In case anyone finds it useful when decoding recon data and trying to get an estimate for what it means at the surface, here's a table of dropsonde conversion factors based off of various heights. Just multiply the observed wind at that height and you'll get a surface observation. Note that these are the mean conversion factors; not all hurricanes will fit this mean profile and there are extreme cases where the standard conversion ratios can be off by 10-20% in either direction. Low-level invests are typically flown around 1000ft or 850mb; normal recon flights are flown around 700mb.