Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 01-10-2016, 18:46   #1
Registered User

Join Date: Jul 2013
Posts: 26
Indicated wind speed on earth.nullschool

I'm looking at hurricane Matthew in the Caribbean and its current highest indicated wind speed on earth.nullschool is about 50 knots. But the news and the National Weather Service reports sustained speeds of 130 knots. Why this huge discrepancy?
__________________

__________________
Mirror16 is offline   Reply With Quote
Old 01-10-2016, 18:54   #2
Registered User

Join Date: Jan 2008
Location: SF Bay Area (Boat in La Paz)
Boat: Valiant V40
Posts: 295
Re: Indicated wind speed on earth.nullschool

earth.nullschool, windty, etc etc are displaying results of global models (essentially GRIB files). These compute average winds within cells of some dimension (on the order of km's, exact size depends on the model.) Thus, they do not usually predict maximum velocities correctly, nor do they accurately predict highly localized structures. The numbers NHC report are often the results of specific measurements, sometimes satellite, sometimes buoys, often from hurricane chasing aircraft.

Plus, their predictions are based on more comprehensive hurricane-specific models.
__________________

__________________
jamhass is offline   Reply With Quote
Old 02-10-2016, 07:02   #3
Registered User

Join Date: Jul 2013
Posts: 26
Re: Indicated wind speed on earth.nullschool

Thanks for the education jamhass. How accurate are the GRIB-based wind speed models in less extreme weather?
__________________
Mirror16 is offline   Reply With Quote
Old 02-10-2016, 07:26   #4
Registered User

Join Date: Jan 2008
Location: SF Bay Area (Boat in La Paz)
Boat: Valiant V40
Posts: 295
Re: Indicated wind speed on earth.nullschool

It depends ...

On the particular model, on the location, etc etc.

Some models do better than others in some cases, some not so. If you look at several different model results and they all agree, you can have pretty good confidence in the result. It is hard to predict which model works best under which conditions and/or locals. That is where experience helps, and makes really experienced weather gurus and navigators quite in demand.

Consider the NHC presentation of different hurricane track models. Sometimes they all agree nicely, sometimes not.

Location near land is often problematic. Local conditions impact winds and weather significantly and are not always well represented in the models. Newer models with finer grid structures tend to do a better job with local conditions, but even then they can vary a lot. That said, many locals have regional-specific models that do quite well. Example, SF Bay. Others, not so, example Sea of Cortez.

Even when models agree, and you are not near particular land features, you can figure on gusts being 50% higher (roughly) than steady wind predictions. Some models allow you to see gust predictions.

What we do (before passages especially) is watch several models for our route for a few days and compare them, making our route plans accordingly. Even then, sometimes we get surprised. For example, last year we crossed from La Paz to Mazatlan right between 2 hurricanes, neither of which was predicted to head towards the Sea of Cortez, both of which took unexpected turns in that direction. Fortunately, both died rather sudden deaths and did not affect us beyond our blood pressures, and the sailing proved magnificent!
__________________
jamhass is offline   Reply With Quote
Old 02-10-2016, 07:39   #5
Registered User

Join Date: Nov 2013
Location: Slidell, La.
Boat: Morgan Classic 33
Posts: 860
Re: Indicated wind speed on earth.nullschool

This buoy, NDBC - Station 42058 Recent Data, located about 60 miles to the northwest of the 8:00 AM reported center,
shows steady winds of 35 knots, gusts to 47, and peak wind in the last hour of 52 knots. The anemometer height is only 15 ft, and the current sea state is 24, so chances are that these numbers may not be representative, but the wave height does seem to correlate with the wind speed.

According to the 8:00 AM EDT advisory, hurricane force winds extend only 25 miles from the center.

Provided the buoy stays on line, we should be able to watch the wind shifts and pressure fluctuations to gain a small amount of insight, as it appears that the eye is about to pass directly over it.
__________________
jimbunyard is offline   Reply With Quote
Old 02-10-2016, 07:54   #6
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 15,953
Re: Indicated wind speed on earth.nullschool

Quote:
Originally Posted by Mirror16 View Post
I'm looking at hurricane Matthew in the Caribbean and its current highest indicated wind speed on earth.nullschool is about 50 knots. But the news and the National Weather Service reports sustained speeds of 130 knots. Why this huge discrepancy?
Mathematical models vs. sensors.

b.
__________________
barnakiel is offline   Reply With Quote
Old 02-10-2016, 15:16   #7
Registered User

Join Date: May 2016
Location: mackay, queensland. australia
Boat: e.a jack (builder), g.l watson (designer), 6.2 mtr wll sailboat
Posts: 428
Re: Indicated wind speed on earth.nullschool

sometimes it takes a while to place the curser ring on the highest wind strength / and that can change fast


Click image for larger version

Name:	nullschool.PNG
Views:	47
Size:	209.7 KB
ID:	132177
__________________
knockabout is offline   Reply With Quote
Old 02-10-2016, 15:33   #8
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Anything entertaining.
Posts: 3,968
Re: Indicated wind speed on earth.nullschool

Quote:
Originally Posted by jamhass View Post
It depends ...

On the particular model, on the location, etc etc.

Some models do better than others in some cases, some not so. If you look at several different model results and they all agree, you can have pretty good confidence in the result. It is hard to predict which model works best under which conditions and/or locals. That is where experience helps, and makes really experienced weather gurus and navigators quite in demand.

Consider the NHC presentation of different hurricane track models. Sometimes they all agree nicely, sometimes not.

Location near land is often problematic. Local conditions impact winds and weather significantly and are not always well represented in the models. Newer models with finer grid structures tend to do a better job with local conditions, but even then they can vary a lot. That said, many locals have regional-specific models that do quite well. Example, SF Bay. Others, not so, example Sea of Cortez.

Even when models agree, and you are not near particular land features, you can figure on gusts being 50% higher (roughly) than steady wind predictions. Some models allow you to see gust predictions.

What we do (before passages especially) is watch several models for our route for a few days and compare them, making our route plans accordingly. Even then, sometimes we get surprised. For example, last year we crossed from La Paz to Mazatlan right between 2 hurricanes, neither of which was predicted to head towards the Sea of Cortez, both of which took unexpected turns in that direction. Fortunately, both died rather sudden deaths and did not affect us beyond our blood pressures, and the sailing proved magnificent!
Thanks for the mini education. Might you be kind enough to share the addresses of the models that you use, along with some of your other favorite weather links please? I'd surely appreciate seeing them firsthand, & what as yet unknown weather education they may provide.
__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is online now   Reply With Quote
Old 02-10-2016, 16:05   #9
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 5,472
Re: Indicated wind speed on earth.nullschool

Quote:
Originally Posted by UNCIVILIZED View Post
Thanks for the mini education. Might you be kind enough to share the addresses of the models that you use, along with some of your other favorite weather links please? I'd surely appreciate seeing them firsthand, & what as yet unknown weather education they may provide.

Take a look at Model Guidance

It shows lots of models, their coverage areas and a few details such as update frequency.
__________________
StuM is offline   Reply With Quote
Old 02-10-2016, 17:12   #10
Registered User

Join Date: Apr 2010
Location: Canada
Boat: Fountaine Pajot Antigua 37
Posts: 68
Re: Indicated wind speed on earth.nullschool

"Knockabout" is correct, you have to be patient and also hit the right spot.
Yesterday I recorded 93 kts at one instance but then couldn't duplicate it or get higher than 90 and 91 after that.
__________________
wannacat is offline   Reply With Quote
Old 02-10-2016, 17:54   #11
Registered User

Join Date: Jan 2008
Location: SF Bay Area (Boat in La Paz)
Boat: Valiant V40
Posts: 295
Re: Indicated wind speed on earth.nullschool

Quote:
Originally Posted by StuM View Post
Take a look at Model Guidance

It shows lots of models, their coverage areas and a few details such as update frequency.
That, plus some portals (windty for example, and Airmails Grib portal) allow you to select from a small set of models. Well worth practicing when you have broadband rather than trying them out via SSB emails!
__________________

__________________
jamhass is offline   Reply With Quote
Reply

Tags
school, wind

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
B&G Hydra 2000 wind direction but no wind speed Airjordi Marine Electronics 3 15-07-2015 02:43
Google Earth plugin doesn't start Google Earth balticsailor OpenCPN 11 02-07-2015 03:07
Link to Earth.nullschool.net ? Abaft OpenCPN 2 22-05-2014 20:14
[SOLD] Davis Wind Wizard Wind Speed Indicator SailorHarry Classifieds Archive 0 21-12-2013 10:24
Wind Flag Overlays for Google Earth ? SvenG Navigation 0 28-09-2010 19:15


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 08:44.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.