Tag Archives: severe weather

NYC Weekend Weather – Hurricane Arthur – Jul 3, 2014

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Lots going on in the realm of weather over the coming weekend. First, to start off with today, the Storm Prediction Center has again placed our area under a slight risk of severe weather this afternoon and evening. We could see a repeat of the type of storms from last night as a cold front makes its approach from the west. Even though temperatures are lower today and sunlight limited, there’s still more than enough instability in the atmosphere to fuel a few strong to severe thunderstorms later today. Because we’re looking at another round of possibly torrential rain from today’s storms, many areas are under a flash flood watch. Part of this moisture is due to the influence of Hurricane Arthur to our south.Untitled3

Hurricane Arthur

As of this morning, Arthur strengthened into the 2014 Atlantic Hurricane Season’s first hurricane and is currently sitting offshore of South Carolina with sustained winds of about 90mph. Forecasters are increasingly confident that Arthur will have enough time over warm water and low wind shear areas to grow into a Category 2 storm before getting recurved out to sea and making extratropical transition.

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Track Forecast for Hurricane Arthur

Arthur is now forecast to brush by the Outer Banks of North Carolina sometime later today, and move to just about the 40N, 70W benchmark offshore of the Northeast by 8PM Friday. Given this current forecast track, confidence is increasing that we’ll continue to see heavy rain and showers through out Friday into Friday night, though not directly from Arthur itself. Rather, Arthur will be interacting with that cold front mentioned above to throw a wrench in everyone’s July 4th plans. Conditions should begin to improve rapidly Saturday as Arthur accelerates northeast, pushed by the cold front. We should see a return to sunny skies and seasonable weather Saturday with highs around the low 80s. Of particular concern are areas in Southeastern New England, which could see tropical storm conditions on Friday night into Saturday morning. Any deviation westward of this current forecast track would mean increased impacts on the Northeast, so this storm is worth watching closely. Regardless, high surface and dangerous riptides will be present on all Atlantic shorelines.

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NYC Afternoon Weather Update – Severe Tstorms in Vicinty – Jul 2, 2014

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You may have already experienced it, but if you haven’t you’re probably seeing some huge clouds forming on the horizon. We’re in for some stormy weather this evening, as the Storm Prediction Center and our local forecast office have us under a Severe Thunderstorm Watch. The hot, humid atmosphere, along with ample sunshine earlier today, has made the atmosphere moderately unstable, with CAPE values in the 2000-3000 J/Kg. This, along with mid-upper unidirectional shear will supply ample energy for strong to severe storms, with the greatest threat being frequent cloud to ground lightning and damaging winds.

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As you see above, there are already strong storms in our vicinity. The storms north of the city have met severe thunderstorm criteria (wind gusts in excess of 58mph, hail greater than 1/4″ in diameter, or a tornado). More storms are forming to our southwest, so NYC itself should not be immune to the threat later on. Check out this image of a classic towering cumulonimbus (thundercloud) below!

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NYC Nowcast – Jun 13, 2014

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You’ve felt the air warm up and become more humid as the warm front that brought our first round of rain passed through earlier today. Now, we’re getting set for a second round of heavy showers and thunderstorms associated with a pre-frontal trough that’s slowly progressing east towards the area from Eastern Pennsylvania.

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Ahead of this line of showers and thunderstorms, the air has destabilized readily with the ample sunshine earlier this afternoon. CAPE (Convective Available Potential Energy – a measure of how much fuel there is for thunderstorms to feed off of) is between 1000-1500 J/Kg over Northeastern New Jersey and NYC. This should allow for this line of storms to hold up and perhaps strengthen before hitting NYC. In fact, a couple sever thunderstorm warnings have already been posted for cells over Northeastern New Jersey.

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NYC Nowcast – Afternoon Tstorms – May 22, 2014

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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.

UntitledMid-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
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.
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NYC Weekend Weather – May 2, 2014

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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 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)
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.

 

Deep South Severe Weather Outbreak – Apr 28, 2014

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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
Major severe weather outbreak over the Deep South viewed from space

NYC Weekend Update & Severe Weather in the Plains

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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
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 988mb
Note the strong low pressure center forecast to develop over the lee side of the Rockies – central pressure of 988mb
Upper air charts for Sunday afternoon. Note the strong vorticity maximum (area of dark red) over eastern Colorado.
Upper air charts for Sunday afternoon. Note the strong vorticity maximum (area of dark red) over eastern Colorado.

 

Cool gif – Severe Thunderstorms in the Plains, Apr 3, 2014

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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.

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Really Cool Graphic – All Reports of Severe Hail from 1950-2013

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Another neat graphic from Storm Prediction Center’s SVRGIS: all reports of severe hail over .25″ in diameter from 1950-2013! Again, note the relative scarcity of severe hail west of the Rockies, but look at the density of hail reports over Mississippi and Georgia. Also, check out the dense patch of hail reports just east of the Front Range in Colorado.
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Really Cool Graphic – Tornado Tracks from 1950-2013 Mapped

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Just a super interesting graphic that the Storm Prediction Center put together using GIS data. What you’re seeing is a graphical representation of the track of each tornado that’s impacted the continental United States from 1950-2013. Notice the density in Tornado Alley, a region of the country where geography is conducive to the large scale weather patterns that produce tornadoes. Also, check out the general trend of a northeast vector to the tornado tracks. Lastly, note that although tornadoes are considerably less common in the Northeast, they still do occur with some frequency.

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