Sunday, October 28, 2012

Forecast for Monday, October 28, 2012

Hurricane Sandy has actually continued to look slightly better on the visible satellite imagery at early afternoon on this Sunday as a hurricane structure. There appears to be thunderstorm activity wrapping around the center of circulation creating an eye and eye wall feature. While Sandy appeared to be more of a comma shape rather than a donut shape just a day ago, it appears that this hurricane has so far been able to fight off changing the overall structure. However, we still anticipate the transition into a very potent Nor'easter throughout Monday as it will be interacting with a strong, negatively tilted trough that will actually suck the system into our coastline. The blocking high pressure area will help with that steering, causing this system to make a left turn that is sharp enough to make the system run into our coastline in a perpendicular fashion. Prior to the transition process, enough warm water and lowering shear values exists to allow this to possibly strengthen slightly as it maintains tropical characteristics. However, strengthening is likely as this hurricane transitions into a Nor'easter. There is little reason to believe at this time that Sandy will escape the extra-tropical transition.

Conditions will continue to deteriorate this evening and tonight. Strong winds will begin to impact the eastern areas…particular Southeastern New Jersey and Delaware. As we approach late night, these strong winds will spread inland towards Interstate 95. By Monday Morning, the entire region will be dealing with strong winds with damaging winds developing from southeast to northwest throughout the day. Monday Afternoon into very early Tuesday Morning will be the period with sustained, damaging winds just about everywhere. This morning on the surface wind field analysis of Hurricane Sandy, the hurricane force winds have actually evolved on the southwest side of Sandy which was expected to form on the northeast side as it typically does in a tropical cyclone. This is interesting and I will be watching that very closely as this could end up being the case given the expected transition. However, I still expect the highest surge levels on the northeast side of Sandy. Overall, at the peak of the winds, most areas will be dealing with sustained winds of 35 to 55 MPH. Somewhere around the center of Sandy, there will be an enhanced area of destructive winds for a time possibly approaching sustained levels of 60 to 75 MPH. You know that these wind speeds in gust form can create serious damage. These will be sustained winds! Gusts will range from 55 to 75 MPH across the interior with gusts exceeding 80 MPH along the swath of hurricane force winds. The wind field is one of the largest ever with a tropical cyclone and should only get larger as it transitions! This couldn't be worse news with a system that will take likely several days to go from off our coast into Central Pennsylvania. Some slow weakening will eventually occur as it moves inland, but not before initially strengthening into a violent Nor'easter.  There is an unavoidable opportunity for numerous downed trees and power lines. Power outages lasting two weeks might become common. Many utility companies are already calling for outage lengths of ten days or more. It is also without a doubt that there will also be structural damage from these winds. The winds can also be enhanced between city, high rise buildings…in fields…and along the coast. It will sound scary at times…as the force of this wind will cause an unforgettable noise combined with the raindrops hitting your structure. You will also hear cracking sounds as trees and branches fall. At night, this will be occurring in darkness. Blue flashes in the distance will likely be seen as a result of transformers blowing. Don’t make the tragic mistake of comparing the winds to Irene. This will be a much more prolonged period of wind and this wind is already hitting the surface buoys. During Irene, this wind wasn't quite reaching the surface and we had a hard time spotting the winds that were expected with it.

Rainfall of only two to three inches may occur in our northern areas. Across the heart of our region, three to six inches of rain appears likely. Our southern and western areas will likely see the highest rainfall amounts as they should lie on the southwest quadrant or the rainiest part of Sandy. Here, 6 to 12 inches is possible with locally higher amounts. All poor drainage areas and flashier streams and creeks have the potential to be affected by flash flooding and sharp rises region-wide. Major river flooding is quite possible in areas that see over five or six inches of rain. Some of our waterways will also be significantly impacted by tidal/coastal flooding. Outer-bands have already arrived this afternoon and they should increase this evening. The main bands arrive Monday and persist into Tuesday Morning before they become more showery in nature.

A life threatening storm surge is expected. 4 to 8 feet storm surge is likely along our entire coastline, with the higher end numbers north and east of the landfall point. Monmouth and Ocean Counties in NJ have the highest chances of seeing record surge values…but should this landfall occur to the south of Atlantic or Cape May Counties…these counties could very well be put in danger of record surge as well. Again, even if it is not at record levels…it will be life threatening and still significant.

There will be the threat for isolated and brief tornadoes…but potentially very fast moving to spin up…especially northeast of the landfall. With cloudy skies and cooler temperatures, instability will be very modest. In addition, the change in structure will make this slightly less likely than with Irene. But nevertheless, the potential is there.

Factors making this storm worse include…

1.)    Full Moon
2.)    Leaves still on many trees catching the wind more
3.)    Leaves clogging storm drains increasing poor drainage
4.)    The storm coming in perpendicular
5.)    Unusually large wind field
6.)    Slow movement making conditions prolonged
7.)    Infrastructure and trees hit hard by several other recent storms
8.) Ground becoming saturated in advance of the strongest wind

As Sandy moves into Central Pennsylvania and Western New York on Wednesday and Thursday, we still will be influenced being that it is so large. Showers and clouds can be expected, although some sun may poke through the clouds. Colder air will wrap around the back side and this means that a few wet snowflakes may occur in the showers, especially west of the city. Wednesday and Thursday will remain windy and I could see gusts still in the 30 to 45 MPH range. Lingering flooding is likely at this point.