Category Archives: Severe Weather

NYC Weather Update – Jul 15, 2014

NYC, Rain, Severe Weather, Storms, Thunderstorms, , , , , , , , , ,

A correction from yesterday – I had said today may see less potential for severe weather. In fact, the Storm Prediction Center once again has most of the NYC metro area under a slight risk for severe thunderstorms later today.

1

Based on current satellite trends, it does appear there will be some breaks in the clouds this morning and afternoon. This will allow sufficient sunshine and daytime warming to fuel strong to severe storms across our region again later today. In the upper atmosphere, largely unidirectional winds from the south-southwest, a favorable jet stream set up, and approaching cold front suggest the potential for storms with damaging wind gusts and even some hail. Flash flooding is again a distinct possibility.

As you see below, portions of our area saw up to 1-1.5″ rain yesterday, and these same areas are in the target zone for severe storms today as well. With the upper level winds lining up from the south-southwest, training (where multiple storms hit the same location over a period of time) of storms is likely. This will enhance the risk for flash flooding.

2

 

A note about the term unidirectional winds: Unlike a hurricane, severe thunderstorms thrive on upper atmospheric energy, and unidirectional winds at all levels are more conducive to imparting a rotation on a rising parcel of air (rotating thunderstorms can produce tornadoes).

Otherwise, expecting a warm, humid day, with highs in the mid 80s and some sun before storms arrive later in the afternoon. It will be cooler and more comfortable tomorrow with this stormy cold front having passed us!

NYC Afternoon Weather Update – Jul 9, 2014

NYC, Severe Weather, Thunderstorms, Weather Update, , , , , , , ,

The Storm Prediction Center has again placed western and interior portions of the NYC region under a slight risk for severe weather today. The atmospheric setup this afternoon is similar to yesterday, with plenty of solar heating and humid air leading to moderate instability. At this hour, CAPE values (a measure of instability) are already hitting 1500-2500 J/Kg across the area, with greater instability further south.

There are already a few scattered thunderstorms forming over Eastern Pennsylvania. These storms are not yet hitting severe limits, but conditions are favorable for further development and increase in areal coverage. With winds aloft mostly unidirectional from the southwest, damaging wind gusts would be the primary threat. Storms that form to the southwest of NYC near the Philadelphia metro area and Central New Jersey would be the ones to watch for immediate impacts in the city.

These storms are still several hours away, and it remains to be seen whether they will hold up upon encountering the cooler and stabilizing influence of marine air infiltrating along south-facing shores with the southwest winds and a sea breeze. Last night, the line of severe thunderstorms weakened just before it hit NYC, sparing us from some wicked weather for the night. The same case may unfold again today, but the situation bears monitoring.

Screen Shot 2014-07-09 at 2.11.03 PM

Screen Shot 2014-07-09 at 2.01.04 PM

Screen Shot 2014-07-09 at 1.59.51 PM

NYC Nowcast – Strong to Severe Thunderstorms Approaching

Nowcast, NYC, Severe Weather, Thunderstorms, Tornadoes, , , , , , , , , , , ,

Severe thunderstorms are approaching the area from our west. Several distinct bowing segments of severe thunderstorms have been making their way steadily towards our area from Central Pennsylvania since earlier this afternoon.

These storms have a history of producing damaging wind gusts and even a few tornadoes. Sundown over some of the areas under the current Severe Thunderstorm Watch areas in our region may weaken these storms, however, overall atmospheric conditions are quite favorable to the forward propagation of this line.
Screen Shot 2014-07-08 at 8.09.44 PMScreen Shot 2014-07-08 at 8.11.29 PM

Screen Shot 2014-07-08 at 8.19.11 PM

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

Cool Images, Nowcast, NYC, Severe Weather, Weather Update, , , , , , ,

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.

Screen Shot 2014-07-02 at 5.45.51 PM

Screen Shot 2014-07-02 at 5.44.46 PM

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!

unnamed

NYC Nowcast – Jun 13, 2014

Nowcast, NYC, Rain, Severe Weather, Thunderstorms, , , , , , , , ,

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.

Screen Shot 2014-06-13 at 4.28.48 PM

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.

Screen Shot 2014-06-13 at 4.29.13 PM

NYC Nowcast – Afternoon Tstorms – May 22, 2014

Nowcast, NYC, Outside of NYC, Severe Weather, Thunderstorms, Weather Update, , , , , , , ,

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.
Untitled

Untitled3

NYC Nowcast – May 10 @ 2:40PM EST

Nowcast, NYC, Rain, Severe Weather, Thunderstorms, Weather Update, Weekend, , , , , , , , ,

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.

Screen Shot 2014-05-10 at 2.37.04 PM

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.

Screen Shot 2014-05-10 at 2.35.22 PM

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.

NYC Weekend Weather – May 2, 2014

NYC, Outside of NYC, Rain, Severe Weather, Thunderstorms, Tornadoes, Weather Update, Weekend, , , , , , , , , ,

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

Outside of NYC, Severe Weather, Storms, Thunderstorms, Tornadoes, , , , , , , , , , ,

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 Weather Update – Apr 28, 2014

NYC, Rain, Severe Weather, Weather Update, , , , , , ,

After a beautiful start to the work week, we are looking at a wet and cool mid-week before things clear up this coming weekend.

A low pressure center that is currently pounding the Midwest and Lower Mississippi Valley with hail, tornadoes, and severe storms will slowly move into the Great Lakes region. Once it does so, a strong area of high pressure situated over Quebec will prevent the low from making steady progress.

Therefore, Tuesday-Thursday will each see a chance for rain showers, in particular on Wednesday when a warm front associated with the aforementioned low pressure center makes its approach towards our region. Due to the long duration of the precipitation event and the possibility of heavy downpours Wednesday, there may be some localized small stream and urban street flash flooding.

Temperatures Tuesday and Wednesday will be quite cool with highs only in the mid 50s caused by onshore winds from the cool Atlantic waters flowing from the southeast and east ahead of the warm front. Once the warm front passes through on Wednesday night, temperatures will jump dramatically as we enter the warm sector behind the warm front and ahead of an advancing cold front. High temperatures Thursday could easily top 70.

A persistent low pressure center is forecast to track very slowly across the Great Lakes this week.
A persistent low pressure center is forecast to track very slowly across the Great Lakes this week.

Friday should see an end to this period of active weather as the high pressure over Canada weakens and finally allows this low to lift out of the area. Highs will be pleasant in the mid to upper 60s.