Initial results show that the precipitation episodes occurred in the northeast quadrant of the cutoff cyclone in an environment of weak conditional stability and anomalously large precipitable water values. Forcing for the first precipitation episode was dominated by lower-tropospheric warm air advection, while the second and third episodes exhibited a combination of warm air and vorticity advection associated with transient disturbances rotating around the cutoff cyclone center. The heaviest rain fell during the third precipitation episode when synoptic and mesoscale forcing remained focused over southern New England for several hours, as the cutoff cyclone stalled over Virginia. Deep easterly flow during this period contributed to orographic precipitation enhancement (suppression) on the east (west) slopes of north-south oriented terrain features in New England.
Operational model guidance during the event alerted forecasters to the potential for heavy rainfall over New England, however, precipitation forecasts exhibited notable timing, placement, and intensity errors, even at forecast projections less than a day. In particular, the Eta and GFS model forecasts did not adequately resolve the transient disturbance responsible for the second precipitation episode, and suffered from significant phase errors in forecasts of the third precipitation episode. However, high resolution models were able to predict the orographic enhancement of precipitation during the third precipitation episode. These results highlight the multi-scale nature of cutoff cyclones, and the challenge these cyclones present to operational quantitative precipitation forecasts.