windspeed.info --- SF Bay Area wind/weather information by e-mail. $Header: /mnt/zonker.u1/poulton/weather/ftp/RCS/windspeed.info,v 1.52 2006/05/08 19:23:37 poulton Exp $ === Windspeed mailing lists === These lists are maintained by listserv "AT" opus.scs.agilent.com : wind_afternoon Automatic hourly wind reports from noon to 6 pm daily. wind_thresh Automatic wind reports when the wind is over 15 knots (during daylight hours). wind_24 Automatic wind reports every hour. wind_talk Discussion other than current wind reports. To unsubscribe: send e-mail to listserv "AT" opus.scs.agilent.com with the contents unsubscribe To subscribe: send mail with the contents subscribe To switch to a once-a-day digest for wind_talk, send set wind_talk mail digest To switch back to separate messages for wind_talk, send set wind_talk mail ack For more info about these mailings, the data and listserv, send this: info You can also get windspeed reports by e-mail on demand - simply send a message to windreport "AT" opus.scs.agilent.com (the contents don't matter). But please do not poll this hourly; it loads the machine too much and can cause all the wind reports to stop. The current hourly report is available on the web at http://poulton.net/windsurf There are web archives of the wind_talk mailing list at http://poulton.net/windsurf === Machine and Domain Names === You may see either 'jr.scs.agilent.com' and 'opus.scs.agilent.com' as the server machine names; either one works. === Policy on what should be posted === For wind_thresh, wind_afternoon and wind_24: I post hourly reports from Northern California airports. Other *current* wind reports (e.g., from windtalkers) are okay. Send these to "windspeed "AT" opus.scs.agilent.com" and they will go to all four lists. Anything else that should be announced to Bay Area windsurfers in general, e.g., cleanup days, sewage spills, threats to windsurfing access locations. Please also post these to rec.windsurfing if possible. For wind_talk: Sailing reports. Rescue reports and safety tips. Equipment discussion. Equipment for sale. No images, please. "Secret" sites: As a matter of courtesy, if you talk about a site here on the list, please be willing to share the information (driving directions, hazards, wind patterns) needed to sail there. General mailing list etiquette: Please avoid posting non-windsurf items. It doesn't matter that the list has been quiet, or that the cause is noble, or that there is a horrble virus threat to every computer on the Internet. If the topic is not windsurfing, most people will be uninterested, some will be annoyed, a few will unsubscribe and our community will be poorer for their absence. When you *reply* to a message, remember that most mailers will reply to the whole mailing list rather than just the original author. If that is your intent, fine, but when sending a personal message, please remember to address the message to just that person. If you're using Outlook, Explorer or Netscape to write e-mail, turn off the ``HTML encoding.'' Those of us on UNIX systems can't read it and don't care enough to save it and then view it with a Web browser. Similarly, avoiding including attachments; many people can't read them even if they avoid being mangled by the listserver. If you have a questionable item to post, e-mail the list owner. If you see a violation of these guidelines and you need to respond, send a gentle reminder to the perpetrator *only*. Please, please, please try to refrain from discussing it on the list. === How to post messages === To post to wind_talk, send e-mail to wind_talk "AT" opus.scs.agilent.com. === About the data === The windspeed data is reported in knots. It was formerly converted to mph, but that conflicted with the SFO phone, etc, so everything (except the Bay Area forecast) is now in knots. Pre-June92 data files I have stored are in mph, but all are marked with mph or knots. You can get windspeed reports on demand - simply send a message to windreport "AT" opus.scs.agilent.com (the contents don't matter). The standard report will come by return e-mail. Please don't set this up for regular polling because that will load my workstation unduly. Problems to windspeed-request "AT" opus.scs.agilent.com. === Multiple mailings === Sometimes we get two mailings per hour. The reason is as follows. The primary network data source that supplies all the current readings (don't ask where) sometimes gets slow. My scripts retry, but the result is that data from this source is often 15-30 minutes after the hour. I also have secondary sources, but the data there is watered down for use by "the public"; In particular, the wind direction is reduced to w, nw, n, etc. I dislike using this source for SFO because there is a big windsurfing difference between 260 and 290 degrees. My compromise is to mail with the secondary data if the primary source does not come through by 14 minutes past the hour. You can tell these readings because the direction ends in "4" (indicating a resolution of 45 degrees in the direction). When the secondary source does come through, we get a second mailing with the better data. === Reporting locations === NWS and the FAA maintain separate weather operations at SFO. The FAA operates the 877-3585 "ATIS" recording, while NWS does the reports we get by network. They share the temperature and dewpt instruments, but for wind the NWS has one instrument near the intersection of the two main runway pairs, while FAA has 6 instruments around the runways. One other important difference is that FAA reports magnetic directions, while NWS reports true directions. To convert, add 17 degrees (rounded to 20, generally) to the FAA (phone) report to get true readings. The terminal forecasts use true directions as well. There are broadcasts on 118.05 MHz every 30 seconds called "Shoreline Departure". This used to be station "SOSF" but this is no longer reported. It is at 810 feet elevation (the ridge peak is at 1000-1200 feet) and at the nearer end of the ridge. It usually reads 2-3 knots higher than the meters at the airport. It requires an aircraft-band scanner to receive. The $20 Radio Shack aircraft radio can just barely get this from Coyote and 3rd Ave. Real (digital) scanners cost $100 (AC-powered) to ~$200-300 (walkie-talkie size); they can get this signal from at least as far south as Palo Alto. For Palo Alto, use 120.600 MHz. For Moffett Field, use 283.000 MHz. San_Luis_O is San Luis Obispo down the coast, not San Luis Reservoir. Travis_AFB is about 20 miles NW of Rio Vista and seems to have similar conditions to Rio. "Oak_500mb" is the 500 millibar reading from the twice-a-day weather sounding balloons released from Oakland Airport. When the jetstream is overhead, this will show westerly around 50 knots, which tends to add some extra push to whatever surface pattern we have. The Dread ASCII Graphics Map of the California Coast With Apologies to NOAA map MSC-9. '#' marks the points used to mark coastal forecast region boundaries. ---------------- CA - OR border -------------------- # Pt St George Crescent City 41.8 deg lat + + Eureka 40.8 + Cape Mendocino 40.4 + + Pt Cabrillo Ft Bragg 39.4 # Pt Arena 38.9 + Bodega Bay Santa Rosa 38.4 B26 + Pt Reyes 38.0 B26 + GG SF 37.7 + Pillar Pt Half Moon Bay 37.5 B12 + San Jose 37.4 + Pigeon Pt 37.2 + Santa Cruz 37.0 B42 # Pt Pinos Monterey 36.6 + Pt Sur 36.4 + + Pt Piedras Blancas 35.6 + San Luis Obispo 35.3 # Pt Sal Santa Maria 34.9 + Pt Conception Santa Barbara 34.5 +++++++++ + LA, etc 33.8 + ------ CA - Mex border 32.5 === Examples of decoding the "cryptic comments" === SKY /CRYPTIC COMMENTS heights/100ft ----------------------------------- clr Clear clr /st w-n mdt cu e-se Clear, stratus west to north, moderate cumulus east to southeast 5 sct /fbnk w-n Scattered clouds at 500 feet, fogbank west to north 30 sct Scattered clouds at 3000 feet 30 -sct Thin scattered clouds at 3000 feet clr /h alqds Clear, haze all quadrants 7 sct 12 bkn Scattered clouds at 700 feet, broken clouds at 1200 clr /cu tcu omtns ne-e Clear, cumulus and towering cumulus over mountains northeast to east clr / k nw Clear, smoke northwest 35 sct 250 sct /mdt cu dsnt ne= Scattered clouds 3,500 feet, scattered 25,000, moderate cumulus distant northeast 15 -sct 40 -sct 120 -sct /k15 -sct cbs dsnt ne-e mdt cu dsnt s sw ag fire 3w few ac ne-s 1,500 thin scattered, 4,000 thin scattered, 12,000 thin scattered, smoke tops 1,500 feet, thin scattered cumulonimbus distant northeast through east, moderate cumulus distant south to southwest agricultural fire 3W?, few altocumulus northeast through south === Common wind patterns === A common pattern for good summer days is to have 5-10 knots W to NW during the night and morning, often with a lull around noon where the wind drops and shifts to N to NE. In the next two hours the wind will swing around to NW and pick up to 15 to 20 knots between 2 and 6 pm. If the sky is clear or low clouds are clearing, a good morning breeze (NW 8-10 knots) usually means a good afternoon wind. When the marine clouds come far into the bay (e.g., morning overcast over the whole bay), SFO may remain under the clouds and have fairly mild wind readings (~~15 knots) all afternoon, but Coyote and 3rd can be cranking if they are beyond the clouds. This is most easily seen from the multi-city "sky" sections: if SFO is reporting *low* clouds (e.g, "9 sct" or "8 bkn") then it is under the marine clouds. If Hayward is clear, then the cloud line is somewhere over the Bay, and Coyote and 3rd are probably blowing hard. The clouds run in a stream only a couple of miles wide from SFO to Hayward; about the time the clouds get to Hayward the wind at Coyote and 3rd will shut off. When we get very thick marine layers (more than 1500 feet), we will often get fog coming over the hills way down the peninsula. This often causes a west wind over much of the Peninsula, but may cut off Coyote (wrong direction for the NW-facing San Bruno gap, plus the wind is more diffused). This will generally show up as a SFO wind direction less than 290. Sometimes Oyster Point and Flying Tigers will blow in this case, and the winds can be higher than those recorded at SFO. 3rd Ave can also have significantly steadier winds. If the fog is coming over the hills as far south as Woodside, then Palo Alto is a good bet. Wind on the water is generally 2-5 knots more than that recorded at the Palo Alto airport. I did some correlation experiments several years ago and concluded that the SFO-Stockton pressure differential was the best pressure to check at noon to predict afternoon SFO winds. My rule of thumb: -0.07 from SFO to Stockton is best. If the gradient is deeper, we tend to get fog coming over the whole Peninsula range, which gives us 10-15 knots everywhere. I.e., it feels "windy" in Palo Alto, but it's still only 10-15 knots at SFO and Coyote is actually worse. My second indicator is SFO-Truckee or SFO-Tahoe - this should be less than +0.10 or so. More indicates high pressure in the Great Basin (east of the Sierras) which can lessen the suck from the California Central Valley. Another good indicator is the marine layer depth, which I have just recently found a source for. A marine layer which is ~1000 feet deep and has a small Temp-DewPt value (less than 3 deg C) is ideal, as this fills the San Bruno gap, but does not flow over other parts of the Peninsula. Depending on where the fog line is, other good locations may be Crissy or Berkeley. If the fog/clouds are coming well inland each night, Rio Vista and San Luis Res are generally good. These locations tend to crank up late in the afternoon (4 to 6 pm), blow all night and subside sometime mid-morning. They fairly often get over 25 knots. In the winter, look for storms with good rotation. Before it hits, go to Half Moon Bay for flat-water sailing in the south winds. After it passes by, go to the usual summer spots (Coyote, 3rd, Crissy, etc) and sail in the clearing NW wind. All you get is 3-8 hours on either side, so you have to move quick. Sometimes we also get just a major W or NW jet-driven wind which can last longer. === Instrument readings vs wind at sailing sites === Winds near Coyote point typically are well correlated with SFO numbers. This is not surprising, since Coyote is just 3 miles downwind from SFO. The major gotcha is that there is a wind line caused by the southern edge of the San Bruno gap which is near the shore at Coyote for the typical direction of 290. Wind directions of 310 or more tend to bring the wind all the way to the shore. Directions less than 290 will decrease the wind at SFO somewhat, but they tend to move the wind line way offshore at Coyote, making the wind line a mile or two offshore for a direction of 270 or less. In these conditions, Coyote can be practically becalmed. I think winds at Crown Sterling tend to follow the same pattern, but I don't sail there often enough to say for sure. Winds in the channel at 3rd Ave are generally well correlated with the SFO reading. (When we had SoSF_SBrMt, that was even better.) The major exceptions occur when stratus clouds ("fog") go over the airport. The wind gets gusty as the clouds approach and they can drop quite a bit if the clouds completely cover and pass the airport. You can tell when this happens because the temperature gets down within a few degrees of the SFO dewpoint temperature, usually about 55 F (the ocean temperature). The direction at the San_Carlos station is useful for telling if the wind is blowing over the highway 92 pass by San Mateo. When 92 is blowing, San_Carlos reads about 280; when it is not, San_Carlos gets 330 to 020. This is about twice as much directional shift as we see at 3rd under these conditions. The windspeed at San_Carlos seems to be 3-10 knots less than at 3rd, so it is not very helpful. Natural Bridges: Ed Scott wrote: > I use the Long Marine Lab sensor [for the Natural Bridges site], which > is on Ken's reports [as "NatBridges"], has a link through the Slug > Video cam, and is on the buoy reports on the COTW pager. If the COTW > sensor reads 11 or above, I check the LML sensor, and if it's blowing, > I go. I find that the COTW sensor [ on Ken's report as "cNatBridge"] > reads 10 lower than the actual conditions on a W or SW wind. > If San Bruno is 280 or more, Candlestick rips. More southwesterly > winds (<280 at San Bruno) is better for Oyster Pt. and Flying Tigers. > On a west or southwest, Candlestick is blocked by San Bruno Mountain. === Tides and Hazards === These discussions use location-adjusted tide values. The new tide program (xtide 1.2, Sep 95) seems to underestimate the tidal height at higher-than-usual low tides (which will lead to more water than expected). The program also calculates "safe" times for 3rd and Palo Alto. These are chosen at pretty conservative levels: +2.5 for 3rd and +4.0 for Palo Alto. At these heights, I sail with no worries. At both sites I sail in as much as a foot less after reminding myself where the bars are. (One foot typically corresponds to 40-60 minutes time difference.) Disclaimers: The calculated tide levels may be wrong, or the measured "safe" levels may be wrong. Sandbars shift, people leave anchors or other trash in shallow water. You might be sailing with a fin deeper than mine. A near-miss by an asteroid might produce an extra low tide. Lawyers may be lurking just below the water surface at any time, any place. Shit happens. So use your own judgement at all times and don't blame me if you hit something. For sailing at Palo Alto, we used to need a tide level of at least 4 feet. With the new dock, 2.5 feet seems to be okay if you stay in the little harbor channel until you pass the downwind point. The "deep"-water channel runs right next to the white poles; everything else near the shore is mud flats at +1 to +2 feet. Hazards: there seems to be something hard at about +6.0 near the downwind point several hundred yards out. Dumbarton Bridge: Take favorite route from 101 to dumbarton bridge (Marsh Rd., Willow Rd., or University Ave). when heading eastbound towards the highrise proper, you will see an exit for "ravenswood wildlife refuge" or somesuch to the right just before reaching the highrise. Take it and follow it parallel to the bridge. It goes under the highrise to the north side. Park there, that's where the launch is. Pretty obvious. There's a matching exit for Westbound traffic to use if you're coming from the east bay. I noticed during the extremely low morning tides the first week of Jul (there was water only in the channel itself) that there is some sort of small pile of debris on the western mudflats, about halfway between the western edge of the channel and the western shore, and maybe 2 hundred yds from the launch point at a 60deg angle from the longitudinal axis of the bridge. It's about the size and shape of a race car tube frame (?). I've never noticed it before and wonder if it is newly arrived. Anyway, it might be a problem when sailing in lowish conditions, but probably not when near high tide. It's the only noticable debris I've seen out there on the east or west flats btw. For 3rd Ave, +3 feet is the safe limit for the old launch by the blue tanks (3 ft using the SM-adjusted tides, a little over +2 feet for GG height). At the new launch (fenced lot) +2.5 feet is fine. +2.0 feet is still okay for launching but is beginning to make hazards of the 4 sandbars between the launch and the channel. The bars are: 1) along the edge of the channel, from the channel marker towards the bridge - 0 ft near the marker, +1.5 ft near the bridge; 2) about halfway from the old launch to the channel marker - +1 ft; 3) two bars within 400 yards of the new launch, maybe 0 feet. These each stretch upwind starting approximately on a line between the new launch and the channel marker. March 2000 survey of 3rd: I checked out the bars at 3rd at a -0.5 tide. The map at http://sfports.wr.usgs.gov/cgi-bin/zoom_sb.cgi?x=172&y=227 still seems mostly accurate. The launch is at the yellow corner in the lower left. Notes: The map shows the channel-edge bar going upwind from the 4th bridge support, but ending halfway to the marker. The bar does not end, but continues right up past the marker, gradually getting lower, with the lowest spot immediately upwind of the marker at about -0.5 ft. This bar comes back up to 0 ft about 200 yards upwind of the marker. At lowish tide, if you run out of wind, you can walk down this bar towards the end of the bridge when the water is still too deep to walk straight to the launch. The construction folks have dredged out under the bridge for 100 feet, but you'll want to angle towards the shore before then anyway. Right next to the bridge, there is a 100-foot-wide beach in a shallow inside bend in the levee. The last egress ramp is on this beach, but beware of two rock fields imemdiately upwind of this beach! If the water is low enough to see the beach, you will probably hit the rocks (some are 2 feet above the bottom in this area). If you do go under the bridge, the water gets 1-2 feet shallower past the fishing pier. The best bottom for walking in appears to be under the power lines. Recommended low-water sailing path: from the new launch, go off the wind a bit to avoid the leeward end of the bar 300 yards from shore. Then bear upwind to pass the upper ends of the next three bars, passing just upwind of the marker. For Coyote Point, 0 feet is fine (you have to walk out 100 yards, but the mud is less than 6 inches deep). There was a recent report of a sandbar at about -1 feet just outside the swim area, however. There is also now a post broken off at about +1 ft, situated halfway between the two remaining posts on the side of the swimming area next to the launch beach. Another sailor reported a 1" pipe at a 45 degree angle, top at about +2.5 ft, about 3/4 of the way along the swim area and maybe 50 yards upwind from the poles (just downwind of a beam reach from the upwind corner of the swim area). At Crown Sterling, 1 foot is enough to launch, but you need 2.5 feet to be clear of the sandbars. The main one lies across a line between the Crown Sterling launch and the pole in the water just south of the runway piers (this line is nearly directly across the usual wind). It sits about two thirds of the way from the shore to the pole, running roughly parallel to the wind direction, maybe half a mile long. The upwind end is at 0.0 feet, the downwind end is at +0.4 feet. There is another at around -0.5 ft around 100 feet upwind of the pole and another downwind of the pole (may be continuous). There is some other kind of obstruction at -1 to 0 ft further out along the same line. Near the shore, there is a pole with its top at +1.0 ft; it is 125 yards north of the hotel and 30 yards from the shore. Mariott's requires at least +5 feet (SM-adjusted, or +4 GG) to launch. Haskins Ave requires about +3 feet to launch. Michael's Beach needs about 0 feet to launch. In all the above locations, remember that there are often big rocks sitting on the bottom in otherwise just-barely-passable water. (Kirk broke an ankle that way.) Oyster Point, Candlestick, Crissy field and Berkeley seem to have no problems at low tides. Point Isabel is also pretty much always sailable. One must always pay attention to the submerged rocks near the access point, no matter what the tide level is. Also, the water can get pretty shallow near the opposite shore---the new housing development in Richmond. At Powerlines (Sherman Island) some of the levee riprap at the launch openings goes under water at high tides, creating hazards if you sail too close (I broke a finbox this way). At San Luis forebay, 219 feet is the danger level (it's pumped, not tidal). You *need* a weed fin later in the summer. === Site-specific etiquette === Fisherman at some locations have had their lines broken by too-close windsurfers. They asked that we not sail within 100 yards of any fishing areas - a reasonable request. The fishing areas I know of at sailing sites would include the pier at Candlestick, the pier at Oyster Pt, the point between Oyster Pt and Tigers, the pier at Crown Sterling and the point just north of the main beach at Coyote. === Safety Equipment === Everyone should have these: Full wetsuit If you sail on the coast, at Crissy, Treasure Island, or in the channel at 3rd, you should never wear a shorty. Breakdowns happen. Hypothermia starts in 30-90 minutes and swimming in can take much longer. You need to dress for the day that something breaks. Spare 6-foot downhaul line This can be used for many emergency repairs to get yourself in. Flasher This is *the* way you can be seen and rescued after dark. Strongly recommended: Radio - waterproof marine radio in waterproof bag This is the big-ticket item ($200), but it makes a huge difference in emergency response times. Rechargables need to be charged every 2-4 weeks. Alkaline batteries are much, much better - these can be replaced once a year. No "waterproof" radio will last very long without protection. REI has waterproof bags. Without a radio, you flag someone down and send them in to make a phone call. The coast guard arrives from Treasure Island 45 minutes later and starts searching. A downed windsurfer is hard to see among whitecaps and finding the rescuee usually takes *hours*. With a radio, you call the coast guard direct and they can come straight to you in 45 minutes. This made my day when I broke my ankle in 30 knots at 3rd. Wetsuit hood (carried) This increases the time you can stay in the water without hypothermia. Heat loss from the head will be the main loss if you have a good suit. 25-50 foot line. This can be used for towing or for keeping people involved in a rescue together. Hook Knife to cut your way out of a kite line entanglement Tools: knife, screwdriver, hex key if your mast base uses it. Unresolved: Emergency fin replacement. Dubious value: Cell phone in waterproof bag Probably can't talk directly to the rescuers this way. At the mercy of cell coverage. Will ruin the phone if the waterproof bag ever leaks. Flares, whistles, dye markers === Mailing list additions and deletions === Send requests for mailing list additions and deletions to listserv "AT" opus.scs.agilent.com. The legal commands are given below: Everything appearing in [] below is optional; everything appearing in <> is mandatory. Recognized requests are: help [request] -------------- Without arguments, this file. 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