Marine Weather and Tides
9/17/2018 XTide broke when 1and1 "upgraded" my server. It has been esculated. I am sorry for the problem.
|Sunrise 6:58AM||Sunset 7:06PM||Sunday September 23, 2018 5:41 AM PDT (12:41 UTC)||Moonrise 5:49PM||Moonset 4:27AM||Illumination 98%|
7 Day Forecast for Marine Location Near Petaluma, CAHourly EDIT Help
Area Discussion for - San Francisco/Monterey Bay Area, CA  (on/off)  Help NOTE: mouseover dotted underlined text for definition
|Fxus66 kmtr 231147|
area forecast discussion
national weather service san francisco bay area
447 am pdt Sun sep 23 2018
Synopsis An upper level trough moving across far northern
california will likely maintain a cooling trend for inland areas
today. High pressure will begin building inland to our north and
east tonight. This will result in dry offshore winds and fire
weather concerns for the north bay hills from tonight through
Tuesday. Also, expect much warmer conditions by Tuesday and
Wednesday, with temperatures warming well above seasonal
averages. Temperatures will cool late in the week as an upper low
approaches from the west.
Discussion As of 3:30 am pdt Sunday... Water vapor satellite
imagery shows an upper trough beginning to move across the pacific
northwest and far northern california early this morning. Would
typically expect the marine layer to deepen and onshore flow to
increase under such a scenario, but latest observations indicate
this is not happening. In fact, latest fort ord profiler data
shows the marine layer remaining relatively shallow with a depth
of about 1000 feet. Also, onshore pressure gradients have been
trending weaker. In addition, low clouds early this morning are
less extensive compared to 24 hours ago. These factors call into
question previous forecast thinking that the cooling trend would
continue today, especially inland. Based on current trends, the
most likely outcome will be temperatures near persistence in most
areas. And, with less coastal stratus, some coastal areas may
experience slight warming today.
After the upper trough moves off to our east late today, an upper
ridge is forecast to build off the coast of the pacific northwest
and southward along the northern california coast. Also, surface
high pressure will build inland to our north and east by late
tonight, causing winds in the hills to shift from westerly to
north or northeast, especially in the north bay mountains. Locally
gusty offshore winds in the north bay mountains could result in
critical fire weather conditions at higher elevations from tonight
through Tuesday. See fire weather discussion below for details on
the fire weather watch and fire weather concerns.
Building high pressure aloft during the first half of the week and
weak offshore flow will result in a robust warming trend from
Monday through Wednesday. Widespread highs in the 90s are likely
across inland areas by Tuesday and Wednesday. Coastal temperatures
will be more difficult to predict as they will be very dependent
on the strength of offshore flow. Current WRF model indicates
very weak onshore flow will prevail at the surface with light
offshore flow just above. Such a scenario would mean coastal temps
will mostly remain in the 70s to lower 80s. But if offshore flow
is stronger than anticipated, coastal areas could warm well into
the 80s or even a few lower 90s by Tuesday and Wednesday.
The upcoming warm-up will result in uncomfortably warm daytime
conditions across much of our area from Tuesday through Thursday,
but heat risks are expected to remain low to moderate for the most
part due to long autumn nights and cool overnight lows.
A rex block is forecast to develop offshore by midweek as an upper
low begins to undercut the upper high. The models agree that the
low will slowly undercut the ridge and approach the california
coast during the second half of the week. Cooling due to the low's
approach will likely commence as early as Thursday, but only a
slight downturn in temperatures is expected that day. Much more
significant cooling is then anticipated by Friday and Saturday.
Both the ECMWF and GFS generate spotty light precipitation as the
low moves inland by early Saturday. Since this is still 7 days
out, will hold off on adding any rain chances to the forecast.
The longer range models forecast a second upper low to move
onshore by early october. The 00z ECMWF is particularly
interesting with this second system, forecasting widespread
significant rainfall across our area on october 1st and 2nd.
Aviation As of 4:47 am pdt Sunday... In 72 hours it went from|
clear skies (thu) to southerly surge stratus fog (fri) to
widespread coastal stratus fog (sat), and now stratus fog coverage
confined to the immediate coast mainly from san mateo county south
to pt conception including the salinas valley. Satellite also shows
a few patches of stratus and fog near pt reyes.
Inland skies areVFR while on the coast the marine layer remains
compressed favoring vlifr-ifr CIGS and visibilities for the morning.
The 12z tafs are a blend of persistence and WRF model output. A dry
cool frontal boundary, a temporarily steepened northerly pressure
gradient, NW winds and additional compression and downslope drying
has entered the boundary layer reducing the marine stratus and fog
areal coverage as previously described; continuing erosion due to
weak cool air advection, not enough to mix out the marine inversion,
and NW winds should help lift vlifr-ifr toVFR fairly quickly later
on in the morning. Inland skies continueVFR. Low confidence on
stratus and fog coverage tonight into Monday morning.
Vicinity of ksfo...VFR tempo ifr cig 12z-15z. Light westerly wind
increasing by late morning with gusts possible up to 20-25 knots
in the afternoon and evening.VFR forecast tonight and Monday.
Sfo bridge approach... Similar to ksfo.
Monterey bay terminals... Vlifr-ifr til 17z-18z,VFR patchy MVFR late
morning into early afternoon. Ifr probably redeveloping tonight and
Fire weather As of 3:00 am pdt Sunday... Fire weather watch
remains in effect for the north bay mountains from 11 pm Sunday
night through Tuesday afternoon. North to northeast winds will
develop over napa county tonight and drive humidity lower during
the pre-dawn hours of Monday. This offshore wind event looks
moderate, especially in terms of wind strength, but confidence is
pretty high on offshore pattern developing. Fuels remain
critically dry, so any new starts will be susceptible to the
winds, low humidities and dry fuels. Biggest threat area looks to
be napa county hills, northeast sonoma county and around mt tam.
Winds will ease during the day Monday as temperatures warm up
Offshore winds then look to redevelop of similar magnitude Monday
night into Tuesday morning, but with an even drier air mass then
moving in. Overnight humidity recoveries could then well be
confined to around 20 percent or even less. Temperatures are
forecast to continue climbing and widespread 90s are likely across
inland areas Tuesday and Wednesday. But winds are expected to be
light after Tuesday. Cooling is forecast late in the week.
Marine As of 4:06 am pdt Sunday... A trough will remain nearly
stationary along the california coast while strong high pressure
becomes stationary off the pacific northwest coast. Gusty
northwesterly winds will spread across the coastal waters today
while onshore winds become gusty over the bays this afternoon and
evening. An extension of high pressure will build into the
northern great basin tonight and again Monday night into Tuesday.
Winds over the coastal waters and bays will be much lighter by
later Monday, possibly becoming variable or light southerly early
Tuesday morning. Westerly to northwesterly winds return Tuesday
afternoon into Thursday.
Mtr watches warnings advisories
Tday Sca... Pigeon pt to pt pinos 0-10 nm from 9 am
sca... Pt arena to pigeon pt 10-60 nm
sca... Pigeon pt to pt piedras blancas 10-60 nm
sca... Pt pinos to pt piedras blancas 0-10 nm from 9 am
sca... Pt arena to pt reyes 0-10 nm
sca... Mry bay from 2 pm
public forecast: dykema
fire weather: dykema blier rww
visit us at
Weather Reporting StationsEDIT (on/off)  Help NOTE: Click on distance to see the station location on a map
Wind History for Richmond, CA(wind in knots) EDIT (on/off)  Help
Airport ReportsEDIT (on/off)  Help Click EDIT to display multiple airports
|Petaluma Municipal Airport, CA||3 mi||47 min||N 0||7.00 mi||Overcast||48°F||48°F||100%||1011.8 hPa|
|Novato / Gnoss Field, CA||6 mi||67 min||N 0||1.25 mi||Fog/Mist||48°F||46°F||94%||1011.8 hPa|
|Napa, Napa County Airport, CA||17 mi||48 min||N 4||10.00 mi||Fair||49°F||48°F||97%||1010.8 hPa|
|Santa Rosa, Santa Rosa Sonoma County Airport, CA||23 mi||49 min||N 0||10.00 mi||Fair||47°F||45°F||93%||1010.8 hPa|
Wind History from O69 (wind in knots)
|1 day ago||Calm||Calm||Calm||Calm||Calm||Calm||Calm||N||NW||NW||W|
|2 days ago||N||Calm||Calm||Calm||Calm||Calm||Calm||Calm|
EDIT RT Ports Option Weekend mode (on/off) (on/off)  Help One Week of Data
EDIT (on/off)  Help One Week of Data
Weather Map and Satellite Images(on/off)  HelpWeather Map
GOES 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.
Link to Loop
Other links: Northern Pacific Contential US Full GOES-East
Wind Forecast for San Francisco/Monterey Bay Area, CA (8,2,3,4)(on/off)  Help
Ad by Google
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 numerious 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.