September 2017 Archives - New York Metro Weather

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Maria and Lee Head Out To Sea, Beautiful Weekend on Tap for the Northeast

September 29, 2017/by Steven Copertino

Good Afternoon!

Today is the first in a series of more Fall-like conditions over the East with mild temperatures, low humidity, and crisp/cool nights. An area of high pressure has moved into the area behind the cold front that passed the area a few days ago, and is providing very clear and calm conditions for the entire Northeast. Our source region for the air mass overspreading the region is fresh from Canada, so expect these pleasant and drier conditions to last throughout the day and into the evening hours. Winds should be light, but generally out of the northwest for the remainder of the afternoon. With cooler mid level temperature and relatively sunny skies, most of the area should see temperatures get up to the upper 60’s to lower 70’s, with some cooler readings likely farther into New England.

Later on in the day, a weak but compact area of low pressure associated with a mid level trough will begin to push towards the area and bring an increasing chance of clouds by sunset. The mid level system with this area of low pressure is rather impressive for this time of year and would usually be a pretty impressive clipper system for the area if it were deeper into the year, but regardless this system will begin to increase the threat of showers and possibly even a low-topped thunderstorm across the area late this evening. The change in temperature from the ground, into the mid levels of the atmosphere is also rather impressive, and this could become further enhanced as the low nears the warmer coastal regions late this evening and into very early tomorrow morning. At this time we expect any of the heavier activity to be rather isolated, but we would not be surprised to see reports of gusty winds, heavy rainfall, occasional lightning, as well as the potential for some very small hail or graupel. This activity may become more focused over the LI sound and near Connecticut where the increased temperature differential may spark some more feisty showers and thunderstorms. Regardless, we should see overnight lows drop down into the lower to middle 50’s, with some area north and west likely getting down into the 40’s before dawn.

Loop of the current observations over the Northeast this afternoon showing relatively calm and cooler conditions. Also note the energetic low pressure system over the great lakes (CoD Weather)

As we head into tomorrow and the area of low pressure degrades into a weak trough, we should see another area of high pressure begin to build into the Northeast as well as the Mid-Atlantic states for the remainder of the weekend. For both Saturday and Sunday, skies will be pretty much mostly sunny with some mid level clouds at times. Winds will also be light, but gradually shifting back to a more northerly component on Saturday afternoon, which should reinforce the overall drier weather. Highs will likely remain in the mid to upper 60’s across the entire area, with some locations near the city seeing highs reach into the lower 70’s. Overnight lows will have a much more crisp feel to them as radiational cooling takes over both nights and allows any heating gained during the afternoon hours to quickly radiate back into the atmosphere. Lows will easily drop into the lower to middle 50’s both evenings, with an enhanced potential for areas north and west to see temperatures drop into the 40’s as well. Overall, it should be an excellent weekend for any kind of outdoor activity with clear skies, light winds, and relatively dry weather.

Another area of strong ridging is expected to develop over much of the nation next week, and when looking at a mid level map one may think that we’ll return to the 80 degree highs that we had this week, but due to the juxtaposition of the ridge, we should see an area of high pressure develop to our north and east which will funnel in cooler onshore winds. This will pretty much put a cap on just how warm things can get next week, though we may have to deal with an increase in low level moisture once again and the potential for fog during the evening hours. At this time, it does not appear likely that there will be any heavy rain threats over the next seven days or so, but we will continue to monitor the latest trends and will have a full update on Monday!

ECMWF model showing a large area of ridging forming over the eastern third of the nation next week. Temperatures will likely be back to above-normal next week, but not as warm as this week.

Maria and Lee Not Long for This World

Once mighty hurricanes Maria and Lee have been reduced to tropical storms this afternoon after accelerating northeastward into a region of increasing shear and decreasing sea surface temperatures. These system will continue to head off to the east over the next few days, before being absorbed by a larger non-tropical low pressure system that may eventually impact portions of Europe with gusty winds and heavy rainfall.

Behind these two systems we have a few area to watch, but nothing imminent to develop. There is a surface trough labeled invest 99L near the southern Florida coast that is producing a large area of disorganized showers and thunderstorms, but has not been able to organize significantly due to strong wind shear that will likely persist over the system during the next few days. Farther east, we have another tropical wave producing a large area of showers and thunderstorms just east of the Leeward islands. This system is also being impacted by strong wind shear from an upper level low to its west that should inhibit any significant development in the short term. However, both system will pose a threat for heavy rainfall and potential flash flooding, so please pay attention to your local NWS office for any flood watches or warnings.Lastly, the models have become less-certain regarding the development of a large tropical gyre forecast to form over the western Caribbean in the next week or so. This system would likely be quite large in nature and would take days to organize, but would still pose a significant threat for heavy rains and flooding. We have plenty of time to monitor future trends, but we still expect that this region of the Caribbean will have at least a medium chance for tropical cyclone development over the next 7-12 days.

This afternoons GFS model showing a very large monsoon gyre developing over the Caribbean in around a week or so. Any tropical development would likely be slow to occur due to the large nature of this system (Phillipe Papin)

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Have a great weekend!

Steve Copertino

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

September 27, 2017/by Steven Copertino

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)

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

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)

Have a great evening!

Steve Copertino

Maria Meandering Offshore, Summer Temps Return In the East!

September 25, 2017/by Steven Copertino

Good Evening!

The tropics are still quite active with both Hurricane Maria and Lee out over the Atlantic this evening, with both storms at Category 1 intensity. Back on Friday, we talked about how Lee was located in a very favorable environment for quick strengthening due a favorable baroclinic background in addition to its very small structure. Lee did in fact intensify quite quickly the past weekend into a strong Category 1 hurricane with winds around 90 mph over the open-Atlantic, thousands of miles away from land. Lee has been a very interesting storm to follow, as it resembles more of the norm that we have seen over the past few hurricane seasons where a disturbance or weak storm will wait until reaching around 20-25N before really beginning to strengthen. Regardless, Lee should remain in a relatively favorable environment for the storm to at least sustain itself for another two days before shear dramatically increases and sea surface temperatures become quite cool. Lee should eventually become absorbed by a larger non-tropical system in the north Atlantic in about 5 days as it gradually heads north at around 10 mph.

Satellite Imagery of a very small Hurricane Lee with winds up to 85 mph

Closer to home, we have Hurricane Maria located off of the southeast United states with winds of around 80 miles per hour. Maria has been exposed to the cool wake left behind by Hurricane Jose which was over the same region just about a week ago. This cool wake has led to the storm losing its once very deep convection and this has in turn led to the inner core of the storm to spread out into a larger and broader circulation with tropical storm force winds extending far away from the center. This is causing a large section of the east coast to experience very dangerous rip currents and increased wave action. Maria should continue to move northward over the next couple of days as it round the side of a large area of high pressure over the western Atlantic. Maria’s forward speed should also remain rather sluggish as well due to the large area of mid level ridging over the Northeast.

Maria will come close enough to the Outer Banks of North Carolina by tomorrow afternoon and evening that tropical storm force winds may occur with any bands of rain that may try and work their way close to the islands. As Maria is just off the coast of North Carolina, a deep trough coming in from the west will begin to affect the hurricane and cause the storm to speed up a bit. As it speeds up, the trough will also pick Maria up and begin to kick it out to the northeast, and finally away from land. At this time, Maria is not a huge threat to land other than rip currents and gusty winds in the Outer Banks, but please follow your local National Weather Service and the National Hurricane Center for more information on this storm over the next few days. Also, please head any warnings at the beaches this week as rip currents and strong waves could possibly be life-threatening if not taken seriously!

GOES 16 loop of both Hurricanes, Maria and Lee churning out over the Atlantic today (Credit: NASA/SPort)

GOES 16 loop of both Hurricanes, Maria and Lee churning out over the Atlantic today (Credit: NASA/CIRA)

Summer-like Weather Returns…For How Long?

The area of strong mid level ridging parked over much of the Northeast continues to bring very warm temp[temperatures for this time of the year to the region, with many stations across the area seeing highs in the upper 80’s to lower 90’s-which is around 10-20 degrees above normal for this time of year. This area of ridging will also provide clear skies and prevent any chances of rain over the next few days, despite an increase in dewpoints over the past thirty-six hours. Temperatures through Wednesday should remain in the middle to upper 80 range, with some locally higher temperatures expected away from the coast. With the increased low level moisture, there will also be a risk for fog each evening, which could reduce visibility down to less than a quarter-mile at times. Lows will be generally mild through the middle of the week, with temperatures remaining in the middle 60’s to lower 70’s.

Later in the week, a large mid level trough will swing down from Canada and kick out the ridge that has been providing the area with summer-like temperatures for the past few days. This trough should deliver a nice cool-down as the Canadian air really begins to settle in towards the start of the weekend. Highs will likely fall back into the 70’s across much of the area, with low in the 40’s and 50’s, which should make things feel a lot more like fall. As of right now there does not appear to be any significant precipitation events over the next 5 days, but will be monitoring any trends over the next few days!

There are some indications in the medium range guidance that more summer-like temperatures may try and return to the east for the first week of October, but we will cover that in more detail later this week as the exact details and timing become more clear!

ECMWF model showing a mid level trough working into the Northeast this weekend with another ridge hot on its heels (Accuweatehr Pro)

Have a great evening!

Steve Copertino

Maria Finally Departs the Caribbean and Jose Fades. Whats Next?

September 22, 2017/by Steven Copertino

Good Evening

Back on Monday we highlighted the potential for Maria to become an extremely dangerous Category 4 or even 5 Hurricane before reaching the small island of Dominica in the Lesser Antilles, and unfortunately that is exactly what happened. Maria rapidly intensified into a Category 5 hurricane with 160 mph winds just before making landfall on the small island, and then preceded to head from SE to NW, leaving the entire island in its core for at least three hours. The storm was the second Category 5 land falling hurricane this season, tying the 2007 with Dean a Felix. Details are still very spotty, but the pictures, video, and first-hand accounts of Dominica are heart-breaking. Most, if not all of the homes on the island have suffered severe damage, with some houses being completely destroyed. Due to the topography of the island, devastating mud slides and land slides were common, which swept away homes, roads, and well-built concrete structures. Its hard to believe that we’d have a storm that would rival the total devastation that Hurricane Irma caused just a few weeks ago, but we could be looking at yet another situation where an entire island community has seen complete devastation. With the peak of the Cape Verde season quickly coming to a climatotlogical end, we should see the frequency of storms impacting this region begin to wind down, but I would not be surprised to see one or two more systems during the month of October given the active state that we are currently in.

Damage from Hurricane Maria when it hit the island of Dominica as a Category 5 hurricane with winds of up to 160 miles per hour (Credit: The Guardian)

Due to the high, mountainous peak of Dominica and the amount of time that Maria spent traversing the island, the inner eyewall of the storm become disrupted and fractured, but not for long. On Tuesday the storm began to rapidly regain strength after dropping to a Category 4 hurricane. Recon missions throughout the day found that the storm had an incredibly compact eye of around 5-8 nautical miles and the winds rose from 155 mph to 175 mph during the course of the day, with the pressure falling to an incredible 908 millibars, making the storm the tenth strongest on record for the Atlantic basin.

Recon also released numerous dropsonde instruments which provide a vertical profile of various locations in the storm, and some of these probes happened to measure extreme winds of around 190-195 mph at the surface, but it is not certain whether these were instantaneous gusts or actually representative of the storms strength. Regardless, the storm began to approach the US Virgin islands late in the day on Tuesday and into the evening. Very deep convection began to develop quite rapidly around the center of the storm, and before long, concentric eye walls began to develop. This marked that the storm was about to attempt an eyewall replacement cycle before hitting Puerto Rico. It was clear that the storm would have issues completing this process and then intensifying once again due to the storms intensity and the size of the outer eyewall, but it also signaled for new dangers to arise. The storms wind field grew quite substantially as it approached Puerto Rico early Wednesday morning, causing the carious weather stations to be blown apart in addition to both weather radars on the island.

The storm raged ashore with winds in the 155 mph range, making Maria a strong Category 4 hurricane on the Saffir-Simpson scale. Maria went on to produce prolific flooding, wind damage, and cut a path of carnage across the island that would send all of its inhabitants into darkness as all of the power facilities went down during the storm. Details are also still rolling in slowly on the extent of the damage to the island, but it may be safe to say that the Puerto Rico that existed before Maria is no longer there. Estimates say that power may not be restored to some portions of the island for possibly up to 4-6 months. Additionally, much of the infrastructure will need to be rebuilt, which will be a daunting task in of itself. The next few weeks and months may be quite rough for the locals, but with resilience and endurance the people of the island will be able to overcome this disaster and restore their home to levels greater than before Maria.

GOES 16 imagery of Hurricane Maria making landfall on the island of Puerto Rico with winds of up to 155 miles per hour

Maria has since left the Caribbean, and land interaction along with an increase in vertical wind shear have been affecting the system. The storm weakened down to a Category 2 on Thursday, but has since regained some strength and is now a 125 mph Category 3 hurricane. The storm is currently located very close to the Turks and Caicos, producing winds up to tropical storm force on the islands along with torrential rainfall as it slowly heads NNW at around nine miles per hour. Maria should keep this heading over the weekend and into the early portion of next week, but some key aspects of this forecast remain in question. While it is quite likely Maria misses the United States, the American model has been trending strong with the riding out ahead of Maria in the past few runs, bringing the storm precariously close to the Outer Banks of North Carolina. Again, such a solution looks unlikely right now, but with the remnants of Jose still meandering around, we truly will not know just how close the storm passes to the east coast before it makes its famed passage out to sea.

Trend loop of the GFS model showing the westward trend over the past 5 runs (Courtesy of TropicalTidbits)

So What Else?

Well, we have the remnants of tropical storm Jose which has finally become post-tropical after 70 advisories by the National Hurricane Center. For reference, this storm has been ongoing since Hurricane Irma was north of Hispaniola! The remnants of this storm should gradually dissipate over the next few days and really should not be much of a threat besides increased wave action and showers. Elsewhere, Tropical Storm Lee has come back to life after shedding about three different low level circulations over the past three days and is located well out in the open Atlantic, just east of a large upper level low. Lee is an extraordinarily small system and is reminiscent of Hurricane Michael from 2012 in that of it is relying heavily on baroclinic process to form convection and strengthen. Given its size and the upper level conditions, I would give the storm a higher than normal odds of becoming a small hurricane over the next few days.

Lastly, our eyes turn to the western Caribbean as the month of September begins to fade. Medium and long range models are showing that this area of the Atlantic basin may become much more active during the next few weeks as a large area of upper level divergence sets up right over extremely warm sea surface temperatures of around 31-32 Celsius. This upper level divergence over very warm waters would promote a large amount of deep convection to form, which could eventually lower pressures in the Caribbean and cause a tropical system to form. This is all at least 8-12 days out at this point, but the signals are there that we should begin to monitor this region for potential tropical cyclone development as we near the beginning of October.

I will have a full update on Maria and any other threat that may pop up on Monday!

ECMWF model showing large scale rising over the western Caribbean in about 10 days. Conditions could become quite favorable for tropical cyclone genesis by this time.

Have an excellent weekend!

Steven Copertino

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