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NYC Weather Update – Post-Tropical Storm Hermine – Sep 4, 2016

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Although tropical storm warnings are still up for the five boroughs, coastal Connecticut, Long Island, and New Jersey, it appears at this time that the threat from Hermine is diminishing. The center of Hermine is now located well out into the Atlantic Ocean, and even if it does make its eventual turn to the north and northwest, it will be far enough east of us that most impacts should be on the moderate side.

Rest of today – over the last few days, Hermine has continuously trended east of the official National Hurricane Center forecast track, and has still not made a turn to the north or northwest. It is still forecast to make that turn today, bringing it closer to shore, and increasing clouds in the area. Winds should pick up as well, with high temperatures around 80ºF.

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Post-tropical cyclone Hermine this afternoon

Labor Day (Monday) – assuming that Hermine does make its projected turn towards the coast, Monday would entail a chance for rain, as well as strong winds, possibly approaching tropical storm force. High temperatures are only expected to reach into the upper-70s in this scenario. Could be a tough day for the Caribbean Day Parade.

Personally, I do not believe Hermine will produce tropical storm conditions (sustained wind greater than 39mph, less than 74mph). during this time, the confidence in this track forecast has been low, and any turn towards the coast has yet to verify. That said, nothing about this complex storm would be surprising, and a shift in storm track 50-60 miles west could dramatically increase the likelihood of the city receiving tropical storm conditions. Primary impacts will still be moderate to major coastal flooding with multiple tide cycles of storm surge and large waves leading to serious beach erosion in some places.

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Based on latest track forecasts and current position of Hermine, NYC rests in a zone of 30% chance of experiencing tropical storm force winds, with the probability increasing sharply further east.

Tuesday – could end up being a pretty decent day if Hermine is further off to the east at this point. If that happens, we’ll probably see decreasing clouds and improving conditions with high temperatures in the mid-upper 80s. If Hermine sticks around, then we could see another day of wind and rain.

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Will be posting another update tomorrow.

 

 

NYC Labor Day Weekend Weather – TS Hermine – Sep 2, 2016

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I wrote that I would not be posting any updates while on vacation unless there were to be a special event that warranted it. Well, the likely approach of the remnants of Tropical Storm Hermine into the offshore waters in our region certainly warrants this special update. As of now, it appears that Labor Day itself will be the only day when we could see significant impacts from this storm, but this could change. I will likely have another update Sunday.

Rest of today – sunny, and pleasant with a high in the low-80s. This will be by far the best day of the long weekend.

Saturday – increasing clouds, high temperature around 80ºF.

Sunday – mostly cloudy, with chances for rain increasing in the afternoon. Cool, with highs only in the mid-upper 70s.

Labor Day (Monday) – tropical storm conditions possible, strong and gusty winds, and possible periods of heavy rain, especially in coastal areas. Dangerous rip currents at the beaches, as well as moderate to major coastal flooding. Mostly cloudy otherwise with high temperatures in the upper-70s.

Tropical Storm Hermine this morning
Tropical Storm Hermine this morning

Tuesday – with the remnants of Hermine currently forecast to linger off of the coast of the Northeast, we could see another day of possible tropical storm conditions. Warmer, with high temperatures in the low-80s.

Tropical Storm Hermine’s Forecast

Since the inception of Hermine as a tropical wave off the coast of West Africa, forecasters have had difficulty in accurately capturing the track and intensity of this storm. Its approach towards our region is no different. The forecast is complicated by the fact that Hermine will be completing a process of extratropical transition. A complex set of interactions between it and a frontal boundary adds a high degree of uncertainty towards the late period of this forecast.

Forecast Track

As of this morning, the National Hurricane Center’s official 5 day forecast called for Hermine to continue tracking rapidly northeast just inland of the Southeast coast as it initially interacts with a frontal boundary in its vicinity. During this period, it is expected to weaken, but by Saturday evening, it is expected to re-emerge over open water off the North Carolina Coast. At this point, Hermine is expected to have completed extratropical transition. It will begin another interaction with a baroclinic frontal zone, which is expected to significantly slow its forward progress down. This slowing will likely also lead to the storm erratically meandering off the Northeast coast, possibly doing a loop.

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Some major forecast model’s current output for Hermine
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GFS ensemble models (spaghetti models), white denotes the consensus track

Intensity Forecast

During the period that the storm is over land, it will weaken continuously. However, by Saturday evening, when it is expected to re-emerge over open water, and complete extratropical transition, it will gain in strength. The extratropical transition will impart energy from baroclinic forces (interactions between airmasses of differing pressures), and the storm is expected to re-intensify into a strong extratropical storm with sustained winds of 60-65mph.

Impacts

The intensity and location of these impacts will depend greatly on the eventual track for this storm.

Tropical storm watches are in effect for the entire New Jersey coast. Heavy rain in coastal areas. Strong sustained winds, winds gusting in excess of 50mph in some coastal areas. Beach erosion along with coastal flooding, possibly for an extended period of time. High surf and dangerous rip currents.