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Cooler Conditions Finally Take Over, But Will They Last?

Good Evening! 

A cold front moved through sections of the Northeast late last night, bringing areas of showers, gusty winds, and more importantly a sizable airmass change. Within a period of only a few hours, the cold front knocked us into more autumnal conditions, with dewpoints dropping from the unusually high low to middle 60’s, back into the low 30’s-leading to a much more crisp feeling to the air today. Additionally, cooler temperatures aloft have left the entire area with much cooler highs as well, with most of the Northeast seeing highs in the middle 50’s to lower 60’s, with even a few areas in Pennsylvania and New York seeing temperatures stuck in the upper 40’s. Conditions have also become quite windy across the area behind the cold front-with many stations reporting northwesterly winds gusting in the 20-30 mph range through the afternoon and into the early evening hours. This northwesterly flow has also worked to bring in cooler air over the relatively warm Great Lakes, which has generated some lake-effect clouds this afternoon that has mainly been focused over New York state, with some low-topped cumulus clouds over Pennsylvania. Further east over the metro area, we’ve seen a mix of sun and clouds over the area as some trailing upper level cirrus clouds quickly move from southwest to northeast on the eastern side of the upper level trough.

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As we head into sundown, gusty conditions will likely remain in place for most of the area, except for portions of central Pennsylvania and western New York. The cirrus deck that has been in place most of the day will continue to diminish over the next few hours and head off to the east as the upper level trough continues to lift out. This will allow for skies to become quite clear this evening, and with low humidity, clear skies, and diminishing winds, we will have at least marginal conditions in place for radiational cooling to take over. Temperatures will likely fall into the “cold” levels this evening as lows dip down to the upper 30’s and lower 40’s for the immediate NYC metro area. Further north and west, lows could get into the low to middle 30’s, which could cause patchy frost to develop in the areas that see the wind really calm down over the next few hours. The NWS has issued numerous Frost advisories over the Northeast, so make sure to bring in any plants that may be vulnerable to frost conditions this evening.

Tuesday will likely be another calm and cool day for the Northeast as surface high pressure begins to build in from the south and west by tomorrow afternoon. Highs will likely range from the upper 50’s to lower 60’s, with areas further north and west likely seeing readings a few degrees lower. Humidity will also remain very low tomorrow, and though this may feel like its a big deviation from the normal, but tomorrows highs will likely be right around seasonable for this time of year. The building high pressure will allow for lows tomorrow night to fall back into the low to middle 40’s tomorrow evening, and with lower overall winds patchy frost may be more likely across the area.

3km NAM showing much cooler conditions overall for the Northeast

3km NAM showing much cooler conditions overall for the Northeast

Later This Week and Beyond

As we look ahead into the later part of the week and past the weekend, we are likely to see mid level ridging rebuilding over the east by Thursday, which should lead to a small increase in highs for a coupel of days. We should be looking at temperatures rising into the low to middle 70’s pretty much every day for the rest of the week, and then again this weekend as a second area of mid level ridging begins to build into the East by Saturday. This pattern should last us into the early to middle part of next week, before the overall pattern begins to shift largely due in part to large scale convective patterns in the tropics becoming more concentrated in this area of the globe. When this happens, we tend to see a large area of riding set up over the western United States, with a trough eventually setting up in the east. Such a scenarios would be a large departure from the normal over the past few weeks of warm and dry weather, as the eastern trough would likely bring below-average temperatures and an increased rain potential during the period. While the individual model runs seem to disagree about the exact timing of when a coherent area of troughing will set up over the east, the ensembles have been rather consistent that around the  October 24th-28th period, the likelihood for this scenario is high.

Due to the level of enhanced convection over the tropics during this time as well in conjunction with leftover warm waters over the Atlantic, we may also have to keep an eye on the tropics to see if we can manage to get a late season storm out of this pattern.

We will have more on this pattern later in the week!

ECMWF Ensembles showing a deepening trough beginning to set up over the east by the middle of next week

ECMWF Ensembles showing a deepening trough beginning to set up over the east by the middle of next week

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Have a great night!

Steve Copertino

The NAM showing a strong jet streak in the Northeast on Wednesday night.

Heavy Rain and Storms Possible Tuesday through Thursday

 

Happy Labor Day! We are finally enjoying some warm, sunny, summery conditions after a few days of chilly and unsettled weather had dominated the region. This is because a large, full-latitude, but short wavelength trough has moved into the Central US, which is a direct downstream response to the amplified wavebreaking that occurred from a recurving typhoon in the Western Pacific. This amplified pattern has also helped/reinforced a very strong, blocking ridge in the Atlantic, and it’s this trough’s interaction with the blocking Atlantic ridge that could lead to a few rounds of heavy rain and thunderstorms, though not necessarily a washout. Also, our area initially being downstream of this deep trough has led to strong southwesterly flow out ahead of it, and thus a large warming trend in the Eastern Seaboard.

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Cold temperatures on Friday morning (Tropical Tidbits)

More Tranquil Weather Returns, Harvey’s Remnants Possible for the Weekend

 

Good morning! After a cloudy, wet day on Tuesday, today will much improved, as a Nor’easter moves farther into the Atlantic. Mostly sunny skies are expected with dry westerly winds by this afternoon. These conditions will help temperatures rise into the middle to upper 70s, with some spots possibly reaching 80 degrees. These temperatures are near or slightly below normal.

Clear skies and light winds are expected for most of the night. This will lead to some radiational cooling with temperatures dropping into the 50s over the Interior Valleys and Pine Barrens and into the lower to middle 60s over more urban and coastal areas.  Then a cold front associated with a shortwave trough will be moving through the Northeast on Thursday. More clouds are likely to mix with sunshine with temperatures rising into the upper 70s to lower 80s, ahead of the cold front.

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gert

Dual Rain Threats This Week, Tropical Storm Gert Intensifying Off the East Coast

Good Evening! 

Today started off decently clear and warm over much of the area, but as the day progressed onward, the elongated area of high pressure just to our south began to move offshore. As it did so, this allowed low level moisture and cloudiness to begin to filter over the region, but still allowed conditions to remain slightly below-average, with highs locked in the upper 70’s to lower 80’s. As of this evening, cloudiness has begun to increase in earnest across the area in response to an impulse of mid level energy working its way north and east along mid level trough. In addition to cloudy skies, this impulse of energy has also sparked some showers over the northern portions of the Mid-Atlantic, with sections of Maryland, Delaware, Pennsylvania, and southern New Jersey all reporting light to moderate showers moving across that area this evening. This area of showers should continue to head east-northeast over the next few hours, but may have trouble making too much northern progress as there is some residual mid level dry air over portions of northern NJ and Long Island. This mid level dry air has also been noted on this evenings radar, as numerous areas of virga (rain not able to reach the ground due to dry conditions) popped up and quickly dissipated soon after.  Overall, conditions should remain cloudy with a chance of a light shower the further south you go, but with increasing moisture, light southerly winds, and increasing clouds at all levels-radiational cooling will be very hard to come except for locations in northern Pennsylvania as well as central New York. This will keep low temperatures in the mild range of the upper 60’s to lower 70’s, with temperatures around 5 degrees cooler to the north and west.

This evenings latest high resolution GEOS 16 visible satellite imagery, regional radar mosaic, surface observations, and WPC frontal locations.

This evenings latest high resolution GEOS 16 visible satellite imagery, regional radar mosaic, surface observations, and WPC frontal locations.

Tuesday Through Friday 

Tuesday morning will likely start off with numerous clouds and possible showers over the region, and another shortwave trough begins to move just to the southwest of the area, bringing another new batch of mid level instability and moisture. At this time, it appears that the best chance for steady rain will be tomorrow morning, likely over the southern portions of the New York Metro area, with locally heavy areas of rainfall possible. As the day progresses, the steadiest rain should begin to head east and off the Mid Atlantic coast. This will likely give way to improving conditions by the mid afternoon hours, with some clearing possible the further away from the coast that you area. With the mid level still feeding moisture in from the south and east, any clearing will likely allow for some instability to build up. Though we will have some instability and weak wind shear to work with tomorrow over the interior, the models indicate an area of sinking air associated with a dissipating mid level system to our north. This should greatly reduce the potential for thunderstorm coverage, but in general isolated shower and thunderstorm development is likely across portions of New York and Pennsylvania tomorrow afternoon and into the evening hours. With the lack of severe parameters coming together, the overall threat for severe weather should be quite low tomorrow, but some stronger storms could produce gusty winds, very heavy rainfall, and even small hail.

As we get closer to New York City, cloud cover and much more stable/sinking air over the region should generally limit and thunderstorm development through the evening hours, and any storms that track close to the area should be on the weakening trend and will likely die-off. With winds coming off of the Atlantic, tomorrow evening will likely be another mild and somewhat-muggy one as lows will likely stay in the low 70’s to upper 60’s across much of the area.

Wednesday should be a much more pleasant day across the Northeast, as dry air behind the mid level disturbance begins to overspread the area, knocking out much of the cloud cover during the early morning hours of the day. Mid to upper level ridging will allow for temperatures on Wednesday afternoon to get quite warm, with highs likely reaching up into the upper 80’s and into the lower 90’s across the region. Few clouds are expected through the evening hours, as a backdoor coldfront pushes from north to south across our area, working to lower dewpoints region-wide.

Thursday looks to be relatively nice for the majority of the day, as the backdoor coldfront halts its progress around the Mid Atlantic region, keep the area warm, but less humid during the day. With dry northwesterly flow established, conditions should be mostly clear across the area. This looks to change later in the evening, as a large mid level system over the Great Lakes looks to approach the Northeast after sunset and into Friday. This system will be accompanied by a strong cold front, which could be responsible for shower and thunderstorm development late Thursday and into Friday, but at this time, it does not appear that this system will carry much of a severe weather threat as well as a flooding threat. This will likely have to be reassessed later in the week, so check back for updates!

This afternoons NAM model showing the progression of Tropical Storm Gert off the east coast, as well as a mid level system over the central part of the county, which may work to bring showers and thunderstorms over our area later this week,

This afternoons NAM model showing the progression of Tropical Storm Gert off the east coast, as well as a mid level system over the central part of the county, which may work to bring showers and thunderstorms over our area later this week

Tropical Storm Gert Nearing Hurricane Intensity 

As of 5pm this evening, Tropical Storm Gert was located roughly 450 miles to the west-southwest of Bermuda, and moving north at around 8 miles per hour. Gert has taken advantage of a relatively favorable environment today characterized by low vertical wind shear, very warm sea surface temperatures, moist air, and slow storm motion. This allowed the storm to develop intense thunderstorms near the core of the system, which in turn began a period of intensification to just below hurricane status-at 70 mph. Recent visible satellite images from the GOES-16 satellite showed that the cloud tops of Gert were warming a little, maybe indicating a brief halt in the intensification process, but with the storm located over very warm water and under a favorable environment, it appears quite likely that Gert will become a hurricane within the next 12-18 hours.

Gert will continue to track to the north as it rounds the western edge of the Bermuda high tomorrow, likely continuing to strengthen as it does so. Gert will likely begin to accelerate and take on more of an easterly component later tomorrow, as a shortwave trough moves over the Northeast. As the storm begins to interact with the shortwave trough over the northern Atlantic ocean, it will likely begin its extra-tropical transition by late Wednesday. Thereafter, the storm is likely to remain a powerful extra-tropical system, which may eventually threaten portions of Europe further down the line. Impacts for the east coast will be limited to increased wave swells and a high risk of rip currents. The main risk from Gert will be help by any maritime craft venturing off the east coast this week.  Elsewhere in the Atlantic, there is an area of disturbed weather located in the far eastern Atlantic which may try to gradually develop into a tropical cyclone over the next few days as it heads generally WNW at 15mph.

GOES-16 visible satellite imagery of Tropical Storm Gert off of the southeastern coast of the US this evening (Courtesy of simuawips.com)

GOES-16 visible satellite imagery of Tropical Storm Gert off of the southeastern coast of the US this evening (Courtesy of simuawips.com)

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Have a great evening!

Steve Copertino