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Wednesday, December 2, 2015

New LuckGrib site -

The LuckGrib blog has moved to a new site:

I hope you will find the new site much more readable and informative.

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Wednesday, November 4, 2015

LuckGrib version 1.1 - available now

Version 1.1 of LuckGrib has been accepted by Apple and it is now available on the Mac App Store.

As always, all feedback is welcome.

Thursday, October 29, 2015

LuckGrib V 1.1 - available soon

The next version of LuckGrib, version 1.1, has been submitted to the Apple App store.  It normally takes around a week for them to review the app, after which it should be available on the App store.

First, I would like to thank all of the people who volunteered to become Beta testers for me.  Without  your help, this release would not have happened.  Version 1.1 of LuckGrib is now using the GPU to draw its graphics.  Without the test coverage I received on the various types of machines my Beta testers had, I would not have had confidence that LuckGrib was really working.  There are a few of you who went above-and-beyond in your help in tracking down subtle OpenGL issues - thank you!

For those of you who were not part of the Beta program, I think you are going to like this next version.  A lot.  I'm really happy with how its turned out, and feel, with this new version, LuckGrib is  now delivering what I wanted when I first thought about building it, a little over a year ago.

Its has been roughly 11 months since I first started working on LuckGrib.  With this version now complete, I'll start working on the next version.

I have some ideas on features I would like to add to the next version.  If you have ideas for what you would like to see in a new version, please let me know.

As I write this, I'm on my sailboat, s/v Luckness, in Fiji, preparing for my passage to New Zealand.  I'm studying the weather daily, sometimes downloading refreshes to the weather models twice a day. As a user of the application, I appreciate the effort "the developer" put in to make using it so easy.  Comparing GFS and CMC models is trivial and intuitive.  Planning on where I expect to be one day after leaving, two days out, three days out, etc is also very easy.

If you are a sailor and are reading this article without having yet purchased this application - do yourself a favor - buy it.  You won't regret it.

If you're a weather enthusiast and are looking for a Mac application to study GRIB models, I don't think you'll find anything better - certainly not at the price.

Enjoy Version 1.1!

   (currently on s/v Luckness in Fiji.)

PS.   The beta program for Version 1.1 is now closed.  If you are interested in participating in the beta program for the next version, please let me know.

Saturday, September 19, 2015

Beta testers required

[Updated: Sept 30/2015 - see end.]

A new version of LuckGrib is currently going through Beta testing.  This new version has an entirely new draw infrastructure, which along with other changes, has improved performance dramatically.  LuckGrib version 1.0 was fast.  LuckGrib version 1.1 is much, much faster.

The latest beta has been tested by a small group of people, I am hoping to expand the program to cover a wider variety of Mac hardware before releasing the application to the Apple Mac app store.

If you are interested in LuckGrib and would like to help this application improve, let me know and I will send you details on how to get the latest Beta version for your testing.

Please email  If you could include your machine type and year along with the display type and whether or not it is a retina display or not, that would be appreciated.

There are additional changes planed in the future.  If you would like to remain part of the beta program and help expand this programs functionality, let me know.

Thank you!

[Update: Sept 30/2015]

The third beta has now been released.  This new version is looking very promising, however it is currently experiencing problems on Mac's with Retina displays as well as Mac's with two GPUs (such as a 15" MacBook pro.)  If you're interested in seeing this software released on the Mac, and have a Mac with a Retina display or dual GPUs, please consider joining the Beta program.

Wednesday, August 5, 2015

LuckGrib version 1.0 is now available

After months of development, and hard but interesting work, LuckGrib has gone from an idea in my head, through several rough prototypes, then on to evolving and growing more capable which eventually lead to a beta program involving 7 versions - LuckGrib version 1.0 is done.

I submitted LuckGrib 1.0 to the Apple App store last week.  This morning I received an email from Apple that the application had entered the 'in review' status, and an hour later I received a final email that the app was approved and would soon be available on the App Store.


LuckGrib has been a work of passion for me over the last 6 months.  I have a background in software architecture, computer graphics, math, import/export of a variety of file formats, some user interface, a little animation.  This application has touched on a lot of what I've learned over the last 30 years and it has been a fun project to work on.

Creating LuckGrib would not have been possible 10 years ago.  Its an app that is designed from the bottom up to run well on the hardware we have available to today.

To learn more about LuckGrib, there are video's on YouTube (search for LuckGrib) and a review written by David Burch, which I referenced in a blog post a little earlier.

Of course the best way to learn about LuckGrib is to buy a copy and try it out.  If understanding weather is important to you, I believe you'll enjoy and appreciate LuckGrib.

Please let me know what you think of this new app.  If you have any suggestions for improvements, don't hesitate to contact me.

If you like the app, please leave a comment on the App Store.

Craig McPheeters,
s/v Luckness,
August, 2015.

First public review of LuckGrib

I started development of LuckGrib while sailing in New Zealand, around December 2014.  Over the next four months I dove deeply back into software development and the bulk of LuckGrib was formed.

I formed a beta program early in 2015 and had help from many other people who were using early copies of LuckGrib and providing me feedback.

Toward the end of the beta program, once the program had started to resolve itself into what was closer to its final form, I invited David Burch into the beta program.

I have never met David and only know him through the excellent books he writes.  Through my activities as a sea kayaker and now as a sailor, I ended up reading three or four of his books, and it struck me that they were always very well written and informative.

David is the author of the excellent weather book, Modern Marine Weather, which I have read cover to cover several times.  When I started as a sailor I had a lot to learn, and books such as David's were enormously useful to me.

It turns out that David has a Mac and uses it daily in his work.  He agreed to join the beta program for LuckGrib and was able to quickly provide me with some feedback on the application.  He is deeply involved in modern weather forecasting, using a wide variety of sources.  My impression is that he's a little leading edge.

David has a blog, writing on all sorts of topics of interest to the weather community.  He recently wrote a review of LuckGrib and provided me with a quote that I can (and have) used in the description of the app on the Apple App store.

The quote he provided is:

"The LuckGrib viewer is elegant, fast, and functional.... a must have app for all sailors using Macs for weather work." —David Burch, Director of Starpath School of Navigation and author of Modern Marine Weather.
His review can be found at:

Wednesday, July 22, 2015

What is GRIB?

[Update: The new location of this article is here.]

A GRIB file is a file based on the WMO GRIB standard for encoding gridded fields.  There are two versions of GRIB files, version 1 and 2 - LuckGrib supports both.  GRIB files typically contain weather information and other environmental information such as wave state.

There are a number of Environmental Modeling Centers (EMC's) which generate weather information, such as the U.S. National Center for Environmental Prediction (NCEP), the Canadian Meteorological Center (CMC), the UKMET service, the European ECMWF among others.  NCEP and CMC have made their products freely available.

The GRIB data generated by one of the ECM's typically contains information on many different parameters (for example: wind; pressure; rain; and temperature.)  Each parameter may be present at different levels of the atmosphere, for example, consider wind at the surface through to the upper atmosphere.  Additionally, each set of parameters and levels will also be available at different time steps - GFS produces forecast data for every 3 hours through to 16 days.  The number of different parameters, levels and time steps available will vary from model to model.

NCEP creates a number of operational and experimental products - the main product produced by NCEP is the GFS model.  GFS seems to have the widest variety of parameters, levels and time steps of the publicly available models.

In very general terms, the different ECM's each have their own computer simulation of the environment along with a suite of algorithms based on their own interpretation of the physics involved in the changes to an atmosphere over time.  The simulations are initialized with a set of initial conditions, which are the most recent set of observations of the atmosphere available.  Given these initial conditions, the ECM's computer simulation is run which generates the set of parameters at the various levels at each time step.

The output of these models will have no human review or correction.  The GRIB data received by the public is the direct output of the model.  By contrast, the official forecasts generated by an organization such as the U.S. National Weather Service (NWS) will take into consideration all of the available weather models along with a variety of other sources, such as satellite images.  The professionals then apply their considerable experience to study all the various, possibly conflicting, pieces of information to generate their own forecasts.  A single GRIB file is useful, but you need to be aware that the model is just one estimation of what may happen in the future.

As you would expect, the area of numerical weather prediction is an active research area with many people studying and improving each of the different models.  There are studies which compare the skill levels of the different computer models - while some of the models do have higher general skill levels than others, none of the models are able to perfectly predict the weather.

Generally, the weather forecasts will be fairly accurate over the short term, perhaps one or two days.  As the forecast progress further in the future, the accuracy of the prediction may decrease quickly.  Many people feel that forecasts beyond four or five days have little predictive value, although how accurate a GRIB forecast is depends greatly on the type of system being forecast.  Storms, fronts and hurricanes are examples of systems that may be poorly forecast in a GRIB file.  Where there are alternative source of information available for these features, you should access them, along with the GRIB data.

There are also effects related to land which can introduce uncertainty.  For example, the wind forecasts along shorelines may be inaccurate due to their being influenced by local effects (gap effects, wind shadows, etc.)

While you are able to download GRIB files with forecasts out to 16 days, the portions of the forecast which are beyond 7 to 10 days may only be useful in studying the model itself - a 10 day or longer forecast has little value in predicting the actual conditions to expect at those time intervals.

A good exercise when starting to work with GRIB files, or when working with a new GRIB model, or examining weather in a new area, is to download a 10 day forecast and then update it every day.  After a few weeks, have LuckGrib show the most distant estimate of the original forecast and then step through the newer files until you are looking at a 1 day or newer file.  (Simply use the up/down arrow keys to step through the files.)  You will notice that all of the different forecasts for the same day and time may vary quite drastically.  This is a valuable lesson to learn - don't put too much trust in long term forecasts.

Ensemble models

Some of the models available are based on an ensemble approach - LuckGrib supports one ensemble model, the CMC model from Canada.  In a traditional approach, the initial conditions of the atmosphere is gathered, the computer forecasting software is run and a single set of data is created to describe the forecast.  

An ensemble model alters this approach slightly.  An ensemble model will run the computer simulation many different times, each time with slightly different initial conditions and possibly different model physics.  The idea is that if you alter the initial condition, or model, slightly, before running the simulation, then if the outputs of all of the runs are fairly similar, you can have more confidence in the result.  If small changes in the initial conditions result in wildly different outcomes, then the system is unstable and it is difficult to know what the true forecast should be.

There is an interesting discussion of the ensemble approach here.

One ensemble model, the CMC model generated by the Canadian government, runs the computer simulation 20 times.  Professional forecasters are able to download the result of all 20 computer runs and compare them.  The CMC model also generates a set of averages.  When you hear someone referring to the "CMC ensemble" or simply the "CMC" data, they are likely referring to the average data created by the ensemble.  Some people prefer to work with ensemble average data, believing that it is more accurate than a single non-ensemble run.


This has been a brief discussion of this topic.  For more depth on the topic, perform your own Google searches, or better yet, read all about it in a book such as Modern Marine Weather, by David Burch.

And with thanks to...

All of the GRIB models in LuckGrib are being downloaded directly from NCEP/NOAA.  Many thanks to that group for making all of their weather information freely available - they are providing a tremendous service to the community of people interested in weather prediction.