T1500Z-210111T0500Z/ San Francisco- Coastal North Bay Including Point Reyes National Seashore- San Francisco Peninsula Coast-Northern Monterey Bay- Southern Monterey Bay and Big Sur Coast- 818 AM PST Sat Jan 9 2021 ...HIGH SURF WARNING IN EFFECT FROM 7 AM TO 9 PM PST SUNDAY... * WHAT...Dangerously large breaking waves of 23 to 28 feet, locally in excess of 30 feet at favored breakpoints. These waves will also result in an increased risk of strong rip currents and coastal erosion. * WHERE...San Francisco, Coastal North Bay Including Point Reyes National Seashore, San Francisco Peninsula Coast, Northern Monterey Bay and Southern Monterey Bay and Big Sur Coast Counties. * WHEN...From 7 AM to 9 PM PST Sunday. * IMPACTS...Large breaking waves can sweep people off jetties and rocks, and into dangerous seas. Life-threatening swimming conditions and localized beach erosion can be expected. Cold water rescues or drownings are more likely with these waves and stronger rip currents. * ADDITIONAL DETAILS...While west-northwest swell will gradually subside Monday into Tuesday, high astronomical tides will coincide with larger than normal waves resulting in an increased risk of minor coastal flooding. PRECAUTIONARY/PREPAREDNESS ACTIONS... Everyone should remain out of the water due to life-threatening surf conditions. Stay off of jetties, piers, and other waterside infrastructure. && $$
4 follow-up statements
508 WHUS46 KMTR 100340 CFWMTR Coastal Hazard Message National Weather Service San Francisco CA 740 PM PST Sat Jan 9 2021 CAZ006-505-509-529-530-101400- /O.CON.KMTR.SU.W.0001.210110T1500Z-210111T0500Z/ San Francisco- Coastal North Bay Including Point Reyes National Seashore- San Francisco Peninsula Coast-Northern Monterey Bay- Southern Monterey Bay and Big Sur Coast- 740 PM PST Sat Jan 9 2021 ...HIGH SURF WARNING REMAINS IN EFFECT FROM 7 AM TO 9 PM PST SUNDAY... * WHAT...Dangerously large breaking waves of 23 to 28 feet, locally in excess of 30 feet at favored breakpoints. These waves will also result in an increased risk of strong rip currents and coastal erosion. * WHERE...San Francisco, Coastal North Bay Including Point Reyes National Seashore, San Francisco Peninsula Coast, Northern Monterey Bay and Southern Monterey Bay and Big Sur Coast Counties. * WHEN...From 7 AM to 9 PM PST Sunday. * IMPACTS...Large breaking waves can sweep people off jetties and rocks, and into dangerous seas. Life-threatening swimming conditions and localized beach erosion can be expected. Cold water rescues or drownings are more likely with these waves and stronger rip currents. * ADDITIONAL DETAILS...While west-northwest swell will gradually subside Monday into Tuesday, high astronomical tides will coincide with larger than normal waves resulting in an increased risk of minor coastal flooding. PRECAUTIONARY/PREPAREDNESS ACTIONS... Everyone should remain out of the water due to life-threatening surf conditions. Stay off of jetties, piers, and other waterside infrastructure. && $$
376 WHUS46 KMTR 100909 CFWMTR Coastal Hazard Message National Weather Service San Francisco CA 109 AM PST Sun Jan 10 2021 ...LARGE LONG PERIOD NORTHWEST SWELL WILL BRING HAZARDOUS CONDITIONS ALONG THE COAST THROUGH SUNDAY... ...KING TIDES WILL CAUSE MINOR COASTAL OVERFLOW AND FLOODING MONDAY MORNING THROUGH MONDAY AFTERNOON... .A new large, long period northwest swell arrives on Sunday which will result in breaking waves from 23 to 28 feet, and locally up to 30 feet at favored breakpoints. A High Surf Warning will be in effect through much of Sunday for an increased risk of rip currents and large shore break. Sea surface temperatures remain cold, down in the lower to mid 50s. Cold water drownings occur each year with these events but are avoidable by remaining a safe distance from the coastline. Continued vigilance is advised. Additionally, King Tides have returned to the region and will ebb and flood on Monday. Large, long period swell and highest high tides of the year will overlap and allow the intrusion of seawater into low lying areas, generating minor coastal flooding. The highest of the high tides is expected on Monday morning. Thus, the surf zone/area beaches will be hazardous leading up to it and through Monday afternoon. CAZ006-505-509-529-530-102300- /O.NEW.KMTR.CF.Y.0001.210111T1100Z-210111T2300Z/ /O.CON.KMTR.SU.W.0001.210110T1500Z-210111T0500Z/ San Francisco- Coastal North Bay Including Point Reyes National Seashore- San Francisco Peninsula Coast-Northern Monterey Bay- Southern Monterey Bay and Big Sur Coast- 109 AM PST Sun Jan 10 2021 ...HIGH SURF WARNING REMAINS IN EFFECT FROM 7 AM THIS MORNING TO 9 PM PST THIS EVENING... ...COASTAL FLOOD ADVISORY IN EFFECT FROM 3 AM TO 3 PM PST MONDAY... * WHAT...For the High Surf Warning, dangerously large breaking waves of 23 to 28 feet, locally in excess of 30 feet at favored breakpoints. These waves will also result in an increased risk of strong rip currents and coastal erosion. For the Coastal Flood Advisory, minor coastal flooding expected. High tides expected in the mid to late mornings with low tides in the late afternoon to early evenings. The High Tide at San Francisco will meet or exceed 7 feet each morning. * WHERE...San Francisco, Coastal North Bay Including Point Reyes National Seashore, San Francisco Peninsula Coast, Northern Monterey Bay and Southern Monterey Bay and Big Sur Coast. * WHEN...For the High Surf Warning, from 7 AM this morning to 9 PM PST this evening. For the Coastal Flood Advisory, from 3 AM to 3 PM PST Monday. * IMPACTS...For the High Surf Warning, Large breaking waves can sweep people off jetties and rocks, and into dangerous seas. Life-threatening swimming conditions and localized beach erosion can be expected. Cold water rescues or drownings are more likely with these waves and stronger rip currents. For the Coastal Flood Advisory, flooding of lots, parks, and roads with only isolated road closures expected. * ADDITIONAL DETAILS...With a large northwest swell occurring at the same time as the high astronomical tides, larger run up and coastal erosion along coastal areas is possible. PRECAUTIONARY/PREPAREDNESS ACTIONS... If travel is required, allow extra time as some roads may be closed. Do not drive around barricades or through water of unknown depth. Take the necessary actions to protect flood-prone property. Everyone should remain out of the water due to life-threatening surf conditions. Stay off of jetties, piers, and other waterside infrastructure. && $$ CAZ506-102300- /O.NEW.KMTR.CF.Y.0001.210111T1100Z-210111T2300Z/ North Bay Interior Valleys- 109 AM PST Sun Jan 10 2021 ...COASTAL FLOOD ADVISORY IN EFFECT FROM 3 AM TO 3 PM PST MONDAY... * WHAT...Minor coastal flooding expected. * WHERE...Shorelines of the North San Francisco Bay and San Pablo Bay. * WHEN...From 3 AM to 3 PM PST Monday. * IMPACTS...Flooding of lots, parks, and roads with only isolated road closures expected. * ADDITIONAL DETAILS...With a large northwest swell occurring at the same time as the high astronomical tides, larger run up and coastal erosion along coastal areas is possible. PRECAUTIONARY/PREPAREDNESS ACTIONS... If travel is required, allow extra time as some roads may be closed. Do not drive around barricades or through water of unknown depth. Take the necessary actions to protect flood-prone property. && $$
893 WHUS46 KMTR 102139 CFWMTR Coastal Hazard Message National Weather Service San Francisco CA 139 PM PST Sun Jan 10 2021 ...LARGE LONG PERIOD NORTHWEST SWELL WILL BRING HAZARDOUS CONDITIONS ALONG THE COAST THROUGH SUNDAY... ...KING TIDES WILL CAUSE MINOR COASTAL OVERFLOW AND FLOODING MONDAY MORNING THROUGH MONDAY AFTERNOON... .A large, long period northwest will continue to result in breaking waves from 23 to 28 feet, and locally up to 30 feet at favored breakpoints. Thus, a High Surf Warning remains in effect through Sunday evening. While the swell and associated waves begin to subside overnight and into Monday morning, large breaking waves will continue to impact the coast. Additionally, high astronomical tides will coincide with these larger than normal waves to produce minor coastal flooding. The peak of the high tides is expected on Monday morning when the intrusion of seawater into low lying areas is most likely. Thus, a Coastal Flood Advisory has been issued for early Monday morning through Monday afternoon. CAZ006-505-509-529-530-110500- /O.CON.KMTR.SU.W.0001.000000T0000Z-210111T0500Z/ /O.CON.KMTR.CF.Y.0001.210111T1100Z-210111T2300Z/ San Francisco- Coastal North Bay Including Point Reyes National Seashore- San Francisco Peninsula Coast-Northern Monterey Bay- Southern Monterey Bay and Big Sur Coast- 139 PM PST Sun Jan 10 2021 ...HIGH SURF WARNING REMAINS IN EFFECT UNTIL 9 PM PST THIS EVENING... ...COASTAL FLOOD ADVISORY REMAINS IN EFFECT FROM 3 AM TO 3 PM PST MONDAY... * WHAT...For the High Surf Warning, dangerously large breaking waves of 23 to 28 feet, locally in excess of 30 feet at favored breakpoints. These waves will also result in an increased risk of strong rip currents and coastal erosion. For the Coastal Flood Advisory, minor coastal flooding expected. High tides expected in the mid to late mornings with low tides in the late afternoon to early evenings. The High Tide at San Francisco will meet or exceed 7 feet each morning. * WHERE...San Francisco Peninsula Coast, San Francisco, Coastal North Bay Including Point Reyes National Seashore, Southern Monterey Bay and Big Sur Coast and Northern Monterey Bay. * WHEN...For the High Surf Warning, until 9 PM PST this evening. For the Coastal Flood Advisory, from 3 AM to 3 PM PST Monday. * IMPACTS...For the High Surf Warning, Large breaking waves can sweep people off jetties and rocks, and into dangerous seas. Life- threatening swimming conditions and localized beach erosion can be expected. Cold water rescues or drownings are more likely with these waves and stronger rip currents. For the Coastal Flood Advisory, flooding of lots, parks, and roads with only isolated road closures expected. * ADDITIONAL DETAILS...With a large northwest swell occurring at the same time as the high astronomical tides, larger run up and coastal erosion along coastal areas is possible. PRECAUTIONARY/PREPAREDNESS ACTIONS... If travel is required, allow extra time as some roads may be closed. Do not drive around barricades or through water of unknown depth. Take the necessary actions to protect flood-prone property. Everyone should remain out of the water due to life-threatening surf conditions. Stay off of jetties, piers, and other waterside infrastructure. && $$ CAZ506-110500- /O.CON.KMTR.CF.Y.0001.210111T1100Z-210111T2300Z/ North Bay Interior Valleys- 139 PM PST Sun Jan 10 2021 ...COASTAL FLOOD ADVISORY REMAINS IN EFFECT FROM 3 AM TO 3 PM PST MONDAY... * WHAT...Minor coastal flooding expected. * WHERE...North Bay Interior Valleys. * WHEN...From 3 AM to 3 PM PST Monday. * IMPACTS...Flooding of lots, parks, and roads with only isolated road closures expected. * ADDITIONAL DETAILS...With a large northwest swell occurring at the same time as the high astronomical tides, larger run up and coastal erosion along coastal areas is possible. PRECAUTIONARY/PREPAREDNESS ACTIONS... If travel is required, allow extra time as some roads may be closed. Do not drive around barricades or through water of unknown depth. Take the necessary actions to protect flood-prone property. && $$
143 WHUS46 KMTR 110512 CFWMTR Coastal Hazard Message National Weather Service San Francisco CA 912 PM PST Sun Jan 10 2021 ...HIGH SURF WARNING EXPIRED AT 9 PM PST THIS EVENING... ...KING TIDES WILL CAUSE MINOR COASTAL OVERFLOW AND FLOODING MONDAY MORNING THROUGH MONDAY AFTERNOON... .High astronomical tides will coincide with these larger than normal waves to produce minor coastal flooding. The peak of the high tides is expected on Monday morning when the intrusion of seawater into low lying areas is most likely. Thus, a Coastal Flood Advisory has been issued for early Monday morning through Monday afternoon. CAZ006-505-509-529-530-111400- /O.EXP.KMTR.SU.W.0001.000000T0000Z-210111T0500Z/ /O.CON.KMTR.CF.Y.0001.210111T1100Z-210111T2300Z/ San Francisco- Coastal North Bay Including Point Reyes National Seashore- San Francisco Peninsula Coast-Northern Monterey Bay- Southern Monterey Bay and Big Sur Coast- 912 PM PST Sun Jan 10 2021 ...COASTAL FLOOD ADVISORY REMAINS IN EFFECT FROM 3 AM TO 3 PM PST MONDAY... ...HIGH SURF WARNING EXPIRED AT 9 PM PST THIS EVENING... * WHAT...West to northwest swell continuing to decrease overnight through Monday. The High Surf Warning expired at 9 pm PST this evening. At 8 pm swell heights at buoy 59 located 400 miles northwest of San Francisco have lowered to 11 feet every 15 seconds. 8 pm swell heights at Point Arena and Bodega Bay buoys have lowered to 13 to 15 feet with 15 second periods. Strong rip currents and minor coastal erosion are still possible overnight mainly along the southern coastline as swell heights decrease to 15 feet and lower by early Monday morning. For the Coastal Flood Advisory, minor coastal flooding expected. High tides expected in the mid to late mornings with low tides in the late afternoon to early evenings. The High Tide at San Francisco will meet or exceed 7 feet each morning. * WHERE...San Francisco Peninsula Coast, San Francisco, Coastal North Bay Including Point Reyes National Seashore, Southern Monterey Bay and Big Sur Coast and Northern Monterey Bay. * WHEN...For the High Surf Warning, expired at 9 PM PST this evening. For the Coastal Flood Advisory, from 3 AM to 3 PM PST Monday. * IMPACTS...Large breaking waves are often life-threatening and can easily sweep people off jetties and rocks into dangerous seas. Large waves can produce localized beach erosion. Cold water rescues or drownings are more likely with these waves and stronger rip currents. For the Coastal Flood Advisory, flooding of lots, parks, and roads with only isolated road closures expected. * ADDITIONAL DETAILS...With a large northwest swell occurring at the same time as the high astronomical tides, larger run up and coastal erosion along coastal areas is possible. PRECAUTIONARY/PREPAREDNESS ACTIONS... If travel is required, allow extra time as some roads may be closed. Do not drive around barricades or through water of unknown depth. Take the necessary actions to protect flood-prone property. Everyone should remain out of the water due to life-threatening surf conditions. Stay off of jetties, piers, and other waterside infrastructure. && PRECAUTIONARY/PREPAREDNESS ACTIONS... A Coastal Flood Advisory indicates that onshore winds and tides will combine to generate flooding of low areas along the shore. && $$ CAZ506-111400- /O.CON.KMTR.CF.Y.0001.210111T1100Z-210111T2300Z/ North Bay Interior Valleys- 912 PM PST Sun Jan 10 2021 ...COASTAL FLOOD ADVISORY REMAINS IN EFFECT FROM 3 AM TO 3 PM PST MONDAY... * WHAT...Minor coastal flooding expected. * WHERE...North Bay Interior Valleys. * WHEN...From 3 AM to 3 PM PST Monday. * IMPACTS...Flooding of lots, parks, and roads with only isolated road closures expected. * ADDITIONAL DETAILS...With a large northwest swell occurring at the same time as the high astronomical tides, larger run up and coastal erosion along coastal areas is possible. PRECAUTIONARY/PREPAREDNESS ACTIONS... If travel is required, allow extra time as some roads may be closed. Do not drive around barricades or through water of unknown depth. Take the necessary actions to protect flood-prone property. && $$
The office that day
Everything else NWS San Francisco Bay Area, CA issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jan 9, 2:35 AM PST | Small Craft Advisory | MTR | 6 days | |
| Jan 9, 2:42 PM PST | Small Craft Advisory | MTR | 48 hr |
Nearby
High Surf Warnings in California, 2021Every high surf warning in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.