Posts

John Homenuk

Prolonged onshore winds, tidal flooding on area shores

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While the main story of the past several days has obviously been Hurricane Joaquin, the synoptic pattern results in several weather hazards regardless of the storms path. As mentioned a few days ago, the path of Joaquin was a concern, but hazardous weather was likely to occur whether the storm tracked toward our area or not.

As a large high pressure system builds from our north toward Southeast Canada and New England, the lowering pressures to our south and east will aid in a continually tightening pressure gradient. At the surface, east/northeasterly winds will continue to surge toward the area coasts — specifically the New Jersey coast — resulting in increased wave heights. With rising tides and seas, coastal flooding is likely to occur through the weekend.

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Francesco Paparatto

Impressive Rain Storm 3/29 – 3/31

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An impressive storm system is going to effect the Tri-State area this weekend into early Monday morning. The set-up in the upper atmosphere (500 mb) supports a long duration rain storm with frequent moderate to heavy rains which increases the flood threat, especially in areas where there is still snow / ice and if you live in a flood prone zone.

Timing:

Start: 12pm-1pm Saturday

End: 5am-7am Monday

This equates to 40+ hours of rain falling which when all is said and done could add up to 4+ inches of rain in some spots of the Northeast. Obviously the rain is not going to be heavy for 40+ hours. In fact, there may even be a brief break in the action before it starts up again. Nonetheless, we are still looking at a washout weekend with a potent coastal storm developing.

The 00z GFS 500 mb map by 2pm tomorrow is beginning to show a phase with the northern and southern stream energies in the atmosphere which will result in a strong surface low developing. By this time, rain is streaming up the coast into the northeast ahead of the surface low with the heaviest falling over Long Island.
Fast forward into early Sunday morning, and now those energies have completely phased with the H5 trough now closed off. At this time, very heavy rain is falling throughout NY state, the northern tier of PA, NNJ, and NYC into LI.
By Sunday night, the closed off low deepens with the H5 trough now going negative, prompting the coastal low to slow down and bring training moderate to heavy rainfall over parts of the coast from PA into NJ into NYC.
What is happening here is we are seeing the effects of Atlantic blocking and what it could do to east coast storms. Throughout this winter, we have been in a relatively zonal flow due to a constant +NAO with only a north-Atlantic ridge trying to help slow the flow down.
This time, the combination of positive heights into Greenland and eastern Canada have forced this storm to CUT-OFF from the jet stream and almost come to a stall off the coast of NJ. The good news is this will not be some 950 mb bomb of a storm that is bringing hurricane force winds to the area. It is expected to remain on the weak side with the worst of the winds along the immediate coast, where 30-40+ mph gusts can be expected.
RAIN MAP
Region wide, we are looking at 1.50-2.50 inches of rain for the most part. In further assessment, I can see how red-shaded areas receive possibly more than 3 inches of rain due to the positioning of the stalling low pressure storm off the coast of NJ. Some pieces of guidance support this notion of sending bands of rain over this area which would enhance rainfall totals. Obviously flooding in NNJ near the rivers could be a concern, but I do not believe rivers are in danger of flooding since it has been pretty dry of late. However, that does not mean roads that flood easily will not flood. So please keep that in mind.
Enjoy this miserable weekend,
Frank

 

John Homenuk

Ice Jam along Delaware River raises major flood concerns

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Observations from this afternoon confirmed a major ice jam along the Delaware River near Trenton, and concern is rising for flooding potential along and near the river and its banks as the ice melts. Water levels have risen over 7 feet since last night. Latest reports suggest initial flooding occurred this afternoon near Market Street and Route 29. The National Weather Service has issued Flash Flood Warnings along the Delaware River from Trenton southward to Philadelphia for the potential of river flooding. The warnings continue through the morning hours on Thursday January 9th.

An ice jam occurs when pieces of floating ice, carried with the stream’s current, accumulate at an obstruction to the streams flow. The ice cams can develop near river bends, banks, mouths, or even points where the slope of the river decreases. The water held back can rise rapidly and cause significant flooding. Moreoever, if the obstruction breaks suddenly, flash flooding can rapidly occur downstream. This is the concern of forecasters this evening.

Ice jam on the Delaware River near Trenton as photographed on January 8, 2014.

Ice jam on the Delaware River near Trenton as photographed on January 8, 2014.

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John Homenuk

Periods of heavy rain expected today

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An unsettled weather pattern, which has settled into the area the second half of Labor Day Weekend, will rear its ugly head today as widespread showers and thunderstorms develop throughout the area. Areas of heavy rain have already developed early this afternoon, both over parts of New York City and also over Western and Central New Jersey. Limited instability should muddle what otherwise could have been a marginal setup for severe thunderstorms, but weak shear and lots of moisture suggest the potential for slow moving thunderstorms capable of producing heavy rain and leading to flash flooding.

Water Vapor Satellite imagery from the afternoon of September 2nd, 2013 showing moisture streaming into the area ahead of a cold front.

Water Vapor Satellite imagery from the afternoon of September 2nd, 2013 showing moisture streaming into the area ahead of a cold front.

The showers and thunderstorms are expected to continue through Monday evening, and may even linger into Tuesday morning across parts of the area — especially over Connecticut and on the Eastern end of Long Island. A more stable, cooler and less humid weather pattern is on the way by the middle of next week, but unfortunately Labor Day will have to be sacrificed in the process. Stay tuned for further updates including potential watches, warnings and advisories on the heavy rain and flooding potential.