May 17, 2011 Storm Updates

Below, storm updates will be posted on the heavy rain and thunderstorm event that is currently affecting the area. Scattered showers and thunderstorms, some of them strong, are expected on Thursday and Friday, though separate storm updates will be posted for these storms.


9:40 PM: Rain Finally Returns

Since the last update was posted, rain continued to dissipate just off the coast, and eventually the rain off the coast of Long Island/NJ mostly dissipated as well, with only a few showers and thunderstorms remaining. Parts of the area, especially west and south of NYC, saw some continued to see some clearing in the cloud cover. Over the last 1/2 hour, however, rain has been finally able to move into the coast, and is now headed towards the immediate NYC area.

The area of rain and thunderstorms seen in the previous radar southeast of Delaware has moved up the coast while maintaining its intensity, and as it moved into New Jersey, it began to intensify, the first time rain has intensified over New Jersey since this morning. The area of storms is currently just east of central NJ and is moving NNW. There is some slight uncertainty regarding whether it reaches the NYC area at its full intensity or if it weakens before reaching the area, but should it maintain its intensity, a round of heavy rain and thunderstorms will affect northern NJ, SE New York and NYC starting around at least 10:30 PM or 11:00 PM.

Meanwhile, there is also an area of rain and thunderstorms affecting parts of Long Island and southern Connecticut. This area of rain is currently weakening in southern Connecticut, however it is an improvement over this afternoon when the rain could not even reach the coast without completely dissipating. These areas will continue to see scattered showers and thunderstorms.

Tonight And Tomorrow: The two rounds of rain affecting the area will be followed by more. The water vapor loop shows additional storms developing well off the coast of North Carolina, and the regional radar also shows storms off the coast moving towards the area. These storms are still having some trouble moving towards the area, and some are still weakening, though additional rain and thunderstorms are expected across the area tonight, locally heavy, with a general 1/4 to 1 inch of rain across the area with locally higher amounts.

There is some uncertainty for tomorrow, as some models show a scenario like that of today while others bring more heavy rain. I will discuss this more in an update tomorrow morning, though at this time, I am expecting tomorrow to bring occasional rain and thunderstorms as well, with parts of the day dry and other parts of the day wet. These occasional storms will continue through Wednesday night.

Brief Longer Range Update: Thursday, Friday and Saturday will each bring similar conditions, with fog potential early on, skies clearing to become partly to mostly cloudy, followed by increasing clouds and widespread showers and thunderstorms developing by the late afternoon and evening hours. Some of these storms have the potential to be strong or potentially severe, but the potential for severe thunderstorms is not a big one. By Sunday, a much warmer air mass will return, and temperatures will rise into the 80s across parts of, if not most of the area. There is the potential for temperatures to reach the mid 80s sometime early next week ahead of the next rain maker, which will produce showers and thunderstorms with the exact timing uncertain. More information on the longer range will be posted over the next few days.


5:30 PM: Rain Unexpectedly Dissipating Offshore

When posting the last update late this morning, there was a solid area of moderate to heavy thunderstorms headed towards the area. It appeared that it would reach the area and bring additional heavy rainfall, but before it was able to do so, most of the rainfall headed towards New Jersey/NYC dissipated while additional moderate to heavy rain and thunderstorms continued to affect Long Island and southwestern Connecticut.

Since then, most of the afternoon has been the same, with rain and thunderstorms constantly dissipating just off the coast of NJ while Long Island and southern Connecticut continued to see storms, but the storms affecting Long Island are beginning to weaken as well. Today was not expected to be a constant washout, but all of the rain was not expected to simply dissipate offshore. In addition, parts of New Jersey are even seeing breaks in the cloud cover when rain was supposed to fall.

Most models did show rain for today, but the 00z and 06z NAM did correctly show most of the rain this afternoon staying in Long Island with little to no rainfall from NYC and further west. These runs bring in heavy rain tonight, with a similar scenario tomorrow bringing dry conditions once again. The short range NMM/ARW models also did not show much rain today while bringing heavy rainfall tonight and tomorrow. The other short range models, such as the RUC, show heavy rain later tonight, but they continue to repeat the same mistake by bringing the offshore rainfall inland within the first 2-3 hours of the run.

With the rain still dissipating off the coast of New Jersey, it is difficult to determine when rain will return into most of the area again and how strong it will be, but with the latest observations, dry conditions are expected to continue through the evening hours, possibly lasting even beyond the evening. Depending on what happens over the next several hours, I may have to lower forecast rainfall amounts across parts of the area. More information will be posted on this later tonight.


10:50 AM: Another Round Of Heavy Rain

The storms that affected the immediate NYC area early this morning are currently focusing on areas north/east of NYC, with heavy thunderstorms currently affecting central Long Island and SW Connecticut. These storms are moving northwest, and will begin to end within the next 1/2 hour. Meanwhile, scattered thunderstorms have been affecting NYC and northern NJ, bringing locally heavy downpours.

The latest radar is indicating a large area of heavy rain and thunderstorms well southeast of NYC, moving NW as well. The tilt of the storm is moving the areas of rain towards the NW while shifting slightly north at the same time, as we’ve seen with this morning’s storms, and this area of rain is expected to affect New York City, western/central Long Island, SW CT, far northeast NJ, and SE New York within the next 1-2 hours. NYC is expected to be in the SW edge of this area of rain, and places just southwest of NYC may not see much impact from this area of rain.

The next update will be posted this afternoon.


9:15 AM: Heavy Rain Just Starting

Early this morning, a band of heavy rain and thunderstorms set up over the immediate NYC area, extending from western Long Island/NYC/NE NJ into southeastern New York, where 1/2 to just over 1 inch of rain fell just this morning. This brings the estimated storm totals through this point to 1/4 to 1 inch in Long Island/S CT, and 1 to 3 inches in NYC, northern NJ and southeastern NY. Radar estimates show that as much as 4 inches of rain have fell so far in NW NJ, specifically in Sussex and Somerset counties.

The band of heavy thunderstorms is still mostly offshore, steadily moving NW, but is drifting north, currently affecting eastern Nassau county and central Westchester county. There is an area of moderate to heavy rain southwest of the main band, which will affect western Long Island and extreme northern New Jersey with additional rain over the next 1-2 hours.

A break in the rain is expected for the central and western parts of the area late this morning into parts of the early afternoon, but this is only the start of the heavy rain and thunderstorms, which will last through Wednesday night. More rain and thunderstorms will move into the area later today, bringing more localized downpours, with the heaviest storms likely to be tonight into tomorrow. Stay tuned for more storm updates later today, as well as another update this evening briefly discussing the time frame beyond this storm, including scattered strong thunderstorms for Thursday/Friday and a significant warm up next week that will bring NYC’s temperatures above the 80 degree mark for the first time this month.

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