Archive for southwesterly flow
Back door cold front to provide cool conditions
Posted by: | Comments08/11/10 5:11 PM
A back door cold front will move south this evening driving a cooler marine air mass into the Northern Mid Atlantic by tomorrow morning. Clouds will continue to increase as the evening continues as lifting become stronger over the region. A few scattered showers will develop towards morning, but will really increase in coverage by the late morning hours.
The back door cold front is expected to stall just to the south and southwest of the Philadelphia metropolitan area by tomorrow afternoon and will linger over the Delaware Bay through this weekend. The hot and humid air mass over the Tennessee Valley will try to move over the Marine air mass in place through this weekend, which will lead to broken to overcast cloud cover and scattered showers. The best potential for scattered showers will be found over eastern Pennsylvania and the Delaware River Valley through this weekend, while locations further to the east like central and eastern Connecticut will have less of a threat of showers and more scattered cloud cover. If the high pressure system builds far enough south and west, Sunday may end up being a rather pleasant day for the immediate New Jersey coast, Long Island, and Connecticut. However, any shift to the east of the cold front will put an end to the clearing skies rather quickly. Temperatures through this period will range from the upper 70′s to mid 80′s for highs and lower to mid 60′s for lows.
A strong trough will become established over the Great Lakes by Monday and will remain over the central Great Lakes through next week. This will lead to a strong southwesterly flow being established from the surface up to 500 MB, which will transport the hot and humid air over the Southeast right into the Northern Mid Atlantic. Meanwhile, cold fronts will stall and weaken to the west of the region, leading to a constant threat of showers and strong to severe thunderstorms as disturbances attempt to move into the Philadelphia and New York City metropolitan area.
For details on your location, visit the NY NJ PA Weather Local Seven Day Forecast!
-- Weather When Posted --
- Temperature: 82°F;
- Humidity: 61%;
- Heat Index: 85°F;
- Wind Chill: 82°F;
- Pressure: 29.85 in.;
Premium Members Post: Flash flooding threat for next week
Posted by: | CommentsThe 500 MB pattern for next week is setting up for what could be a rather hot, humid, and stormy pattern for the Northern Mid Atlantic. Why am I concerned? Read below!
-- Weather When Posted --
- Temperature: 87°F;
- Humidity: 52%;
- Heat Index: 90°F;
- Wind Chill: 87°F;
- Pressure: 29.9 in.;
Hot and humid start of the week, gift from Colin provides relief
Posted by: | Comments08/09/10 10:00 AM
As high pressure now positions itself off the Mid Atlantic coast and a southwesterly wind becomes establish throughout the lower levels of the atmosphere, a far more humid air mass is in place for the Philadelphia and New York City metropolitan areas.
With high pressure off the coast and a southwesterly flow well established, the Northern Mid Atlantic is in for a few days of hot and humid conditions with highs in the upper 80′s to lower 90′s and dew points around 70. In short, not a very comfortable strength of weather conditions.
However, the remnants of Tropical Storm Colin will provide a gift to the Northern Mid Atlantic! As the remnants of Colin become entrained in a trough over the Canadian Maritimes, the trough will intensify and build southwest towards New England. Initially, disturbances from Ontario will move northwest to southeast over the Hudson Valley and Connecticut providing a threat for isolated thunderstorms each afternoon today through Wednesday.
By Wednesday evening though, a back door cold front will finally start to work south and southwest through the New York City metropolitan area with variable cloud cover, scattered showers and thunderstorms, and winds veering from the southwest to the north and northeast. The back door cold front will work south through the Philadelphia metropolitan area by Thursday as well. The air mass behind this back door cold front will be cooler with highs in the lower to mid 80′s and with dew points falling off into the 50′s.
The strength of the back door cold front will be determined by the strength of the trough over the Canadian Maritimes. I expect this trough to weaken by Friday while the trough over the Northern Plains strengthens, which will lead to a southwesterly flow at 700 to 500 MB to become established. As a result, the back door cold front will retreat on Friday into New England with a return of hot and humid conditions again for this coming weekend into early next week.
For details on your location, visit the NY NJ PA Weather Local Seven Day Forecast!
-- Weather When Posted --
- Temperature: 80°F;
- Humidity: 65%;
- Heat Index: 82°F;
- Wind Chill: 80°F;
- Pressure: 30.06 in.;
Strong to severe thunderstorm today will usher in excellent weekend conditions
Posted by: | Comments08/05/10 9:15 AM
The Philadelphia and New York City metropolitan area has been under the influence of a hot and humid southwesterly flow, however the reign of hot and humid conditions will come to a short end as a strong cold front approaches from the west.
The clear skies over all of the Philadelphia metropolitan area and much of the New York City metropolitan area will help to heat the lower levels of the atmosphere and create a marginally unstable atmosphere. As a cold front, currently over the Ohio Valley and the eastern Great Lakes, marches eat towards the Northern Mid Atlantic this afternoon; a line of strong to severe thunderstorms will form along the front and drive through the region this afternoon and evening. Ahead of the cold front, temperatures will rise into the upper 80′s over Connecticut to mid 90′s over the Delaware River Valley while dew points remain in the upper 60′s to mid 70′s. The air mass will be moisture loaded ahead of this cold front providing the thunderstorms with plenty of fuel.
The one draw back for this severe threat is that the best upper level dynamics will be focused further north, over New England. The primary threat for this afternoon and evening from these thunderstorms will be strong wind gusts from bowing thunderstorms and very heavy rainfall due to the high level of moisture all the way up to 500 MB. This environment currently does not support strong super cell thunderstorms like in previous threats, instead the thunderstorms will be more linear in nature. The strongest thunderstorms will feature frequent lightning, small hail, heavy downpours, and wind gusts exceeding 50 mph. There will be a threat for localize flash flooding from some of these thunderstorms given the high rainfall rate potential.
Once the cold front exits, the Northern Mid Atlantic will be under the influence of Canadian high pressure from tonight on through this weekend. Initially, the Polar air mass will lag behind leading to dew points remain high into tomorrow morning. However, as the day continues tomorrow dew points will crash through the 60′s and into the 50′s. Temperatures tomorrow will still reach the upper 80′s to lower 90′s, especially over the Delaware River Valley where the combination of a northwesterly wind supporting down sloping and the dry air will allow temperatures to spike. The cooler and dry conditions can be expected for Saturday and Sunday with low humidity and temperatures in the upper 70′s and 80′s for highs and 50′s and lower 60′s for lows.
The high pressure system will drift off the coast by Monday with a return southwesterly flow for the start of next week. Humidity will increase each day for Monday through Wednesday along with the threat for isolated strong to severe thunderstorms.
For more details on your location, visit the NY NJ PA Weather Local Seven Day Forecast.
-- Weather When Posted --
- Temperature: 80°F;
- Humidity: 69%;
- Heat Index: 83°F;
- Wind Chill: 80°F;
- Pressure: 29.73 in.;
Quiet evening expect as high pressure drifts off shore
Posted by: | Comments4:44 PM 08/02/10
High pressure is now right off the New Jersey coast, which has kept the majority of the showers and thunderstorms well to the northwest, west, and south of the Northern Mid Atlantic. This high pressure system, which initially introduced a far more pleasant end to July than what we experienced for much of the month, will not set up a return to hot and humid conditions for the start of Augusts.
A southwesterly flow will continue to become established at all levels of the atmosphere over the next 24 hours. Through tonight, I expect most locations will remain dry and the low level moisture will remain low enough to not produce any substantial areas of fog. However, by tomorrow afternoon, an increase in humidity will be felt as dew points drive close to 70 degrees. Considering highs will be around 87 to 91 degrees tomorrow, that’s a rather humid air mass, especially compared to the past few days.
The Northern Mid Atlantic will return to a pattern that yields to atmospheric conditions. The first, discussed above is a hot and humid air mass with highs around 85 to 90, lows around 65 to 70, and high humidity. This air mass, which is set up by the southwesterly flow from the surface to 700 MB is from the Gulf of Mexico and will be transported right into the Northern Mid Atlantic. The second condition is the return of strong to severe thunderstorms to the Northern Mid Atlantic. Once again, the models are gun ho with strong cold fronts crashing through this air mass. However, given that the Polar Vortex will still be positioned well to the northwest over the Hudson Bay, the brunt of these air masses will remain over the northern Great Lakes, St. Lawrence River Valley, and New England. As such, these cold fronts will approach, weaken, create enough lifting for strong to severe thunderstorms, but are limited in any significant air mass change through this weekend and into early next week. In fact, I’m pretty confident that GFS MOS guidance and thus your TV seven day forecast will see a slow increase in high temperatures each day from now until we get to Thursday or Friday with highs around 88 to 91 degrees for the region for both Saturday and Sunday. These thunderstorms from Wednesday on through this weekend will feature the potential for heavy downpours, frequent lightning, large hail, and strong wind gusts.
The one question mark going into the end of this forecast is the potential impact of Tropical Depression 4 on this pattern. By the weekend, indirect influences like subsidence from the circulation of the tropical system, will be felt on the Mid Atlantic. To what extent and how far north is an unknown, however there will be some influence.
For details on your location, visit the NY NJ PA Weather Local Seven Day Forecast!
-- Weather When Posted --
- Temperature: 78°F;
- Humidity: 47%;
- Heat Index: 79°F;
- Wind Chill: 78°F;
- Pressure: 30.17 in.;
Premium Discussion Overview for July 31, 2010
Posted by: | CommentsThe last day of July is here! Is it me or did this month go really fast? I heard this has to do with getting older, so for this birthday (August 3rd, by the way!), I have decided to become 29 rather than 31 because I need more time in the day. Anyway, today I discuss the impacts from an approaching area of low pressure for tomorrow and also the developments in the Tropical Atlantic! Are you a Premium Member? Get the details on Premium Membership here!
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-- Weather When Posted --
- Temperature: 75°F;
- Humidity: 50%;
- Heat Index: 78°F;
- Wind Chill: 75°F;
- Pressure: 30 in.;
Another excellent day of weather expected, rain on the way for tomorrow
Posted by: | Comments07/31/10 11:40 AM
High pressure over the eastern Great Lakes and southern Mid Atlantic will continue to produce excellent weather conditions through this evening. With the exception of increasing clouds for this evening, the weather conditions for today will pretty much mirror the same as yesterday with highs in the lower 80′s and low humidity.
However, the pleasant conditions will not last for tomorrow. A low pressure system, currently over the mid Mississippi Valley this morning will track towards Delaware by tomorrow afternoon. The combination of high pressure over New England by tomorrow morning with this approaching low pressure system will lead to the establishment of an easterly to northeasterly wind over much of the Northern Mid Atlantic. This easterly wind will push a marine air mass into the coast, thus stabilizing the atmosphere. In short, this means the threat for thunderstorms, or at least strong to severe thunderstorm is very small to nonexistent. If anything, a strong thunderstorm slipping north from Maryland may impact southeastern Pennsylvania and extreme southern New Jersey, but that about it. Even in that case the thunderstorm will rapidly become elevated and lead to just a heavy downpour with some thunder. Overall, scattered showers can be expect with variable cloud cover. Temperatures will rise into the 70′s and lower 80′s for highs, making tomorrow the coolest of the entire seven day forecast.
The low pressure system will exit by Monday morning with a few lingering showers and then clearing skies. High pressure will take hold by Monday afternoon and remain in control through Tuesday with light winds and slowly modifying temperatures back into the 80′s to lower 90′s. The high pressure system will become established off the Mid Atlantic coast where a strong Western Atlantic Ridge will become established in the upper levels. As a result, the southwesterly flow will return at all levels of the atmosphere from the surface to 500 MB. With this southwesterly flow will come the return of moderate to high humidity, high temperatures in the upper 80′s to mid 90′s, lows around 70 degrees, and a constant threat of strong to severe thunderstorms in the afternoon for Wednesday into next weekend.
For details for your location, visit the NY NJ PA Weather Local Seven Day Forecast!
-- Weather When Posted --
- Temperature: 75°F;
- Humidity: 50%;
- Heat Index: 78°F;
- Wind Chill: 75°F;
- Pressure: 30 in.;
Showers and thunderstorms through the day
Posted by: | Comments07/13/10 8:16 AM
Showers and thunderstorms are developing throughout the Philadelphia and New York City metropolitan this morning as a series of mid level disturbances and a cold front to the west approach from the west and southwest.
The cold front approaching from the west is weakening and will not have much of an impact on the temperatures nor humidity over the northern Mid Atlantic for the rest of the week. However, the increased lifting over the New York City and Philadelphia metropolitan areas will lead to wide spread showers and thunderstorms through today and into much of Wednesday. These thunderstorms will primarily remain below severe levels, however will be capable of producing very heavy downpours and could potentially lead to flash flooding in urban locations and along small rivers.
The showers and thunderstorms today will keep temperatures in the 80′s due to the cloud cover, however humidity will remain high through the day leading to rather muggy conditions.
The cold front will weaken over eastern Pennsylvania into a weak trough with little in the way of air mass change by tomorrow. As weak disturbances continue to move along the cold front, a constant threat for showers and thunderstorms will remain through the week for the entire northern Mid Atlantic. However, the sustained southwesterly flow and warm 850 MB temperatures will keep temperatures in the upper 80′s to mid 90′s with dew points in the 60′s and 70′s. These conditions are expected through Saturday with no signs of any significant change to the air mass and weather pattern into early next week.
For details on your location, visit the NY NJ PA Weather Local Seven Day Forecast!
-- Weather When Posted --
- Temperature: 77°F;
- Humidity: 78%;
- Heat Index: 79°F;
- Wind Chill: 77°F;
- Pressure: 29.96 in.;
Premium Discussion Overview for Monday July 12, 2010
Posted by: | CommentsThe summer pattern continues! Is there any end in site? Get the latest information and analysis with the Premium Discussions at NY NJ PA Weather! Not a Premium Member? Get the details here!
-- Weather When Posted --
- Temperature: 77°F;
- Humidity: 57%;
- Heat Index: 79°F;
- Wind Chill: 77°F;
- Pressure: 29.94 in.;
Hot and humid pattern established, thunderstorm threat increases
Posted by: | Comments07/12/10 8:39 AM
The hot and humid conditions continue today, along with the threat for strong to potentially severe thunderstorms.
The surface high pressure system is now off the coast, which means a southwesterly flow is well on the way of being established. A rather muggy morning has been experienced thus far, however the amount of low level moisture, measured in dew points on the map to the left, is nothing compared to what will be experienced the rest of the week.
Today is going to be the lowest the dew points will be for this week, which is rather concerning since dew points are already in the mid 50′s to lower 60′s in central/eastern Pennsylvania already. Note over the Ohio Valley and Tennessee Valley that dew points are building into the upper 60′s and lower 70′s. These locations currently are being influenced by the air mass that will be over the northern Mid Atlantic by tomorrow afternoon.
So clearly the air mass this morning is warm, increasing in moisture content, and rather unstable. All that is needed is a lifting mechanism, and the water vapor satellite picture shows plenty of potential for that!
There are a few interesting features I want to point out. Closer to home, there is clearly a disturbance, located at 700 MB, that is going to move towards the northern Mid Atlantic this afternoon. This disturbance is already producing isolated showers over parts of eastern Pennsylvania and I expect isolated strong to severe thunderstorms developing this afternoon as this disturbance moves east. The morning soundings that are coming in show that the most likely severe threat today will be very heavy downpours, wind gusts over 45 mph, and frequent lightning. While all of the Philadelphia and New York City metropolitan area will be at risk for thunderstorms today, the most likely areas will be eastern Pennsylvania, western New Jersey, the Hudson Valley, and Connecticut.
Further to the west, the remnants of Tropical Depression Two is becoming entrained in a long pattern of disturbances from the southern Plains right into the Ohio Valley. The enhancement of tropical moisture into this train of disturbances will aid in developing some impressive thunderstorms through the week, capable of producing isolated yet very heavy rainfall amounts. The mid level circulation that is still present even several days after landfall also has me concerned for the development of an MCS by the end of this week over the Ohio Valley and potentially for the northern Mid Atlantic.
A warm front will move through tomorrow afternoon with another round of showers and strong to severe thunderstorms. This warm front will enhance the increase in low level moisture throughout the northern Mid Atlantic setting up for a very hot and humid air mass for the rest of this week.
A series of cold fronts and disturbances will move from the Great Lakes and attempt to move through the northern Mid Atlantic. The set up of the 500 MB pattern through this week produces a southwesterly flow at 500 MB. This set up leads to cold fronts slowing down and washing out over the northern Mid Atlantic. With the western Atlantic ridge continuing to build in strength, I see little support for any change in the air mass through this coming weekend. The theme through this period will be a hot and humid with highs in the 80′s and 90′s and lows in the mid 60′s to mid 70′s along with a constant threat of showers and thunderstorms each afternoon.
For more details on your specific location, visit the NY NJ PA Weather Local Seven Day Forecast!
-- Weather When Posted --
- Temperature: 77°F;
- Humidity: 57%;
- Heat Index: 79°F;
- Wind Chill: 77°F;
- Pressure: 29.94 in.;
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