May 18, 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.


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6:10 PM: Storms In Long Island

The band of rain has cleared places west of NYC for the main part, though heavy storms continue to affect places north and east of NYC. The strong storms previously mentioned as heading towards central Long Island have not weakened, and are producing very heavy rain and thunderstorms in western/central Suffolk county. These storms are also extending into parts of southwestern Connecticut and northern Westchester county, NY.

Storms will begin to weaken in Long Island within the next 1/2 hour as the main band moves away, with the bands in SW Connecticut shifting north, moving through and just north of Bridgeport. Rain is expected to intensify in parts of Orange County, NY as the area of storms moves into that area.

Behind this area of rain, however, the new storms approaching the area are significantly weakening, and the convection offshore is also weakening. Additional rain is expected this evening and tonight, but the current band of rain is likely the heaviest the area will see through tonight.


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3:40 PM: Heavy Rain Returns

Since this morning's post, mostly dry conditions were observed with rain falling to the SW and NE of the area. Some scattered showers were observed in the area, though most places saw clearing in the cloud cover, with mostly to partly cloudy skies observed around noon. As mentioned this morning, today was expected to stay quiet until the mid afternoon, when convection offshore would move into the region and produce more rain. The area of rain has reached the area, and is now starting to produce widespread moderate to heavy rain that will continue through the late afternoon and evening hours.

Looking at the latest radar, a long band of moderate to heavy rain and thunderstorms is stretching NW, from the waters southeast of NYC through NYC itself and all of northern New Jersey. Northeast of the band, scattered thunderstorms are quickly forming across southwestern Connecticut. This band will continue to shift towards the NW/NNW, spreading heavy rain into southeastern New York, western Long Island, and southwestern Connecticut, with rates generally between 1/2 and 1 inch of rain per hour. There are strong thunderstorms in the eastern part of this band moving towards central Long Island, more specifically near western Suffolk county, and while these strong storms may weaken in intensity when they reach the coast, they will still be capable of producing moderate to heavy rain.

This band is not the last one that will produce rain today. The latest water vapor loop shows that there is plenty of storm activity offshore that will move north, then northwest towards the NYC tri-state area. Some of this activity may very well weaken before reaching the coast, but it is still expected to produce additional rain in the area. The bands later tonight may target places further east than the current band over the area, and some breaks are expected in between the bands, but the next few rounds of rain will help add to the already high rain totals across the area, with radar estimates showing that almost the entire areas has seen over 1.5 inch of rain up to this point since Sunday.


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Wednesday, 5/18
9:20 AM: More Rain Likely Later Tonight, Preview Of Next Week

While the area of storms that approached northern NJ last night weakened as it reached the area, more storms affected the area overnight, focusing especially from NYC and further east. The most recent rainfall to affect places west of NYC was from a heavy rain shower earlier this morning that moved through NW NJ/Orange County while intensifying. The radar as of now is not very impressive, with only widespread showers across the region with some of those showers weakening/dissipating. The short range models also do not show much, if any significant rainfall during the day, with more rainfall during the night.

Looking at the current observations, most of the rain is expected to stay to the SW and NE of NYC, especially with an area of heavy thunderstorms currently southeast of Delaware headed towards southern New Jersey, Delaware and SE Pennsylvania. Some clearing in the cloud cover is even possible in the short term in the immediate NYC area before more clouds return later on, with occasional breaks in the cloud cover also possible later on today.

Some showers and storms are expected through the early afternoon, with an area of storms off the coast of North Carolina potentially affecting parts of the area early this afternoon should it reach the region without collapsing or changing direction, but the better risk of more widespread heavy rain in the area is likely to wait until at least the mid afternoon at the earliest when convection offshore should approach the region, with the evening and overnight hours more likely to bring widespread rain into the area. Stay tuned for more updates on this later this afternoon.

Longer Range: The main long range models continue to show summer-like 850 mb temperatures for next week, getting as high as 18 to 20 degrees celsius, which in a typical summer day can bring 90 degrees. The GFS is colder with surface temperatures, showing lower 80s in NYC on Tuesday, with the DGEX showing warmer temperatures getting as high as the upper 80s near NYC. The exact temperatures are uncertain at this time, though it appears that there may be an onshore wind on Sunday/Monday, limiting temperatures, with Tuesday and Wednesday likely to bring temperatures into the lower to mid 80s in NYC. There is also the risk of severe weather with the warm up, which will be discussed in a full update tonight.