Tropical systems and wind shear forecasts

[Portastorm]

There has been an awful lot of divergent views I have read in the last 48 hours on wind shear and wind shear forecasts.

Just how accurate are these wind shear forecasts? Should we consider them more from the "look at the trend they suggest" viewpoint as compared to taking them literally? Just curious ... it seems like as many times as these forecasts verify, they don't.

I'm just kinda curious as several pro mets seem to be banking on wind shear forecasts 48 hours out ... when they might change.

[wjs3]

I would say that shear forecasts are just as good as any other model guidance...they are guidance, just that.

They are better in the shorter term than in the longer term, and better in areas where there's a lot of data than when there's not (so open water can be difficult), and some models (pro mets can weigh in here) do better in the tropics than others.

Have you looked at shear forecasts yourself? Do you know where to find them? If not, let me know and I can send you to a couple of places.

[Portastorm]

I'd love to see links to those maps, thanks!

[wjs3]

OK, for current shear conditions and shear trend, try CIMSS:

http://cimss.ssec.wisc.edu/tropic/

You'll want to click on NW Atlantic (first set of links on the left) for most relevant images.

For model output, I use these sites (I'm sure there are better ones...others fire at will!)

http://met.psu.edu/tropical/tcgengifs/

Under each of the models there is a set of shear measures (and a set of zonal shear measures....use the SHEAR, not Zonal shear). I generally use the 850-200 MB shear. There are situations where you might only look at the 850-500 MB, but don;t worry about those for now.

A third thing to do is go grab the latest SHIPS output. I just learned this the other day...they are FTP'd here:

ftp://ftp.nhc.noaa.gov/pub/atcf/stext/

Click around near the end of the FTP list and you'll find SHIPS for the storm of interest. ONe line in the report lays out estimates of the shear period by period.

Lastly, another model visualization:

http://www.meteo.psu.edu/~gadomski/ewalltropatl.html

Use any of the 4 panel charts. In the lower left frame there is a wind shear direction and speed panel.

Let me know if you have questions...anyone else have input here?