[R] National Weather Service Data

Philip herd_dog @end|ng |rom cox@net
Mon Jul 6 18:29:16 CEST 2020

I am trying to access National Weather Service forecasting data through the rNOMADS package.  I’m not sure if the Weather Service software – grib2 – loaded correctly.  Second, some of the examples in the rNOMADS documentation seem to run correctly but I’m not sure what the output means.  Any anvise would be greatly appreciated.

1 - I tried to load the wgrib2 software from instructions in the following website:


2 – the instructions say that if it loaded correctly I should get a laundry list similar to what is below from the command: >system(“wgrib2”).

The list I get looks different.  Below is the first 20 or so entries.  How can I check to see if the wgrib2 loaded correctly?

wgrib2 v0.1.9.9 9/2013 Wesley Ebisuzaki, Reinoud Bokhorst, Jaakko Hyvätti, Dusan Jovic, Kristian Nilssen, Karl Pfeiffer, Pablo Romero, Manfred Schwarb, Arlindo da Silva, Niklas Sondell, Sergey Varlamov
-0xSec           inv  X      Hex dump of section X (0..8)
-MM              inv         reference time MM
-N_ens           inv         number of ensemble members
-RT              inv         type of reference Time
-S               inv         simple inventory with minutes and seconds (subject to change)
-Sec0            inv         contents of section0
-Sec3            inv         contents of section 3 (Grid Definition Section)
-Sec4            inv         Sec 4 values (Product definition section)
-Sec5            inv         Sec 5 values (Data representation section)
-Sec6            inv         show bit-map section
-Sec_len         inv         length of various grib sections
-T               inv         reference time YYYYMMDDHHMMSS
-V               inv         diagnostic output
-VT              inv         verf time = reference_time + forecast_time (YYYYMMDDHHMMSS)
-YY              inv         reference time YYYY

3 – As I said, some of the documentation examples work and for some I get error messages.  Below is an example of one that seemed to work but I don’t understand the output.

#GribInfo - page 20
urlsOut <- CrawlModels(abbrev="gfs_0p50",depth=2)
ModelParameters <- ParseModelPage(urlsOut[2])#[1] is most recent model
MyPred <- ModelParameters$pred[grep("06$",ModelParameters$pred)]
   Levels <- c("2_m_above_ground","800_mb")
   Variables <- c("TMP","RH")
   GribInfo <- GribGrab(urlsOut[2],MyPred,Levels,Variables)
GribInv <- GribInfo(GribInfo[[1]]$file.name,"grib2")

The command GribInv$inventory returns:

[1] "1:0:d=2020070606:TMP:800 mb:6 hour fcst:"                "2:148450:d=2020070606:RH:800 mb:6 hour fcst:"           
[3] "3:414132:d=2020070606:TMP:2 m above ground:6 hour fcst:" "4:571266:d=2020070606:RH:2 m above ground:6 hour fcst:" 

This is supposed to be temperature and relative humidity 2 meters above the ground and at 800 milibars for 2020 – July 6 – at ZULU time 0600.  But I have no idea what the numbers 414132 – second line – mean.

Any advise would be greatly appreciated.

Philip Heinrich

From: stephen sefick 
Sent: Thursday, July 2, 2020 3:20 PM
To: Philip 
Cc: r-help 
Subject: Re: [R] National Weather Service Data

I am unfamiliar with Rnomads. Could you provide a minimal reproducable example? You are more likely to receive help this way.

On Thu, Jul 2, 2020, 18:06 Philip <herd_dog using cox.net> wrote:

  Is anyone out there familiar with rNOMADS?  It is a package to get into National Weather Service forecasting data with R?

  I'm not sure the Weather Service software named wgrib2 loaded correctly because some of the stuff won't run and I can't make much sense out of some of the output.

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