Archive for north carolina coast
Heavy rain focusing along the coast
Posted by: | Comments03/29/10 10:40 AM
Strong frontogenesis at 700 to 850 MB is enhancing the rainfall along the New Jersey coast northeastward through Long Island and much of Connecticut.
The rain will continue to remain moderate to heavy with rainfall rates of 0.25″ to 0.50″ per hour over much of the areas labeled as heavy on the map to the left. Moderate rain will continue to build west as the surface low redevelops along the North Carolina coast.
This rainfall will produce flash flooding and significant major ponding on the roadways from Cape May to Monmouth Counties of New Jersey, all of the five boroughs of New York City, Long Island, and central/eastern Connecticut. The intensity of the rainfall may also reduce visibility below 2 miles at times as well.
Caution should be taken through this evening especially for the rush hour as winds also begin to increase from the east as the surface low consolidates off the coast.
-- Weather When Posted --
- Temperature: 53°F;
- Humidity: 87%;
- Heat Index: 53°F;
- Wind Chill: 51°F;
- Pressure: 29.79 in.;
Everything Coming Into Place
Posted by: | Comments7:24 AM
It is very rare to see all the pieces of a major snow storm come together when the usual 500 MB key indicators are missing to such a great extent. Well, remember this storm because the observational data strongly is pointing in that direction!
The low pressure system that is bringing light snow and sleet to the forecast area this morning has performed an even more important task, that is to sufficiently cool the boundary layer to support frozen precipitation and produce an environment of continuous cold air advection at the surface through much of today. This low was key to this whole event in terms of precipitation type, as there certainly is no question now that this is going to be a very impressive snow storm.
As seen here in the water vapor, this storm is already coming together nicely. The first storm is exiting the forecast area without robbing the second of the deep moisture from the Gulf of Mexico. The upper low is just starting to tilt negative and remains closed. Most importantly, the northern branch of the Polar jet stream is remaining separate from this upper low this morning, which is KEY. This means that the surface low is going to be under the influence of the Sub Tropical jet stream through this afternoon, which will produce a track from Georgia to the North Carolina coast. Note also that moisture is starting to feed into the developing coastal low from the Atlantic. The conveyor belts are also starting to develop. The dry conveyor belt is forming along the Gulf Coast right now. The moist conveyor belt is forming to the east of North Carolina. Finally, the cold conveyor belt is starting to take shape over the Northeast and Mid Atlantic. All of these are hall marks for a major winter storm developing.
I think the radar though really shows what we are dealing with the best. Obviously, the first low pressure system is exiting the forecast area right now, as seen on the radar image to the left. However, a big clue for this storm can be seen over the Southeast. Convective precipitation! Latent heat is being released into the development of this storm. Latent heat release has the ability to further intensify a storm beyond forecasted levels due to the intensification of the thermal gradient at the mid levels. Further, convective precipitation is also forming along and north of the warm front, which indicates a slightly elevated convective environment. In basic terms, this means that the potential for convective snowfall and thunder snow is become a reality for this storm tonight!
-- Weather When Posted --
- Temperature: 28°F;
- Humidity: 92%;
- Heat Index: 28°F;
- Wind Chill: 17°F;
- Pressure: 30.06 in.;
After A Close Call, Moderating Conditions
Posted by: | Comments6:20 AM
The low pressure system off the North Carolina coast is impressively deepening, and heading east-northeast this morning. The man area of precipitation is already moving towards the Atlantic and well south of the forecast area. However, with a stiff northeasterly fetch off the Atlantic, I still can’t rule out a few ocean effect snow showers over the New Jersey coast and Long Island. I don’t expect anything significant, but I think those snow showers should be kept in mind for this evening. Otherwise, a partly cloudy and breezy day can be expected with winds from the north and northeast around 10 to 20 mph. Gusty conditions can be expected along the immediate coast and over the coastal waters as the low passes to the south.
The arctic air mass that has been in place, and that has supported several minor snow events for the forecast area, is on the way out starting tonight. High pressure of Pacific/Polar origin will move into the forecast area tonight from the south. The track of this high pressure system, though the Southeast, will support a southwesterly wind pattern from the surface to 850 MB. However, the moderation of temperatures will only push temperatures back to near normal levels. Otherwise, dry conditions can be expected through Thursday.
-- Weather When Posted --
- Temperature: 17°F;
- Humidity: 78%;
- Heat Index: 17°F;
- Wind Chill: 6°F;
- Pressure: 29.64 in.;
Light Snow Falling, But Will The Snow Get Heavier
Posted by: | Comments6:29 PM
The light snow has started to fall over the majority of the forecast area. I like where I stand with the idea of a coasting to 2 inches over much of the forecast area with slightly more off the coast.
Pressure is falling quickly off the North Carolina coast and convection is quickly building over this location. However, at this point I don’t see any indication of a closed low pressure system nor the back building over northern Virginai, Maryland, nor central/eastern Pennsylvania that would make me go beyond my forecast for this evening.
It is interesting, and something to keep an eye on, that cloud tops are rapidly cooling over much of the forecast area back down through coastal North Carolina. However, the speed of the precipitation shield does not suggest any slowing down.
Key Observations To Watch:
1. The thermal gradient at the surface and at 850 MB is showing signs of tightening. This may lead to the potential Mesoscale lifting that I was concerned about yesterday. We’ll see if any of that develops along the New Jersey coast tonight.
2. Precipitation trends over eastern Pennsylvania: When the coastal low finally gets its act together later this evening, if any preciptiation begins to develop rapidly, then that means the coastal low is taking over and that precipitation along the coast will intensify. I don’t think this will happen right now, but clearly the threat of this happening is not over yet.
3. Continued Cooling Of Cloud Tops: There is an upper level disturbance driving through the Mid Atlantic right now. That’s why there is enhancement along the coast on the water vapor. If cloud tops continue to cool and expand then the rate of rising air is increasing, which means lifting will be increased as well. More lifting, a more intense low pressure system, and heavier precipitation. Again, not expecting that, but of course I wasn’t expect the expansion of precipitation to this point either.
-- Weather When Posted --
- Temperature: 33°F;
- Humidity: 59%;
- Heat Index: 33°F;
- Wind Chill: 28°F;
- Pressure: 29.79 in.;
Freehold
77°
Philadelphia
81°
Sussex
73°
Allentown
77°
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