Significant Storm Update

Significant coastal storm has been dropping torrential downpours across the state all day and as the system continues to undergo rapid and further strengthening we are now beginning to introduce the strong wind aspect of the storm.  Numerous weather stations across the state, particularly across the coastline have reported wind gusts as high as 40-50 mph.  Flash flooding, downed trees, and power outages will continue to be the biggest threats as we move into the overnight hours.

As of this writing, our system is already very strong with a 984mb closed low just east of NJ.  Based on the trend of greatest pressure falls, the low should continue moving NNW and push into northern NJ and through SE NY.  Computer forecast models strengthen the system down to the mid-970 mb range which is very, very impressive:

With the last few updates there was big focus on the development and strength of the low-level jet streak and it appears that computer forecast models will be spot on with the extremely anomalous speed of the low-level jet with 925mb (~2500' off the ground) winds expected to exceed 90 knots and the 850mb (~5000' off the ground) low-level jet exceeding 100 knots.  This is extremely, extremely impressive and shows how much wind potential exists just off the ground.  The question just is how much of this wind energy is tapped into and how much of these winds are brought down to the surface.  Currently we see the low-level jet streak off to the SE of the state with 925mb winds as high as 65-75 knots and 850mb winds already as high as 80-90 knots.  Not only will these values continue to increase within the jet streak as the storm continues to strengthen but the core of the low-level jet max may even push into extreme SE parts of CT during the overnight hours.  If this does happen and any of this energy is tapped into, the potential will certainly increase for wind gusts along the coast to exceed 65-70 mph.  This likelihood will certainly exist just off to our east across RI and far SE MA:

The major concern over the next several hours outside of torrential downpours and flash flooding is with regards to the wind potential.  As of this writing, we're continuing to see winds increase, particularly along the coast.  Over 35,000 folks are without power as of this writing and this number should continue to rapidly rise.  The latest run of the Hi-Resolution Rapid Refresh (HRRR) computer forecast model shows very strong damaging wind gust potential, particularly across the CT coast.  the bufkit sounding for Groton, CT at 1:00 AM suggests sustained winds of 47 knots (54 mph) with gusts potentially upwards of 61 knots (70 mph).  Winds of this magnitude would yield scattered to widespread wind damage.  

One of the keys to developing these damaging gusts will be how the low-level temperature profile establishes over these next few hours.  Computer forecast model soundings show a weak unstable layer developing from the surface up through about 875mb which is noted by steepening lapse rates (strong temperature decrease with height) in this layer.  This is quite evident across coastal CT, however, the signal is much more weak inland.  This is one factor which could prevent widespread damaging wind gusts across inland CT.  

Breaking this down:

Torrential Downpours

Torrential downpours continue to batter the state of CT, however, a dry slot is beginning to work into the southwest part of the state now.  Torrential downpours will continue across central and eastern CT for the next few hours before the intensity begins to let up quite a bit.  Rainfall will transition from steady and heavy to more on and off.  Flash flooding continues to be a risk.

Strong to Damaging Wind Gusts

Sustained winds and wind gusts will continue to increase in magnitude over the next several hours as the low-level jet continues to strengthen in response to the rapid deepening of the low pressure center.  The worst of the winds will be confined to the CT coast where wind gusts at the height of the storm could exceed 65-70 mph.  Winds will become sustained as well between 40-45 mph.  Scattered to perhaps widespread tree damage is possible here along with widespread power outages which we are already beginning to see.  Further inland, strong to damaging wind gusts are possible as well, however, these will be more isolated in nature.  This will still yield isolated pockets of tree damage and power outages inland.  This potential will last through 2-3 AM before winds begin to subside.  However, late tomorrow morning the winds begin to rapidly increase again as the system departs.  With strong mixing expected and steep low-level lapse rates, we will be looking at statewide wind gusts upwards of 40-50 mph.  With a very wet ground this as well will lead to pockets of tree damage and further power outages.