Tag Archives: thunderstorms

NYC Weather Update – May 11, 2015

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This week will be a tale of two airmasses, starting with a warm, moist, maritime tropical one, and transitioning to a more seasonable, cool, dry, continental polar airmass (don’t be alarmed, polar refers to the origin of this airmass, not necessarily the temperatures, although some light frost might occur later this week far inland). In terms of sensible weather, you will notice a marked change between warm, humid, summer-like weather Monday and Tuesday, and cool, windy, and crisp spring-like conditions to end the week.

Rest of today – basically a repeat of Sunday, high temperatures topping out in the low-80s. There is a very slight chance of showers and thunderstorms over the inland areas west of NYC where some instability might develop from daytime heating. South-facing shores will be noticeably cooler and cloudier due to an onshore wind from the south off the ocean.

Tuesday – some fog and clouds early, then mostly cloudy with a chance for rain and thunderstorms in the afternoon ahead of an approaching cold front. High temperatures remain much above normal in the low-mid 80s.

Wednesday – the aforementioned cold front makes its passage, and brings in its wake a return to more seasonable weather. Average temperatures for this time of year are only around 65ºF, and that’s just about where we will end up on Wednesday under mostly sunny skies. There will be a noticeable wind from the northwest as well, making it feel extra crisp.noaad3

Thursday – sunny and dry, with a slight rebound in temperatures into the upper-60s.

NYC Weekend Weather – Apr 30, 2015

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This week ends with clouds and some small chance of rain, but we’re in for a real sweet stretch of pleasant conditions and warmer than average temperatures from Sunday into early next week. In fact, we could be hitting 80 by Tuesday ahead of a cold front that could bring some thunderstorms with it, before we cool back down into the low-70s, which is still above normal.

Friday – due to the influence of a weak area of low pressure to our south, we will be seeing generally cloudy skies, with some very slight chance for scattered showers in the southernmost portions of the region. Temperatures will be moderate by northeast winds circulating counterclockwise around the low pressure to our south, yielding high temperatures in the upper 50s to near 60, just a few degrees below normal.

Saturday – as the aforementioned low pressure system slides off to the east over the Atlantic, clouds should gradually decrease. Temperatures will also rebound somewhat to around normal with a high in the mid-60s. However, there could be just enough instability in the atmosphere to spark a couple scattered showers or thunderstorms.

 

gfs_namer_081_1000_850_thickSunday – by this time, an area of high pressure will have developed over the Carolinas. This setup will favor the influx of a warm airmass from the Gulf of Mexico. Skies will clear, and temperatures will be noticeably warmer in the low 70s.

Monday – another gorgeous day to start the week, with sunny skies and high temperatures in the mid-70s (10º above normal). Don’t say I told you so, but if there were a day to skip work, this would be it.

Climate Prediction Center's 6-10 forecast for temperature. Our odds are very good for getting warmer than normal temperatures.
Climate Prediction Center’s 6-10 forecast for temperature. Our odds are very good for getting warmer than normal temperatures.

Tuesday – although it will be even warmer Tuesday than it will be Monday, with highs possibly topping 80, it won’t be quite as pleasant since clouds will be building up ahead of a cold front that will bring our next chance at rain.

NYC Weather Update – Oct 20, 2014

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This week will be a colder repeat of last week, with a wet mid-week period, but better conditions going into the weekend.

Tuesday – an area of low pressure with an accompanying cold front moving in from the Great Lakes will give us a chance of showers, especially in the afternoon Tuesday. Ahead of the front, temperatures will warm up to the mid-upper 60s under mostly cloudy skies.

Wednesday – the low pressure above will spawn a secondary low off the coast of the Mid-Atlantic. This low pressure center will be the main weather-maker for the mid-week period. Forecast models point to a stubborn storm system that will meander slowly off the Northeast. Multiple bands of rain will rotate around this low. There will be enough instability with the vorticity associated with the low to allow for the possibility of thunderstorms, despite the fact that this low will be a colder core low. Temperatures will only be in the upper 50s with a unpleasant north to northeast wind.

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GFS model output for Wednesday, Oct 22, 2014 @ 8PM EDT
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GFS 500mb vorticity and height – notice the concentric circles indicating a closed low off the coast of the Northeast and New Engalnd. The darker yellows indicate areas of increased vorticity and energy.

Thursday – the rain should subside by around noon Thursday, but before all is said and done, we could get another  1-1.5″ of rain. The rainfall will mainly be concentrated to the east of the Hudson River, including NYC and Long Island. Temperatures will remain cool in the mid-50s with winds diminishing from the north and northwest.

Friday – the low will lift away, it will dry out, and clouds will diminish as temperatures also rebound back into the lower 60s to end the week.

NYC Weekend Weather – Oct 2, 2014

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Friday and Sunday will be the sunny and pleasant bookends to what will be a stormy and rainy Saturday this weekend.

Today – we’re looking at sunny skies and high temperatures in the low 70s. Clouds will begin to build back in later in the evening as the storm maker for Saturday begins to move in from the west.

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NAM high resolution model output for Saturday at 10AM EDT
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Weather Prediction Center forecast map for Saturday

Saturday – a negatively tilted frontal system will be moving over the area Saturday, with the worst of the rain coming between about 10AM-3PM. We will be in the vicinity of a triple point (junction between a cold, stationary, and occluded front, this feature is common with mature mid-latitude cyclonic systems) that will be draping south from a strengthening low pressure center that will be moving northeast into Ontario during this timeframe. A thunderstorm is not out of the question given the atmospheric dynamics. Temperatures should hover around the 70 degree mark despite the cloud cover and rain because of the potential for us to briefly enter a warm sector between the stationary front and cold front.

Sunday – we get a crisp blast of autumn air behind the frontal system passing through Saturday. Sunshine returns just in time for the annual BikeMS NYC, which yours truly will be participating in. Cool temperatures will be only in the mid-upper 60s.

Monday – good weather sticks around for the start of the work week with high temperatures around 70.

Our next chance for precipitation should come Tuesday-Wednesday. The low pressure center responsible for the rain Saturday is forecast to close off and retrograde (move west instead of east, with prevailing upper level winds) over central Canada. An impulse of energy will rotate around this center and lead to another cold front passing through our area.

 

NYC Weather Update – Sept 9, 2014

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This week features a rather active pattern, with several chances for precipitation starting with today.

Tuesday – there is some small chance for scattered rain showers today associated with an area of low pressure that is currently located over North Carolina. However, this chance of rain will be primarily confined to areas south of the city. As the area of low pressure slowly moves offshore of the Mid-Atlantic states, the pressure gradient will strengthen, allowing for a persistent easterly wind to continue transporting cool, maritime air into the region. Temperatures will remain on the cool side, with highs similar to yesterday in the mid-70s.

Wednesday – conditions will improve somewhat as the aforementioned area of low pressure exits east over the Atlantic. We will still not be able to escape a cool, onshore wind from the northeast, so even though clouds will diminish, high temperatures will again struggle to reach 80.

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Cold front approaches on Thursday

Thursday – the most substantial chance for rain this week will arrive with the passage of a cold front late in the day Thursday into the overnight hours. Warmer air from the southwest ahead of the cold front will translate to about average high temperatures in the low 80s under cloudy skies. As the cold front nears, showers and some thunderstorms will be possible. Current timing of the forecast models suggest that the bulk of the rain will not arrive until the evening hours.

Friday – conditions will improve Friday as high pressure builds in again in the wake of the cold front passing Thursday. Temperatures will drop back into the mid-70s with cooler, Canadian air filtering in from the north behind the front.

Tropical Storm Edouard?

Tropical wave off the coast of Western Africa
Tropical wave off the coast of Western Africa

A vigorous tropical wave moved offshore of Western Africa earlier this week, and is being monitored for possibility of tropical storm formation later this week. Environmental conditions are forecast to remain favorable for development with low wind shear and warm sea surface temperatures. This storm may bring some impacts to the East Coast of the United States, but it is too early at this point to know the scope of that impact.

 

NYC Weekend Weather Update – Sept 4, 2014

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We’re still in the grips of a warm and humid airmass, despite some cooling off last night due to the passage of a weak cold front. This warm trend will not break until a stronger cold front passes through the region on Saturday.

Friday – expect high temperatures once again in the mid-upper 80s, albeit with increasing cloud cover as stratus cloud decks start to filter in ahead of the aforementioned cold front.

GFS model output for 2PM EDT Saturday
GFS model output for 2PM EDT Saturday

Saturday – unfortunately, the timing of the cold front above does mean it will bring adverse impacts to our weekend plans. Showers and thunderstorms are likely to precede and accompany this frontal passage, particularly later in the day Saturday into Saturday evening. High temperatures ahead of the front will remain warm in the mid-80s, somewhat cooler near the shore. There will be a noticeable cooling with this round of storms.

Sunday – Clouds will diminish through the course of the day Sunday as a much cooler regime works its way into the area. High temperatures will only be in the upper 70s for Sunday and the beginning of the weak.

Monday – Skies will be mostly clear, and temperatures will be much cooler in comparison to Labor Day, with highs only in the upper 70s (~10 degrees cooler than Labor Day). High pressure building over us will lead to an onshore wind flow, bringing in a cool, maritime polar airmass.

Cool onshore flow due to high pressure Monday
Cool onshore flow due to high pressure Monday

 

NYC Weather Update – Labor Day Weekend

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Rejoice! The long awaited Labor Day Weekend is upon us. Although I’d love to say that the weather will be fantastic throughout, but unfortunately there will be a few disturbances traversing the region the second half of this weekend. Thunderstorms accompanying these disturbances may literally rain on the annual West Indian Day Parade in Brooklyn on Monday.

Friday – the remainder of today will be a picture perfect, fall-like day with high temperatures hovering right around 80. A pleasant, dry airmass is in place in association with an area of high pressure that’s currently sitting over us.

Saturday – essentially a repeat of Friday, but with a bit more cloud cover.

Sunday – high temperatures on Sunday will be considerably warmer than Saturday, since the area of high pressure sitting over us now will have moved to the east, building up southwesterly winds and allowing for an influx warm air to penetrate the region. Expect more humid and warm highs between the mid-upper 80s. A weak frontal boundary will be approaching Sunday, and transit the region late Sunday into Monday. This will be our first shot at rain and thunderstorms, some of which may deliver some heavy rain.

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Labor Day – the timing of the aforementioned frontal passage will be critical in terms of sensible weather Monday. It currently looks like Monday will be partly cloudy, with highs again in the mid-80s. There will be an increasing chance of scattered thunderstorms later in the day Monday leading into Tuesday as another weakening cold front nears the area.

Tuesday – the return to the work week will continue to feature warm and humid highs in the mid-upper 80s and a continued chance of thunderstorms as that cold front works its way through.

NYC Weather Update – Jul 21, 2014

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This will be my last weather update for the next 3 weeks as I will be traveling to Costa Rica during that time.

Tuesday – things will heat up on Tuesday as the high pressure center responsible for the what has been a refreshingly cool and fair stretch of weather moves to the southeast. This will allow warm, tropical air to move back into the area, setting the stage for high temperatures to climb well into the mid-upper 80s under partly cloudy skies.

Wednesday – the hot weather will intensify Wednesday as temperatures near or top 90 with a noticeable increase in humidity as well. Warm, humid air will be sandwiched between the Bermuda high and an approaching cold front. Scattered showers and thunderstorms are possible later in the day Wednesday. Inland areas to the west of NYC are most likely to see precipitation Wednesday.

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Thursday – the aforementioned cold front will move further east, giving the city itself its best chance of a soaking rain on Thursday. Given the humidity and amount of water available for storms Thursday, flash flooding is possible within the heaviest downpours, otherwise mostly cloudy with temperatures in the mid 80s. I wouldn’t be surprised if a few strong to severe thunderstorms popped up Thursday.

Friday – the cold front will clear our area and exit to the east, while cooler air filters down from Canada. High temperatures will return to the low 80s with mostly clear skies.

The Weekend – looks like the weekend itself will be another nice one, with high temperatures in the low 80s both Saturday and Sunday. There is a chance of showers and thunderstorms Sunday leading into what appears to be a fairly active weather pattern for the beginning of next week.

 

NYC Weather Update – Jul 15, 2014

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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.

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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.

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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

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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.

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