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Author Topic: Reading wind reports that don't agree  (Read 3037 times)
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timothymcmackin
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« on: June 03, 2011, 05:56 PM »

Hi, all. I've run across this situation before but have only now thought to capture it and ask about it. I figured that I knew how to read wind reports at a basic level, but I'm running into reports that don't make sense to me.

Strong spring winds are gone here in inland NC; we're well into the summer doldrums with weak winds and the dreaded "calm" and "variable" forecasts. I checked the wind forecast this evening (friday) anyway and got a pleasant surprise for tomorrow:


(This is from windfinder.com.)

If I read it correctly, this summary forecast predicts:
14:00 (2pm): 8mph winds from the SW
17:00 (5pm): 7mph winds from the SW
20:00 (8pm): 8mph winds from the S

Wind from the SW is great for my local flying field, so I'll happily take 7-8 mph winds from the SW! To get some more detail I zoom in and look at the hour-by-hour forecast:



What? This doesn't match the summary forecast at all. This forecast predicts:
14:00: 3mph winds from the E
17:00: 6mph winds from the WNW
20:00: 1mph winds from the ESE

The two forecasts don't match all, either in wind speed or in direction. I don't see how the summary forecast can be an average of the hour-by-hour, or even snapshots of the hourly. They're too different. How can the summary forecast call for 8mph winds when the hourly forecast doesn't break 6mph? This is two views of the same forecast on the same site.

Is this a glitch in the forecast, a rounding error that separates wide vs. narrow forecasts, or my mistake in reading the report? I figured that most sites would have the same weather information for this airport (RDU) but maybe some sites are more accurate than others with the info?
« Last Edit: June 03, 2011, 06:01 PM by timothymcmackin » Logged
Magpiesfooty
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« Reply #1 on: June 03, 2011, 07:04 PM »

Viewing wind forecasts almost make me laugh. Weather forecasting has come a long way but the ability to tell you what the wind is going to do at a specific hour is entertaining but not a science. Is that saying that the will will be doing that exact thing at the top of the hour predicted?  Coordinated Universal time or local time, local time, I know, but will it do this once during the hour that it is forecast?  All of the hour of the forecast??  Let the weather people stick to things that they can predict with some level of confidence and leave the wind forecast in a range as should be expected, like southerly winds at 5 to 15 mph.  With this I at least know to leave the heavy artillery at home. 15 - 25... take it all but be careful with the lighter stuff.  15 - 25 with gusts up to 30+. Caution should be used with the good stuff and nothing light.  Anything higher, stay at home and watch a good kite video or read a kite book.
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timothymcmackin
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« Reply #2 on: June 04, 2011, 03:57 AM »

Well, I know that forecasting the weather in general is always a guessing game. I suppose that predicting the wind is even more so. I was just hoping that at least these forecasts would be internally consistent! Otherwise, what good are they?  Smiley

Even my modest five-kite collection can handle wind from next to nothing to about 20 mph. All I need to know is the direction the wind is coming from so I can know when the wind is blowing off the lake and onto the field. So when the forecast consistently says wind form the SW, I keep checking the current NOAA wind report from the airport to see if it's right, and it often is. But in these cases when the forecast can't even agree with itself, I might as well flip a coin. It's frustrating. Oh, well; it's my own choice of hobby!
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Magpiesfooty
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« Reply #3 on: June 04, 2011, 06:29 AM »

Sometimes I think that it is amazing how accurate the weather forcasters are!  I have noticed that since they are watching areas of high and low pressure, they are sticking their necks out and forecasting the wind several days in advance. You used to only get the wind for today, tonight, and tomorrow, but now, they extend it for 2 or 3 days.  Outside of the doldrums of summer; here in Texas you can almost predict the wind just by viewing the temps and patterns on the extended forecasts. You know that a sharply higher temperature after a cold snap will generally be a windy day.  Winds just before and after a cold front will generally be gusty, but from opposite directions. Just watch the L's and H's on the maps. Close together, wind, far apart or an H directly over head generally means calm winds. L's are a little more unpredictable. If there is an L overhead, generally there is an H nearby and it would be windy, but likely stormy as well. Isn't mother nature, wonderful?
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Magpiesfooty
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« Reply #4 on: June 04, 2011, 06:34 AM »

Another thing you can do is get the zip code of your flying field, or if it is school or a park, it may have it's own weather bug station. Once you know this, check Weather.com or if you can stand the pooh that you get along with it, choose Weatherbug.com. Enter the zip code or landmark and you have the weather near your flying field at your finger tips.  I think that both work with smart phones.  Have fun.
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timothymcmackin
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« Reply #5 on: June 04, 2011, 10:08 AM »

Quote
If all that fails, carry a few different kites to fly in various conditions.

Well, yes, I've got a range of kites from a 4D to a Rev 1.5 mid-vent, but if the wind is truly "variable," no kite will fly. I busted my Zephyr a month or two ago flying in lousy conditions like that: decently strong wind that couldn't decide which direction to come from. I was headed up the window when a gust from the side sent the kite into an entirely unplanned forward flip and roll-up. At the time I had never done a roll-up before and didn't know what to do except say "woah -- cool!" I was in brief control with the lines wrapped, headed toward the ground, trying to think of what to do, when another gust hit and the kite unrolled, rocketed into the ground, and broke the LS ferrule (fortunately nothing else). Bad idea to fly in that kind of wind. So I'm trying to wait until the wind picks a direction and sticks to it.

Quote
Another thing you can do is get the zip code of your flying field, or if it is school or a park, it may have it's own weather bug station.

This field (Lake Crabtree park in Durham, NC) is less than 2 miles (as the crow kite flies) from RDU int'l airport, and I figured that big airports would provide the best possible weather forecasts and reports. In fact, one of the rules of thumb I know to use is to look at the direction that the airplanes are taking off and landing from, because they prefer to take off and land going into the wind.  But I haven't thought to combine what the airport says with what the maps show about incoming high and low pressure fronts -- I figured that the forecast would take that into account. Maybe more thought is needed to figure out what the kite-related conditions are going to be. Thanks for the tips.
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lylenc
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« Reply #6 on: June 04, 2011, 11:01 AM »

The soccer field I fly at is two miles from an airport, but the field is downhill next to trees and a creek. The airport's readings are 30 feet above their ground level so they are usually reporting higher wind speeds. You'll get used to the varying conditions after you've flown the field a while and get to the sweet spots and dead spots. I try to keep an eye on all the wind cues: trees, tall grass, fluff from plants, spider webs, flags, etc. I also use a kite's ribbon tail attached to a dowl for a wind indicator right at my kite bag on SUL light and variable days.

The wind here tends to vary from 0 mph to some level, depending on the day. The wide wind range days like 0 - 12, with five minute fluctuation cycles are the most challenging and usually call for an early beer break. On a light wind day, my SUL got caught in a whirlwind that came up from behind me. That was a thrill, figuring it was going to be trashed before I got out. I let the kite sit in the eye of the whirlwind while I determined the best way out. Finally decided to go out the same way it went in by following the rotation and giving as much slack as possible but still maintain control ... it worked thankfully.
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Craig     Walla Walla, WA     Just One More!
Magpiesfooty
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« Reply #7 on: June 04, 2011, 08:20 PM »

If you have a TV station doing weather that has, "isobars" those squiggly lines that go around the H's and the L's on the map, those are lines of equal pressure, every where on that same line, has the same barometric pressure, if you see the lines bunched up or close together, this means a great pressure differential and there will be higher winds, the closer, the higher the winds. If you see the lines widely spaced or worse yet, no line near your area for miles, you can be assured that your winds will be light. If you notice, they target themselves around H and L pressure centers.  Generally higher barometric pressure means light winds and clear weather, while lower pressure generally means potentially stormy or windy conditions, but not always so, look at the closeness of the isobars and sudden shifts in Barometric pressure.  Also learn your cloud formations and from which direction your change of weather comes from.  Sometimes the sky can tell you much more than the winds can at the time you look.  And now for the sports for today, let's turn it to Bob at the sports desk.  LOL!   Good luck.
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Ken Bour
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« Reply #8 on: June 18, 2012, 03:07 PM »

I am also having a bit of difficulty with windalert.com.



If you look at the pic above, the forecasts are pretty high (circa 5-10 MPH), but the red dots/lines are supposed to be the actual readings and they are not even close to the forecast. Am I reading it incorrectly?

Thanks, Ken

[14 Aug 2012: KB modified to remove attachment and insert image.]
« Last Edit: March 05, 2013, 11:57 AM by Ken Bour » Logged

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Tmadz
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« Reply #9 on: June 18, 2012, 03:35 PM »

Windalert also consolidates several reporting stations for you. I can see them in your screen grab, but not all stations are the same. Some are in congested areas, some only report hourly or sporadically compared to airports or harbors that report multiple times an hour. You have to figure out what types of stations are near you and sort out the "wheat from the chaff."

I just did a search on zip code 60504. You can scroll over the reporting points and see were the reporting station is. I know where the airports are and all of the readings that are in the 20's plus I would believe today. The wind is howling out of the SSW. There was one reading that said it's 8mph out of the north and I know where that reading was done along the Illinois river. That might have been the case when the reading was made or it was swirling and was a bad reading. Two miles away the municipal airport reading was 30mph SSW.

You just have to look at the bigger picture (region) and not look for a forecast more than 12-24hrs out to get a reasonably close forecast. Nothings 100%.
« Last Edit: June 18, 2012, 03:37 PM by Tmadz » Logged
Tmadz
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« Reply #10 on: June 18, 2012, 03:39 PM »

If you have a TV station doing weather that has, "isobars" those squiggly lines that go around the H's and the L's on the map, those are lines of equal pressure, every where on that same line, has the same barometric pressure, if you see the lines bunched up or close together, this means a great pressure differential and there will be higher winds, the closer, the higher the winds. If you see the lines widely spaced or worse yet, no line near your area for miles, you can be assured that your winds will be light. If you notice, they target themselves around H and L pressure centers.  Generally higher barometric pressure means light winds and clear weather, while lower pressure generally means potentially stormy or windy conditions, but not always so, look at the closeness of the isobars and sudden shifts in Barometric pressure.  Also learn your cloud formations and from which direction your change of weather comes from.  Sometimes the sky can tell you much more than the winds can at the time you look.  And now for the sports for today, let's turn it to Bob at the sports desk.  LOL!   Good luck.


I got this from an earlier forum string

http://hint.fm/wind/
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tpatter
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« Reply #11 on: June 18, 2012, 04:44 PM »


Wind is like a stream - a few obstacles here and there can completely change its direction, rotation, speed, etc.

Many times on the field that I typically fly on, I've seen a flyer on the north end of the hill with a southerly wind and a flyer on the south end of the hill with a north-westerly wind.    Then again, when its smooth, it can be very smooth.  Luckily, it generally quite flyable being somewhat in the middle.

I guess what I'm saying is that I've given up on published data (at least in my area) to give me any kind of real wind information beyond 'its blowing' or 'its not' and sometimes not even that!  Smiley

-Tom
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Ken Bour
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« Reply #12 on: June 18, 2012, 06:15 PM »

I think I am beginning to understand the problem and have posted a WANTED ad for a Kaindl Windmeter 2. At least, then, I'll have a more reasonable approximation as to the winds where I am going to attempt flying...

Ken
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Gamelord
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« Reply #13 on: June 18, 2012, 06:51 PM »

Another thing you need to keep in mind when viewing weather reports is where the weather station is located.  Normally these are high up on top of buildings or in areas where there are wide open fields like airports etc...  Most kite flying is done well below the top of high buildings and air traffic control towers.  What the weather station is predicting or reporting is most likely not what you will be flying in.
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Ca Ike
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« Reply #14 on: June 18, 2012, 07:55 PM »

Wind alert is probably the best site/mobile app to use.  IT takes the reading directly from actual stations.  In some areas they do virtual stations using colleted trend data and actual observations.  By far they are the most accurate and will tell you the conditions at the station closest to where you want to fly.  Weather channel is probably the best forecast site and the winds will be pretty close to the range given.  THey also use historical data to predict trends.  Don't use hourly  forcasts though except to get a generall idea of the range over a few hours.
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