Tried a few DVB-T service scans today in the rainy weather and unsurprisingly rain degrades the UHF reception. Even the Digitenne Flevoland multiplex wasn't always error-free enough to show in the scan. DVB-T service scan for 2011-12-15.
Updated the Weather station Utrecht Overvecht page to give the latest measurements. In the background it changed from an rrdcgi page to a perl page so I could easily add those measurements.
Great pictures and videos of lightning striking (or moving up from ..) transmitter towers and other tall structures. Showing that lightning can strike twice in the same spot in the same thunderstorm. Or even 11 times in the same thunderstorm striking the WKYT / WTVQ towers in Lexington, Kentucky. Great stuff with lots of attention to detail and great stories behind the making of the pictures and videos by Dan Robinson. Posted on the tx-list in a discussion about lightning safety in transmitter towers.
Luck in Iceland with research into the ash plume from Grímsvötn volcano:The IMO has a mobile weather radar on loan from the Italian Civil Response Authorities. When Grimsvötn erupted it was placed near the village Kirkjubæjarklaustur, about 80 km from the volcano. The weather radar is used to monitor changes in the height of the volcanic plume, but those are indicative of the strength of the eruption.The mobile weather radar helps understand the size and direction of the ash plume, without having to get too close.
Source: Update on volcanic activity in Grímsvötn - Iceland Meteorological Office. I am a fan of Iceland, I want to go visit it again some day.
In between fatherhood today I found some time to do adjustments on the barometric pressure sensor for the weather station project which had a notable difference with the two nearest weather stations. Simply by adjusting the offset until the readout was near to the current values for De Bilt from actuele waarnemingen KNMI. Which gets interesting because the KNMI website has a 15-30 minute delay. The current offset is somewhat less than 1 millibar/hectoPascal but the pressure was dropping today. Maybe I should try to get that last bit on a day with more constant air pressure. For now it is a good approach.
Just did an interesting adjustment: moved the solar sensor from the shade to the full sun. The readouts are interesting:2011-05-01T14:02:00+0200 Solar 8.299400 mV 2011-05-01T14:04:00+0200 Solar 119.853104 mVAccording to the w1retap documentation this means the sun power is 24.63 Watt/m^2 in the shade and 355.75 Watt/m^2 in the sun at the moment.
Update 2011-05-02: Mounting the solar sensor outside is a bit more 'interesting' as it has to look up at the sky (logically) but at the same time I want the other two sensors in that housing to be in the shade in the future 'weather hut'. I found a description of mounting a 1-wire hobby-board solar sensor which has a good suggestion. Downside is that I will need more space in our backyard for the 'weather experiments'.
Interesting bit with the pressure measurements at the moment. I now have two running sensors, the old one from the Conrad weather station and the new one from Hobby-Boards. The new one is calibrated for 2 meter above sea level which matches the height reported for our street and backyard at Actueel Hoogtebestand Nederland. And as a reference there is the measurement from De Bilt and Cabauw at the actuele waarnemeningen Nederland knmi. And there is a big disagreement between our shed and the officials. For today 12:00:
I've been mapping the difference between the old sensor and the measurement from De Bilt at the weather station page and it seems to be nearly constant. I first thought the age of the old sensor was showing. But with two sensors here showing about the same difference with official sensors I'm not sure what the cause is.
- The 'old' sensor (Conrad) in the shed: 960 hPa
- The 'new' sensor (Hobby-Boards) in the shed: 988.8 hPa
- KNMI measurement De Bilt: 1012.8 hPa
- KNMI measurement Cabauw: 1012.5 hPa
First thought after I finished typing: move the sensor outside. But that does not 'fix' the problem.
Update 2011-05-02: More thinking and reading made me wonder if 'above sea level' has different meanings between the US (where hobby-boards calculated the offset for me) and the Netherlands, but that doesn't seem to be the right way. If I try to follow the calculations at Air Pressure and Altitude above Sea Level - The Engineering Toolbox it seems I miss 19 meter height above sea level.
Difference: 21 hPa, using the formula above I can get the closest to that difference with a height of 19 meters in that formula:101325 * (1 -2.25577*(19/10000))^5.25588 Runtime warning (func=(main), adr=42): non-zero scale in exponent 99172.15726627368573690675
De gemeente Utrecht publiceert gewoon welke fietspaden in Utrecht gestrooid worden en inderdaad, de Troelstralaan waar ik in Januari 2010 last had van de sneeuw staat er niet op.
Blijkbaar blijft de gedachte: we strooien gegeven fietspaden, en niet de fietsroutes.
Almost winter holiday feeling: this morning it took over 15 minutes to dig the car out of the snow. It took a bit of searching to find a door to the car which would actually open, three were frozen. But I managed to open the car and get it moving. And traffic was slow, but doable. Finding a parking space where it would be possible to get out again was also 'interesting', and I hope I chose the right one...
This morning it was 2⁰C out in the shed as measured by the weather station. The computer is still running ok, according to smartmontools the current disk temperature is 22⁰C so that is still reasonable.
The climate (in the shed) is different from what I expected: humidity is (so far) within limits of what the current PC (a Dell optiplex GX270) can handle. I expected humidity to become a problem before temperature. Temperatures are at the moment dropping below 'operating range' and a couple of cold days are coming up here in the Netherlands.You can view the results at the weather station page but remember this is in the shed. Real measurements done with (something resembling) meteorological standards will be later.
But these measurements have learned me a few things and helped with a few decisions for the project sundial weather station:
The flickr picture is also some experimenting with the gimp.
- The humidity in the shed is not much of a problem.
- The temperature might be, but if a really low-power PC in an IP66 housing can survive an outdoor climate, it should survive in the shed.
- The conrad temperature sensor is not very precise in outdoor temperatures. So the 'outdoor' temperature / humidity will be measured using 1-wire sensors hooked up to the future weather station computer. The Netley Marsh 1 wire weather station has nice ideas and pictures how this can be done and a small 'sensor house' like the one they use would fit better in our back garden than a full-size Stevenson Screen (the official name of the white 'meteorological hut' which tries to shield thermometer and hygrometer from local influences).
With all the interesting weather today on the Northsea I added the Northsea area at weather.idefix.net with fresh weather maps every hour.
Interesting weather happening, windspeed Northsea reported at 24 meter/second with 29 meter/second gusts (87 and 105 kilometer per hour).
Update 15:10 EHKV reporting ///42G64KT wind (78 kilometer per hour sustained, 119 kilometer per hour gust). Wind without direction isn't parsed correctly by Geo::METAR so the weather.idefix.net plot for 15:00 CET has no wind for EHKV.
Update Geo::METAR local version updated, /// is 'measurement broken'. But the plotscript still can't draw a windvane for that measurement.
Update 16:20 Last report from EHPG (hiding under the scale on weather.idefix.net): EHPG 111425Z AUTO 20049G64KT 170V270 5000NDV -DZ FEW005/// BKN007/// OVC008/// 10/08 Q0978 49 knots, 64 knots gusts: 91 kilometer per hour sustained, 119 kilometer per hour gust. Windy! EHPG is oil platform P11-B. Maybe I should add a map 'Northsea' to the weather maps.
Het waait stevig.. let ook op de windvlaggetjes op weather.idefix.net Nederland 2010-08-23 14:00 .. vooral de waarnemingen over zee hebben tot 9 Beaufort! Waarnemingsposten EHKV en EHQE.
Update: Op 15:00 nog meer harde wind, windkracht 10 op EHKV weather.idefix.net Nederland 2010-08-23 15:00.
EHKV = oil platform K14-fa-1c in the Northsea.
I've done some work on the weather map site. I'm improving the plotting script to have a better abstraction of data and plotting so I can do plots for multiple countries.
As a first I'm plotting Denmark. The reasons are simple: it's a not too big country and has a reasonable number of weather stations.
A night with a heavy thunderstorm and high numbers of lightning strikes detected. No local damage, we just saw hailstones come down, break up and the parts still fly around for over a meter. So we were glad we weren't outside at that time.
No this is not the result of an artillery attack on a swimming pool, this was the weather in Oklahoma city on 16 May 2010. Source: Monster hail storm slams Oklahoma city - TornadoVideos.Net
En de goede vulling van het afgelopen weekend was... het jaarlijkse paastreffen van de ligfietsvereniging nvhpv op de camping Harskamperdennen.
De foto's die ik gemaakt heb: Paastreffen 2010 - Foto's Koos van den Hout
- Vrijdag erheen gefietst, bij Vechten afgesproken met wat andere ligfietsers uit Zuid-Holland. Daar moest ik nog even mobiel Internet gebruiken om mezelf op te geven voor de xs4all IPv6 proef. Daarna via een leuke route richting Harskamp, daar de tent opgezet en 's avonds gegeten bij de chinees in Harskamp.
- Zaterdag ben ik er zelf op uitgegaan met de wardriving box achterop de fiets richting Wolfheze, Heelsum, Renkum, Bennekom en terug via Ede. Dat leverde maar liefst 4684 nieuwe netwerken op. Ik ben onderweg wel natgeregend, heb zelfs in Wolfheze een potje staan schuilen. Toen ik terugkwam was het ligfiets-ringsteken al geweest (had ik graag bij gefotografeerd, maargoed). Wel werd er nog een stunt uitgehaald met wat mooi versierde ligfietsen die ik wel op de gevoelige CCD kreeg.
- Zondag zou de georganiseerde toertocht zijn maar het weer was prutje en de toertocht werd afgelast. Toch zijn Mirjam en ik een stukje gaan fietsen door de bossen. Waar alles nat en modderig was, dus ik had een vieze fiets.
- Maandag terug liep eerst mijn ketting er af, toen schoot de kettingbuis weer los en bleef de ketting 'lastig' doen. Later in de rit brak zelfs mijn ketting. Gelukkig was er iemand met een kettingpons in de groep die de ketting gerepareerd heeft (schakels ertussenuit) waardoor de ketting ook minder slecht liep. Bij thuiskomst maar gelijk de fietsen uitgebreid schoongespoten en de kettingen gesmeerd. Toch ben ik denk ik toe aan een nieuwe ketting en tandwielen. En een kettingponsje is denk ik wel een goeie uitbreiding van de onderhoudsspullen bij mijn ligfiets.
Alle hulde voor de organisatoren die er weer een prima evenement van gemaakt hebben!
Interesting weather this morning: snow started between 7 and 8, and it was nearly melted away again before 11. Overview on webcam.idefix.net Uithof archive Monday 8 March 2010.
Some actors are annoyed by being typecast in the same roles constantly, but some cities can be typecasted too: I watched WarGames (1983) yesterday and noted in a number of shots of Seattle it was raining. Now I'm watching Firewall (2006) and I think I haven't seen an outdoor scene yet without rain.
I visited Seattle myself and it's not that bad.