Whats the best way to see what weather was like to check different forecasts?

tudorsailor

tudorsailor

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I am keen to try out the openskiron forecast and compare it to my regular Predictwind. Since I will be in the Ionian next week I have been looking at wind near Zante. For this afternoon, Predictwind PWG has 30kn but Predictwind PWC 6Kn. OpenSkiron on zgrib shows 36kn
Is there a way to see what the wind was like over the past 24hours

Second question is what is the most userfriendly Gribviewer. Zygrib is not nice as once the wind is loaded it is difficult to see the land. The interface is one reason I stick to PreictWind

Thanks

TudorSailor
 
ExpeditionLT for the grib viewer. The display is completely customisable so (with some work) you can get whatever you want. It's free.

What is Openskiron and are you sure it's not just a remanipulation of the GFS? The numbers you quote sound like it might be.

No idea re. Weather records for the Ionian.
 
OpenSkiron is allegedly and new/better forecast. The website is http://openskiron.org/en/ The author posted it here some time ago. He says............ The openWRF Grib files are from runs of a WRF-ARW model at 12km and 4km resolution. It is a newer model using better initialization data and generally more accurate.

I will try ExpeditionLT

THanks

TudorSailor
 
tudorsailor said:
I think ExpeditionLt is now PredictWind offshore free viewer https://www.predictwind.com/grib-files/#offshore-download

Looks nice

TudorSailor
Click to expand...

They're not the same thing. PW used to recommend Expedition LT before they developed the Offshore App as their grib viewer. However I can't for the life of me find a download link to ExLT this morning, so it seems to be unavailable, which is sad.

You could try the PW offshore app but I'm not sure how easy it is to load third-party GRIB files into it. You might try the free version of Adrena, which IIRC had some similar display controls to ExLT: http://www.adrena.fr/en/AdrenaFree/adrenafree.html

Re. the weather data, I've had a check this morning and Met Office WOW does have worldwide coverage but not much near Zante:

http://wow.metoffice.gov.uk/

Davis Weatherlink, a collection of private/domestic weather stations and more professional data, has a station on Kefalonia:

http://www.weatherlink.com/map.php?station=spartia
 
bitbaltic said:
They're not the same thing. PW used to recommend Expedition LT before they developed the Offshore App as their grib viewer. However I can't for the life of me find a download link to ExLT this morning, so it seems to be unavailable, which is sad.

You could try the PW offshore app but I'm not sure how easy it is to load third-party GRIB files into it.
Click to expand...
The skiron website has gribs in bz2 zipped files to make them smaller. I found that I can uncompress them with 7-Zip and then they display nicely

Thanks for all the suggestions

I will spend the next couple of weeks working out if skiron lives up to the authors assertions

TudorSailor
 
tudorsailor said:
I am keen to try out the openskiron forecast and compare it to my regular Predictwind. Since I will be in the Ionian next week I have been looking at wind near Zante. For this afternoon, Predictwind PWG has 30kn but Predictwind PWC 6Kn. OpenSkiron on zgrib shows 36kn
Is there a way to see what the wind was like over the past 24hours

Second question is what is the most userfriendly Gribviewer. Zygrib is not nice as once the wind is loaded it is difficult to see the land. The interface is one reason I stick to PreictWind

Thanks

TudorSailor
Click to expand...

Try weather underground ( https://www.wunderground.com ) there's a station on Zante with plenty of history.

Have you played around with ZyGrib settings? Something as simple as changing the thickness of the coastline makes a big difference:
 

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tudorsailor said:
I will spend the next couple of weeks working out if skiron lives up to the authors assertions

TudorSailor
Click to expand...
Good luck! That's an extremely difficult undertaking.

I've tried before, 2 weeks won't scratch the surface.

I used a very low resolution methodology of screen shots of GFS gribs against local airport actuals saved into Evernote a few times a day, really not easy but a start. Plus you need to assume the airport data's accurate and measured at 10m.

Good luck, it would be interesting if you could share any data on here.
 
tudorsailor said:
I am keen to try out the openskiron forecast and compare it to my regular Predictwind. Since I will be in the Ionian next week I have been looking at wind near Zante. For this afternoon, Predictwind PWG has 30kn but Predictwind PWC 6Kn. OpenSkiron on zgrib shows 36kn
Is there a way to see what the wind was like over the past 24hours

Second question is what is the most userfriendly Gribviewer. Zygrib is not nice as once the wind is loaded it is difficult to see the land. The interface is one reason I stick to PreictWind

Thanks

TudorSailor
Click to expand...


Strange though it may seem , it is difficult to assess forecasts objectively. Weather is just too variable in space and time. My oft repeated phrase is that weather does not know itself to within one Beaufort force. Just read the many subjective “assessments” on the forums to see how opinions vary. If you or anyone else wishes to compare different forecasts then use data from “official” sources such as data buoys and synoptic observing sites. Instruments, observing practice and site exposure will be to a common standard worldwide.

Do a check over a long period. Small samples will be of little use. And at several locations. Data buoys and light vessels around the UK and France will be as good as anything. You can get hourly values online from the US Buoy sites. See http://www.ndbc.noaa.gov/radial_search.php?storm=ep1 and http://weather.mailasail.com/Franks-Weather/Nw-Europe-Official-Weather-Actuals .

Do not fall into the trap of comparing zyGrib with XCWeather, Pasagewather or many o others. they are all the same US GFS output. Differences between the various so-called detailed forecasts are likely to be random. None starts with a detailed analysis. That means that their claim to provide detailed forecasts are a nonsense. They may show an improvement on the GFS because they put in topography on the scale of their grids. I say “MAY” because of their lack of detail in their starting analyses.

There is close cooperation between developers of weather models so that none is likely to be significantly better than another. The initial data analyses are critical which is why the major centres run ensembles of many runs. At times PW will outperform Opemskiron or theyt.com and vice versa. Overall, the GFS is as good as anything freely available. It will beat the detailed models for periods over 1 to 2 days. Used with a little intelligence it will be as good or better for shorter periods. At least, that is my experience. I see no pint in paying for any objective forecast – unless, for some reason, it is for ease of access. “Detailed” forecasts that you pay fore may beat the GFS over short periods from time to time. They will not over periods > 24 hours.
 
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As I sit in a massive thunderstorm in the southern Pelopenese, I wonder why the specialised sailing forecasts show rain and wind, but it's only the general sites such as weatherpro that predicts thunderstorms.
TudorSailor
 
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Wow, certainly picked right day to look at Frank's recommended site

But I do still wonder how this forecast has the thunderstorms, but most others do not. Are the thunderstorms predicted "manually"

PART 3
FORECAST UP TO 21 SEPTEMBER 04 UTC

NORTH ADRIATIC
NORTH NORTHEAST 4 OR 5. SLIGHT. POOR. PROBABLE THUNDERSTORM

CENTRAL ADRIATIC
NORTH 5 OR 6 SOON 4 OR 5. MODERATE. POOR. THUNDERSTORM

SOUTH ADRIATIC
WEST NORTHWEST 5. SLIGHT OR MODERATE. POOR. THUNDERSTORM

BOOT
WEST NORTHWEST 5. MODERATE. POOR. THUNDERSTORM

MELITA
WEST NORTHWEST 5 OR 6. MODERATE. POOR. PROBABLE THUNDERSTORM

GABES
NORTHWEST 5 OR 6. MODERATE

SIDRA
WEST NORTHWEST 5. MODERATE. POOR. THUNDERSTORM

NORTH IONIO
NORTHWEST 4 OR 5. MODERATE. POOR. THUNDERSTORM

SOUTH IONIO
WEST NORTHWEST 4 OR 5. SLIGHT OR MODERATE. POOR. THUNDERSTORM

TudorSailor
 
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Tudorsailer: if you're interested in graphical representations of thunderstorm probability (no doubt all computer-generated), see here: http://www.weatheronline.co.uk/weat...&MAPS=gww&CONT=grgr&LAND=GR&ZEIT=201609200600

Or, with many more options (for pilots), here: http://www.flyingineurope.be/thunder_&_turbulence.htm
From the above, this page shows lightning activity in real time over Greece. It's easy enough to see if it might be heading your way: http://en.blitzortung.org/live_lightning_maps.php?map=14
Thor seems to be picking on the Crimea this morning.

(Turbulence, of course, is strongly associated with thunderstorm activity, both being of more than passing interest to fliers. But vertical instability in general is related to gustiness, which is obviously something which keenly interests sailors.)
 
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tudorsailor said:
Wow, certainly picked right day to look at Frank's recommended site

But I do still wonder how this forecast has the thunderstorms, but most others do not. Are the thunderstorms predicted "manually"

……………………
TudorSailor
Click to expand...


I assume that you are looking at websites issuing automatically generated texts and GRIB files. Most GRIB services (zyGrib, many iPad apps, XCWeather, Windguru etc) just provide data straight from the computer. These data include gust speeds, rainfall rates and CAPE. The last of these is an instability index. With values over 1000, lightning and thunderstorms are possible. The larger the number, the greater the risk.

Some services and apps including WeatherPro (a MeteoGrouo service) have built in software to use these data and other information to give “weather” in words or symbols as well as wind, cloud cover, rainfall data that come straight from the computer weather model (usually the US GFS).

The NAVTEX/Inmarsat texts, like most VHF marine forecasts, are written by forecasters at national Met centres. There is human interpretation of the computer output added to local experience. This is why I always say, and do so in Reeds Weather Handbook, that we sailors should always heed GMDSS services.

GRIB data from such as zyGrib and the various apps are more useful overall than GMDS texts. However, these human forecasts are a vital warning service. I would never rely on automatically generated texts for safety purposes – fog, gales or storm force winds, squalls etc. I do my planning using GRIBs. I use GRIBs to get a handle on whether that “westerly” is more SW than NW. I use the GMDSS to check that wind strengths are not going to be more than we can cope with sensibly or that fog is or is not going to be a major problem.
 
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