Weather apps: Am I alone in distrusting them?

[Cpt Pat]

I recently visited a neighbor's boat. He was excited to show me his new Iridium Go and Predict Wind software.

The screens were undeniably pretty and colorful. A far cry from the monochrome hand-drawn NOAA charts I've been using both as a skipper and Instrument Pilot in airplanes for decades.

So I asked: where are the 500 millibar charts? And what is the seastate in those areas on your displays? Who reviewed those charts before publication? What is the delay between acquisition of the raw data and publication? Where are the hazardous weather warnings on those charts?

When asked why I needed all that, I explained that:

• With the 500 millibar charts, you can visualize the upper level dynamics driving the weather and get a feel for the dependability of the surface forecasts.
• So far as seastate: the wind isn't going to kill you - but the seastate might. I've been out in dangerous breaking seas in nearly no wind - and that is the worst combination of all. There is no direct correlation between local wind and seastate, beyond the generation of usually benign wind-waves.
• If a meteorologist didn't sanity-check the forecast - then I'm trusting a robot to do pattern analysis. Computers are very poor at analyzing subtle patterns. Human meteorologists do a far better job at that. They have this mental process called 'intuition" that improves with experience.
• Weather data delayed is weather data denied. Old forecasts are dangerous forecasts in rapidly deteriorating weather. Just read about the wreck of the El Faro to see how delayed but pretty-colored weather charts generated by a robot can lead a skipper into an inescapable box. In an airplane, you can generally outrun or turn around to escape unexpected weather - not so in a boat moving at 6 knots.
• And when I called up one of my sets of NOAA charts (https://ocean.weather.gov/shtml/P_brief.php) and pointed at a developing gale marked on the chart, I asked where that warning was on his charts. His reply: "There's an app for that." A separate app... "By the way," I said, "do you see that name in the legend box labeled "FCSTR" on the NOAA Sea-state Analysis chart?" That's the NOAA forecaster's name -- an actual human being. They sign their charts!"

Being surrounded by Silicon Valley technophile skippers, I felt very alone until a little research brought up this slide deck titled: Delete Your Weather Apps from a recent US Sailing symposium: https://www.ussailing.org/wp-content/uploads/2018/12/Delete-Your-Weather-Apps-Chris-Bedford.pdf. The author, a meteorologist, makes the same points but much more elegantly than I. (I hope you will look over that document before flaming me...)

I smiled and gave my Pactor Modem a little pat of gratitude.

[sail sfbay]

I like Windalert and have downloaded on my cell phone as an app: https://www.windalert.com/

I also us: https://www.windfinder.com/forecast/...n_gate_bridge#

[tkeithlu]

The more we become automated, the less raw data you get. Actually, it's worse than that. You no longer get the work of the first person to digest the raw data, that being your signed weather map. The same is true with a chartplotter; it's a step removed from a paper chart. The multiply digested information requires less of the user; you need some weather expertise to digest the raw stuff for yourself, just as you need skill to plot your position on a paper chart. The user of the digested stuff can be ignorant of a threat you consider real.

I think you are suggesting, and I agree with you, that being fed pablum as weather information is ultimately dangerous, just as relying only on a GPS plottter is ultimately dangerous. You learned to read weather for your pilot's license, so did I, and we both learned to read marine charts. We are not satisfied with the derivative information, want to know on what basis a prediction was made, and are safer because we and others can do it.

You're more expert that I am, but I agree with your position on all of this.

[Suijin]

I think it's wise to distrust, to a certain extent, ALL forecasts unless you have confidence that you're looking at a settled weather pattern.

That said I agree that apps/uninterpreted weather information are not sufficient by themselves for forecasting for the very reasons you mention. But they do have their value when evaluating weather. For example, PredictWind allows you to choose among different models and run animations of isobars over time. This visualization can be extremely useful in creating a mental model of larger weather patterns at work in following 1-5 days.

Your friend may not have been fully aware of the full extent of information available. Seastate is certainly available.

[Snore]

Timely question! I am just finishing an article on this topic.

IMHO you need PW AND LickGrib. LuckGrib will let you download the 850 and whatever else you want (except the full Euro model). The other method is to send an email to one of the auto-responding servers for what you want. Then view the emailed GRIB in the viewer of your choice.

And yes you can get the 500mb in LG, as well as the standard forecasts in PW.

Doing a FLL to USVI delivery, I came to like having the big GFS pressure GRIB from West Texas to 60 and from north of the Great Lakes to 15N. Pulling that once every day or two, supplemented by twice a day wind gribs and I was set.

Having the ability to load the vessel’s polars into PW made routing a snap. Add to that the “comfort” routing option and the system comes up with a recommended route to avoid winds/waves above the set values.

While I am somewhat a technophile, I realize anything you download still needs to be reviewed. At the end of the day it is your tail out there. Only PW gives data from the GFS and European model.

[AedanC]

Windy (the red App, not the Blue one) also gives access to GFS and ECMWF (Euro) models. It also can display a far wider range of parameters than PW.

[Discovery 15797]

Originally Posted by Cpt Pat

So I asked: where are the 500 millibar charts? And what is the seastate in those areas on your displays? Who reviewed those charts before publication? What is the delay between acquisition of the raw data and publication? Where are the hazardous weather warnings on those charts?

In full disclosure, I also use PredictWind with the Iridium Go setup. I find it completely invaluable offshore.

First, you must realize that you are comparing synoptic charts with prognostic charts. 2 different animals.

Synoptic charts are compiled 4 times daily from current observations, and past observations, and prognostic models which is analyzed by humans, who then predict what may happen in the near future. (Thus, synoptic charts are actually delayed weather reports.)

Prognostic charts are compiled 8 times daily from past observations, current observations, and use numerical weather prediction models (made by humans) to predict what may happen in the future within the next 5 days or so. (I personally found that 3 days out is generally most accurate.)

Both charts have value, both charts have limitations. Both are useless by people who don't understand how to correctly interpret the information and data.

WRT your specific questions...
The PredictWind provides 4 different models. The isobars are readily available and displayed on different views in the software.
The GMDSS report can also be downloaded. This is the identical "human" forecast that you get when you download a synoptic chart. The GMDSS highlights the warnings.
The software displays wave, cloud, temperature, rain, gust, and (most importantly) Convective Available Potential Energy (CAPE) data (which synoptic charts do not provide).
As explained above, the synoptic charts show delayed info, the prognostic charts show future info.
Synoptic charts do not provide sea state; predicted sea state is provided in the GMDSS reports and analysis. While the PredictWind software does provide predominant wave information (height and direction and period), it is not good at showing mixed and confused sea states. (Actual sea state is sometimes very different than predicted.)

IMHO, the PredictWind software and service is most valuable offshore. It is also easier to explain to (learning) crew why I make certain routing decisions. (I don't always like the routing suggestions of the software). Additionally, I get up-to-date info and data more often compared to synoptic charts (although the GMDSS reports are still only compiled 4 times daily.)

Unfortunately, too many people never learn to read or try to understand weather charts and associated weather data to make informed decisions. Also, many people never learn to use software like PredictWind and thus either don't utilize it's full capabilities, or distrust it. Also, if you don't understand the information either the synoptic chart or prognostic chart provides, both are pretty damn useless.

The problem is not with the software (I find it especially valuable offshore), it is with the human. Just as there are 'sailors' who rely solely on chart-plotters for navigation and have never learned to plot courses on a paper chart or read and comprehend pilot guides and notices to mariners. Those same 'sailors' will look at fancy weather chart pictures on the screen yet never learn the difference between synoptic and prognostic charts, or take time to analyze CAPE data, read GMDSS reports, etc.

[Discovery 15797]

Originally Posted by Discovery 15797

Synoptic charts do not provide sea state; predicted sea state is provided in the GMDSS reports and analysis. While the PredictWind software does provide predominant wave information (height and direction and period), it is not good at showing mixed and confused sea states. (Actual sea state is sometimes very different than predicted.)

Sorry, this was supposed to be synoptic charts and prognostic charts do not provide sea state. They both provide predominant wave height, direction, and period. But, IMHO neither is very good at the specific state of the sea at your position in the ocean.

Also in my experience there is a direct correlation between local wind direction and sea state. For example, localized winds that run counter to strong currents create a confused surface sea state. Offshore a strong squall is capable of generating confused seas that contradict prevailing waves with surface chop that is anything but benign and leads to a very rough ride. Which again is reason to learn how to read the charts and comprehend the information in the GMDSS report/analysis.

[Snore]

Originally Posted by AedanC

Windy (the red App, not the Blue one) also gives access to GFS and ECMWF (Euro) models. It also can display a far wider range of parameters than PW.

I was not aware that windy worked with GO. Please confirm.

[Discovery 15797]

Originally Posted by Snore

I was not aware that windy worked with GO. Please confirm.

Windy does not work with Iridium Go. (They say is is a licensing agreement issue, but I suspect it has more to do with the lack of GRIB viewing software that is not browser based.

Windy is like the swiss army knife of "internet" only weather viewers. It has some pretty cool features as long as you are tethered to the internet.

But, it also completely lacks any features that would be useful for departure planning, route planning, polars, GDMSS analysis, etc.

[Snore]

Originally Posted by Discovery 15797

Windy does not work with Iridium Go. (They say is is a licensing agreement issue, but I suspect it has more to do with the lack of GRIB viewing software that is not browser based.



Windy is like the swiss army knife of "internet" only weather viewers. It has some pretty cool features as long as you are tethered to the internet.



But, it also completely lacks any features that would be useful for departure planning, route planning, polars, GDMSS analysis, etc.

That is what I thought- but original post made it sound otherwise.

Thanks