30 September through
After a rather warm dry summer (and most of September) a big synoptic pattern change took place across the Northeastern Conus. Instead of ridge overhead or nearby, an unusually deep trough and cutoff low began building into the region on the closing days of September.
The GFS forecasted a very wet
event 10 days (or more) out, developing some sort of tropical system and
bringing it up the coast on the leeside of the trough. At least one model run
made it looks a little like the "Perfect" storm, some sort of intense
surface low hugging the coast as it raced up from
Tropical Storm Matthew formed
At the same time, an upper air
low that had brought an unusual rain event to portions of
To make things more
interesting, yet another tropical storm formed, Nicole, near
Initially a synoptic low
pressure and its associated warm front, located well north of the tropical
stream of heavy rain, produce isentropic lift and a band of moderate to heavy
rain of its own, during the morning hours of September 30. Up to two inches of
rain fell across portions of the
Thursday looked to be the day
of our biggest weather problems. There were legitimate concerns on the
possibility of high winds, torrential rainfall and possibly even severe weather
with isolated supercells, due to very strong low level wind shear. A Flood
Watch has been issued early Thursday morning by the shift. A Wind Advisory was also issued,
upgraded to a High Wind Warning across the higher terrain to the east of the
As it turned out, a dry slot
actually moved into most of our region as the warm begrudgingly lifted north of
However, things began to
change by nightfall. An impressive heavy swath of rain was moving slowly
eastward right along and just behind the cold front, into our region from the
west. Dewpoints surged into the low 70s, ambient temperatures into the upper
70s. A few thunderstorms did form along this line, one of which proved to be
The remnants of Nicole moved right along the front as it crossed into our region overnight. Massive rainfall rates and accumulation ensued. Rain easily fell at an inch an hour or more much of the overnight across much of the region. Rain continued well into Friday, but at lesser rates, closer to a third to half an inch per hour.
When the rains left by Friday
afternoon, 6-8 inches of rainfall had fallen across our region, much of that in
the western portions of the Capital region! As of 900 PM on the evening of
Two consecutive days of record breaking rain fell on September 30th and October 1. The last time there have been two back to back record rainfalls on the record books, were the last two days of December 1948.
Minor to moderate flooding
occurred across our entire HSA, but not until October 1st. There were water rescues
in places like
Above: Liquid equivalent precipitation forecasts
from the GFS (upper left),
Above: NAM12 liquid equivalent precipitation
forecast initialized 1200 UTC 29 September and valid 1800 UTC 2 October. Note the multiple bands of extreme rainfall
being predicted as well as the extreme values well over 5” within the
bands. Also note the relative minimum
Above: Winds and isotachs at 925 hPa for the GFS
(upper left), NAM (upper right), ECMWF (lower left) and 850 hPa from the GGEM
(lower right) for 4 consecutive runs.
Note that NY and western
Above: Surface winds and isotachs from the NAM12 initialized
at 0600 UTC 30 September valid 1800 UTC 30 September, 0000 UTC 1 October and
0600 UTC 1 October. Note the predicted
surface winds were much weaker than the predicted 925 hPa winds. However, due to the southerly wind direction,
some channeling through the
Above: GEFS winds and anomalies at 925 hPa and 850 hPa
initialized 1200 UTC 30 September and valid 1200 UTC 1 October. Note that NY and western
Above: GEFS MSLP and PWAT and anomalies initialized at 1200 UTC
29 September (left), and 1200 UTC 30 September (center and right), valid at
0000 UTC 1 October (left and center) and 1200 UTC 1 October (right). Note the PWAT values between 3 SD and 5 SD
above normal. These were originating in
the subtropics and tropics, were values very rarely seen, and suggested extreme
amounts of moisture streaming over the northeastern
Above: GEFS probabilities for 3.00” in 36 hours (left), 4.00” in 48 hours (center left and center right), and 5.00” in 48 hours (right), initialized between 1200 UTC 29 September and 1200 UTC 30 September, valid at various times on 1 October to early morning on 2 October. Note the probabilities above 60% over a large area for all the amounts. Large areas of > 60% probabilities for these QPF values is extremely rare, and suggests high confidence for widespread rainfall amounts at or above these QPF values.
Above: SREF 850 winds and anomalies initialized 09Z 30
September and valid 1200 UTC 1 October.
Note that NY and western
Above: SREF MSLP, PWAT and anomalies initialized at 0900 UTC
30 September and valid 0000 UTC 1 October (left) and 1200 UTC 1 October
(right). Note the PWAT values between 3
SD and 5 SD above normal. These were
originating in the subtropics and tropics, were values very rarely seen, and
suggested extreme amounts of moisture streaming over the northeastern
Above: SREF probabilities for 3.00” in 36 hours and 4.00” in 48 hours initialized at 0900 UTC 30 September and valid 1200 UTC 1 October (left) and 0000 UTC 1 October (right). Note the probabilities above 60% over a large area for all the amounts. Large areas of > 60% probabilities for these QPF values is extremely rare, and suggests high confidence for widespread rainfall amounts at or above these QPF values.
Above: GEFS plume loops for
Above: SREF plume loops for
Above: Soundings from Upton, NY (OKX) at 0000 UTC 1 October (left) and 1200 UTC 1 October (right). Note the extreme PWAT values, and the instability.
Above: MSAS loops of MSLP and wind barbs showing the development and progression of the surface low pressure center.
Above: Loops of water vapor satellite imagery. Note the plume of tropical moisture surging
through the northeastern
Above: Loops of visible satellite imagery. Note the stream of tropical moisture into the
Above: Loop of radar reflectivity through the event.
Above: Stage 4 total rainfall through the event. Note the widespread 5.00”+ rainfall amounts, and in some cases above 8.00”.
Above: Hydrographs from Rosendale on Rondout Creek, Prattsville on Schoharie Creek and Coldbrook on Esopus Creek.
Above: Hydrographs from Mount Marion on Esopus Creek, Little Falls on the Mohawk River, and Kast Bridge on West Canada Creek.
Above: Hydrographs from Hope on Sacandaga River, Hinckley on West Canada Creek and Gilboa Dam on Schoharie Creek.
Above: Hydrographs from Delta Dam on the
Above: Hydrographs from
Any comments, questions or suggestions, please mail to:Neil.Stuart@noaa.gov