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» Online Classroom   »   » Public Discussion of Marine Weather   » Microscale meteorology

Author Topic: Microscale meteorology

 - posted February 28, 2019 02:16 PM      Profile for Chgodave           Edit/Delete Post 
Hello. Sometimes micro and mesoscale meteorology are grouped together. Sometimes even used interchangeably (mistakenly, of course). My question is "Is there any use for microscale models in sailing, and if so, what are those models?" Thanks
From: Chicago
David Burch

 - posted February 28, 2019 04:38 PM      Profile for David Burch           Edit/Delete Post 
In our weather course we think of mesoscale as systems and forecasting in the range of 30 to 300 nmi. And we use the same concept for oceanography (ie mesoscale eddies) and meteorology.

Anything below 30 we might think of "microscale" and then cover squalls and microbursts. Several cases of tall ship sinkings have been attributed to microbursts.

I do not know of any attempt to apply studies like those of Tetsuya Fujita and Allen Pearson to marine work. They concentrate on tornadoes and on gusts at airports.

We do get into the below 30 mile size with the simulated radar reflectivity that is available in the HRRR model and in the FV3-GFS. The data source and GRIB viewing program called LuckGrib has very nice data on this. We also discuss the use of this data in our textbook Modern Marine Weather. We have one example online where a squall several miles across was tracked moving across Puget Sound.

We might note too that the UW has a WRF model with 1.3 km resolution that in principle shows some features in this range. see www.starpath.com/local

But that would be all I know about this topic for sailors.

From: Starpath, Seattle, WA
David Burch

 - posted February 28, 2019 04:46 PM      Profile for David Burch           Edit/Delete Post 
Just thought of another example. Recently we tracked several gust fronts moving across Lake Michigan, well ahead of a fast moving front. These narrow features showed up nicely in the radar images, but i am not sure if they were in the HRRR model forecasts.
From: Starpath, Seattle, WA
David Burch

 - posted March 01, 2019 10:40 AM      Profile for David Burch           Edit/Delete Post 
Dave Wilkinson has brought up a good point on this topic, which i forgot to mention.

Some years ago the high resolution models, meaning 3 km NAM and higher were referred to as mesoscale models, even though they are much smaller than the 30 mi mentioned earlier. This stresses two points, one is the terms are nebulous and vary with applications, but we might also note that these days these models are referred to as "regional" or "local" without reference to meso or micro scales.

The other factor too of course is the scale of the model is not necessarily the measure of system scale. Generally a system to be studied has to span ~5 grid points to be represented. So in that sense, 3 km would cover systems of some 15 km, meaning ~8 miles or larger features.

From: Starpath, Seattle, WA

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