Wind field maps

[Theo Mandel]

  Hi,

I am looking to create wind maps for certain hurricane fields. I have downloaded the entire list of historical shapefiles but I am unsure which fields and how to use them in order to get something that looks like the below (taken from an example I found online).

http://rstudio-pubs-static.s3.amazonaws.com/7372_987babcddbda4cc382c227f28d57d780.html 

It seems like the data I have downloaded only contains data for the eye of the storm and doesn't have any data relating to how wide it is or how the wind speeds change with width?

Any help on this will be much appreciated.

Thanks,

Theo

[Ken Knapp - NOAA Federal]

Hi Theo

That link you provided is interesting. IT shows how to use H*wind analysis to determine maximum winds during a strom's lifetime. The H*Wind analysis, however, is very different from best track data.

HWind is a 2D wind field at every instance (I think at 6 hour intervals) of the storm. It can be thought of as an instantaneous view of the wind structure of the storm.

The best track data - from which IBTrACS derives - contains substantially less detailed information. IBTrACS, however, does contain some information on a storm's wind structure, but not as detailed since it is not a complete 2D field. You will find information on wind radii (or wrad). Those variables describe the extent (or distance) a certain wind speed is felt (or exists). This is provided for 4 quadrants. For example, if wrad34_ne = 100, that means that wind speeds of up to 34 knots can extend as far as 100 naut. miles from the storm center in the Northeast quadrant (please note that wrad34_ne isn't the exact name, but should be sufficient to help determine what the column names mean. .... For column name definitions, please see the documentation on the IBTrACS website.

I hope this helps.

-Ken

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[Theo Mandel]

Sorry for the delay but thanks for your reply Ken, that makes sense. Do you have any advice on how to best get that information into a mapping solution (GIS)?

[Ken Knapp - NOAA Federal]

Hi Theo

Sorry, but I am not too familiar with GIS. I suspect that you could use the wind radii parameters to draw the shapes of the wind extent ... which would look similar to Fig 1 from this paper: https://journals.ametsoc.org/view/journals/wefo/32/3/waf-d-16-0196_1.xml (it shows the 34 knot wind radii every 6 hours). But I don't know how that would be done in GIS (and that paper wasn't likely made from a GIS image but more likely from an operational image from the forecast system).

Best regards-

-Ken

To view this discussion on the web visit https://groups.google.com/d/msgid/ibtracs-qa/28501191-95e6-4641-8646-fba918886d79n%40googlegroups.com.

[Theo Mandel]

Ok, no worries. Thanks for your help Ken.

[BA Racoma]

Hi Theo and Ken!

I have some suggestions if you want to use GIS to plot the 34kt wind radii from IBTrACS, similar to the paper Ken linked. 

If you're using the shapefiles you can look for the attribute field that lists the wind radii as Ken mentioned.

From here you have two options

1. Plot them straight using the radius as the "size scale field": https://gis.stackexchange.com/questions/49153/creating-different-diameter-circles-round-points-using-qgis

2. You can create a new shapefile using the wind radius field as a buffer: https://gis.stackexchange.com/questions/366893/qgis-making-circles-of-specific-diameter-from-attribute-in-point-layer

The first option is quick and straightforward plotting, but you can't do further processing with the wind fields as they are only for visualisation. The second option might take a long while to run especially if there are many points, but from there you have a new shapefile to use that you can use for processing.

Take note that I haven't tried these yet for IBTrACS, but I hope these suggestions help.

-BA

[Theo Mandel]

Hi BA,

Thank you for getting in touch. In IBTrACS, each 34kt point has actually 4 radii (ne, se, nw, sw). I am guessing this would complicate things as I would have to create a quadrant for each in the correct direction instead of just creating one circle based off one point?

Thanks,
Theo

[BA Racoma]

Hi Theo,

Thank you for pointing that out. I didn't realise that each point has 4 radii.

If you're using QGIS, one option would be to use the Shape Tools plugin (https://plugins.qgis.org/plugins/shapetools/), and then use the "create pie wedge" function.

For each quadrant (ne, se, nw, sw) you can specify their azimuths accordingly (0-90, 90-180, 180-270, 270-360) and then proceed to use the matching radius field. 

As an example, here are the shapes of the wind extent of the 6-hourly R34 of Chan-Hom, plotted somewhat similarly to Fig 1 of the paper Ken linked.

I hope this helps!

-BA