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copied!<p>After downloading the data file, I can read directly with raster. I choose band 221 that (if I am not wrong) it is what you need according to <a href="http://www.nco.ncep.noaa.gov/pmb/products/gfs/gfs.t00z.pgrb2f00.shtml" rel="noreferrer">this table</a>:</p> <pre><code>library("raster") t2mc <- raster('gfs.grb', band=221) > t2mc class : RasterLayer band : 221 (of 315 bands) dimensions : 361, 720, 259920 (nrow, ncol, ncell) resolution : 0.5, 0.5 (x, y) extent : -0.25, 359.75, -90.25, 90.25 (xmin, xmax, ymin, ymax) coord. ref. : +proj=longlat +a=6371229 +b=6371229 +no_defs data source : /home/oscar/gfs.grb names : gfs </code></pre> <p>You don't need the whole extent so you use <code>crop</code> to get the desired extent:</p> <pre><code>e <- extent(-40,40,20,90) tt <- crop(t2mc,e) </code></pre> <p>I have tried to display the <code>tt</code> raster with <code>plot</code> without success. However, it works correctly with <code>spplot</code> if you use a different extent (89.5 instead of 90):</p> <pre><code>e <- extent(-40,40,20,89.5) tt <- crop(t2mc,e) spplot(tt) </code></pre> <p>Now we have to add the administrative boundaries:</p> <pre><code>library(maps) library(mapdata) library(maptools) ext <- as.vector(e) boundaries <- map('worldHires', xlim=ext[1:2], ylim=ext[3:4], plot=FALSE) boundaries <- map2SpatialLines(boundaries, proj4string=CRS(projection(tt))) </code></pre> <p>and change the palette:</p> <pre><code>rgb.palette <- colorRampPalette(c("snow1","snow2","snow3","seagreen","orange","firebrick"), space = "rgb") spplot(tt, col.regions=rgb.palette, colorkey=list(height=0.3), sp.layout=list('sp.lines', boundaries, lwd=0.5)) </code></pre> <p><img src="https://i.stack.imgur.com/53ReY.png" alt="spplot result"></p> <p>If you prefer the <code>latticeExtra::layer</code> approach, you can achieve a similar result with this code:</p> <pre><code>library(rasterVis) levelplot(tt, col.regions=rgb.palette, colorkey=list(height=.3)) + layer(sp.lines(boundaries, lwd=0.5)) </code></pre>

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