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Steven Copertino

Cold Front to Bring Northeast Relief, Lee Becomes a Major Hurricane

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Good Evening! 

Today was yet another hot and humid day across much of the Northeast with highs reaching up into the middle to upper 80’s over much of the area. Coastal sections of New Jersey, Long Island, and Connecticut were able to see lower temperatures due to easterly winds off of the cool Atlantic where highs stayed in the upper 70’s and lower 80’s throughout much of the day. Much of the day today was quite sunny and clear, which further added to the “summer-like” feel in addition to dewpoints reaching up into the upper 60’s and lower 70’s. The good news is that a cold front is working its way into sections of western Pennsylvania and into portions of New York this evening, and will bring some welcomed change to the area as soon as tomorrow!

This front will continue to march along, but have little in the way of any precipitation associated with it due to a lack of deep moisture content from the south.  There may be some small showers and brief downpours as this front continues east and interacts with subtle mesoscale features, but overall the evening should remain dry once again. As we head into the very early morning hours of Thursday, we have to watch for an increased chance of showers and some gusty winds along with Mid Atlantic and Northeast coasts. By this time, the cold front will be interacting with Hurricane Maria, which will be located to the southeast of the Delmarva peninsula. Widespread shower activity is not anticipated at this for the New York metro area as this front steadily chugs east, but the front could slow down a bit and bring in some additional moisture once it nears the Massachusetts and Rhode Island area.

Loop of Hurricane Maria off the Mid Atlantic coast along with the cold front that will be steering it out to sea over the next few days (Simuawips.com)

Loop of Hurricane Maria off the Mid Atlantic coast along with the cold front that will be steering it out to sea over the next few days (Simuawips.com)

Thursday will be a much more comfortable day across the entire Northeast, with the mid level trough associated with the cold front moving into the region. Behind the cold front, we should see light winds out of the northwest, with mainly sunny skies. Dewpoints will also drop quite dramatically as well, so tomorrow should be quite a pleasant day compared to the past few. Highs tomorrow will range from the low to middle 70’s near the coast, with cooler temperatures in the mid 60’s to lower 70’s expected further away from the coast. Again, the area will remain rather dry due to a lack of moisture and this should last through tomorrow evening as well. Tomorrow night will be a nice change and certainly have more of a fall feel to it as radiational cooling takes hold and really allows temperatures to drop for the first time in a while. Lows tomorrow evenings should range in the upper 40’s to lower 50’s along the coast, with low to middle 40’s further north and west.

Friday and into the weekend looks to be much of the same, with much lower dewpoints, light winds, and mostly sunny skies with highs in the middle 60’s to lower 70’s through Sunday. The only real chance for showers looks to be on Friday evening and into Saturday morning as another cold front moves into the area to reinforce the cooler weather. The shortwave associated with the front will have limited energy and moisture to work with, so the threat of heavy rainfall seems quite low at this time. Overall, it should be a beautiful weekend for the area, but not quite fall weather yet!

Farther out, medium range guidance continues to suggest that a very large area of mid level ridging will develop over the eastern third of the nation by the beginning of next week. However, do to the positioning of this ridge, we may be able to escape the heat and humidity like we had this week due to the potential for an area of high pressure to bring more onshore winds. This will allow temperatures to remain in the middle to upper 70’s with some increased moisture and a few rain chances, though nothing looks too significant at this time. We may see this pattern persist into next weekend as well, with potentially warmer temperatures once again taking over, but we will have further updates on that later in the week!

Loop of the cold front driving out the high dewpoints in the area and ushering a more seasonable airmass for the next few days

Loop of the cold front driving out the high dewpoints in the area and ushering a more seasonable airmass for the next few days

Lee Becomes the Fifth Major Hurricane of the 2017 Season-Watching the Caribbean 

Hurricane Lee made a very impressive comeback from back when it died in the central Atlantic about a week ago now. Earlier this afternoon, the storm was upgraded to a Category 3 with sustained winds up to 115 miles per hour. Lee is thousands of miles away from land and will stay that way as it continues to accelerates to the north, but it may add to the amazing superlatives that this hurricane season has racked up so far. It could push 2017 ahead of 2004 for the most active 30-day period (ACE wise) in recorded history. Later in the day tomorrow, Lee will begin to feel the effects of higher wind shear, which should start to drastically weaken the cyclone until its absorbed by a larger system in the North Atlantic. Lee has had an impressive journey over the past week or so, and will be remembered as being one of the only major hurricanes to not affect land, thankfully.

Unfortunately, our eyes will be turning to the Western Caribbean as we said they likely would be back in last weeks posts. The global models are starting to really hint on a large gyre of tropical moisture festering and eventually moving north, possibly into the Gulf of Mexico. This is all very far out, but systems like these tend to take days before becoming a named system, and sometimes they just remain disorganized masses of thunderstorms that can produce widespread flooding. Regardless, we will be closely following any developments over the next few days since the Caribbean is the climatological breeding ground for strong cyclones in October, and we currently have very favorable conditions for a system to take advantage of if one does wind up forming. As of right now, I would say that there is a medium chance of tropical cyclone formation in the NW Caribbean and Gulf of Mexico in the 7-10 day period.

Animation of the ECMWF model showing a large, cyclonic gyre taking shape in the Caribbean/Gulf of Mexico in 6-10 days (Courtesy Phil Pappin

Animation of the ECMWF model showing a large, cyclonic gyre taking shape in the Caribbean/Gulf of Mexico in 6-10 days (Courtesy Phil Pappin)

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Have a great evening!

Steve Copertino

Miguel Pierre

Cooler Weather Returns by This Weekend Over the Northeast

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Good morning! Today will be another very warm and humid day, as mid-level ridging remains over the Northeast. Some low clouds and patchy fog again in some spots early this morning, should gradually burn of during the next few hours. Then more sunshine filtered by some high clouds, well help temperatures rise to well above normal again this afternoon. Highs will be the mid-upper 80s, away from the coast. Easterly winds may will keep some coastal sections cooler, perhaps only mid-upper 70s or lower 80s for highs.

A large mid-upper trough moving in from the Midwest and Great Lakes, will finally break down the ridge for rest of the week.  A cold front associated with embedded shortwave energy along this through, will be approaching by tonight. Some showers and thunderstorms are still possible with some weak instability building ahead of the front, mainly over Interior parts of the Northeast later this afternoon and evening. But a lack of moisture and dynamics will keep this activity mostly isolated or widely scattered in coverage.

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Steven Copertino

PM Rain Exits, Storms and Cooler Weather Possible This Weekend!

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Good Evening!

After a relatively hot and humid day across the entire Northeast and Mid Atlantic regions, we have seen large-scale thunderstorm development courtesy of the mid level shortwave that we discussed back on Monday. This shortwave was located to the west of the area, and with CAPE values of around 2000-3000 j/kg^2, PWATS near 1.5″, and strong low level lapse rates, the weak amount of energy associated with the disturbance was more than enough to set off numerous showers and thunderstorms around 2pm. Due to a significant lack of vertical wind shear, these storms were not able to move all that much from where the initial updrafts formed, and thus most cells rained themselves out over time. However, when these updrafts collapsed and the rain cooled air rapidly sunk to the surface, it created new boundaries which served to provide breeding grounds for renewed storm development. In some locations we saw this happen three to even four times over, which caused serious street flooding.

In addition to the street flooding, cool/dry air aloft allowed for some of the more robust thunderstorms to develop marginal to severe hail stones, with some reports of stones reaching the 1.75″ mark! Some folks may have noticed that these storms were also producing a cooler rain than one would expect during August, and this also can be attributed to the cooler air aloft. These drops were whats know as “Big Drops” (I know, very creative) and form when an updraft just isn’t able to keep ice suspended long enough to freeze sufficiently to reach the ground as hail. However, a few thousand feet up in the atmosphere, these drops were frozen, and when they crashed into one another, they create a negatively charged particle in the atmosphere, called an electron. When enough of these electrons build up in an updraft, they connect with positively charged particles (protons) at the surface, the path they take to get to one another creates lightning! With a ton of ice in the atmosphere from numerous updrafts this afternoon, there was a very impressive amount of lightning that went up across the area. Some of this lightning even caused damage to houses and property, with some areas losing power. Otherwise, today’s storms mainly posed a very heavy rain, lightning, and gusty wind threat.

As of six o’clock this evening, most of the showers and thunderstorms that formed early this afternoon were finally beginning to wind down. Lightning activity over the area has greatly weakened over the past hour or so, and this also points towards a gradual dissipation of the rest of the thunderstorm activity. As this time, we think that the heaviest showers and thunderstorms should dissipate by sundown, with only a few lonely cells remaining thereafter. Some residual cloud cover is likely as we head into the overnight hours, and this will help to keep overnight lows rather mild, with temperatures dropping to around the low to middle 60’s.

This evenings latest regional radar. high resolution visible satellite, surface observations. and severe warnings, showing the bulk of the heavy rain dying off. This trend should continue as we head deeper into the evening (Courtesy of Simuawips)

This evenings latest regional radar. high resolution visible satellite, surface observations. and severe warnings, showing the bulk of the heavy rain dying off. This trend should continue as we head deeper into the evening (Courtesy of Simuawips)

Thursday and Beyond

Thursday should start off just as the past few days have, with any low clouds quickly burning off by the mid to late afternoon hours. This will allow afternoon temperatures to climb significantly during the afternoon hours, with highs likely reaching the middle 80’s to lower 90’s across the area. With a moist airmass in place tomorrow, we should see the region destabilize once again by the mid to late afternoon hours, similar to as we saw today. The main difference will be that tomorrow does not look to have a coherent area of forcing to initiate thunderstorm development, so any thunderstorms tomorrow afternoon will likely have to rely on convergent boundaries from local sea breezes. This activity will likely be limited to a heavy rain and lightning threat given the lack of favorable parameters for anything outside of heavy thunderstorms. Storms should gradually fade tomorrow evening, leaving generally mild and humid conditions in their wake.

As we head into the first half of the weekend, a large shortwave trough diving out of Canada will provide a threat of heavy rain and possibly some thunderstorms over the area as moisture begins to surge north from the Gulf States. This system will be watched closely, as it does have a very favorable upper level jet streak which could potentially enhance a heavy rainfall threat over our area. A strong cold front looks to push through late Saturday and into Sunday, which should bring not only cooler temperatures to our area, but also much lower humidity compared to what we’ve been seeing-which should make for an enjoyable end to the weekend!

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(Detailed Discussion With Doug Simonian)  

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Have a great evening!

Steve Copertino & Doug Simonian 

 

Miguel Pierre

Premium Long Range: Cooler, Active Pattern Next Week…More Changes Late Month?

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Good morning! More summer-like weather with more heat and humidity will continue for the rest of the week,with some scattered showers and thunderstorms possible each afternoon or evening. But it appears the Western Hemispheric pattern will undergo another more significant changes to support some cooler weather again for next week.

First changes, will start occurring over North Pacific as usual this week. An upper-level low will be near the Aleutian Islands or Southwest Alaska. This will cause a high-amplitude ridge to build over the West Coast by early next week. This will result in a larger trough digging and encompassing much of the Central and Eastern US over for next week.  Then cooler airmasses from Canada will be invading the CONUS, with temperatures well below over the much of the Northern and Central Plains and into parts of Great Lakes and Ohio Valley.

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