Meanwhile, at the surface, remnant low level circulation of Ida
likely tracks along or just off the south coast of New England,
placing CT/RI/MA on the cool side of the storm. If this storm track
verifies, a chilly windswept rain with gusty NE winds would
materialize, as models suggest a robust 45 kt low level NE jet north
of the surface low. This may result in a low risk of wind gusts
strong enough for minor tree damage given fully leaved trees.
Furthermore, this track would place the cool sector over CT/RI/MA,
shunting any severe weather/tornado threat offshore. Although, still
2-3 days away, so mesoscale details can change between now and then,
specifically the axis of heaviest rainfall. New 12z GFS storm total
rainfall has a swath of 2-4" across CT/RI and south of the MA Pike.
New 12z GEFS supports this idea with 4+ inch probs across the same
area. 12z EC farther north with axis of heaviest rain across
northern CT into Greater Boston area, with amounts up to 6 inches.
12z EC ensembles support this heavy rain signal, with low risk of 4+
inch probs across CT into RI. Thus, this heavy rain signal combined
with current flows of small rivers and streams much above normal
/not much capacity remaining for additional rainfall/, further
increases the flood threat. This combined with 1) remnants of Ida
yielding PWATs 2+ inches, strong mid level Fgen in response to
confluent flow over New England and an anomalous 140kt jet streak
over southeast Quebec (+2 SD), with RRQ over CT/RI/MA, enhancing QG
forcing for ascent. All of these parameters are supportive of a
flood watch for CT/RI and southeast MA, including Cape Cod and the
Islands. This flood watch may need to be expanded northward tonight
or Tue, if forecast confidence increase on heavy rain axis shifting
northward. We will have to watch closely where the confluent zone
sets up, as there will be a sharp north to south qpf gradient,
yielding big qpf bust potential.