This past Thursday was truly an afternoon that many people, especially those in Staten Island, Queens, Brooklyn, and Plumsted, NJ, will never forget. In an incredible sequence of events, a severe cluster of thunderstorms developed near a warm front and progressed eastward, then interacting with favorable low-level helicity, eventually producing a swath of damaging winds and isolated tornadoes which impacted highly populated areas in the New York City metro area. It's no coincidence that the majority of tornadic events in our area occur along a warm frontal boundary--or directly following or prior to the passage of one (more often the latter). Warm fronts can provide favorable boundaries for severe thunderstorms to develop---where temperature differentials exist. More importantly, the can be focal points for enhanced low level shear, as was the case on Thursday.

The radar images from the afternoon of the storms themselves are extremely impressive--both on a regional, local, and mesoscale level. The image to the right shows the entire storm system from it's initial development to it's weakening on long island. The storms initially developed in Northeast New Jersey on an axis of increasing instability--that was developing after the warm front passage earlier in the day. The storms were also accompanied by a very strong low level jet...and a strong upper level system which was featuring very strong winds just above the surface (around 975mb). We mentioned in our forecast discussions that any convection would mix these dangerous winds down to the surface--but the convection that developed was much stronger than anticipated. It's also interesting to watch the loop several times, when you will begin to notice that as the storms were passing through the 5 boros, a noticeable circulation developed and moved from Staten Island to the Connecticut shore.

A more local radar view shows an extremely impressive development as the storms moved through the area. The circulation discussed above was certainly not a mirage--it was actually an extremely impressive reflection of very strong low level winds. The image to your right depicts the storm relative velocity radar image around the time of the tornado in Northern Queens. The inbound and outbound winds (moving towards/away from the radar beam) were extremely strong in similar areas..forming a strong couplet, where rotation was strongest. This is where the tornado was observed. In addition, even in areas where the tornado did not touch down, the extremely strong winds depicted here (-94kts max negative velocity/86kts max positive velocity) acted to translate to the surface..with a 125mph wet macroburst observed in Northern Queens as well.

As you can imagine, the damage that was suffered was extensive--and severe, causing one casualty in the New York City 5 boros. To your left, the severe wind reports are detailed throughout the 5 boros. A noticeable path of wind damage can be seen from Park Slope, Brooklyn through Bayside, Queens. It's not a coincidence that these wind reports fall right within the same area detailed to have the strongest winds and couplet on the radar image above. The easily-seen path of the strongest winds is impressive, but even more impressive is the amount of reports throughout the area. It has certainly been a very long time since our area has seen a severe thunderstorm of this magnitude.  (Click read more for more, including a video)




There is a lot to be learned from this event, although we would obviously prefer it wouldn't take damage and a fatality for us to learn our lesson. We know now that warm fronts with a surface low just northwest of our region--timed well in the afternoon with instability--mean business. Will we get the same result the next time we have a similar set-up? Probably not. Yet, we experienced what those types of set-ups can produce. We also know now that strong winds just above the surface are a dangerous thing when combined with good low-level helicity. Tornadoes aside, those two combined to develop a 125mph macroburst that arguably caused the extent of the widespread wind damage. Finally, we learned the power of modern communication systems. We relayed warnings and information to thousands of users with our website and our twitter account. The influx of weather technology and the relay of important warning and safety information has never been more important. We would like to send our thanks to the National Weather Service, the forecasters we communicated with, the people on Eastern US Weather Discussion forums, and our friends and followers on twitter for providing extremely timely, useful, and at times life saving information. We leave you with a youtube documentation of the storm from Park Slope, Brooklyn where the National Weather Service confirmed a tornado touchdown. For more information on the official tornado and macroburst, click here. For an entire thread dedicated to the storms and damage information, click here. Thanks for choosing New York Metro Weather Blog as a source for your weather information.