Below are plots of SYNOP/BUOY/radiosonde BUFR coverage for January April 2018 - reports as decoded at ECMWF, some reports not in standard BUFR are not decoded. Daily coverage (updated automatically) is available from the Monitoring Maps
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Surface (SYNOP) coverage
About 85% 86% of stations now report in BUFR (86% in October 2017). We are seeing increasing numbers of BUFR reports from "new" stations, i.e. that did not distribute reports in TAC; unfortunately some of them have large pressure biases. (In July 2017 Spain in the last quarter Ukraine and Kazakhstan started sending BUFR reports from about 160 'extra' stations, Chile and Peru have also started sending 'new' stations.) The more established BUFR-only stations from Iceland are mostly good quality. Coverage for Europe is essentially complete apart from three NMSs (Bulgaria, Moldova and the Former Yugoslav Republic of Macedonia). For some countries stations/reports designated for national use as "additional data" only are received in TAC but not in BUFR. Light blue markers indicate that fewer BUFR reports are received than SYNOP reports - in most cases the BUFR is six-hourly but the SYNOPs are three-hourly.
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(Grey: TAC reports but no BUFR, Purple: BUFR reports but no TAC, Red *: position error. Light/dark blue indicates that there are less/more than 60% of the reports available in BUFR.)
BUOY coverage
On 6 June 2016 ECMWF started passively monitoring BUFR BUOY data in its operational system, assimilation of pressure data started in July 2016, many alphanumeric (FM18) reports ceased on 2 November 2016. For drifting buoys the BUFR feed is almost complete now helped by the fact that fewer data producers are involved (there are about 20 Indian and a few Japanese drifting buoys not using the approved template as yet). In mid-2016 there were 51 pressure-reporting buoys reporting in BUFR but not in FM18, some of these were moored buoys including 7 PIRATA or RAMA buoys which also report subsurface temperature and salinity. Template 315008 is used for moored buoys and 315009 for drifting buoys. More details of the marine data can be found in the E-SURFMAR pages (one issue is the move from 5-digit to 7-digit identifiers, this means that some newer buoys cannot really be coded using FM18). The plot below does not include the moored buoys that currently report in TM13 (SHIP) code - at some point these will start using the 315008 template. Note that about half the buoys, shown in light blue, do not report pressure (especially those in the tropical Pacific and the Mediterranean, they are deployed to measure SST and currents).
(Grey: TAC reports but no BUFR, Dark blue - BUFR reports including pressure, Light blue - BUFR reports without pressure. Circles/triangles - drifting/moored buoys.)
Ship data
In 2017/18 a number of European ships started using new EUCAWS hardware and software. They report (with identifier EUC*) in BUFR only. 
Argo data
Most Argo reports are available in BUFR, with higher vertical resolution (information from Adam Maycock, Met Office). It has been announced that Argo buoys will stop reporting in the alphanumeric TESAC code on 1 July 2018.
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About 75% of stations report in BUFR, about 39% 40% report native BUFR with roughly 35% reporting reformatted TEMP (see "structure" page and plots below). The proportion of native high-resolution reports has grown over the last few months (now up to 31%32%), principally due to the roll out of new software in the USA. A few BUFR reports are incomplete (eg data above 100 hPa missing). Reports from the ASAP ships are now only available in BUFR format (most ASAPs changed identifier in late 2017). In late 2017 Finland stopped reporting alphanumeric TEMPs followed by Norway in January 2018. In the second half of January about 16 land stations were reporting in BUFR but not in TEMP (at least two of these are relatively new to the GTS and never reported in TEMP code).
(Grey: TAC reports but no BUFR, Purple: BUFR reports but no TAC, Red *: position error. Blue: both BUFR and TAC, light blue indicates fewer ascents in BUFR. Triangle - ship report, X - wind-only report.)
The plot below distinguishes native BUFR (stations reporting valid radiosonde drift positions): high/low resolution (dark/light blue, using 300 level threshold) from reformatted TEMP (orange). There are now high resolution reports from all continents.
