Monterey Bay Marine Forecast
|Rest Of Today...W Winds 15 To 25 Kt With Gusts Up To 30 Kt. Wind Waves 6 To 7 Ft. W Swell Around 2 Ft At 11 Seconds.|
|Tonight...W Winds 10 To 20 Kt With Gusts Up To 30 Kt. Wind Waves 8 To 9 Ft. Nw Swell Around 2 Ft At 11 Seconds.|
|Sun...W Winds 15 To 25 Kt With Gusts Up To 30 Kt. Wind Waves 7 To 8 Ft. Nw Swell Around 2 Ft At 11 Seconds.|
|Sun Night...Nw Winds 10 To 20 Kt With Gusts Up To 30 Kt. Wind Waves 7 To 8 Ft. Nw Swell Around 2 Ft At 11 Seconds.|
|Mon...W Winds 5 To 15 Kt. Wind Waves 6 To 7 Ft. W Swell Around 2 Ft At 11 Seconds.|
|Mon Night...W Winds Up To 10 Kt. Wind Waves 6 To 7 Ft. Nw Swell Around 2 Ft At 11 Seconds.|
|Tue...Sw Winds 5 To 15 Kt. Wind Waves 5 To 6 Ft. W Swell 2 To 3 Ft.|
|Wed...W Winds Up To 10 Kt. Wind Waves Around 5 Ft. W Swell Around 2 Ft. Locally Lower Winds And Seas Across Sheltered Portions Of The Bay.|
|226 PM PDT Sat May 8 2021 .Synopsis for the Central California Coast and Bays Including the Monterey Bay...Greater Farallones...and Cordell Bank National Marine Sanctuaries... A 1035 mb high over the eastern Pacific will remain nearly stationary while a thermal trough of low pressure will develop near Cape mendocino. This will keep strong northerly winds blowing over the coastal waters with the strongest winds offshore and west of Point Reyes. The strong northerly winds will produce large wind waves over a small northwest swell. Breezy north winds to continue at least through early next week with lighter NW winds by Tuesday and Wednesday as the pressure gradient eases.|
| Area Forecast Discussion|
National Weather Service San Francisco Bay Area
128pm PDT Sat May 8 2021
An early season offshore wind event will result in critical fire weather conditions across portions of the North and East Bay through early Monday. A Red Flag Warning is in effect through 6 am Monday for the North Bay mountains and the East Bay Hills as well as the East Bay Interior Valleys. Otherwise, expect a sunny and pleasant weekend with mild temperatures near the ocean and bays and warm temperatures inland. Offshore winds will ease by Monday, but high pressure will maintain inland warmth through midweek. A cooling trend is forecast for the second half of next week.
as of 01:24pm PDT Saturday...The current ridging pattern continues to offer gusty offshore winds especially over higher elevations in the North and East Bay. Mt St Helena saw some reduction in winds during the late morning, going from 70+ mph gusts to gusts around 50 mph, but the winds have become more widespread around the San Francisco Bay. A few lower elevation obs around the Bay Area reporting 15 to 25 mph gusts and these winds look to last into the late afternoon. The dry, offshore flow will also allow for temperatures to rise to well above average highs for the afternoon with a few interior locations peaking in the 90s.
By nightfall, winds will focus again on the mid to higher elevations in the North and East Bay. This combined with poor nighttime humidity recoveries, continues fire weather concerns. For more information on the fire weather conditions, please see the "Fire Weather" section below.
Sunday offers a minor shortwave trough which will weaken the offshore flow during the day, and may slightly reduce the afternoon high temperatures. This cooling may only result in a few degrees difference in most areas compared to Saturday afternoon. Unfortunately the trough will move South and East into that evening, allowing for winds to strengthen into the late night again for higher elevations in the North and East Bay.
The ridging pattern continues for Monday and Tuesday, calling for both afternoons to see well above average temperatures and dry conditions. Tuesday, however, sees the ridge move more eastward, decreasing the offshore flow, and weakening the overnight winds.
Further into the next work week: The ridging pattern begins to flatten for the Bay Area and the longer term models and ensembles see this as a start for a cooling trend. Coastal areas will see more immediate results in this trend but even the most interior locations look to fall around 5 degrees below average for the next weekend.
As far as precipitation is concerned, the ECMWF (European Centre for Medium-Range Weather Forecasts) and a fair portion of its ensemble families lean on a trough developing after the 220 hour mark in the forecast and bringing in rain chances. The deterministic model keeps this trough on the narrow side and prevents rain chances from becoming widespread. Between the amount of time out this forecast is and how much of a threading of a needle this output is, there isn't too much confidence in the ECMWF verifying. Other models and ensembles follow more of the common/seasonal flow, which keeps the Bay Area dry.
As of 12:54pm PDT Saturday...No planned changes at this time to the ongoing Red Flag Warning. Its in effect for zones 507/510/511 through 6 am Monday. It may need to be extended but will leave as is for now while the pattern/event is still evolving. So far the event has unfolded as expected but if anything humidity is lower than expected and gusty offshore winds slightly stronger than models were indicating. General idea was this would be a moderate early season event. The northerly gradient from SFO to Arcata peaked around 10 mb last night (thats strong) and is producing gale force winds over the ocean and the strong winds across the hills. The offshore gradient from the Nevada desert was never forecast to be strong during this event and is currently around 6 mb, so this is more of a north vs offshore pattern. Often times the marine layer and associated air can be tough to scour out, especially when the local SFO to Sac gradient remains onshore. We are holding onto west winds along the coast and into the Bay. Despite that humidity values are crashing to some pretty extreme readings with values from 7-9% at places like Napa/Concord and Livermore. We often will only see single digit values down across interior Monterey/San Benito. So we clearly have dry air in place. Hard not to imagine that the drought and low soil moisture is at least in part leading to such low humidity. Values this low help to lower the fuel moisture readings and can exacerbate fire behavior and spotting/ignition potential.
For this afternoon expect northerly winds to continue across the Warning area with a gradual decrease this evening but no big downward trend in wind speeds. Models do indicate some humidity recovery overnight but that may be overstated. Given current trends and expected synoptic pattern not expecting much recovery above 30% for the current warning locations.
Expect another warm and dry day on Sunday with steady/dry northerly breezes across the region. Latest fuel analysis shows values at or near record dryness. In this type of pattern a few days of hot/dry/breezy weather will rapidly dry out the fine fuels and impact the ERC values adversely.
On Sunday night there could be another uptick in winds, especially across the Napa hills with gusts in the 45-55 mph range. Will continue to monitor the current end time of 6 am Monday. Warning may need to be extended as Monday looks to continue a similar pattern of persistent offshore winds, warm temps and low humidity.
Latest trends now show possibly another uptick in winds Monday night into Tuesday as the next shortwave drops into the Great Basin. Under this pattern we turn more Northeast/east in direction with continued drying through the day Tuesday.
Pretty high confidence that pattern turns onshore by Weds as the ridge flattens and shifts eastward. Pattern looks more seasonable 2nd half of the week into next weekend with onshore winds and near normal temps. Extended range does suggest a trough beyond mid month with at least some cooler wx. The biggest impact from these early May heat/drying events can be to really dry the fuels. Ahead of the June 2008 lightning event we had record heat in mid May 2008.
as of 01:24pm PDT Saturday...Stationary surface high pressure over the eastern Pacific will result in additional northwest gales over most of the coastal waters with afternoon and evening gusty west to northwest winds over the bays. Seas dominated by wind driven waves with a small northwest swell.
.MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...Red Flag Warning...CAZ507-510-511 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 GLW...Pt Arena to Pigeon Pt 10-60 nm GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm SCA...SF Bay until 9 PM SCA...Mry Bay until 9 PM