HENRI’s S TRACK SHIFTS SLIGHTLY BACK TO THE RIGHT; INLAND FLOODING INTO MTNS OF NJ …southeast NY ( the Catskills) western CT western Mass COULD BE SEVERE
In general there are no major changes with regard to the evening update for hurricane HENRI but there is some additional information which needs to be brought to your attention which may not be getting the focus that it needs to.
It s now a HIGH PROBABILITY that Hurricane HENRI, will impact along the Northeast US coast, from NYC to Boston this weekend. HENRI will likely be weakening at landfall but the track of HENRI, from south to NW will drive a much higher than normal storm tides INTO to coastal areas. In addition, the combination of the Full Moon and the numerous concave shapes of the coastal areas from New York City to Cape Cod and Boston Bay will also enhance the potential storm tide and will likely produce much more significant coastal flooding than one might see with a weakening hurricane or garden-variety tropical storm on the northeast US Coast.
The 8–9 PM Aircraft reconnaissance reports showed that HENRI was still a hurricane although it was barely such. The latest recon plane found the pressure of 988 MB and a maximum flight level wind of 75 knots and a surface wind gust to 65 knots.
While it is not the purpose of this report to focus on the issue of media coverage in the big cities of the Northeast (hype or not?), there are some points which need to be made regarding East Coast hurricanes which are often forgotten when there is an East Coast hurricane event.
The typical East Coast hurricane that parallels the coast or even comes up along the coast will be much stronger on the eastern side than on the western side. There are several reasons for this. Hurricanes are essentially ocean driven heat engines that get their energy source from the ocean. But addition, the friction is much less over the water than it is over land. Moreover, the large circulation of a hurricane or a tropical storm is quite considerable and it pulls in air masses from many different directions. Hurricanes traveling along or parallel the East Coast, such as the track that HENRI is taking, will always suck in a tremendous amount of dry air from the eastern US which of course is not tropical at all. This dryer air mass will cause significant disruption to the core of a hurricane over time. This is why slow moving East Coast hurricanes typically weaken as they come up the coast.
Indeed if you look at the history of major East Coast hurricanes that have been particularly destructive over the last 150 years, almost all of them have featured rather rapid movement along or up the coast greater than 40mph. This fast forward speed restricts the ability of the dry air from the eastern CONUS to get entrained into the core of the hurricane. This means much less weakening. HENRI is not a fast-moving hurricane and it is pulling in a considerable amount of dry air from the eastern US which we can see on the afternoon satellite pictures
Eventually this dryer air will get pulled into the core of the system as it approaches the New England coast and the eastern tip of Long Island. In addition, the ocean water temperatures are also considerably cooler compared to the water temps that one finds in the Gulf Stream or the western Atlantic Ocean. These cooler ocean water temperatures will also begin to restrict and weaken HENRI as the system approaches land.
We can see this in the latest model data which shows that the wind field collapses quite rapidly once it makes landfall and eastern Long Island / southeast Connecticut / Rhode island or perhaps southeast Massachusetts. NYC may not see any wind gusts up to/ over 35mph.
In addition the latest projections from the hurricane models show the intensity of HENRI weakening rapidly before landfall as well as after landfall.
If we look at the latest model data from Saturday afternoon and Saturday evening, we see that HENRI’s turn to the Northwest is not quite as severe as what the model data was showing on Thursday and on Friday. Some of the models showed such a turn to the northwest that the low level center of HENRI would track across western Long Island and cut across the New York City metro area. That kind of radical turn to the Northwest is no longer showing up on most of the models at midday. And the latest 18z Saturday evening models, both large-scale and a small scale, do not have HENRI hitting New York City directly at all.
With respect to the actual track most of the model data but not all are in very good agreement that HENRI will bend to the northwest as it approaches the eastern tip of Long Island or southeastern New England. The Northwest track will continue and the system will pass through Connecticut passing into New York state north of NYC, and probably north of NYC and into the Hudson Valley by Monday.
This track which is more to the east with respect to NYC / western Long Island means that that region will experience more of a North wind as opposed to an East wind. This means that there will not be a buildup of water in NYC Harbor. Instead the North wind will actually be blowing the water out of the harbor so the areas of western Long Island and NYC and northeast coastal NJ will not be seeing any sort of moderate coastal flooding
With respect to actual coastal flooding, nothing in this discussion really changes the concern and threat. The track of HENRI into southeast New England and eastern Long Island / eastern Connecticut will cause moderate to significant coastal flooding. The other factors such as the shape of the coast and the bays in these areas as well as the full moon are still there.
The other aspect to this forecast which is probably not getting enough attention is the amount of rain. Even though the system as a tropical Cyclone will fall apart rapidly once it makes landfall, the low-level core will continue to pull excessive amounts of tropical moisture from south of Long Island. The interaction of the Upper Low (a pocket of relative cold air) in the mid-levels of the atmosphere will enhance the rain fall in the New York City metro area, the Catskills, the Hudson Valley and much of central and southwest New England. The areas which have elevated terrain such as northeast Pennsylvania, northern New Jersey, southern New York, will have the rain enhance because of orographic lifting.
As these images show there is going to be a significant area of extremely heavy rain for most of central and southern New England and portions of southeast New York. Although some private forecasters continue to show extremely heavy rains — up to 10 inches in northeast Pennsylvania / the Poconos, the shift of the track on the latest models runs more to the east of NYC means that the threat of extreme heavy rain in northeast Pennsylvania is much reduced. Of course this area will see significant rain of several inches but probably not the 10”+ rainfall amounts that some were talking about earlier on Saturday. The Catskills however are facing the threat of serious destructive flooding as the water cascades down the mountains in the valleys and the same can be said for northwest Connecticut and much of western Massachusetts.