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Heavy Rain Threat Friday, Monday’s Eclipse Conditions Coming Into View!

Good Evening! 

Today was another warm and relatively clear day across the entire northeast, but we did see higher dew points begin to creep in which allowed for a “muggier” feel to the day during the peak of the afternoon. With a northwesterly flow in place in the mid levels of the atmosphere, more dry air from Canada allowed for mostly sunny conditions across the region, with come occasional cumulus clouds rising up and eventually collapsing due to any kind of support. As the day progressed, an area of  surface high pressure off to our north and west also helped to keep conditions relatively calm, with light northwesterly winds lasting the entirety of the afternoon. With light winds, dry mid levels, and predominately sunny skies, temperatures were able to gradually rise into the mid to upper 80’s across the area, with cooler temperatures located over portions of interior Connecticut and New York.

Conditions remain quite pleasant this evening as much of the metro area is sandwiched in between two stalled fronts, with the northern front holding back cooler temps and lower dew points, and the southern front holding back oppressive dew points and warmer temperatures. Regardless, as the sun begins to set, the area should be able to cool down quite a bit thanks to a hefty amount of radiational cooling likely to take place due to the aforementioned high pressure, light winds, dry mid levels, and clear skies. This should allow low temperatures to bottom out into the upper 50’s to lower 60’s-with some of the more interior locations possibly dropping into the lower 50’s by early tomorrow morning.

This evenings latest high resolution visible satellite imagery from the GOES 16 satellite, regional radar mosaic, surface observations, and frontal positions from the Weather Prediction Center (courtesy of Simuawips)

This evenings latest high resolution visible satellite imagery from the GOES 16 satellite, regional radar mosaic, surface observations, and frontal positions from the Weather Prediction Center (courtesy of Simuawips)

Thursday and Friday 

Tomorrow morning should start off much like how today did, with relatively clear skies and cool temperatures to begin with. The main difference will be that the area of high pressure will begin to retreat and move off the coast, which will lead to more winds coming from the Atlantic, which will lead to increasing dew points as temperatures begin to rise. While we will have prevalent onshore winds to deal with during the day, a mid level ridge axis will be moving over the area, which should allow temperatures to rise into the low to middle 80’s area-wide-with some cooler conditions possible along the immediate coasts. As the mid level ridge pushes up and over our area early tomorrow afternoon, a shortwave trough will be moving over the Great Lakes region, which will drape a warm front over portions of Pennsylvania and the Mid Atlantic states.

As this front continues to advance east, it will bring an increasing chance of showers and possibly a few thunderstorms over the Northeast. Conditions will likely stay more tame back towards the metro area as the onshore flow keeps the atmosphere relatively stable, so only a gradual increase in mid to high level clouds is expected through the mid to late afternoon hours. Later in the evening, the threat of showers and an isolated thunderstorm will be increasing as the front draws closer and moisture convergence gradually increases. Expect lows to be much more mild Thursday night due to increased cloud cover and the threat for showers-with temps likely staying in the upper 60’s to lower 70’s.

Friday looks to be the most unsettled day in the forecast period as the area of low pressure associated with the large trough over the Great Lakes continues to move to the north and east. This will allow for the warm front to completely overspread the region by early Friday morning, likely bringing a period of locally heavy rainfall with it as it marches north and east. At this time it appears that the heaviest rain may fall over portions of New Jersey, Pennsylvania, C/S New York, and Connecticut, but this could easily change if thunderstorm development becomes more prominent during the morning hours further to the south of the NYC area. Otherwise, Friday will likely feature at least a moderate chance of showers and an isolated thunderstorm up until the later portion of the afternoon, when a renewed threat for heavy showers and thunderstorms may redevelop over Pennsylvania and warm air advection surges north over the Northeast. It seems that the overall severe threat on Friday will be quite low due to the increased cloud cover, but if some patches of sun do develop, then stronger destabilization of the atmosphere may take place, which could lead to more widespread/strong storm development. The primary threat will be heavy rains on Friday, which should last into the evenings hours and possibly even into the early morning on Saturday. Overall, confidence in flash flooding is low at this time, but with deep tropical moisture nearby and forcing from the warm front present, it would not take that much to chance for heavy showers and storms to develop and drop torrential rainfall within a short period of time. Details will likely need to be fine-tuned over the next 48 hours, so be sure to check back for the latest.

This afternoons European model, showing very high precipitable water values surging in behind a warm front progged to move through the area Friday AM with a chance at some locally torrential rainfall.

This afternoons European model, showing very high precipitable water values surging in behind a warm front progged to move through the area Friday AM with a chance at some locally torrential rainfall.

Saturday and Beyond 

Most of the area should still be within the residual warm sector on Saturday morning, but with the best jet dynamics and lift displaced off to the west, the threat for heavy rain will begin to gradually fall. The shortwave trough should continue to move east during the day, with conditions likely improving as the day goes on. Highs will likely be able to reach into the low to middle 80’s ahead of a cold front tracking east from the Ohio Valley. This front should usher in much drier air and bring in some cooler temperatures as well, as it mixes out the atmosphere.

Sunday will likely be much-improved from the previous two days as high pressure begins to build over the area. This should allow for clear skies, light winds, and generally pleasant conditions across the region, with highs likely reaching into the low to middle 80’s across the area-which is right around normal for this time of year. Conditions will be ripe for radiational cooling on Sunday evening, so expect low temperatures to drop down into the lower 60’s with relatively low dewpoints.

Monday will be the day that will have the most focus on the weather, not for any severe weather or tropical cyclones, but for the partial solar eclipse that will take place during the afternoon hours. While we are not in the path of totality, most of the area will still be able to experience a rather cool and rare occurrence. However, the big question right now looks to be if there will be any cloud cover. As of right now, the conditions look to be quite favorable for safely viewing the partial eclipse, with mid level ridging overhead and surface high pressure just offshore-providing light onshore winds over much of the metro. This is however five days away, and predicting cloud cover for a three-hour window is rather difficult, but we can say that signs are encouraging at this time for a pleasant viewing experience! Be sure to check back over the next few days for updates!

The European 51 member ensembles showing cloud cover percentage. Monday the 21st is highlighted, with little cloud cover expected from a vast majority of the ensembles! (Courtesy of WxBell)

The European 51 member ensembles showing cloud cover percentage. Monday the 21st is highlighted, with little cloud cover expected from a vast majority of the ensembles! (Courtesy of WxBell)

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Have a great evening!

Steve Copertino

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

simuawips (9)

Saturday’s Rain Threat Gives Way To More Variable Conditions Next Week

Good evening! 

Today started off rather pleasant with clear skies, light winds, and rather moderate temperatures. However, as the broad area of high pressure that remained in control for the past few days began to gradually shift offshore and into the west Atlantic, a broad mid level trough began to edge into the Northeast this afternoon. As this trough gradually progressed east, the airmass change could be felt as dewpoints rose into the middle to upper 60’s across the area, which made for a much more “muggy” feel to the afternoon than the past couple of days. On the lee side of this disturbance, mid levels winds are coming from the southwest, which is acting to advect a good deal of moisture from the south. This moisture has continued to overspread the Northeast this afternoon as a weak warm front moved from north to south across the metro area. With some weak ascent and forcing associated with the front, some showers and thunderstorms have popped up over portions of the Mid Atlantic and portions of Pennsylvania, where severe parameters are supportive of locally severe weather. In fact, an isolated supercell has developed over northern Virginia this past hour, and may eventually reach the DC metro area.

Closer to the NYC metro, the atmosphere remains much more stable than our surroundings (as has been the case this entire year so far). Instead of thunderstorms developing this afternoon, we’ve seen widespread cloudiness take over. Some residual showers from dissipating thunderstorms over Pennsylvania are currently making their way into western New Jersey, but no hazardous weather is expected as any showers/thunderstorms encounter the stable airmass overhead.

As the evening marches on, more leftover showers may entire from the west and bring some brief heavy downpours and occasional lightning, but generally cloudy conditions are likely for the remainder of the night. The combination of the higher dewpoints, southerly winds behind the warm front, and cloudy conditions will almost ensure that raditional cooling will be non-existent this evening. Lows should unanimously mild, reaching the middle 60’s to lower 70’s across the region.

This evenings latest high resolution GOES-16 visible satellite imagery, regional radar mosaic, surface observations, and frontal postilions-showing showers and thunderstorms mainly concentrated to the west of the area this evening (Courtesy of Simuawips)

This evenings latest high resolution GOES-16 visible satellite imagery, regional radar mosaic, surface observations, and frontal postilions-showing showers and thunderstorms mainly concentrated to the west of the area this evening (Courtesy of Simuawips)

Saturday Into Saturday 

Tomorrow morning will likely start off quite unsettled as the mid level warm front to our south and west begins to move over the area with deep tropical moisture entrenched within. Precipitable water values will also increase markedly, into the 1.5-2″ range, so any showers and thunderstorms that develop early Saturday morning have the potential to produce very heavy rainfall in a short period of time. Though, with weak mid level lapse rates, any updrafts that do go up tomorrow morning will be extremely short-lived, and will likely form and die over the same location. Later in the morning, the warm front should lift through the region, possibly clearing out any residual showers and weak thunderstorms out of the area, and allowing for a brief period of sun poking through the clouds. Depending on how much sun the area sees late tomorrow morning and early afternoon will determine just how much the area can destabilize, which will have implications on the rest of the day. Model guidance suggests that the western portion of the New York metro area does in fact clear out enough during the afternoon hours that instability on the order of around 1000-1500j/kg^2 develops. By this time, it appears likely that a mid level trough will begin to nose into the Northeast, with a favorable upper level jet streak also making an appearance.

The combination of these factors could possibly lead to the development of some scattered showers and thunderstorms-some of which may be strong to severe. As of this evening, it appears locations west of NYC will have the best potential to see any robust thunderstorms, with the main threats being gusty winds, sub-severe hail, frequent lightning, and very heavy rains. This activity will be highly dependent on the timing of the best forcing arriving from the west, as well as just how much we can clear up and destabilize tomorrow after the initial batch of rain in the morning. Overall, widespread severe thunderstorm development does not appear likely tomorrow.

As we head into the evening, any residual showers and thunderstorms should gradually head east and weaken as the frontal system associated with the mid level trough begins to push over and out of the area. Behind the front we should have a less humid airmass, but with the risk of cloud cover, temperatures are not that likely to fall all that much-with lows generally in the low to middle 60’s.

Sunday looks to be a huge improvement over today and Saturday, as the shortwave trough that moves through on Saturday heads to our east and begins to usher in a cold front. This cold front not only looks to clear out any substantial cloudiness that may linger over the area, but should also be quite efficient at greatly reducing dewpoints from the 70’s, to lower 60’s over the entire area. With sunny skies, light winds, and low humidity, Sunday will be near-perfect for any outdoor activities , though there may be a risk of rip-current’s along the coasts, so please make sure to monitor beach conditions if you are planning a beach day. Highs will likely be comfortable-with temperatures reaching into the upper 70’s to lower 80’s, and lows getting down to the low to middle 60’s.

This evenings RPM model showing the progression/development of showers and thunderstorms later this evening and into tomorrow afternoon, followed by an eventual clearing on Sunday (Courtesy of WSI)

This evenings RPM model showing the progression/development of showers and thunderstorms later this evening and into tomorrow afternoon, followed by an eventual clearing on Sunday (Courtesy of WSI)

Monday and Beyond 

Previous model guidance runs had Monday being the next potential period for heavy rain, but have since backed off this idea quite a bit. This is due in part to the models incorrectly handling a weak tropical system that has been tormenting forecasters for the better part of the last nine days or so. This low was originally forecast to interact with a stalled frontal boundary located to the south of the region on Monday, which would in turn spawn another wave of low pressure. The tropical low pressure system has once again failed to develop, and this had lead to some significant changes in the model guidance for next week. It now appears that the same frontal boundary will not be able to push as far north as previously thought, mainly due to a lack of a surge in precipitable water values/moisture associated with the tropical system. So in short, this means that any precipitation on Monday will likely be much more spotty in nature than previously thought, with very meager amounts of instability and lift to work with over our area. At this time, we would not be surprised at all if this rain threat continued to deteriorate over time and does not amount to much of anything north of the Mason-Dixon line.

Otherwise, it appears that the northern stream will remain quite active for this time of year and could potentially lead another disturbance down our way by the middle of next week, with moisture surging ahead of this disturbance as we have seen many times before. However, at this time it seems that these rain threats will be transient in nature, with ridges likely building in behind-leading to a brief period of calm weather before the next rain chance.

This afternoons European ensembles, showing another unsettled period shaping up next week, with a trough over the central part of the US, and a ridge positioned over the south. This would lead to multiple disturbances rolling over the ridge, and into the Northeast.

This afternoons European ensembles, showing another unsettled period shaping up next week, with a trough over the central part of the US, and a ridge positioned over the south. This would lead to multiple disturbances rolling over the ridge, and into the Northeast.

For more information and posts like this one, make sure you sign up for Premium Forecasts — where multiple detailed articles, videos, and interactives are posted each day. Also, come interact with our staff and many other weather enthusiasts at 33andrain.com!

Have a great evening!

Steve Copertino

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Weather Education: Jet Streaks and Upward Vertical Motion

Good afternoon, everyone! We are starting a new series of videos called “Weather Education”, where we give educational videos regarding some of the commonly used meteorological terms we use to make forecasts. We detail what these terminologies mean, and how they are applied in weather forecasting. Anything from how to read a forecast sounding, how to forecast banding of precipitation, how does a low pressure form and deepen, temperature advection, frontogenesis, the differences between an extratropical and tropical cyclone, forecasting severe weather, and much more will be covered!

Today’s debut video will focus on one of the more classic topics in synoptic meteorology: jet streaks and upward vertical motion. Often times in looking for areas where lift will be enhanced for precipitation, low pressure formation, and even thunderstorms, we look to see where localized wind maximums in the jet stream — or jet streaks — are located. And from there, we look to see where a certain region is relative to these jet streaks. The above video details why jet streaks are so important, why certain regions of the jet streak favor rising or sinking air, and how these jet streaks were crucial in the formation of the Blizzard of 2016 and Hurricane Sandy.

We hope you find this video informative! We are really excited to debut this video series, and hope to continue these videos pretty often. Any feedback is greatly appreciated, as well as suggestions on other topics you guys would like covered!