News & Events for Chesapeake Bay

Weather App Shootout – Round One

Date Posted: 2018-04-24
Source: Bob Sherer, Contributing Editor



Editor’s Note: Predicting weather and interpreting data from the numerous computer models used by meteorologists is tricky business. Added to that is the way in which various weather apps present information along with the timing of their updates. In this review of four weather apps, Contributing Editor Bob Sherer conducted a simple evaluation based on his experience on a particularly windy day.

Hank Pomeranz, noted yachtsman, former Navy meteorologist and navigation expert from Southport, NC, reviewed this article before publication. Hank’s observations of this evaluation included insight into recognizing that the multitude of variables in forecasting make it difficult to trust any app, or computer model. Nonetheless, weather reports and apps are valuable for all of us. Let us know what you think.



Where did this 20-knot wind come from? As always, it’s right on the nose. NOAA never predicted it - they said 5 to 10 kts! 

Ever have this happen to you? I’ll bet not a single boater answers “no” to this question. What’s interesting about this event is that only one of four popular weather apps predicted the wind correctly, and even the NOAA Coastal Forecast missed the boat! 

In my ever-widening quest to find the perfect weather app (it doesn’t exist), I bought four of the most popular apps and have begun testing them against each other, along with the NOAA forecast, as I head north this spring. 

Each of these apps predicts more than just wind. They also include waves, clouds, rain, temperature, etc. But for this article, I’ve focused only on wind. This is my first report and is based on conditions we experienced on April 5, 2018 leaving Rodriguez Key for Miami, FL. 

My evaluation format is simple: record the prediction of each app and the NOAA Coastal Forecast and compare them to what actually happens. (If anyone wants to recommend another app for this exercise, please let me know.) The sample size of weather events is just this one day; not a large enough data set to make an empirical-based decision, but the information and observations are real. I’ll conduct further tests as I head north. Perhaps one app, or the NOAA Coastal Forecast, will continue to stand out. We’ll see. Here are the apps I’m using: 


PocketGrib was my first weather app and I have come to depend upon it over the years for coastal cruising. It provides forecasts every three hours for up to eight days in advance, although it will interpolate to every hour if needed. PocketGrib uses the GFS (Global Forecast System) computer model, which is provided free of charge by the National Weather Service (NWS). It is the easiest of all the weather apps to use and the data files are relatively small. The app costs $5.99.



Ventusky is from a Czech meteorological company based in Pilsen. It displays the wind with streaming dots like Windy. One difference is that Ventusky overlays the screen with a grid of numbers showing wind speed, a handy addition. It uses several weather models including GFS but does not have ECMWF, the noted European model that Windy has. Ventusky costs $3.99. 


Windy is a very popular weather app with more options and capabilities than PocketGrib. It shows the wind as a streaming series of dots, almost hypnotic and pleasing to the eye. It has all the best weather models to choose from: ECMWF, GFS, NEMS, NAM, and ICON. The GFS is the same model used by PocketGrib. The ECMWF is the European model that many consider the gold standard. You can Google the acronyms to find out more. I used the ECWWF model in these tests. From the developer of Windy: “Our goal is to provide best weather forecasting service in the world. So far, we have failed to find a sustainable business model.” In other words, it’s free.


PredictWind is from the weather team manager of Alinghi – winner of the America’s Cups in 2003 and 2007. The parent product was developed for America’s Cup races. It uses four models: ECMWF, GFS, and two proprietary models: PWG and PWE. I used PWE for the predictions in my assessment. It’s based on the European ECMWF, but with tweaks learned from Cup racing. The app is free to download but requires a subscription of $28.99/yr. 


Now, back to the morning of April 5, 2018. Our first duty every morning of a leg is to look at our weather apps. 


First up was the NOAA weather report. That was what we expected from the previous night’s report, good news. Anything less than 10 kts is fine from any direction, especially if it’s going to die off in the afternoon. 


Next is the PocketGrib forecast for 11:00 am. At this point, we would be about two hours out of entering the Cape Florida Channel. It agrees with the NOAA forecast, nothing over 10 kts. Looks like a go. If high winds were predicted in the afternoon, we would duck into Caesar’s Creek and either stay there overnight or go up Biscayne Bay to Marine Stadium. So, we had a choice if the weather was not to our liking. However, this forecast said it was good for an outside run to Miami, which we would reach by 1:00 pm. 


Ventusky is next. Note that the wind prediction still indicates nothing over 10 kts. 


The Windy forecast for 11:00 a.m. up near Miami shows 13 kts. This was a little troubling. But then 11 –13 kts. is still okay and it was calmer prior to 11:00 a.m. 


The PredictWind forecast was disturbing. It showed winds of 20 kts. developing late morning. The challenge now was whom to believe?

We wanted to go outside all the way to Miami since it would be faster without the detour through Caesar’s Creek. We had reviewed the NOAA forecasts (by humans) and four apps that present the information with seemingly no human intervention. So, we assessed the situation and allowed hope to overrule the one troubling report of high winds and went outside. By the time we reached the Caesar’s Creek entrance the wind had not yet kicked up, so we moved on. Mistake. Besides, PredictWind was still relatively new to me and my tried and trusted PocketGrib said everything was going to be okay. Once past Caesar’s Creek, I brought up the latest NOAA coastal forecast and sure enough, they had changed it from 10 kts. and decreasing to 5 to 10 to a new forecast of 10 to 15 kts! Thanks a lot NOAA, but by that time I didn’t need a forecast to see the increasing winds speeds.


So, what really happened? Here’s a photo of my wind gauge at 11:30 a.m. The wind was on the nose, spray was coming over the bimini and washing down the dodger and ahead was a sea of whitecaps. This was not a storm; there was no rain, just wind. 


From the Fowey Rock readings, you can see the winds started around 11:00 and peaked between 12:00 and 2:00 p.m. around 20 kts.  

What was displayed by the apps real time? I gave each one another chance at 11:47 to show actual conditions at 11:45. In other words, tell me what’s happening right now. Did they correct themselves?


PocketGrid (not shown) and Ventusky were out for a lunch break. 


Windy was a little closer. 


PredictWind was dead on. 

For this round, I’ll give first place to PredictWind, second to Windy, third to NOAA Coastal Forecast (at least they corrected themselves later), and a tied for fourth to PocketGrib and Ventusky. 

Of course this does not mean that PredictWind is the best app. There is a lot of weather ahead and we’ll see who comes out on top in the long run. I will continue grading the rounds and perhaps at the end of the cruise, I’ll issue an update on who’s the winner. If anyone wants other weather apps to be included, please comment and let me know what app you think should be included. It would also be interesting to have a person’s forecast included in the boxing rounds. Any volunteers? 

We have some exciting weather tests ahead that include the Chesapeake Bay, Delaware Bay and up the coast of New Jersey. I will focus on those days when there is variability in the predictions like the example I showed in this article, so we get a true test. After all, we all want to know the weather – and the best app or service to predict it.

  • Comment submitted by Julia Hedges - Wed, Apr 25th

    Would love to see you add Windfinder Pro and Buoyweather to your comparison.  Thanks for this article. 

  • Comment submitted by Bill Wehmer - Wed, Apr 25th

    Nice write up!  My goto app is also Pocket Grib.  I will have to check out predict wind.  Please post an update when you have more data to evaluate...this was very helpful.

  • Comment submitted by Stacey - Wed, Apr 25th

    Would love to see Marv’s Virtual Weather Buoy information included. It can be found at   thanks so much for doing the research. Will be interesting to see what your future research turns up. 

  • Comment submitted by Bob Shircliff - Wed, Apr 25th

    I'll second Julie's pick of Windfinder Pro. Lots of Loopers also use Marv's Weather Forecast emailed out each day. It would be interesting to see how Marv fares, too. Thanks, Bob!

  • Comment submitted by Clare - Wed, Apr 25th

    I'd like to see WindAlert and WindFinder added to the test.  I have 3 of the four you mentioned plus these two that we use for coastal and ocean passage predictions.  We will also be heading up the east coast from NC in June. Loved what you've done so far.  We have this issue at least once a week. We're cruising the Bahamas at present.  

  • Comment submitted by Don - Wed, Apr 25th

    weather Chanel app is mostly reliable. As a pilot also aviation weather reports give current and forecast winds. All airports with control towers have equipment for real time winds. (Helpful if along coastline or inland) Flight service also has all weather information needed that I use for marine to get the big picture! U need to know how to use the system.  Try 1800-wx-brief for this information. Helps to say ur a student pilot and they will be verry helpful        Don

  • Comment submitted by Marlin Greenfield - Wed, Apr 25th

    very interesting!   Keep it coming as often as possible!   Thank you!

  • Comment submitted by Mark Kiehl - Thu, Apr 26th

    As the author stated, you cannot base a decison on a paticular weather app based on a single day of weather experience.  I have been preforming the test outlined in this article for four months in the FL Keys, but in greater detail, and with more apps.  I found that the value in the weather apps is in the ability to compare wind/wave forecasts based on different weather MODELS.  When several models agree closely, your confidence can ge high in the forecast.  When the models are very different, then anything can happen.  It is nearly impossible to check actual wave direction, period, height in the FL Keys because nearly all measurement stations (bouys) are gone.  

  • Comment submitted by Brian McMahon - Thu, Apr 26th

    During the winter 2018 season in Florida I used Predict Wind guite alot and compared to NOAA weather radio. The unsettling observation from Predict Wind, which shows predictions from multiple models, is how different they can be.  GFS was often way out of sinc with the other models and often wrong.  I settled on their PWG model, which seemed to be correct most often.  In planning trips I found it most helpful to look at the predictions over a 3 or 4 day period to get a general sense of what the weather was doing.  Daily or hourly predictions just don't seem to be accurate enough to rely on them.

  • Comment submitted by Don - Thu, Apr 26th

    Thats exactly why in aviation there is a way in flight by radio to call flight service for real time changes in conditions  Anywhere! No weather forecast is perfect!  Marine forecasts leaves it all up to the captain. Boats move slow so when weather changes fast captains better have a plan to help yourself and passengers! We need changes to reporting information!    

  • Comment submitted by Jackie Rosholt - Fri, Apr 27th

    After getting slammed at the junction of Neusse,Pamlico and Bay Rivers in NC I bought Predict Wind after several boats said they saw us leave the anchorage and thought we were brave. They were relying upon Predict Wind and caught up with us the next day when we stayed over at River Dunes to recover from our harrowing experience. Since then I still use multiple sources and find Predict Wind and NOAA’s to be the most reliable.

  • Comment submitted by Larry - Fri, Apr 27th

    Great idea! Passage Weather might be good to compare also. I use it along with Predict Wind, Windytv and Windfinder Pro. It will be interesting to follow your observations up the coast! Thanks for your effort with this!

  • Comment submitted by Sequoia - Sat, Apr 28th

    thanks, interesting. Have you looked at or used Sail Flow? That Andy Predict wind are my two most trusted. I have found NOAA to be almost useless and inaccurate so many times I ignore it completely now and just use of of the above, and then also use Passage Weather online for longer ocean passages offshore. 

  • Comment submitted by Wayne Foster (capt) - Sat, Apr 28th

    Please note that (not the downloaded app) has a 'compare' button that allows you to look at the four models on one screen

  • Comment submitted by Craig McPheeters - Sat, Apr 28th

    Another, new, app to try out is LuckGrib.  LuckGrib is new to iOS but has been around on the Mac for years.  LuckGrib gives you free access to many different weather models, including GFS, the Canadian GDPS, HRRR, NAM, several models for currents, several wave models and many more.  HRRR is notable in that it refreshes every hour and offers 3km resolution.  NAM also has 3km resolution.  When close to land, the higher resolution can help resolve local weather.  Most models offer the ability to download wind gusts as well as sustained winds, which is useful as a mesure of the wind stability.  Downloaded files are easily viewed with immediate access to the actual values and a meteogram display to see trends.  More at

  • Comment submitted by Angus - Sat, Apr 28th

    Add weatherunderground to your mix pls. It uses aggragated data from all the near by weather stations it broadcasts online. Also, it the choice of NASA Launch control for any of their missions.

  • Comment submitted by Martin Henry - Mon, Jun 18th

    Perdict Wind is our go to utilizing the various models against, PocketGrib, Marine Forcast/NOAA, SailFlow to make a semi solid decision.  Got to remember weather is what is where you’re at...

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