# Why is Wind speed in hurricanes so wrong?

### Answer: Windy displays ECMWF or GFS global forecast model. Neither of them is capable to predict exact peak values.

Reasons:

1. Modeling: Numerical model computes grid that has finite resolution in both space and time (~10km in space horizontally, ~100-1000m vertically, ~1-6h in time). Peak values are smoothed, because of coarse grid resolution.
2. Analysis of input data: Calculations are based on measurements. They come from stations, radars, satellites and other sensors. These sensors are not always reliable, so extremal measurements can be considered as errors during data assimilation and thrown away to avoid damaging the computation.

Conclusions:

1. Numerical models are not good at prediction of local extreme values and phenomena. Examples: tornadoes, convective storms, hails, single convective clouds, single orographic clouds, extreme wind speed in storms or hurricanes.
2. Numerical models are good at prediction of averege and "smooth" values. Examples: average wind in last 3 hours, temperature, humidity, pressure field.

• I don't buy this explanation and here is why. The computer model must be accurate or you will never be able to simulate an accurate outcome due to the dynamics of wind, pressure and temperature. All of which, if it is not accurate would throw garbage out of the predictions. If you are not going by real data then what are you using then?
Example of a predictive outcome based on garbage(data) in will equal garbage data out. What data are you using then for wind speeds and why is that data being skewed in the output
The differences that are being reported in the media is 100 miles an hour. How is that possible coming from real data?

• I also want to point out that why isn't real data being positioned at the old prediction data points. How do you check your accuracy then based on the predictive algorithm to the real data? Why was there no mention of this before putting up this site, seeing that the public has access to this site?

• As a side note I checked the accuracy of this by going to my location and checking all data and it is very accurate when compared to current temps and pressure and winds.

• fyi:

"

Scientists have a new way to measure how fast the wind is blowing.

That's because over the past decade, scientists have learned how to measure the speed of the wind at the ocean's surface by observing how much GPS signals are distorted when bouncing off the moving water waves. Now, a new paper reports that such wind speed measurements can be used with confidence when conditions are right, even to measure the winds of hurricanes.

Improved wind speed measurements could help meteorologists better understand and predict storms, says Stephen Katzberg, a distinguished research associate at the NASA Langley Research Center in Hampton, Virginia.

In the early 1990s, Katzberg and colleagues at NASA were asked to evaluate a U.S. Navy satellite for a civilian application in global ocean altimetry. The U.S. Navy was beginning to use GPS in their satellites and the team became intrigued with the question of whether the GPS signals could reflect off the surface of the ocean.

"Normally GPS signals go to a receiver in your car or cell phones, but some of it reflects off surfaces," Katzberg told National Geographic. "It's an incidental thing that turns out to be pretty practical, especially because GPS now illuminates pretty much the entire Earth."

• @Siff Trump's budget cuts climate science funding by about 60%. Weather services are downgrading their accuracy accordingly. Also, Tornado and Flood early warning systems will be completely dismantled. Republicans are getting what they voted for.

• @Siff Trump's budget cuts climate science funding by about 60%. Weather services are downgrading their accuracy accordingly. Also, Tornado and Flood early warning systems will be completely dismantled. Republicans are getting what they voted for.

Lets keep politics out of this! This is about the modeling.

• @Mekronid Utter nonsense

• So what are you suggesting is that Windy.com is more for entertainment purposes than an accurate monitoring tool? if so, that's a damn shame. Time to go back to the traditional radar resources, you know... the ones that are accurate.

• Yeah ok blame The President for this... Right...
Technology that they use for satellite measurements is actually the GPS system and special x-ray detectors. The technology is already there and being used for this additional purpose. That is why I included the information about how they get the measurement data. GPS is already being used extensively and the resultant reflection off of the water let them calculate the movement of said water. The GPS signal is reused for this purpose. Now you are trying to tell me they are getting rid of the GPS system? I highly doubt that.
I also agree that if the system is not accurate in real time then what data are you feeding it every morning, noon and night and why is the data over my own location so accurate when they use the very same systems to show our current weather. In fact they enhance the system using GPS and the local overland radar is fed into the data as well. I don't understand this explanation that they are cutting the funding....
Is windy.com using real data or not and what is the discrepancy between the real time data and current data from the ground sources. Why would the system be so accurate overland but very "Smoothed" over the water?
Why is there a 100 mph difference between the current data shown on your system and the reported data from the media..
They are saying this storm is 185 mph sustained wind with 225 gusts, yet your data is 100 mhp slower.

• @Siff

Sorry some corrections here. Not x-ray but microwave satellites.

• I use the wind Gust icon and this seems to be very close to the TV info. Once I get past the "Eye" it must be affected by the info that you indicated
Ron

• So if I see a wind speed of 180 / 35mph, what does that mean exactly? What's that first number?

• I really like this tool and hope the team can develop to be as accurate as possible. Wishing this team all the best. This tool is my secondary. I have built a map by putting all traditional sources together. with both of these tools, we can monitor and compare the data easier.
http://www.arcgis.com/apps/View/index.html?appid=7eaab00a59954a03b952e44e0150844a

• News agencies across the World are reporting Irma's wind speeds up to 185MPH. How is it that they all know the wind speeds but Windy.com and the Windy app do not?

I have yet to see Windy show Irma's wind speeds any greater than 80MPH. That makes the app useless. How can any of Windy's numbers be trusted with such grievous errors?

• The first number is the compass heading. 0 means the wind is out of the north (blowing to the south), 90 is east, 180 is south, & 270 is out of the west.

• @DailyRich First number is wind direction. 0=north, 180=south etc.

• You have to remember, depending on the model you are using those are the values at Height. IE 10mAGL is apx 33 ft above Ground Level, some model are at 9k feet and some higher. 10m is about as close to ground level as you can get with model software, and there is all kinds of factors at ground level that can change the wind values. Homes, trees, vehicles, even porches can effect an accurate wind speed at ground level.

• @Siff Where do you get the real data from for everywhere on the planet? It's easy to say you have real data in somewhere like the USA, which is covered by hundreds of observation points, along with upper air measurements taken twice daily. What about everywhere else?

How do you verify a forecast for a location which there is no credible observation data? Remote sensing can help, but it only goes so far.

• @TZ 100% correct TZ. Others in this thread clearly don't understand weather modeling. Windy pulls the model data - NAM 3k, ECMWF 9k or GFS 22k - from NOAA and other agencies and then displays it on a great GUI - all 100% free. Windy does not generate model data. Prior to Windy I was forced to look at the raw data - ugh. I'm hoping soon that Windy can also show other "popular" models such as HRRR, OP4-, BAK40, etc. Also, a skew-t at a click would be wonderful! Keep up the good work. Windy is an invaluable tool for pilots and sailors, who use it every day. As for the haters - take the time to learn how to use Windy - for example, I just now selected Wind Gusts and see 155 MPH near the eye of Irma - very accurate. And study meteorology , it might help you get a clue ... if all that fails, go use some other app/website, most are not free.

Steve