When air flows are blocked by obstructions, such as buildings, trees, mountain ranges, or in this case, a mountainous island, all sorts of interesting effects can occur. Just as flowing water hitting a rock will form swirling eddies, flowing air has the same tendency, which you can plainly see int he image above. We’re usually not able to see these effects so vividly, though you’ll often feel them in the form of turbulence.
One of the lead forecasters at WPC was taking a look at the visible satellite imagery in the Pacific near the Baja California Peninsula and noticed some swirly action. If you take a look, there’s several swirls being caused by a volcanic island called Isla de Guadalupe. There’s also one right next to the coastline. How many can you count!?
We have satellite and radar imagery on our webpage alongside the surface analysis–if you want to take a look, visit our website (www.wpc.ncep.noaa.gov) and take a look under the current weather!
The Storm Prediction Center in Norman, OK has placed western portions of our region under a slight risk for severe weather this afternoon, with the primary threat being damaging winds and hail.
Mid-upper level conditions are favorable for the development of thunderstorms with some rotating updrafts. Unidirectional winds at various levels, as well as wind speed shear, could impart enough rotation on storm cells to cause marginally severe wind damage and some hail. The highest potential will be over Eastern Pennsylvania and New Jersey where sufficient solar heating could produce CAPE (Convective Available Potential Energy, measured in joules per cubic kilogram) values of between 1000-1500 J/kg^3.
Storm Prediction Center in Norman, OK has placed western portions of our region in a slight risk area for severe weather this afternoon
A small cluster of thunderstorms is already initiating along the western New York/Pennsylvania border ahead of a weak cold front. These storms should expand in coverage and increase in intensity as skies are clear ahead of the frontal boundary, allowing for a good influx of energy for storms to feed off of. The current thinking is that isolated severe thunderstorms reach our region by around the 4-6PM time frame. The chances of these storms remaining severe over NYC and coastal areas is low, since there will be a stabilizing influence from the cool marine layer offshore.
A major severe weather outbreak is currently underway for portions of the Deep South from Louisiana up through Tennessee, extending east from the Mississippi to western Alabama. As you can see in this satellite image, there are numerous supercell thunderstorms with high cloud tops piercing into the tropopause, indicative of extremely strong updrafts. Low level helicity (a measure of the vorticity and spin imparted on the air) is also high, along with abundant moisture and convective available potential energy (CAPE) will continue to fuel dangerous storms capable of spawning multiple tornadoes, damaging wind gusts, and severe hail.
Major severe weather outbreak over the Deep South viewed from space
A chilly start to the weekend as we have cold easterly winds off the ocean, and a deck of clouds overhead. Rain will pick up in coverage and intensity as the day goes on, and it promises to be more or less a washout tonight.
Cloud deck building over the area, bulk of the actual rain is still off to our west over Central PA
Fortunately, the frontal system responsible for the rain will clear out of the area by Saturday. Sunny conditions will prevail, with winds turning from the east to the west and picking up to 15-20mph by the afternoon. High temperatures should top out around the mid-upper 50s, right about average for this time of year. Clear skies overnight Saturday will allow for good radiational cooling, and low temperatures could dip into the mid-upper 30s across the region.
Sunday promises to be the best day of the weekend, with high pressure firmly in control over the region. Sunny skies should allow for a mild day with high temperatures approaching 60.
The next storm system moves into the area later Monday into Monday night, with another chance for rain. Temperatures Monday could top 60 again with warm air flowing ahead of an approaching cold front.
Check out this satellite loop of a line of severe thunderstorms over eastern Oklahoma extending northeast into western Missouri. You can see the classic telltale signs of explosive thunderstorm growth here. Notice how at the outset, the line of clouds near the center of the frame are relatively thin, but then balloon out as time goes by. What’s happening here is that the cumulonimbus (thunderstorm) clouds along this line are growing so rapidly that they are hitting the top of the troposphere. Since water vapor has a difficult time penetrating into the stratosphere, it gets forced out laterally instead. Indeed, the Storm Prediction Center in Norman, OK has issued a mesoscale discussion, along with severe thunderstorm warnings and tornado watches for much of the area.
Get out there and enjoy the sunny, mild weather while if you can today. We caught a nice break and got enough sunshine today that we’ll probably top 60 in quite a few spots around NYC. Clouds will increase over the next couple hours. Conditions will steadily deteriorate as a surface low pressures system currently spawning some severe weather over the Plains states tracks northeast into our area. Friday – keep the umbrella handy as periods of showers are likely to occur throughout the day, with increasing coverage and intensity later on in the day into the overnight hours. An steady onshore breeze will usher in much cooler air off the ocean (sea surface temperatures offshore of the region are only in the upper 30s to low 40s). As a result, high temp will hover in the mid 40s.
Saturday – the storm system bringing us rain Friday into Saturday will advance a warm front through the area, and we’ll see a rebound in temperatures and gradually clearing skies. High temps could again top 60.
Sunday – another pleasant and mild spring day as high pressure moves into the area. Mostly sunny skies with a high again near 60.
Monday – our next shot at rain will come Monday-Tuesday of next week, with a storm system forecast to develop in the Gulf. This storm will track northeast through the Ohio valley into the Great Lakes, and a trailing cold front will bring us some steady rain. High temperatures Monday will be around 60 with warmer air flowing from the southwest ahead of the cold front. Long Island and CT shorelines will see cooler highs with an onshore flow.
Our next shot at rain – a low pressure system moving from the Gulf into the lower Great Lakes, and a trailing cold front.
It may be spring now, but it certainly doesn’t look or feel that way for the Great Lakes, most of which are still ice-bound. Superior, Huron, and Erie are still almost entirely covered by ice, while Michigan is less than half covered. The only lake not ice-bound this winter has been Ontario at the far-right. Image from LANCE MODISÂ taken on March 16th.
You may be wondering why Lake Ontario is the exception to the frosty rule here. Ontario’s average depth is about 283 feet, only Superior has a greater average depth (Erie is the shallowest, so even though it’s further south than Ontario, it’s often the first to freeze). Furthermore, Ontario is located at a lower latitude than Superior and Huron, and it’s relatively smaller surface area maximizes its heat retention.
We will be feeling the impacts of yet another storm, in what seems like an endless winter. A low pressure system currently over Cape Hatteras will move offshore into the Atlantic shortly. Once it does so, it is forecast to strengthen rapidly as it moves northeast towards the 40N 70W benchmark, which is associated with prime conditions for growth of strong nor’easters and winter storms.
Currently, forecast models are showing the brunt of the storm hitting Southeastern Mass and New England. In areas, the NWS office in Taunton is confident that there could be up to 12-15″ of snow, in addition to strong winds in excess of 50mph that have led to blizzard warnings for east facing shores of Mass including the Cape.
Impact
For our area, eastern Long Island is expected to see enough of a heavy snow band forecast to rotate around this storm to have winter storm warnings issued. These areas could see 6-8″+ of snow from this storm. Projected snowfall totals drop significantly as you go west, with mid-Island and Central Connecticut forecast to see 4-8″, and points west (including NYC) receiving 2-4″. Wind will also be a factor with a tightening pressure gradient caused by the rapid intensification of the coastal low.
Timing
Light snow is already falling over the area now, but the worst of this storm should take place in the evening and overnight hours. Snow and wind should pick up in intensity from southeast to northwest throughout the day. If you have made plans to travel along the NYC-Providence-Boston corridor, expect travel conditions to become hazardous this evening/night. The most intense part of this storm will be ongoing from about 6PM-1AM, but accumulating snow will begin around 3PM.
Notes
As with most storms this winter, there is still uncertainty as to the final track of the storm. Should the storm track slightly westward, and the deformation axis determining where a heavy band of snow progresses further inland, then areas west of where current winter storm warnings exist could see significantly higher snow accumulation. There is also some indication that a norlun trough might form, leading to a intense snow band projecting west/northwest from the center the coastal low. If this feature does develop, areas that this trough sits over could see much higher than projected snowfall.
Check out this impressive satellite image of the nor’easter that hit us yesterday. It’s now offshore of southeast Maine, and has strengthened considerably, taking on a classic “comma head” structure that is a hallmark of strong surface low storm systems.
Don’t shoot the messenger, but we are forecast to get even more snow Saturday. A clipper system to our northwest over Michigan will combine with another low pressure system moving into the Carolinas later today. Once this system moves offshore, it will begin strengthening and growing into another nor’easter. Luckily, forecast models are currently showing much lower amounts of available moisture (precipitable water) for this upcoming storm. In addition, even though the storm is forecast to pass near us, the bulk of the precipitation is currently forecast to remain over the open ocean. What this means is that we should only see light accumulations of snow, on the order of 1-3″. However, as with the previous storm, there is still a little uncertainty about the final track of this storm, and changes could lead to higher snowfall amounts.
Otherwise, expect milder temps today with windy and sunny conditions prevailing, temps in the low 40s. This should help some of the snow to melt. We should have clear skies for part of the evening to see the full moon on Valentine’s Day. Clouds move in overnight, with snow showers during the day Saturday and a high in the mid 30s. Another weaker clipper system moves in Sunday with another chance for light snow and high temps around freezing. Yet another system is forecast for Monday night into Tuesday, which looks to be snow to start and snow transitioning to rain on Tuesday. Monday’s high near freezing with a warm up Tuesday ahead of the frontal system moving in.
Here’s a graphic showing the snowfall totals from around the area from this last storm.
We’ve enjoyed a period of relative calm as the dry slot (orange outlined in purple below) mentioned earlier pushed in over the area, leading to a lull in heavy precipitation and more of misty drizzle. However, these conditions will not last as the nor’easter will gain strength overnight.
The mid-upper level low that is responsible for bringing in this dry slot will gradually move over the surface low pressure center currently located offshore of central NJ. Once the low pressure systems stack up, the surface low will rapidly deepen. As this occurs, the warm front extending from the nor’easter’s core will rotate to the NW of the storm center.
This frontal boundary will push moist air (greens and yellows in this image below) ahead of it, leading to the formation of a new heavy band of snow – technically a “frontogenetically induced deformation band”. Within this band, snowfall rates may hit 1-2″ per hour, and an additional 4-8″ could accumulate across the region (except eastern Long Island). Interior areas where temps have remained cold could see an additional 8-12″ overnight. You can already see in the radar image below that precipitation is already filling back in across southern NJ and the WAS-BAL-PHL corridor.
