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Manhattanhenge returns, cooler air in control

Just before sunset tonight, the sun will line up with Manhattan’s street grid in a marvelous and picturesque alignment known as Manhattanhenge. Crowned by Neil deGrasse Tyson in reference to Stonehenge, the alignment of the sun on Manhattans streets draws thousands of photographers and tourists during the multiple times which it occurs each year. The phenomenon would occur on the Summer and Winter equinoxes if Manhattans grid was aligned perfectly north to south, but instead the grid is tilted by about 30 degrees east — so it occurs on odd days throughout the year.

Tonight, just after 8pm, the sun will set between the tall buildings of New York City — visible if you are facing west. The best views are typically on the major cross-streets of 14th, 23rd, 34th, 42nd and 57th. The sun will set below the horizon at 8:16pm. Today’s Manhattanhenge will only be a half-disk sun — but Friday’s will feature a full disk sunset down the center of the aforementioned east-side streets.

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Backdoor front brings clouds, cooler air

For the fifth time this Spring, a well defined backdoor cold front has swung southwestward from New England and brought marine air into our area. On the heels of three warm days in a row, with temperatures in the 80’s to near 90 on the last two days, the backdoor front gained steam initially in Maine and moved through New England on Tuesday. By Tuesday Night, the front progressed past New York City and Wednesday morning it was south of Philadelphia. The front featured a dramatic thermal gradient, with temperatures now in the 50’s and 60’s in areas where they were in the 80’s on Thursday. Northeast winds and cooler, more damp air were to blame as clouds infiltrated the area as well.

The culprit in the development of the backdoor cold front is a persistent trough from Eastern Canada into New England and the Northwest Atlantic Ocean. This feature has reappeared several times this Spring season, and continues to bring an abrupt end to any warmups which surge into the area from the Central US. The front will eventually weaken later this week, but troughing is expected to maintain its hold on the areas weather — keeping any major warmups back into the 80’s at bay for the time being.

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Strong storms Tuesday, backdoor front Wednesday

It has been the season of backdoor cold fronts so far this Spring, and yet another one is poised to move southwestward from New England during the middle part of this week. For the time being, our area is nestled just to the south of the backdoor frontal boundary. What  this means for Tuesday is continued, if not enhanced southerly flow and very warm temperatures. Highs in the upper 80’s to lower 90’s are likely throughout the area — and warm temperatures are even possible down to the beaches with an offshore wind direction.

By Tuesday afternoon, however, increased support for lift along the broad frontal zone will increase the chances for the development of showers and thunderstorms. With moderate instability in place and marginally supportive wind fields, strong to severe thunderstorms are a possibility. Dropping from the northwest, these storms will be on the periphery of good upper level support, and may make it as far as the area beaches while maintaining strong to severe intensity. Namely, dangerous lightning and strong winds are a possibility within these storms.

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Scattered showers and thunderstorms this afternoon, beautiful and warm Sunday through Tuesday

As many of us look for outdoor activities during Memorial Day Weekend, the weather forecast becomes a bit more important. Fortunately, for the most part, this weekend looks great.

We do have to get through a chance of showers and thunderstorms this afternoon first, however. Similar to yesterday, there is still plenty of instability in the atmosphere, some moisture at the surface, but drying in the mid-levels of the atmosphere. There is also very little in the way of wind shear, which although can prevent storms from becoming too strong, it also makes them slow to move, and trains them over the same areas. Thus, the threat later this afternoon is for pulsing thunderstorms with the potential for flash flooding and small hail, but not much in the way of strong winds.

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Today’s HRRR model shows scattered showers and thunderstorms in the area developing later this afternoon (PSU E-Wall).

Most models target the NE NJ area, NYC, and SW CT, though other areas are at risk, too. Fortunately, not all of us will get these storms, but it might be a good idea to have umbrellas, just in-case. This afternoon should be a similar, but slightly lesser version of yesterday afternoon.

Moving forward to the rest of the weekend is when the weather looks great. The upper-level troughing will finally move out, and bring in ridging and a deep westerly flow. Deep westerly flow in the presence of a ridge is often some of our warmest setups, as winds flowing from an already warm source are able to downslope as they head towards our area, leading to further warming. Plus, westerly winds can somewhat mitigate sea-breezes.

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Today’s NAM model valid for Memorial Day shows widespread 80s for the entire region, even down by the shore (PSU E-Wall).

Sunday should generally expect sunny conditions with highs around 80 or in the low 80s, with light westerly winds. There is the slight risk of an afternoon shower, but nothing like what we saw yesterday.

Memorial Day should have wall-to-wall sunshine with temperatures in the mid and perhaps even upper 80s in some locations, with westerly winds as well.

Tuesday has the potential to be the warmest of all three days, but there may be a backdoor front approaching. We will most likely remain on the warm side of the front, but an increase in clouds could keep things a tad cooler. Regardless, Tuesday could still hit 80 degrees, and if the clouds hold off, mid to upper 80s are possible once again. The chance of an afternoon shower or thunderstorm exists as the front approaches. This will cool things off a tad once we hit Wednesday.

Along the shore, there will be a bit of a sea breeze developing due to daytime heating, but the westerly winds will act to fight it off somewhat. Thus, temperatures may be a few degrees cooler at times, but generally it will not feel much cooler than inland areas.

EF3 Tornado Confirmed in Duanesburg, NY on Thursday: This town is located about 10 miles northwest of Albany, NY, and a damage survey taken by the National Weather Service indicated EF3 damage, as a house was nearly completely destroyed. More information from the survey can be found here.

In case you are wondering how rare of an event this is, we took a look at data from the National Climatic Data Center, and it showed that in the 20-year period from 1991-2010, there is an annual average of 0.2 EF3 – EF5 tornadoes in New York. This means that a tornado of this strength occurred about once every five years in that period. In other words, although Thursday’s event was certainly an anomalous weather event, and quite impressive to say the least, it has fit the bill of climatology in the past twenty five years.