Sunday, January17, 2021
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Marine Weather and Tides
Half Moon Bay, CA

Version 3.4
NOTICE
8/26/2020 The 7 day forecast is taking about 5 seconds to load but it will eventually load. NOAA is still working on it.
8/18/2020 NOAA continues to have trouble. Wind guest will occasionally be left off graphs. I am working with NOAA to resolve the issue.
12/16/2019 NOAA is having trouble with requests that include wind gusts. I am posting graphs without wind gusts until it gets fixed.
10/9/2019 Updated the Marine Zones.
9/4/2019 Fixed the weather maps due to NOAA moving them.
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.

Sunrise 7:20AMSunset 5:18PM Sunday January 17, 2021 1:52 AM PST (09:52 UTC) Moonrise 10:28AMMoonset 10:09PM Illumination 16% Phase: Waxing Crescent; Moon at 4 days in cycle
NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION.
Marine Forecasts
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PZZ531 San Francisco Bay South Of The Bay Bridge- 829 Pm Pst Sat Jan 16 2021
Tonight..NW winds up to 10 kt.
Sun..NW winds up to 10 kt.
Sun night..W winds up to 10 kt.
Martin luther king jr day..N winds 15 to 25 kt with gusts up to 35 kt.
Mon night..N winds 20 to 30 kt with gusts up to 45 kt.
Tue..N winds 30 to 40 kt with gusts up to 50 kt.
Tue night..NE winds 5 to 15 kt.
Wed..N winds around 5 kt.
Thu..NW winds 5 to 10 kt.
PZZ500 829 Pm Pst Sat Jan 16 2021
Synopsis for the central california coast and bays including the Monterey bay..Greater farallones...and cordell bank national marine sanctuaries... Increasing northwest winds through the night. As seas and breezy winds combine for hazardous seas conditions, particularly for smaller vessels. Winds will shift more northerly tomorrow to tomorrow night and increase as offshore winds pick up over land. These stronger winds will then continue into early next week with gale force conditions likely. The next large, long period northwest swell will arrive Sunday.


7 Day Forecast for Marine Location Near Half Moon Bay, CA
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location: 37.47, -122.48     debug


Area Discussion for - San Francisco/Monterey Bay Area, CA
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FXUS66 KMTR 170543 AFDMTR

Area Forecast Discussion National Weather Service San Francisco Bay Area 943 PM PST Sat Jan 16 2021

SYNOPSIS. A warming and drying trend will continue through this weekend as high pressure builds over the state. Two back to back low pressure systems to our east will produce breezy to gusty offshore flow Sunday night through Tuesday evening. Cooling trend is forecast from Wednesday through Friday.

DISCUSSION. as of 09:03 PM PST Saturday . A little excitement to end the day as the staff here felt a 4.5 magnitude earthquake at the office in Monterey.

It felt and looked a little like summer today despite the calendar saying January. Afternoon highs were generally in the 60s and 70s again with even a few more in the 80s. The region tied a record of 70 at Kentfield and broke a record at Livermore with high a of 76. Similar to yesterday high temperatures of this magnitude are running 10-20 degrees above normal. The look of summer? A very shallow marine layer developed along the North Bay Coast and slid southward through the day. Given the shallow nature it resulted in fog along the immediate coast. Additionally, the afternoon clouds/fog created a sharp temperature gradient along the coast of 10-15 degrees in some places. Expect some patchy fog/low clouds locally along the coast tonight and early tomorrow.

Another warm day is expected again Sunday with highs in the 60s/70s and a few interior 80s. May be able to squeeze out another record high temperature too.

A majority of the focus through Tuesday quickly turns to wind. As noted below it looks like the Bay Area is in store for a good push of wind beginning Sunday evening and continuing through Tuesday. What's impressive is the time of year for offshore flow, duration, and coverage. The latest guidance from the 00Z deterministic runs show a stout offshore gradient from SFO-WMC just under -20mb. Will leave Wind Advisory as it for now starting Sunday evening and continuing through Tuesday. If anything there still appears to be a bigger burst of wind Monday night/Tuesday. As hi-res models capture the Monday night timeframe we may need to upgrade to a high wind warning.

PREV DISCUSSION. as of 02:05 PM PST Saturday . Pinch. Yes, it is January. About the only way we can tell right now is due to a highly active North Pacific that has produced some of the most consistent swell/surf for our area in recent memory. Otherwise a stout upper ridge is dominating the Bay Area and Monterey Bay region, bringing unseasonably warm and dry conditions. Today there has been a weak offshore component to the winds up a few thousand feet. This has really toyed with our area microclimates to the point that we have seen some serious nano climates. A RAWS site down toward Big Sur popped to 90 today, where two ridges away it was only in the mid 70s. This is the power of wind on air in action.

While the offshore flow has only played with the temperatures today, Sunday evening will bring a wholesale shift in what wind can do. The upper ridge that has been dominate for the last several days will be pushed on by upper low pressure as it dives from the north over California. This will setup a tightening pressure gradient across the Bay Area and Monterey Bay regions. Current model forecast are indicating a strong SFO-WMC gradient on the order of 13 to 17 mb, which is a significant offshore wind set up. EC ENS mean standardized anomalies are showing 2 to 3 standard deviations. In short, this is a solid offshore event taking shape. While we have seen strong offshore wind events in the past, the piece that makes this one stand out is the spatial coverage. Typically in our "offshore season", October, we see set ups favor an area such as North Bay. This time around we're looking 925mb winds in the 40 to 55 kt range from North Bay through Monterey County. This is a widespread event.

Two pieces to cover. 1) The wind itself. Sustained winds are forecast to be in the 5 to 20 mph range though populated areas, with the exact value being location dependent. Sustained winds in the hills and mountains are forecast to be in the 15 to 30 mph range. However, in events like this, it's the gusts that really do the damage. Occasional gusts in valley populated locations could be in the 20 to 45 mph range, again depending upon location. While in the hills and mountains, expect to see maximum gusts reach 45 to 60 mph range with the possibility of an isolated site or two trying to jump into the 70+ arena. Winds are dangerous in general due to fall and blowing trees and debris, but a mid-dry- winter wind event like this can be especially concerning for life and property safety. Branches are dry and brittle in many areas which means they are prone to break and fall, while trees may simply topple in some of the stronger gusts. Please know your risk. Take care of anything you need to take of before the wind hits Sunday evening. Wind statistically is the second leading cause of death due to weather in our area. Too many people have lost their lives to falling trees. 2) While we have seen a little rain this winter, it hasn't been a lot and most areas are running about 30% of average on the water year thus far. The rain we have had has helped the larger trees (fuels) to get some moisture in them. However, the fine fuels such as grasses and bushes moisten up quickly and dry out quickly. With the dry warm weather that has been occurring the last few days has shown itself in the fine fuels. Many areas have brown grasses and bone dry shrubs. With the wind set up locking in, fire becomes a concern, mainly in the grasses. Think of it like an early fire season set up. We have dry grasses, gusty winds coming, and plummeting relative humidities. Since the larger fuels still have moisture, we are not thinking of a red flag warning at this point, but will be watching closely each shift to analyze incoming data. In short, fire concerns exist. Be fire smart, don't be that spark.

Looking down the road of the week, models continue to hold on to a slight pattern shift toward the end of the week with a slight chance of rain on Friday. Don't get your hopes up though, the QPF doesn't look that great. Either way, it'd be good to have a cool down and at least a chance of a few drops of rain.

AVIATION. as of 09:42 PM PST Saturday . For the 06Z TAFs. VFR over most of the terminals, but in an almost summer-like set up, stratus has formed over the ocean, stretching from the San Francisco Peninsula southward down the Big Sur Coast. The main impacts so far with the stratus has been locally LIFR conditions on the Monterey Peninsula. Stratus should weaken through the night as offshore winds aloft increase. These winds aloft provide a chance LLWS of about 25-30 kt through Sunday morning and into the early afternoon. VFR conditions are expected on Sunday with breezy onshore winds. Offshore winds aloft will then once again increase Sunday night with the next chance for LLWS around 12z Monday.

Vicinity of KSFO . Stratus is expected to remain out over the ocean, but a few clouds around 400 ft may move over the terminal tonight. Winds aloft will increase and become offshore helping quell low cloud development. However winds loft are expected between 25-30 kts leaving LLWS is in the early morning TAF. Surface winds will increase Sunday afternoon and be onshore with VFR conditions. As winds weaken under mostly clear skies Sunday night, expected round 2 of LLWS as offshore winds aloft increase yet again after 10z.

SFO Bridge Approach . Similar to KSFO.

Monterey Bay Terminals . The stratus deck has continuously moved over and back out from terminals through the night. It's looking like it is getting quite comfortable . at least in the short term. Winds aloft are expected to increase, not enough for LLWS, but enough to help dissipate some of the cloud cover. However, if those offshore winds aloft don't materialize this far south, it's possible for the stratus to remain through the night. VFR is forecast for Sunday with breezy onshore winds. Models are indicating another chance for stratus build up late on Sunday night, but remains outside this TAF package.

BEACHES. as of 07:08 PM PST Saturday . A large, long period northwest swell arrives on Sunday morning and will result in hazardous conditions in the surf zone through Monday afternoon. Forerunners are expected to arrive at 3 to 7 feet with a period of 22 to 24 seconds, increasing the risk of sneaker waves. Swell heights are then expected to build through Sunday with breaking waves of 18 to 22 feet, locally higher at favored breakpoints, expected along west to northwest facing beaches. As a result, a High Surf Advisory is in effect through Monday afternoon for west and northwest facing beaches while a Beach Hazard Statement has been issued for the northern Monterey Bay including Santa Cruz. With unseasonably warm temperatures this holiday weekend, it will likely attract more people to the coast. Individuals should be reminded that our coastline and the cold Pacific waters remain dangerous as these larger than normal waves impact the coast. Extreme caution is advised when visiting area beaches. Never turn your back to the ocean.

CLIMATE. Record Type: Highs (Old Record Temp/Year)

Jan 16th Jan 17th Jan 18th

Santa Rosa 74/1991 71/1991 74/1976 Kentfield 70/2009 71/1994 70/2014 Napa 76/1920 72/1920 76/1920 Richmond 74/2014 73/2009 71/2018 Livermore 75/1920 70/1986 74/1919 San Francisco 72/2014 73/1991 70/1920 SFO 73/2014 70/1991 68/1948 Redwood City 74/2014 77/1948 74/2009 Half Moon Bay 76/2014* 75/2009 72/2009 Oakland Downtown 78/2014* 74/2014 73/2014 San Jose 73/2014 76/1920 74/1920 Gilroy 76/2014 77/2014 80/2014* Santa Cruz 84/2014 83/2014 83/1920 Salinas Airport 84/2014 86/2014* 81/1994 King City 85/1976 86/2014* 83/2009

*Monthly Records

MARINE. as of 08:29 PM PST Saturday . Increasing northwest winds through the night. As seas and breezy winds combine for hazardous seas conditions, particularly for smaller vessels. Winds will shift more northerly tomorrow to tomorrow night and increase as offshore winds pick up over land. These stronger winds will then continue into early next week with gale force conditions likely. The next large, long period northwest swell will arrive Sunday.

MTR WATCHES/WARNINGS/ADVISORIES. Tngt. SCA . Pt Arena to Pt Reyes 0-10 nm SCA . Pt Arena to Pigeon Pt 10-60 nm SCA . Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM SCA . Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM



PUBLIC FORECAST: MM/BFG AVIATION: DK MARINE: DK

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Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
RTYC1 - 9414523 - Redwood City, CA 14 mi59 min W 1 G 1.9 51°F 56°F1020.6 hPa
46012 - HALF MOON BAY - 24NM South Southwest of San Francisco, CA 23 mi33 min NNW 12 G 14 54°F 1019.9 hPa52°F
FTPC1 - 9414290 - San Francisco, CA 23 mi59 min Calm G 1 52°F 54°F1020.2 hPa
46237 - San Francisco Bar, CA (142) 23 mi53 min 52°F9 ft
PXSC1 23 mi59 min 54°F
AAMC1 - 9414750 - Alameda, CA 23 mi59 min NW 1 G 1 53°F 53°F1020.3 hPa
PXOC1 - 9414311 - San Francisco (Pier 1), CA 23 mi59 min Calm G 1.9 53°F 1019 hPa
OMHC1 - 9414769 - Oakland Middle Harbor Met, CA 24 mi65 min W 1 G 1.9
OBXC1 24 mi59 min 53°F 53°F
LNDC1 25 mi59 min NW 1 G 1.9 52°F 1020.1 hPa
OKXC1 - 9414776 - Oakland (Berth 34), CA 25 mi59 min Calm G 1 52°F 1020.1 hPa
46026 - SAN FRANCISCO - 18NM West of San Francisco, CA 27 mi33 min NNE 5.8 G 7.8 53°F1020.2 hPa
TIBC1 - Tiburon Pier, San Francisco Bay, CA 29 mi72 min Calm 51°F 1020 hPa
PPXC1 - 9414847 - Richmond (Point Potrero), CA 31 mi59 min Calm G 1.9 54°F 1020.5 hPa
RCMC1 - 9414863 - Richmond, CA 32 mi59 min Calm G 1.9 53°F 53°F1020.1 hPa
DPXC1 - 9415141 - Davis Point, San Pablo Bay, CA 42 mi59 min ESE 2.9 G 4.1 52°F 1019.8 hPa
MZXC1 - 9415102 - Martinez-Amorco CA 43 mi59 min SW 2.9 G 4.1 53°F 52°F1020.4 hPa
CQUC1 43 mi70 min 52°F
46269 44 mi53 min 49°F 54°F7 ft
UPBC1 44 mi59 min W 5.1 G 6
PCOC1 - 9415144 - Port Chicago, CA 47 mi59 min SSW 2.9 G 5.1 54°F 52°F1020.1 hPa
46042 - MONTEREY - 27NM West of Monterey Bay, CA 48 mi33 min NNW 7.8 G 12 53°F 53°F1019.3 hPa52°F

Wind History for Redwood City, CA
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Half Moon Bay Airport, CA3 mi58 minNNW 31.50 miFog/Mist45°F45°F100%1020 hPa
San Francisco, San Francisco International Airport, CA12 mi57 minN 010.00 miFair51°F47°F86%1019.9 hPa
San Carlos Airport, CA13 mi58 minN 010.00 miFair48°F48°F100%1020.3 hPa
Oakland, Metro Oakland International Airport, CA21 mi60 minN 010.00 miShallow Fog51°F47°F86%1020.3 hPa
Hayward, Hayward Air Terminal, CA23 mi59 minN 010.00 miFair49°F45°F86%1020.8 hPa
Mountain View, Moffett Field, CA23 mi58 minN 010.00 miFair48°F46°F94%1020 hPa

Link to 5 minute data for KHAF

Wind History from HAF (wind in knots)
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Last 24hrN6N6NW5N4N5N3N9N7NW13NW12
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N9--N7N3N4CalmCalmCalmCalmNW6
1 day agoCalmCalmW3CalmSE5NW4CalmCalmCalmS5W3N13
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Tide / Current Tables for Half Moon Bay, California
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Half Moon Bay
Click for Map
Sun -- 02:00 AM PST     4.93 feet High Tide
Sun -- 07:22 AM PST     Sunrise
Sun -- 07:31 AM PST     2.65 feet Low Tide
Sun -- 10:27 AM PST     Moonrise
Sun -- 12:55 PM PST     4.88 feet High Tide
Sun -- 05:18 PM PST     Sunset
Sun -- 07:41 PM PST     0.35 feet Low Tide
Sun -- 10:09 PM PST     Moonset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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3.94.74.94.74.23.632.72.733.64.24.74.94.6431.910.50.40.81.52.5

Tide / Current Tables for San Mateo Bridge, South San Francisco Bay, California Current
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San Mateo Bridge
Click for Map
Sun -- 01:09 AM PST     1.68 knots Max Flood
Sun -- 04:47 AM PST     -0.01 knots Slack
Sun -- 07:21 AM PST     Sunrise
Sun -- 07:29 AM PST     -0.95 knots Max Ebb
Sun -- 10:26 AM PST     Moonrise
Sun -- 10:34 AM PST     0.00 knots Slack
Sun -- 01:02 PM PST     1.05 knots Max Flood
Sun -- 04:07 PM PST     -0.00 knots Slack
Sun -- 05:16 PM PST     Sunset
Sun -- 07:34 PM PST     -1.45 knots Max Ebb
Sun -- 10:08 PM PST     Moonset
Sun -- 10:59 PM PST     0.01 knots Slack
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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1.41.71.61.20.6-0.1-0.7-0.9-0.9-0.7-0.30.30.81.10.90.60.1-0.5-1.1-1.4-1.4-1.1-0.60

Weather Map
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wmap_P
GEOS Local Image of CentralWestCoast    EDIT
NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
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The information on this web site has not been checked for accuracy. It is for entertainment purposes only and should be independently verified before using for any other reason. There are five sources. 1) Documents and manuals from a variety of sources. These have not been checked for accuracy and in many cases have not even been read by anyone associated with L-36.com. I have no idea of they are useful or accurate, I leave that to the reader. 2) Articles others have written and submitted. If you have questions on these, please contact the author. 3) Articles that represent my personal opinions. These are intended to promote thought and for entertainment. These are not intended to be fact, they are my opinions. 4) Small programs that generate result presented on a web page. Like any computer program, these may and in some cases do have errors. Almost all of these also make simplifying assumptions so they are not totally accurate even if there are no errors. Please verify all results. 5) Weather information is from numerous of sources and is presented automatically. It is not checked for accuracy either by anyone at L-36.com or by the source which is typically the US Government. See the NOAA web site for their disclaimer. Finally, tide and current data on this site is from 2007 and 2008 data bases, which may contain even older data. Changes in harbors due to building or dredging change tides and currents and for that reason many of the locations presented are no longer supported by newer data bases. For example, there is very little tidal current data in newer data bases so current data is likely wrong to some extent. This data is NOT FOR NAVIGATION. See the XTide disclaimer for details. In addition, tide and current are influenced by storms, river flow, and other factors beyond the ability of any predictive program.