Add mapping of METAR wx codes to WMO numeric codes

[dopplershift]

This will be useful for plotting weather symbols.

Here's some code I've started for it:

wx_code_map = {'': 0, 'DU':7, 'BLDU':7, 'HZ': 5, 'BR': 10, '-UP':16, 'UP': 16, 'SQ': 18, 'FC': 19,
               'DRSN': 36, 'FG': 45, 'FZFG': 49, '-DZ': 51, 'DZ': 53, '+DZ': 55,
               '-RA': 61, 'RA': 63, '+RA': 65, '-FZRA': 66,
               '-SN': 71, 'SN': 73, '+SN': 75, '-SHRA': 80, 'SHRA': 81, '-SHSN': 85,
               '-TSRA':93, 'TSRA':95, '+TSRA':95, 'PL':0}

I've also attached the relevant WMO manual.

[abkenyon]

Here is what I filled in for all of the METAR codes I found that are actually used. I was thinking of adding this to the metpy.plots.wx_symbols.py script so that it can be imported with the "current_weather" and 'sky_cover' commands. If there is nothing blatantly missing, I will do a pull request soon (or you can copy and paste yourself...it's not like its an intricate portion of code or anything).

wx_code_map = {'': 0, 'FU':4, 'HZ': 5, 'DU':6, 'BLDU':7, 'PO':8, 'DS':9, 'BR': 10,
               '-UP':16, 'UP': 16, 'THDR':17, 'SQ': 18, 'FC': 19,
               'DS':31, 'SS':31, '+DS':34, '+SS':34, 'DRSN': 36, '+DRSN':37,
               'FG': 45, 'FZFG': 49,
               '-DZ': 51, 'DZ': 53, '+DZ': 55, '-FZDZ':56, 'FZDZ':57, '-DZRA':58, 'DZRA':59, 
               '-RA': 61, 'RA': 63, '+RA': 65, '-FZRA': 66, 'FZRA':67,
               '-SN': 71, 'SN': 73, '+SN': 75, 'SG':79, 'PL':79,
               '-SHRA': 80, 'SHRA': 81, '+SHRA':82, '-SHSN': 85, 'SHSN':86,
               '-TSRA':95, 'TSRA':95, 'TSGS':96, 'TSGR':96, '+TSRA':97,
               'TSDS':98, '+TSGS':99, '+TSGR':99}

[jrleeman]

Thank you Abby! If you want to make a PR, that's great. We can always iterate any there.

[bryanguarente]

I filled in even more of the codes here if it is helpful for this:

wx_codes = {'': 0, 'M':0, '-UP':0, 'UP':0, '+UP':0, 'TSNO':0, 'TS':0, 'VA': 4, 'FU': 4, 'HZ': 5, 'DU':6, 'BLDU':7, 'PO':8, 'VCSS':9, 
            'BR': 10, 'MIFG':11, 'VCTS':13, 'VIRGA':14, 'VCSH':16, '-VCTSRA':17, 'VCTSRA':17, '+VCTSRA':17, 'SQ':18, 'FC':19, 
            'SS':31, '+SS':34, 'DRSN':36, '+DRSN':37, 'BLSN':38, '+BLSN':39,
            'VCFG':40, 'BCFG':41, 'PRFG':44, 'FG':45, 'FZFG':49,
            '-DZ': 51, 'DZ': 53, '+DZ': 55, '-FZDZ':56, 'FZDZ':57, '+FZDZ':57,  
            '-RA': 61, 'RA': 63, '+RA': 65, '-FZRA':66, 'FZRA':67, '+FZRA':67,'-RASN':68, 'RASN':69, '+RASN':69, 
            '-SN': 71, 'SN': 73, '+SN': 75, 'IN':76, 'SG':77, 'IC':78, '-PL': 79, 'PL':79,
            '-SHRA':80, 'SHRA':81, '+SHRA':81, '-SHRASN':83, 'SHRASN':84, '+SHRASN':84, '-SHSN':85, 'SHSN':86, '+SHSN':86, 'SHGR':89, 
            '+SHGR':90, '-TSRA':95, 'TSRA':95, 'TSGR':96, '+TSRA':97, 'TSSA':98, '+TSGR':99}

[dopplershift]

Great! We added some to master in #512. Would you be willing to submit a Pull Request to expand that with the ones you added?

[dopplershift]

Fixed in #512 and #535 .