Tuesday, January26, 2021
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Marine Weather and Tides
Union City, CA

Version 3.4
NOTICE
1/26/2021 -- The West Coast Satellite images havd been updated. They now use GEOS-17.
1/1/2021 -- The 7 day forecast are now working well. Thank you NOAA for your support.

Sunrise 7:14AMSunset 5:27PM Tuesday January 26, 2021 2:26 PM PST (22:26 UTC) Moonrise 3:26PMMoonset 5:51AM Illumination 98% Phase: Waxing Gibbous; Moon at 13 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- 140 Pm Pst Tue Jan 26 2021
.small craft advisory in effect until 3 pm pst this afternoon...
.storm warning in effect through late tonight...
Today..SE winds 5 to 10 kt, becoming S 15 to 25 kt with gusts up to 30 kt this afternoon. Rain.
Tonight..S winds 25 to 35 kt with gusts up to 55 kt. Rain.
Wed..SE winds 5 to 15 kt with gusts up to 25 kt. Rain.
Wed night..SE winds 15 to 25 kt with gusts up to 30 kt. Rain.
Thu..E winds up to 10 kt. Rain and a slight chance of Thunderstorms.
Thu night..W winds 5 to 10 kt. Rain likely.
Fri..W winds 5 to 15 kt. A chance of rain.
Sat..S winds 5 to 10 kt. A chance of rain. Winds and wind waves higher in and near Thunderstorms.
PZZ500 140 Pm Pst Tue Jan 26 2021
Synopsis for the central california coast and bays including the Monterey bay..Greater farallones...and cordell bank national marine sanctuaries... A large storm classified as an atmospheric river will move across the region late today through the coming days. Strengthening southerly winds will rapidly strengthen to gale to storm force as the front approaches and passes over the waters, with peak gusts in excess of 55kt across the waters. These winds will generate extremely steep fresh southerly seas at a periodicity of 7 to 9 seconds through tonight and will mix with a moderate northwest swell. Periods of heavy rain and isolated Thunderstorms are possible with the frontal passage tonight. Extreme caution is advised. Winds are forecast to weaken but remain breezy to locally gusty in the wake of the front on Wednesday.


7 Day Forecast for Marine Location Near Union City, CA
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location: 37.6, -122     debug


Area Discussion for - San Francisco/Monterey Bay Area, CA
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FXUS66 KMTR 261820 AFDMTR

Area Forecast Discussion National Weather Service San Francisco Bay Area 1020 AM PST Tue Jan 26 2021

SYNOPSIS. Its the calm before the storm. Rain will develop in the North Bay this afternoon then spread southward through the Bay Area overnight with heavy rain and damaging southerly winds. High Wind Warnings and Flash Flood Watches are in effect throughout the region. The Atmospheric River is forecast to stall over Monterey county on Wednesday bringing copious rain to coastal Monterey county while numerous rain showers will persist throughout the Bay Area into Thursday. Shower activity should end by Friday morning with dry weather for much of Friday. A weak front will bring more light rain Saturday with another strong storm possible by early next week.

DISCUSSION. as of 9:36 AM PST Tuesday . No significant short term changes to ongoing forecast. Freeze Warning was allowed to expire at 8 am. Cold temperatures persist across the region ahead of the incoming AR. This is the type of set-up where we could see some lower elevation snow at the onset of precipitation in the North Bay. However, warm frontal structure of incoming boundary will allow snow levels to rise fairly quickly above the hills of the North Bay.

In terms of the incoming AR. Rain to develop in the North Bay this afternoon, initially steady but light to moderate in the warm sector. Rain will overspread the Bay Area creating a messy evening commute. All attention on the cold front associated with the AR and frontal boundary. Expect heavy rain into the North Bay by 02-04z. First concern will be North Bay 2020 burn areas. Short term rain-rates could approach debris-flow thresholds. In addition local flooding of roads, etc will be quick to occur. The main front will pass through the Bay area around midnight. The next focus will then be on the CZU burn area. Short term rain rates approaching 0.75 will be possible as the cold-frontal boundary passes through. The daylight hours of today will be your last chance to make potentially life saving decisions. The heavy rain occurring during the darkness of night along with winds likely to produce power outages in the Santa Cruz mtns will only add to the confusion of the upcoming night.

The one bit of good news with the latest model trends is the boundary should pass through Santa Cruz county fairly quickly with the heaviest rain ending by around sunrise Weds for the CZU burn area. Daylight will reveal what massive logs, debris and mud do when encountered by heavy rain-rates.

The AR is then progged to stall over Monterey County. The hills above Big Sur will be the perfect lifting mechanism to squeeze out moisture as the boundary will stall for upwards of 24 hours. The Dolan, Carmel and River burn areas from 2020 will be of great concern for mud and debris flow issues. Even without those this is the type of event that usually causes numerous rock and mudslides along Highway 1. Residents of Big Sur should be prepared for extended periods of isolation. The 12z nam is showing amounts from 10-14 inches for the Santa Lucia range which is line with our current forecasts. Our local in-house WRF model is showing extensive storm totals in the Big Sur hills in excess of 20 inches with a bullseye amount in excess of 31 inches. Not forecasting that but sharing what type of data we are looking at as the moisture boundary stalls with upwards of 24 plus hours of 1 inch rates possible in the wettest southwest facing slopes of the Santa Lucia range. While the AR is stalled on the Central Coast the Bay Area will see reinforcing waves of rain through the day Weds into Thursday but rain-rates and amounts during this time frame will be more nuisance than flood-causing. Nonetheless unnecessary travel should be avoided throughout the region to reduce car related accidents tonight through Thursday. Expect power outages and downed trees/limbs throughout the region, especially in the hills.

Shower activity should end by sunrise Friday. Another weak system to bring some light rain Saturday with another moderate to strong system possible by around Monday but this one may be more focused over the North Bay in terms of heaviest precip.

PREV DISCUSSION. as of 4:00 AM PST Tuesday . Now for the much talked above Atmospheric River and its impacts to the region. The longwave pattern shows a trough ridge trough pattern over the EPac. The moisture plume associated with the AR is riding up and over the ridge and is now being focus eastward again toward the West Coast. The final eastward push of moisture is being helped by a low pressure system and associated cold front approaching the PacNW this morning. In the big picture, the overall forecast has not changed that much. This AR is still on track to be hazardous to a large portion of NorCal with heavy rains, gusty winds, and a Sierra snow dump. Locally, pre-frontal rains will first develop over the North Bay mid-afternoon before spreading southward to Big Sur by early evening. The initial push of showers will generally be light to moderate. Given the lower snow levels currently over the area the leading edge of precip may actually fall as snow over the higher peaks of the North and East Bay, Santa Cruz Mts, and peaks of Monterey/San Benito. This is a low confidence part of the forecast. If timing is just right, some minor accumulations would be possible.

Rainfall coverage and intensity is forecast to increase rapidly with the cold front once it arrives. The lastest timing for the cold front will be early evening for the North Bay - the heart of SF Bay close to midnight and finally down to Santa Cruz/Monterey/Big Sur early Wednesday morning. Hi- res models are still showing ample dynamics (strong UL divergence and strong LL convergence) with front leading to increased confidence for a NCFR. This scenario definitely increases the likelihood of rain rate thresholds being met for debris flow concerns on 2020 burn areas. NBM/HRRR/HREF all suggest hourly rates >0.5"/hr with peak intensity >0.75"/hr. A Flash Flood Watch is currently in play to cover this potential for debris flow. If you have not already heeded local county advice don't wait any longer. This morning is the time to act and prepare if you're near a burn area.

Once the front/AR makes it to Big Sur models have been advertising a stall with a slight pivot northward late Wednesday into Thursday. Earlier runs did suggest a northward drift back to near Santa Cruz, but that is looking less likely now, which is good for Santa Cruz. Less rainfall totals, but Santa Cruz will still have to deal with the fropa rain rates. Big Sur on the other hand is starting to look like it could get dumped on if the AR does stall. Ensemble guidance and AR model guidance show this scenario with well above normal PWAT with a moderate AR category. The stall/pivot will be key to overall rainfall accumulations. The other wrinkle in the forecast that could impact rain rates with the fropa or overall rainfall accumulations will be thunderstorms. A slight chance of thunder will be possible with fropa and possibly lingering into Thursday.

Rainfall amounts from Tuesday through Thursday haven't changed too much: 2-3" for most lower elevation/urban locations, locally up to 4" in southwest facing locations such as Santa Cruz. Some rain shadowing due to the coastal ranges will occur, but be less pronounced than usual given the stronger surface dynamics. 3-5" will be possible in the North Bay and interior hills/mountains of the South and East Bay. 6-8" in the Santa Cruz Mountains. 7-10" Mts of Monterey and San Benito Counties. Isolated totals in excess of 10.00" cannot be ruled out across the southwest facing coastal slopes along Big Sur. WPC has highlighted much of the forecast area for excessive rainfall - Day 1 has most of the region in a slgt risk for flash flooding and Day 2 slgt risk over Santa Cruz and mdt risk over Big Sur for flash flooding. One other item of note that could lead to increased potential for flash flooding is the snowpack over the Santa Lucia Mts. The snowpack isn't that big, but the highest peaks likely have 5-10 inches with ample rime. Snow melt will enhance runoff to the watersheds in Big Sur.

The front will also pack a dangerous punch in the way of southerly winds. Southerly winds will increase later today and be strongest over the coastal waters, immediate coast, and higher peaks with gusts 50-70 mph possible. A High Wind Warning remains in effect from Tuesday evening through Wednesday. Other areas will also be windy with gusts 35-50 mph with a Wind Advisory in effect.

The AR will finally move southward Thursday morning/afternoon trending diminishing precip from N to S. A few lingering showers will be possible through Friday morning.

An additional rain chances will be possible Friday night into Saturday.

AVIATION. as of 010:10 AM PST Tuesday . For the 18Z TAFs. A very strong storm system, aka atmospheric river, is at the doorstep of the North Bay and will bring significant aviation impacts through the TAF period. The primary impacts will occurs ahead of and with the main frontal boundary which may be accompanied by embedded deeper convection/thunderstorms. Light to breezy winds this morning will become gusty south to southeast winds by this afternoon to evening. Peak wind gusts along the coast and sites near inland SE oriented valleys could range from 50-65kt as the front nears and passes tonight as a LLJ of 60-70kt exists a few thousands feet AGL. Otherwise, rather gusty conditions of 30-50kt and/or unidirectional LLWS will exists a few to several hours prior to the frontal passage during the afternoon. Ceilings of 1500-4000 feet are expected while visibility will drop as low as 1-2SM during the heaviest rain near the front. Winds significantly in the wake of the front but will remain S-SE and breezy. Secondary frontal boundaries are possible later in the week.

Vicinity of KSFO . An atmospheric river is approaching the region. Winds will increase and back towards the southeast through midday then strengthen and become gusty into the afternoon and evening. Very strong winds are possible ahead of and with the frontal boundary, with peak gusts of 45 to 60kt possible. Additionally, mod to heavy rainfall should be anticipated prior to and with fropa with lighter persistent rain through the TAF period w/ wet run ways. Visibilities will drop as low as 1-2SM during heaviest rain with BKN/OVC cigs 1500-3500 feet. Winds taper off post frontal by tomorrow morning but will remain SE and breezy.

SFO Bridge Approach . Similar to KSFO, lower visibility upon approach during periods of heaviest rain.

Monterey Bay Terminals . Breezy SE winds will gradually strengthen to become very strong and gusty as an atmospheric river approaches the Central Coast terminals. Peak wind gusts of 40-65kt are possible ahead and with the frontal boundary overnight tonight. Additionally,mod to heavy rainfall should be anticipated prior to and with fropa with lighter persistent rain through the TAF period w/ wet run ways. Visibilities will drop as low as 1-2SM during heaviest rain with BKN/OVC cigs 1500-3500 feet. Refer to specific TAFs for LLWS concerns.

MARINE. as of 09:59 AM PST Tuesday . Northwest winds have diminished, but continue with stronger gusts this morning with squared seas around 11 to 13 feet at 11 to 13 seconds. A large storm classified as an atmospheric river approaches the Bay Area that will drastically shift winds to the south to southwest later this morning along its leading front before storm force winds develop Tuesday afternoon across the northern waters then expand southward by late Tuesday. Heavy rain is expected and occasional thunder is possible with the atmospheric river. Strong south to southwest winds and very steep southerly seas at 7 to 9 seconds will result in hazardous conditions across the coastal waters through mid- week. Extreme caution is advised.

MTR WATCHES/WARNINGS/ADVISORIES. Tday. Flash Flood Watch . CAZ505>507-509-511-512-517 SCA . Pt Arena to Pt Reyes 0-10 nm until 3 PM SCA . Pt Reyes to Pigeon Pt 0-10 nm until 3 PM SCA . Pt Arena to Pigeon Pt 10-60 nm until 3 PM SCA . Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 PM SRW . SF Bay from 3 PM SRW . Pt Arena to Pt Reyes 0-10 nm from 3 PM SRW . Pt Reyes to Pigeon Pt 0-10 nm from 3 PM SRW . Pt Arena to Pigeon Pt 10-60 nm from 3 PM SCA . SF Bay from 10 AM until 3 PM



PUBLIC FORECAST: RWW/MM AVIATION: DRP MARINE: DRP

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Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
RTYC1 - 9414523 - Redwood City, CA 13 mi146 min SSE 5.1 G 8.9 50°F 52°F1015.7 hPa (-0.3)
AAMC1 - 9414750 - Alameda, CA 20 mi146 min ESE 8.9 G 13 47°F 51°F1015.3 hPa (+0.0)
LNDC1 20 mi146 min SSE 9.9 G 12 47°F 1015 hPa (+0.0)
OMHC1 - 9414769 - Oakland Middle Harbor Met, CA 22 mi146 min SE 12 G 16
OBXC1 23 mi146 min 47°F 37°F
OKXC1 - 9414776 - Oakland (Berth 34), CA 23 mi146 min SSE 11 G 15 47°F 1015 hPa (+0.0)
PXSC1 25 mi146 min 49°F 42°F
PXOC1 - 9414311 - San Francisco (Pier 1), CA 25 mi146 min SE 14 G 16 47°F 1013.8 hPa (+0.0)
PPXC1 - 9414847 - Richmond (Point Potrero), CA 29 mi146 min SSE 12 G 17 48°F 1015.2 hPa (+0.0)
FTPC1 - 9414290 - San Francisco, CA 29 mi146 min SSW 7 G 12 49°F 52°F1015 hPa (+0.0)
TIBC1 - Tiburon Pier, San Francisco Bay, CA 31 mi135 min SE 5.1 48°F 1014 hPa
RCMC1 - 9414863 - Richmond, CA 31 mi146 min SSE 8 G 13 48°F 52°F1014.8 hPa (+0.0)
PSBC1 - 9415115 - Pittsburg (Suisun Bay), CA 31 mi146 min W 8.9 G 14 50°F 1014.8 hPa (+0.0)
UPBC1 31 mi146 min SW 8.9 G 12
MZXC1 - 9415102 - Martinez-Amorco CA 31 mi146 min SSW 8.9 G 11 48°F 51°F1014.9 hPa (+0.0)
PCOC1 - 9415144 - Port Chicago, CA 32 mi146 min SSW 6 G 12 50°F 51°F1014.8 hPa (+0.0)
DPXC1 - 9415141 - Davis Point, San Pablo Bay, CA 34 mi146 min SSW 8 G 12 48°F 1014.4 hPa (-0.4)
CQUC1 34 mi127 min 50°F
46237 - San Francisco Bar, CA (142) 36 mi146 min 50°F7 ft
SFXC1 - San Francisco Bay Reserve, CA 41 mi161 min SSW 9.9 50°F 1015 hPa33°F
46269 46 mi146 min 47°F 52°F7 ft
46026 - SAN FRANCISCO - 18NM West of San Francisco, CA 46 mi126 min S 14 G 18 51°F1014.5 hPa

Wind History for Redwood City, CA
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Hayward, Hayward Air Terminal, CA8 mi32 minSSE 1310.00 miMostly Cloudy51°F34°F52%1014.3 hPa
Palo Alto Airport, CA10 mi2.5 hrsSE 710.00 miMostly Cloudy48°F34°F58%1015.9 hPa
Livermore, Livermore Municipal Airport, CA12 mi33 minS 1110.00 miOvercast49°F31°F50%1013.4 hPa
Mountain View, Moffett Field, CA12 mi36 minSSE 7 G 1510.00 miMostly Cloudy50°F36°F58%1013.9 hPa
Oakland, Metro Oakland International Airport, CA14 mi33 minSSE 1510.00 miOvercast54°F36°F51%1013.4 hPa
San Carlos Airport, CA14 mi29 minSSE 12 G 1610.00 miLight Rain50°F32°F50%1013.9 hPa
San Jose, San Jose International Airport, CA16 mi33 minS 1110.00 miOvercast51°F34°F52%1014.1 hPa
San Francisco, San Francisco International Airport, CA19 mi30 minS 1510.00 miOvercast52°F36°F55%1013 hPa
San Jose / Reid / Hillv, CA20 mi39 minSSE 910.00 miMostly Cloudy52°F34°F50%1014.6 hPa

Link to 5 minute data for KHWD

Wind History from HWD (wind in knots)
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W16W12NW8--NW8NW4CalmCalmN3NE3CalmSE3E5NE3E4E4SE8S11S6S9S10SE13
1 day agoW7S7SW5S5S9N11NW14
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2 days agoW13W11W9W5W5W3E5E3CalmE4CalmCalmE3SE7SE7SE10SE9S8SE4SW9S8W11W10W10

Tide / Current Tables for Coyote Hills Slough entrance, San Francisco Bay, California
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Coyote Hills Slough entrance
Click for Map
Tue -- 05:38 AM PST     1.45 feet Low Tide
Tue -- 05:51 AM PST     Moonset
Tue -- 07:16 AM PST     Sunrise
Tue -- 10:06 AM PST     7.31 feet High Tide
Tue -- 03:26 PM PST     Moonrise
Tue -- 05:26 PM PST     Sunset
Tue -- 06:41 PM PST     -0.24 feet Low Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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5.354.23.22.21.61.52.64.46.37.37.16.55.44.12.61.40.4-0.1-0.20.51.73.14.5

Tide / Current Tables for Dumbarton Hwy Bridge, South San Francisco Bay, California Current
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Dumbarton Hwy Bridge
Click for Map
Tue -- 12:08 AM PST     -0.00 knots Slack
Tue -- 02:40 AM PST     -0.52 knots Max Ebb
Tue -- 05:19 AM PST     0.00 knots Slack
Tue -- 05:50 AM PST     Moonset
Tue -- 07:15 AM PST     Sunrise
Tue -- 08:21 AM PST     1.18 knots Max Flood
Tue -- 10:57 AM PST     -0.00 knots Slack
Tue -- 02:48 PM PST     -1.40 knots Max Ebb
Tue -- 03:26 PM PST     Moonrise
Tue -- 05:26 PM PST     Sunset
Tue -- 06:24 PM PST     0.01 knots Slack
Tue -- 09:40 PM PST     1.75 knots Max Flood
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.1-0.3-0.5-0.5-0.4-0.10.40.91.21.10.7-0-0.5-1-1.3-1.4-1.2-0.8-0.30.51.31.71.71.4

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Disclaimer:
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.