Early AM Severe Threat: 10/8/14

The latest data and trends continue to highlight at least an elevated threat for some severe weather rolling into the area first thing Wednesday morning.

I want to keep this relatively brief to give an overview of the setup and highlight the pros and cons of such an event occurring. As it stands now, there does exist a threat for damaging wind gusts and even isolated tornadoes.

Tuesday morning, a rather weak disturbance and associated upper level speed max swings through New England. This could result in some spotty drizzle Tuesday morning. The second half of Tuesday looks relatively quiet. Although there is a good amount of shear forecast to be in place, there is not much of a trigger for convection. There could be a passing shower or two and a rogue thunderstorm cannot be ruled out.

It’s really Wednesday morning, between about the time of 3 a.m. and 9 a.m. from New Jersey up through the NYC metro area and southern New England that a few gusty thunderstorms could develop. The nose of the upper level jet is expected to reach the area during the pre-dawn hours. With plenty of shear in place, the computer models are also showing at least some modest instability working into the area. Moisture transport off of the ocean should allow for dew-points to work into the 60s, mainly near and southeast of the I-95 corridor. At the same time, a surface low pressure system should cut up into New York with a healthy 50+ knot low-level jet also rotating through the area. The result is an overlap with several ingredients that would support a few thunderstorms with damaging wind gusts and even isolated tornadoes.

Weighing out the pros and cons…

Pros:
Strong wind shear
Low-level helicty
Upper air forcing
LCL heights
The Euro is leaning toward the more robust NAM model solution
Similar setups in the past have yielded damaging winds and tornadoes

So-so/marginal:
Backing of low-level winds
Strength of the low moving into New York state
Moisture advection

Cons:
Limited instability, especially inland
Timing during the pre-dawn hours
Time of year
Storm mode and possible convective contamination
Narrow overlap of shear and instability

The forecast will continue to be monitored and we’ll see how things are trending during the day on Tuesday.

Evaluating the possible overlap of severe weather ingredients.