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Steven Copertino

Public Analysis: Remnants of Cindy Likely to Bring Heavy Rain, Seasonable Conditions Return Next Week

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Good Afternoon and Happy Friday! 

Getting right into things, earlier this week we highlighted the potential for some heavy rain associated with the remnants of Tropical Storm Cindy, which made landfall along the Texas coastline early Thursday morning. At that time, we stated that there were two scenarios that were likely to play out, one being that the remnants of Cindy would not hold up all that well after landfall, and the other being that they would. Over the past twelve to eighteen hours or so, it has become apparent that the remnants of Cindy have remained quite robust as they traveled over the Ozarks and into the Tennessee Valley, at least in the mid levels of the atmosphere. With very deep, tropical moisture streaming north from the Gulf of Mexico, the significance of having a more coherent remnant system means that the leftover energy will spark widespread showers and thunderstorms through this evening and into Saturday. In addition to the remnants of Tropical Storm Cindy, which has been downgraded to a remnant low pressure area, we also have a cold front surging through the Ohio Valley.

This cold front has been working to funnel all of the moisture from the Gulf of Mexico to the north and east, allowing it to pool up over the eastern third of the nation over the past two days. This has made for a very soupy and humid day today across the majority of the Northeast. We saw some very subtle lift manifest itself over Pennsylvania around noon today, which allowed for some showers to move eastward through eastern Pennsylvania, New Jersey, and New York. Occasional breaks in the clouds and very warm temperatures a few thousand feet off the ground allowed temperatures to spike back into the low to middle 80’s across the entire region, despite sudden temperature drops with any gusty showers that passed through some locations.

As of 630pm, a convective complex was evolving over the eastern half of Pennsylvania, and this complex will continue to head eastward through the evening. With adequate amounts of wind shear, instability, and an extremely moist air mass in place, torrential downpours, frequent lightning, and some gusty winds seem quite likely for those in the path of these showers and storms. Synoptic winds (winds not associated with small scale features) have already been quite impressive this afternoon, so we are quite confident that the probability for tropical-like downpours and gusty winds could cause some localized flooding with debris from trees likely clogging sewers. In lieu of this slight risk for severe thunderstorms, the Storm Prediction Center in Norman Oklahoma has issued a severe Thunderstorm Watch until 10pm this evening. The rest of the evening should remain quite unsettled, with the potential for more showers and thunderstorms behind this complex, so make sure to pay attention to your local NWS office for any potential warnings!

Animated regional radar mosaic, showing the evolution of a complex of showers and thunderstorms approaching the area. The main threats appear to be heavy downpours and gusty winds (Courtesy of College of DuPage)

Animated regional radar mosaic, showing the evolution of a complex of showers and thunderstorms approaching the area. The main threats appear to be heavy downpours and gusty winds (Courtesy of College of DuPage)

Saturday Morning to Evening

As we head into tomorrow morning, things look to remain quite unstable as the energy from the remnants of Cindy approaches the area while the cold front to our east compresses all of the rich tropical moisture into a focal point, located right over our area. During the day today, the high resolution models have been keying in on a very heavy band of rain moving over portions of Pennsylvania, New Jersey, New York, and Connecticut by 7-10 am tomorrow. This band of heavy rain is directly associated with a mid level piece of energy currently located over portions of Kentucky, which will likely continue NE throughout the evening hours. A crucial point here is that since the energy already exists and is well sampled, the models likely have a decent grasp on the situation over the next 12-18 hours. Regardless, as this piece of energy nears our area tomorrow morning, we will have to monitor the situation very closely since any rainfall with this system will likely be quite intense, which could produce localized flash-flooding, and exacerbate and potential flooding issues caused by tonight’s storms.

Thankfully, the rain threat looks to quickly diminish later tomorrow morning, into the early afternoon hours. Any residual showers and thunderstorms look to press off to the east and offshore, leaving much drier conditions in their wake. With clearing skies, westerly winds, and warm low to mid level temperatures, temperatures should be able to climb into the middle 80’s with ease by late tomorrow afternoon, making for a nice rebound. Weak high pressure will be over the region Saturday night. Clear to partly cloudy skies are expect with lows in the 60s in many of the suburbs to lower 70s in NYC and urban areas.

Rapid Precision Models deception of this evening and tomorrow mornings heavy rain threats (Courtesy of WSI)

Rapid Precision Models deception of the possible heavy rain threats this evening, lasting into tomorrow morning (Courtesy of WSI)

Sunday and Beyond 

Sunday looks to be quite beautiful early on, with increasing sunshine during the early morning and afternoon hours and light winds from the west/southwest due to high pressure exiting off the Mid Atlantic coast. With the mid/upper level trough moving over the region during the day, slightly cooler temperatures aloft will limit just how warm temperatures can get, with highs likely reaching into the lower to middle 80s over much of the area. There is some potential for sea-breeze activity to knock temperatures down into the 70’s during the afternoon hours, but this will likely happen on a very small scale. Later in the day, a weak cold front looks to move through the area, and bring at least an increase in cloudiness, with an outside chance at a shower or weak thunderstorm towards the evening hours.

By Monday, troughiness will increase once again over the northern section of the Great Lakes region, which will likely usher in a cooler and much direr air mass compared to what we have been experiencing over the past few days. This area of below normal temperatures looks to continue into at least Tuesday, before we have to watch for the potential of a ridge building over the east, possibly by Wednesday. Mid level ridging may continue to build into the Northeast and Mid-Atlantic through end of the week, with more heat and humidity possible over the east.  As of right now, no significant precipitation or convection is expected, until the trough over Rockies finally shifts east into Northeast/Mid-Atlantic region by next weekend.

This afternoons European Ensembles showing a rather high likelihood of below normal temperatures for the first half of next week.

This afternoons European Ensembles showing a rather high likelihood of below normal temperatures for the first half of next week.

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Have a great evening!

Steve Copertino

 

Steven Copertino

Public Analysis: Unsettled Conditions Continue, Keeping An Eye on Tropical Storm Cindy

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Good Evening! 

As discussed back on Monday, some residual moisture and weak instability worked its way into the area during the morning and afternoon hours, and when coupled with some forcing just to our northeast, we saw scattered showers and thunderstorms develop across much of the region. These showers and thunderstorms had some decent dynamics to work with, with wind shear being high, lapse rates being quite steep, and the upper level jet streak being located in a favorable position for divergence aloft. Since these conditions came together just at the right time, we actually saw some strong to locally severe thunderstorms develop over New Jersey, Pennsylvania, and portions of Connecticut. A segment developed in Pennsylvania and went on to track east, leaving numerous wind damage reports in its wake. Further north, isolated cells developed over southern New York and went on to track into Connecticut, which brought a few small hail reports and isolated wind damage reports.

As of right now, these storms have begun to weaken and are moving off the coast as the best dynamics and instability begin to fade away. Despite the storms and occasional cloudiness, temperatures were able to rise into the low to middle 80’s across much of the area. The cold front which acted as the lifting mechanism for today’s storms will begin to move through the region and bring a drier airmass in its wake later this evening. Clouds should begin to diminish by sunset, which should allow temperatures to fall back down into the 60’s tonight, with lows in the 50’s possible farther north and east of the city.

This evenings latest high resolution visible satellite imagery, regional radar mosaic, and surface station plots, showing the bulk of the shower and thunderstorm activity pushing to the east.

This evenings latest high resolution visible satellite imagery, regional radar mosaic, and surface station plots, showing the bulk of the shower and thunderstorm activity pushing to the east.

Thursday into Friday 

Thursday should start off as a rather beautiful day with low humidity, clear skies, and light winds from the west. Weak high pressure at the surface and aloft will allow the area to stay mostly-sunny during the day tomorrow, with just some upper level cirrus clouds likely approaching the area. Temperatures aloft will be rather mild thanks to the ridging overhead, so expect to see highs in the low to middle 80’s once again tomorrow, except this time it will feel more pleasant due to the lower dew points. Later in the evening tomorrow, low level moisture advection will begin to overspread the area due to a weak warm front aloft. This moisture will be quite rich in nature, as the majority of it is being fed from the deep south and portions of the Gulf of Mexico thanks to Tropical Storm Cindy. Some elevated showers and thunderstorms may try to develop late tomorrow evening as the moisture feed begins to overspread the region, but at the very least it seems likely that clouds will increase in earnest tomorrow night. The increased cloudy skies and rich moisture feed will lead to low temperatures not really being able to fall all that much, with temperatures in the low 70’s likely across most of the area.

This afternoons Rapid Precision model, showing the potential for heavy rains associated with the remnants of Tropical Storm Cindy to affect the region on Friday and into Saturday (Credit: WSI)

This afternoons Rapid Precision model, showing the potential for heavy rains associated with the remnants of Tropical Storm Cindy to affect the region on Friday and into Saturday (Credit: WSI)

The forecast on Friday becomes quite complex as a strong northern stream disturbance begins to interact with the remnants of Tropical Storm Cindy, which will likely be situated over the Ozarks by Friday morning. The aforementioned warm front that we talked about for Thursday evening should be through the area by Friday afternoon, leaving most of the area with partly cloudy skies and warm temperatures once again.

Highs will likely be able to climb into the middle 80’s with ease, but the increasing moisture from the south will also raise the dewpoints over the area, possibly making for a very muggy afternoon. With sunshine likely during the afternoon hours and an abundance of moisture also in place, instability will build over the area, and will be accompanied by some modest wind shear over the area. The pieces will be in place for heavy showers and thunderstorms to go up over the area during the afternoon hours, but the item in question will be whether or not we have a direct trigger to set off any storms. At this time, it appears likely that an adequate amount of mid level energy will be in place to set off the development of some isolated showers and thunderstorms capable of producing gusty winds and very heavy rainfall rates, possibly causing some localized flooding.

As we head into the late afternoon and evening, the threat for more showers and thunderstorms will increase markedly as the direct remnant moisture from Tropical Storm Cindy begin to crash into a cold front located to our west. Again, the main question that will be determining whether or not we see widespread heavy rainfall comes down the need for a “trigger” mechanism. One possible outcome is that Cindy deteriorates after making landfall to the point that the systems energy is dissipated, and all that is left is just some moisture. This outcome would lead to showers and thunderstorms being more scattered during the later portion of Friday, but still have the potential for heavy, tropical downpours.

The second option would be that Cindy does maintain itself as a coherent and trackable system in at least the mid levels of the atmosphere. This would allow the residual lift from the decaying tropical storm to spark numerous showers and thunderstorms during the afternoon hours of Friday, and would carry a much greater threat of torrential downpours and localized flooding concerns. At this time, it is looking likely that what will happen will be a healthy blend of both scenarios, with Cindy retaining some mid level energy that will set off heavy showers and storms just to the west of the NYC area, which will have the potential to track eastward and put down some impressive rainfall totals in a short period of time. This solution is baked up by this afternoons European model and the American model. Since Cindy has not yet made landfall, this solution may still change, so be sure to stay up to date and check back again over the coming days! Also, please keep an eye on the latest NWS products in the event that Flood Watches are issued down the line.

Image showing very impressive amounts of water vapor being advected north over our area, which will greatly increase the threat of heavy showers and thunderstorms.

Image showing very impressive amounts of water vapor being advected north over our area, which will greatly increase the threat of heavy showers and thunderstorms.

Saturday and Beyond

Heavy showers and storms may continue into the early morning hours of Saturday and possibly even the afternoon as the cold front pushes through the area, dragging the rest of the deep tropical moisture with it. There are still some model difference on fast the cold front with tropical moisture moves offshore Saturday afternoon. If the front is slower, a more showers and thunderstorms could linger into Saturday afternoon. But latest model trends have been faster, so we are still leaning to more clearing skies by Saturday afternoon. More sunshine will help temperatures rise into middle 80s on Saturday afternoon.

The cold front and its associated moisture should then begin to shift well offshore, leaving an area of weak high pressure in its wake. Sunday should be quite pleasant, with clearing skies and highs in the lower 80’s, also accompanied by a much more comfortable airmass.

An active northern stream will keep conditions relatively unsettled for the foreseeable future, with a chance at a cool-down later in the week as well.

This afternoons European ensemble mean showing a shot at some cooler weather into the middle portion of next week (Courtesy of WeatherBell)

This afternoons European ensemble mean showing a shot at some cooler weather into the middle portion of next week (Courtesy of WeatherBell)

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