Radar-based precipitation estimates show widespread totals of 3+ inches across the region, with areas >6" or even >8" in areas of Greene County, which lies west of Hudson (click on images to enlarge). This is the region where many of the flood photos and videos are from.
|Source: Weather Underground. Accumulations since 27 Aug.|
As seen in the terrain image below, such flow is oriented normal to the two NW-SE oriented ridges in the Catskills. The radar-derived precipitation maxima lie over these ridges.
Thus, it appears we may be looking at a case of local orographic precipitation enhancement over the NW-SE oriented ridges of the Catskills.