Zezo forum: Dowload "all.grib" file

Dowload "all.grib" file

Post by Ben | 2020-04-15 | 10:04:02

Hi
Just a note that for some time, the all.grib file has been very long to download.
Benoit

16 Comments

Post by zezo | 2020-04-15 | 13:08:15

Maybe some part of the internet between us is congested because of all people staying home.

Anyone else having problems?

Post by Ben | 2020-04-16 | 07:25:57

Hi
This morning, very fast !
Subject closed....
Benoit

Post by zezo | 2020-04-16 | 11:51:33

I also tried from cloud instances in EU and US and got 8-10MB/sec, which is the theoretical limit as the server sits on a 100Mbit link.

But the congestion can be intermittent and/or affect different ISPs.

There was some packet loss to your IP address yesterday, but hard to localize exactly - could be in your last mile provider, my ISP international links or somewhere in between.

Now it's better, and the round-trip time is also considerably better (which also suggests congestion):

yesterday:

ping -s 1500 xx.yy.92.27
PING xx.yy.92.27 (xx.yy.92.27): 1500 data bytes
1508 bytes from xx.yy.92.27: icmp_seq=0 ttl=58 time=212.698 ms
1508 bytes from xx.yy.92.27: icmp_seq=1 ttl=58 time=204.227 ms

vs.

ping -s 1500 xx.yy.92.27
PING xx.yy.92.27 (xx.yy.92.27): 1500 data bytes
1508 bytes from xx.yy.92.27: icmp_seq=0 ttl=58 time=45.454 ms
1508 bytes from xx.yy.92.27: icmp_seq=1 ttl=58 time=44.758 ms

Post by Shelisteam | 2020-05-22 | 11:31:11

all grib - has the diferent data of the wind compared to the game even by 2-3 kn.

GFS - forecast more than 3

What forecast is correct for the game?

Any advice?

Post by zezo | 2020-05-22 | 12:26:36

It should contain almost exactly the game data at points with integer lat/lon (subject to specific rounding difference), but within the square your software uses different interpolation and gives different result.

There is also a 2.0 knots minimum wind limit in the game. It never gets below that, even if the GRIB says 0. That's applied at the last stage of the calculation, so the direction is preserved.

Post by Shelisteam | 2020-05-22 | 19:21:24

ALL GRIB
Data from the daschboard TWS - 7,38
TWS GRIB with standard interpolation - 7,49
TWS GRIB with spatial only interpolation - 7,81
TWS GRIB with SOL interpolation - 7,19

GFS
Data from the daschboard TWS - 7,38
TWS GRIB with standard interpolation - 7,61
TWS GRIB with spatial only interpolation - 8,14
TWS GRIB with SOL interpolation - 7,57

This is on light winds on strong one, differences are highier

Post by zezo | 2020-05-22 | 19:54:38

SOL should be using temporal interpolation.

Without temporal interpolation the results will only match every 3 hours (round 3 hours on UTC)

What tool is this?

Post by Shelisteam | 2020-05-22 | 20:01:13

Qtvlm

Post by zezo | 2020-05-22 | 20:36:05

Vlm used 0.5� gribs, not sure how well qtvlm deals with 1� resolution.

Also found this https://forum-marinsvirtuels.forumactif.com/t849-la-meteo-chez-vlm. Not sure what to make of it ;-)

Post by zezo | 2020-05-22 | 21:36:29

It's also possible that the data in all.grib is incorrect. It used to be a part of the data conversion years ago when VR used V1 data but V2 was easier to use. There were some rounding errors between v1 and v2, so I was converting to get in sync, or maybe my toolchain at the time did not support v2.

So if someone spots a significant difference between NOAA GRIB or VR winds, at integer coordinates and at UTC time of 0,3,6,9,12,... , please drop me a line with the numbers.

Post by Shelisteam | 2020-05-23 | 12:15:46

38�N47'25", 001�E51'05" TWS game 7,65 (dashboard)
TWS from the all.grib - Standard interpolation 7,81
TWS Xygrib 7,17 - Standard interpolation
TWS VLM=GFS NOAA grib - 7,33 - Standard interpolation

Post by zezo | 2020-05-23 | 17:49:04

You have to check the integer points. Like 40N 0E (there are lines there)

Post by zezo | 2020-05-23 | 17:55:35

Right now - 10 minutes before the 18h GRIB

game - 2.9 @ 124
all.grib via zyGrib -> 3.0 @ 125

You should get the same number in qtvlm at 18 UTC, and probably the next 3 hours without interpolation.

P.S @18 UTC - game says 3.0 @118, so 7 degree difference to the grib

data for 21:Z:

game: 6.8@64
grib: 6.1@67

The difference comes from the way VR rounds the wind U/V components. Repeating, all.grib is not modified according to VR rounding rules, just converted from v2

Post by CoreTeam | 2020-05-23 | 12:27:59

@zezo when is the approx GTM time that allgrib is finalized?

Post by zezo | 2020-05-23 | 17:51:11

The file time is in UTC when you list the directory

all.grib 2020-May-23 17:10:11 21.5M application/octet-stream

job is stared at 5/11/17/23 + 10 minutes. It has 2-3 files to get and then generates the output data.