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.
Weather conditions will gradually deteriorate through the course of the day today as an approaching storm system draws closer to our area. Cloud coverage, scattered showers, and possible thunderstorms associated with a warm front should increase in coverage during the course of the day. High temperatures should be on the mild side in the mid-70s.
Thursday – as of now, the National Weather Service calls for the aforementioned warm front to approach but not clear our region by Thursday morning. As such, cooler southeast and easterly winds off the ocean will keep temperatures on the cool side with highs only in the mid-upper 60s. There will be a persistence chance for showers and thunderstorms as multiple impulses of energy ride up and along the frontal system, with a break probably occurring between early Thursday morning and later Thursday afternoon/evening.
Friday – in NYC, although the warm and cold fronts associated with this latest storm are forecast to have cleared through the area by Friday, an upper level low situated over the Canadian Maritimes will continue to allow impulses of energy (shortwaves) to rotate into our area providing the spark for a continued chance of showers and thunderstorms, especially Friday afternoon and evening. This upper low will be slow to move east due to a strong blocking “omega” high pressure center located over the central North Atlantic. High temperatures will again be around the upper 60s.
For Oberlin, conditions will begin to improve earlier with the chance of rain ending by Thursday, partly sunny skies Friday with gradual clearing and highs in the upper 60s.
NAM output simulated radar image for Friday at 2PM EDTGFS model output of 500 mb heights and absolute vorticity for Friday at 2PM EDT
Saturday – we’ll see an tenuous area of high pressure trying to build in from our west. However, there may still be a marginal chance of PM showers. Otherwise, expect gradually improving conditions with temperatures climbing back up into the low 70s.
Sunday and Monday (Memorial Day) – These will be the best days of the weekend with dry, mostly sunny, and warm conditions. High temperatures will continue to climb into the mid-upper 70s Sunday and possibly topping 80 Monday (this applies to both Oberlin and NYC). Next chance at rain will be Tuesday.
A New and Spectacular May Meteor Shower? – About Comet 209P/LINEAR & Camelopardalis
A friend of mine brought to my attention that a newly discovered and possibly brilliant meteor shower is forecast to take place in the early morning hours of Saturday, May 24th.
In brief, Earth is forecast to pass through the debris trail of a comet “Comet 209P/LINEAR” (discovered in 2004) during the overnight hours Friday into Saturday. Researchers are forecasting that the debris trail Earth passes through is one that has accumulated dust from as early as 1800 to 1924. As such, expectations are that we could see about an average of 200-400 meteors an hour (some estimates call for a meteor storm of 1000 meteors an hour!), i.e. between about 3-7 meteors per minute. Furthermore, the setup for this event is such that Southern Canada and the East Coast of the U.S. are ideally positioned to view this event. In the image below, the red line represents the forecast position of the radiant line (point from which meteors appear to emanate and where you would see the highest number of meteors), note that this line runs almost direct over Washington DC. Also, notice that the moon is in waxing gibbous phase, reducing its potential to overpower the meteor shower.
Timing and Visibility
The forecast zenith of this meteor shower is between 2AM-4AM Eastern Daylight Savings Time on Saturday, May 24th. Right now, the forecast for this time window calls for mostly cloudy skies over NYC as well as points east and north (i.e. New England). Partly cloudy skies are forecast the points further south and west (i.e. along the Jersey Shore, Washington DC/Northern, Eastern Virginia, Western Pennsylvania), with the best viewing conditions being in the DC metro area and Eastern Virginia where mostly clear skies are forecast. A word of caution: cloud cover forecasts even this close to the day of are notoriously difficult to pin down due to the fact that even small changes in initial conditions can lead to large shifts in a forecast. However, with high pressure building over the east coast throughout the course of the weekend, we should have generally good chances to view this shower.
My recommendation is that you go check this out in an area with minimal light pollution if you can. I think we’re in for a what I hope will be a good show!
Where to Look
The radiant point for this forecast meteor shower will be situated in the relatively obscure constellation Camelopardalis (named by the Romans for a hybrid animal that looks like both a camel and leopard, now known as a giraffe). As you’ll see below, this constellation is located slightly below the North Star (Polaris), and a bit to the right of the Big Dipper.
You can read a more in-depth analysis of this meteor shower here. I’ve grabbed and edited a couple images from this entry.
All preliminary indications are that this Memorial Day weekend should see fairly good weather, as you can read in the detailed discussion below. First, for your work week forecast:
For the remainder of the day today, there is a slight chance of a pop up shower or thunderstorm as cumulus clouds continue to build. This risk will cease as the sun begins to go down, and cuts off the heat source for these clouds. Overnight lows will fall into the low 50s in the city (not as cold as last night, as some clouds are expected to stick around early and stunt the potential for good radiational cooling), with 40s in the interior.
Tuesday will be the best day of the week, with high pressure briefly building in from the west. This will lead to mostly clear skies and warm temperatures in the upper 70s (also partially due to an incoming warm front).
Beginning Wednesday, we will see a period of unsettled weather as a relatively slow moving storm system approaches. This system will develop over the Great Lakes, and a warm front is forecast to be approaching our area during the day Wednesday. There will be an increasing chance of showers throughout the day as the warm front nears, with the best chance for precipitation in the late evening and overnight hours. Temperatures will be slightly lower than Tuesday in the mid-70s.
HPC’s Day 3 forecast for the US
Thursday there is a bit of uncertainty regarding the eastward progression of the warm front mentioned above. If the warm front has already passed over us, then we’ll be in the warm sector between the warm front and approaching cold front. This would lead to favorable conditions for some thunderstorms. Otherwise, we would expect mostly cloudy skies and a chance for more showery precipitation. High temperatures will be similar to Wednesday.
Friday, with the cold front Thursday having moved through and high pressure slowly building in, we would expect a good day weather-wise. However, as you see in the following image, the center of the now occluded low pressure is forecast to remain nearly stationary off the coast of New England. This is due to a blocking high over the North Atlantic (not pictured). Therefore, a chance of showers is forecast for both Friday and Saturday, with skies gradually clearing from mostly cloudy to mostly sunny Saturday. High temperatures Friday is forecast to be in the low 70s.
Now, the all important initial weekend forecast: as depicted above, high pressure building over the Great Lakes should progress generally southeast towards the Carolinas during the weekend. This should translate into improving weather each day during the weekend and increasing temperatures. Saturday, Sunday, and Monday should see high temperatures climbing from the low to mid 70s, and skies clearing to become mostly sunny.
For those of you reading this forecast who are traveling towards Oberlin and points west, the forecast for those parts is actually even better than for New York City in terms of sunshine, although, as you know temperatures will be slightly cooler in Ohio than here.
We’ve been fortunate that a persistent high pressure off of Nova Scotia has been stalling the arrive of a storm system earlier forecast to bring showers during the midweek period.
Our luck is about to run out, however, as the low pressure center and associated frontal boundaries will finally make their approach over the NYC area.
Thursday – overnight, a warm front is projected to pass through our area, bringing along a chance of drizzle, and the possibility for dense fog tomorrow morning as lower levels of the atmosphere become saturated with the coming southerly flow. Once the warm front passes over us, we will see a noticeable increase in temperatures, with highs forecast to be in the mid-upper 70s and possibly low 80s in interior portions of the region. Although the probability is low, there could be a couple showers and stray thunderstorms as well.
Friday – as the cold front associated with the low pressure center below draws closer, chance of precipitation will increase steadily during the course of the day. To start off, lighter showery precipitation should move in during the morning and early afternoon hours. Thereafter, heavier precipitation, and possibly thunderstorms, will move in especially during the evening and overnight hours. Due to the ground being somewhat saturated from the last round of rain we got, there could be some flash flooding in the heaviest down pours. Temperatures will be a bit cooler than Thursday in the upper 60s to around 70.
L and H correspond to approximate locations of surface low and high pressure centers. Notice the strength (high amplitude) of the associated upper trough and ridge
Saturday (BK Half Marathon Race Day) – good news for you runners out there as it appears the weather will cooperate for race day. The pesky slow-moving frontal boundary responsible for the rain on Friday will finally clear the area early Saturday morning, just in time for the start of the race. There may be some light showers early, but once the front clears conditions should start to improve. I would estimate start time temperature to be in the low 60s, with a high temperature forecast to be in the low 70s.
Simulated radar image from the North American Model (NAM) for Saturday at 8AM EDT
Sunday – a return to nice weather as the cold front has passed through and high pressure builds in temporarily. Partly cloudy with a high in the low 70s.
A batch of strong showers with some rumbles of thunder is approaching the NYC area. For the remainder of the afternoon and evening, strong to possibly marginally severe thunderstorms may pass through ahead of an advancing cold front. Damaging wind gusts and small hail are the primary threats.
Otherwise, expect broken clouds to cloudy skies and nice warm afternoon in the upper 70s to low 80s across the area. A line of thunderstorms is likely to fire up again later this afternoon into the evening hours as the cold front actually approaches.
Atmospheric instability is continuing to increase as we are in the warm sector ahead of the advancing cold front. Low level lapse rates and shear profiles are marginally conducive to the growth of some strong to severe thunderstorms.
We have a similar setup as last week that’s bringing overcast and rainy conditions to the region. A warm front well to our south is causing southeasterly/easterly winds off the cold Atlantic to stream in and saturate the atmosphere. Today, temperatures will be cooler with highs in the upper 50s.
Another mature cyclone with areas of precipitation and associated frontal boundaries
Unsettled weather conditions will continue Friday with the approach and passage of the aforementioned warm front. Temperatures will be warmer in the upper 60s, with a chance for showers and thunderstorms throughout the day.
Saturday looks like a warmer copy of Friday, again with the chance for showers and thunderstorms during the day and with increasing chance for precipitation in the evening/night hours as the cold front depicted above makes its way through. High temperatures will be in the mid 70s despite the cloud cover.
Sunday should be the best day of the weekend (just in time for Mother’s Day), with the frontal boundaries having passed over, skies should clear and allow for temperatures to top out near 80 in the city.
Monday the period of good weather continues to start the next work week, with high temperatures again possibly hitting 80 and mostly sunny skies.
It’s been a wild weather week that started with a tornado outbreak across half a dozen states in the South, and torrential rain fall that dropped as much as 2 feet in Florida, and as much as 6-8″ across the Northeast (resulting in incredible scenes like this landslide in Baltimore).
Fortunately, the weather has taken a turn for the better and will remain that way much of the coming week. This weekend is shaping up to be a nice one with temperatures on Saturday and Sunday reaching into the upper 60s to the low 70s across the region. There is a chance on both days of popup showers or thunderstorms in the afternoon, especially in inland areas with better daytime heating.
GFS model upper air (500mb absolute vorticity) output for this coming Wednesday. Note the strong trough out west (dip in the contour lines), and a ridge over our region (bulge towards the north of contour lines). Ridges correspond with high pressure and good weather while troughs denote low pressure and poor weather.
We’re finally turning the corner on warmer spring temperatures as the start to next week Monday-Wednesday will continue to feature high temperatures consistently in the low-mid 60s (about average). Dry and mostly sunny skies should also predominate as a ridge of high pressure (see above) builds in over our region.
Are you wondering why today is so cool with highs barely touching 50, but tomorrow is forecast to have high temperatures in the low 70s? It’s because there’s a warm front currently situated to our south. Let me clarify the two most common types of frontal boundaries:
A warm front delineates a boundary where the airmass behind the front is significantly warmer than the airmass ahead of it.
A cold front, not surprisingly, applies to the reverse situation and delineates a boundary where the airmass behind the front is significantly colder than the airmass ahead of it.
Currently, a warm front sits south of us, causing an onshore flow (easterly winds) off the frigid Atlantic Ocean. Why the easterly winds? Looking at the image below, you’ll see yellow contour lines that demarcate isobars of pressure. In the Northern Hemisphere, air flows counterclockwise around a low pressure center and clockwise around a high pressure center. The counterclockwise flow also applies to the frontal boundaries attached to a low pressure center.
In our present situation, the air flows towards the east (counterclockwise) south of the west-east oriented warm front (in red), and then from the east to west north of it. Hence, we are experience very cool conditions, and the moisture being funneled off the Atlantic Ocean into our region is fueling these steady showers.
Current surface analysis from the WPC with my overlay showing movement of the warm front to our south.
We should actually see temperatures begin to rise overnight as the warm front pushes through the area. Once this occurs, we will be in what is referred to as the “warm sector”, which is an area that sits behind a warm front and ahead of an advancing cold front. This type of setup is favorable for the development of thunderstorms.
Therefore, Thursday will be a warm, cloudy day with high temperatures in the low 70s and a chance of showers and thunderstorms in the morning.
Friday, with the cold front having passed through, conditions will clear up and we’ll have a nice, sunny day, with temperatures near 70. There will be a chance for afternoon showers.
Saturday continues the trend of nice weather with another day in the upper 60s and mostly sunny skies. Again, there will be a chance for afternoon showers, especially inland where daytime heating can produce enough energy (and instability) to induce those showers.
One other note about today and tomorrow, and that’s the whopping headline numbers for how much rain is forecast to fall, with totals ranging from as high as 3″+ in the western portions of the Tristate to 1.5″+ in the east. This could easily cause flooding in poor drainage areas, small streams, and urban areas.
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
The atmosphere over the area the past couple days has been both exceptionally dry and abnormally cool. This trend will end Friday with the approach of a cold front and low pressure system. Because the air mass currently in place is so dry, it will be difficult for the air to moisten at the outset Friday. Thus, forecasters are calling for a mostly dry day with increasing cloud cover, and rain showers moving in over the course of evening and overnight hours. High temperatures Friday will remain in the low 60s.
North American Model simulated radar image for Saturday @ 2PM EST
Saturday will remain a cloudy day with the chance for showers diminishing but still present. As the simulated radar image above suggests, there should be a break in precipitation between Friday evening and Saturday afternoon. However, it does appear that there is enough upper air support for afternoon showers and even some scattered thundershowers are possible Saturday afternoon. High temperatures will be warmer in the upper 60s. Skies should gradually clear once showers pass through, so the latter half of the day will still be sunny.
Sunday temperatures will cool off again with the passage of the cold front Saturday, however, sunny skies will return with high pressure building. Temperatures should be pleasant in the low 60s. Monday looks at this point to be a clone of Sunday.
Severe Weather in the Great Plains Sunday
It’s definitely severe weather season at this point in the Plains States and Tornado Alley. These areas have been repeatedly pummeled the past few days by severe hail storms. This weekend promises to be no different. As you can see below, a strong low pressure center is forecast to develop in the lee side of the Rockies Sunday with central pressure as low as 988mb.
Meanwhile, in the upper atmosphere, a vorticity maximum (see below) is forecast to form, with an area of strong divergence just to its east near the forecast center of the surface low. Upper level winds will be largely unidirectional. These are all ideal conditions for a severe weather outbreak. As a result, a wide swath of the Plains States from central Texas through Oklahoma, Kansas, and into Southeastern Nebraska have been placed under a Slight Risk area for severe weather by the Storm Prediction Center.
Note the strong low pressure center forecast to develop over the lee side of the Rockies – central pressure of 988mbUpper air charts for Sunday afternoon. Note the strong vorticity maximum (area of dark red) over eastern Colorado.
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.
