Somebody Puleez Explain

[Gary Wyngarden]

Weather forecasting drives me nuts. Winds overnight hit as high as 41 knots at our nearby reporting station at Smith Island in the Strait of Juan de Fuca. That's not all that unusual for this time of year and there was a gale warning out.What's driving me crazy is the pattern of change in barometric pressure and wind velocity. The attached link is a NOAA combined plot of barometric pressure and wind speed for the Smith Island buoy for the last five days. Some of it makes sense to me.On Christmas Eve and Christmas Day for example the falling barometer was followed by an increase in wind speed. Then when the front moved through about 1800 GMT and the barometer started to rise, the wind dropped (albeit temporarily). Then on the 26th the wind dropped again when the front moved through and the barometer started to rise.But then there's last night (shown as about 00 GMT). The barometer was still rising from the passage of the front when the wind kicked up from almost dead calm to more than 35 knots in a couple of hours. Winds in advance of low pressure systems here are almost always southeasters. Had I been looking strictly at changes in barometric pressure, I would have been taken totally by surprise by these gale force southeasterly winds.This is of more than academic interest to me. We're planning a five-month cruise up to Glacier Bay in Alaska in 2007. VHF weather reports in northern BC and in Alaska can be hard to receive, particularly in fjords, and there will be many times we're dependent on our recording barometer for severe weather warnings. Last night's gales would have caught us by surprise and slammed us.Any insights will be appreciated.Gary WyngardenS/V Wanderlust h37.5

 

[Chuck]

Bad weather news

Hate to be the bearer of bad news Gary, but a single station wx observation gives you just that. The entire field has to be looked at, hence weather maps, computers, weather service warnings and forecasts. You just can't do it alone with a single barometer. Retired meteorologist.

 

[Franklin]

Ok

Put a barometer on the bow, a barometer on the stern port, a barometer on the stern starbord and your good to go

 

[Ross]

Check this

link:http://www.wunderground.com/cgi-bin/findweather/getForecast?query=orcas+island%2C+waThis will tell you everything that you want to know about the weather in your neck of the woods.The other thing that you need to look at is the isobars around the high and low centers. The closer the lines are the greater the gradient and therefore the faster the wind speed changes.

 

[Miles]

Rising pressure can mean a lot of wind too

even though the weather may be clearing it's still blowing stink. Especially up here in the NW where winds get squeezed between mountain ranges and funneled through gaps. Changes in atmospheric pressure imply changes in air masses which imply winds. So what you're really looking for is a nice steady high barometer like we get in the summer sometimes.I'd also agree that forecasting based on one station won't work very well. Take a look at the surface forecast for the eastern pacific (link below). Looks pretty nasty, micro-forecasting with single barometer at your location could get you into trouble. Have fun on your trip, I'm sure the WX will be nicer in the summer!

 

[Tom Spohn]

Jeff Renner

has published an excellent book on Marine Weather. I found it worth the read, but find it helps me understand after the fact why the weather did what it did rather than being able to reliably predict it. For predictions I think you will need some form of weatherfax service so you can see the whole pattern and how it is changing. The XM add on offered by Garmin looks good too, but is way too costly for me. Try the link below.http://www.xaxero.com/weathefax200opti.htm

 

[Gary Wyngarden]

Limited Value of Barometer

Thanks guys for your input. In reading the literature you'd swear the only tool you'd need was a barometer. "Ho, the glass is falling. Must be some bad weather ahead."The reality appears to be that even a recording barometer is only of limited value--certainly worthwhile having, but just as certainly not a panacea.However, it really makes you feel vulnerable when you don't have access to VHF forecasts, weather faxes, etc. I guess I'll just have to watch for mares tails, and red skies at night and also just be prepared for what comes--always a good idea.Thanks again.Gary WyngardenSV Wanderlust h37.5

 

[John Nantz]

It's tough to plan

I'm in the same situation as you Gary - having a though time trying to figure out what weather is ahead.On August 18th, on our way back from Sitka to Ketchikan we got wind (no pun intended) of a major seasonal storm and headed for the Southeast (Alaska panhandle). On the way down Clarance Strait is was totally glass and this was a day before the storm was due. We covered as many miles as we could that day and made an overnight stop at Meyers Chuck. The morning greeted us with no mares tails but instead just some mid-level clouds and no wind - i.e., just glass. Above the clouds the sky was a whitish-blue but mostly whitish. The forcast was still for a major blow.By noon (the storm was due that afternoon) there was a very light breeze but as we headed for Ketchikan we stopped to do some fishing off Caamano Point (along with lots of other boats, mostly sport fishing types). Ketchikan was just a few miles away and we thought if something was coming we could easily make it there. Many of the sport-fishing boats were chartered types and surely they would head for safe harbor when it would be necessary. (who needs weather info - just follow the charter boats, eh?)After a while the wind gradually picked up a tad, the clouds thickened slightly, so, besides the fact we didn't catch anything, we decided to head again for Ketchikan. By the time we entered Tongass Narrows, a distance of about 7 or 8 miles, the wind had picked up noticeably and there were white caps everywhere. Behind us we could see some of the fishing boats headed in.Several miles later we tied up in Thomas Basin marina and prepared for the blow. The barometer really fell, the clouds went from occasional to solid overcast and became very dark. Although it got very windy - 30kts maybe?, the real "big wind" never materialized although it could have. A month earlier the end of the dock at Shearwater near Bella Bella blew away with many boats still tied on! The moral of this lesson is just because you're tied to the dock don't assume it's safe.If we didn't have access to Marine Forcasts we could have been really caught off-guard. The wind picked up from a few knots to over 20 in a very short time and while reading the clouds helps it doesn't tell all. You know a system is moving in but you don't know how severe it will become. And, while the barometer fell initially it didn't provide a good warning. By the time it was falling dramatically it would have been too late to run for cover. Chartlet Caamano Pt to Ketchikan: http://mapserver.maptech.com/homepage/index.cfm?lat=55.49330656348913&lon=-131.92630740154666&scale=969756&zoom=100&type=0&icon=0&width=498&height=498&searchscope=dom&CFID=883595&CFTOKEN=41968917&scriptfile=http://mapserver.maptech.com/homepage/index.cfm&latlontype=DMSAttached is a picture of the barometer we used showing 993 mb. I really liked the histogram as it shows the rate of change so you don't have to monitor the pressure continuously. These electronic barometers are sensitive and a cost-effective alternative to the paper drum types. Plus, there is no problem with drying ink.

 

[Fred Ficarra]

And maybe then Gary

After you get it all figured out, maybe I can get on your call-up list for storm warnings. That Christmas breeze you alluded too,,, our trees didn't like it. On Hood Canal it blew like stink! Gusts to 50kts. (guess) That's not so bad except the ground was soaked and thusly soft. Yep, trees fell over and took out our power lines. We were dead in the water until yesterday afternoon. Merry Christmas. Luckily we were on our 10KW standby generator. Worked, sorta. It doesn't like our heat pump. Generator blew up yesterday before the power came back. But I showed it. Just ordered a new, fully automatic, propane fueled 15kw unit. Maybe the neighbors will take our old one after I fix it. But what the hell, the mortgage is paid-off. One thing that sailing has taught me; There is no such thing as good high-wind. When we built this house, I had all trees near it cleared. Pretty obvious why. When the power died, Linda had just opened the garage door to drive to work. (911 supervisor=working on Christmas) She drove her new convertible through falling trees and UNDER the one that took out the power lines. Sailing isn't the only thing exciting in the Northwest.