Date: 1/17/03 8:23 PM From: Luis Soltero To: Bulletins@marinenet.net, henning@obenaus.org, kiwi@sv-kiwi.com, n4azz@winlink.org Copy: Subject: Grib Weather Update Hello Everyone, This is just a reminder that as a FREE public service we offer wwave3 5 day wind forecast for the world in grib format. To access these files simply send an e-mail to gribmail@marinenet.net with "info" in the subject line. More information on our grib service can be viewed on the web at http://www.globalmarinenet.net/gribs.htm. Free grib viewers are available for download from http://www.globalmarinenet.net/downloads.htm What we offer... We offer 5 day wind forecasts derived from the NOAA MMAB Operation Wave Model (wwave3) in grib format. "Why are these gribs any better than other gribs out there", you ask? Good question. Here is the Answer. Grib files that GMN generates originate from computer models created by NOAA. NOAA has several computer models that it uses for forecasting but only two of these model output data that we can use readily. The two models are "Global Forecasting System GFS" and "MMAB Operational Wave Model (wwave3)". GFS is a monster (I don't mean this in a bad way. After all GFS is one of the main forecasting/prediction tool and NOAA). The program models everything from ice concentrations in the upper atmosphere through pressure gradients, temperature, thunderstorms, tornados, predicts weather for both ocean and land masses, etc. Basically everything. In short GFS is a **VERY*** complex model. For people in the business of providing weather to cruisers the GFS extended forecast is really nice. It contains, pressure, temperature, wind dir/speed information all in one file. The grib file contains multiple forecasts computed in 24 hour time slices. The second model (MMAB or wwave3) is a computer program specifically designed to predict wave height, direction, and time period. That is all it does. As a by product it forecasts the surface speed and direction of the wind since it needs this information for computing the wave parameters. Unlike GFS, wwave only computes wind speed over water. wwave generates a 5 day forecast with time slices computed every 3 hours. When it comes to computing Ocean Wind Forecasts GFS falls short. The complexity of the model causes it's surface wind forecasts to be inaccurate for predictions days into the future. Wwave3 on the other hand is usually right on the money. Keep in mind that wwave3 was designed to forecast ocean wind direction and speed where as GFS was designed to forecast snow fall in Kansas + many other things. GFS has many strengths but it simply is not as good as wwave3 when it comes to Ocean Wind predictions. So why this lengthy discussion? Well there are currently 4 provides of grib files. Saildocs and Raytheon use GFS forecasts. MaxSea generates wwave3 forecasts but this data is really only accessible to users of MaxSea software. That leaves GMN... As a FREE public service we felt it was very important for the wwave3 gribs to be made available to the sailing community... i.e. our cruising friends... ie. you! So here they are. Please use them and enjoy. A Tip for Calypso E-Mail users. It's possible to view the grib files straight out of calypso. Here are the instructions. a) Install the grib viewer (see http://www.globalmarinenet.net/downloads.htm) b) Request a grib file by sending an e-mail to gribmail@marinenet.net and put Atlantic in the subject line. (Or any other valid region) c) When the mail arrives double click on the mesg header to open the mail. d) Now double click the attachment. If this is the first time you have tried to read the grib weather using this technique a box will popup on the screen. click on "cnavw" and make sure you check the "always use this program to open this file type" box. Now hit OK. The grib file should now open and display the requested weather forecast. From now on whenever you double click a grib file it should pop open and display the weather. Thanks you for your consideration. --luis Luis Soltero, Ph.D., MCS Director of Software Development Global Marine Networks, LLC Tel: 865-379-8723 Fax: 615-985-0403 E-Mail: lsoltero@globalmarinenet.net Web: http://www.globalmarinenet.net Wireless E-Mail, Web Hosting, Weather and more...