Category Archives: Thunderstorms

NYC Weather Update – Sept 29, 2020

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Apologies for the lack of updates lately. Have had a few things going on keeping me busy. We have a wet beginning to October on the way with tropical moisture accompanying a slow moving cold front. Heavy rain is possible overnight Tuesday, with isolated flash flooding a concern. Temperatures should be around normal (low-70s) until this weekend when a reinforcing cold front brings us down into the mid-60s.

Rest of today – cloudy with chances for rain increasing later in the day as a cold front approaches from the west. High temperatures in the mid-70s. This latter frontal boundary may also spark some showers overnight, with temperatures dropping into the mid-60s. A strong low level jet will be in place overnight, enabling efficient transport of tropical moisture from the south. This will lead to the potential for rounds of moderate to heavy rain, where some training is possible as well. Flash flooding is a concern as places could see 1-2″ of total rainfall overnight. Winds could also be gusty in some of the heavier downpours, which could also produce some thunder. Temperatures generally in the mid-60s.

  • Weather Prediction Center surface forecast for 2AM Wednesday
  • GFS model output for precipitable water valid 2AM Wednesday, showing the potential for heavy rain.

Wednesday – conditions should improve during the day with showers diminishing in the morning. Mostly cloudy with highs in the low-70s. Subsidence (sinking air) with westerly winds could produce gusty winds. Overnight lows in the upper-50s with mostly clear skies.

Thursday – partly sunny with highs in the low-70s. Overnight lows in the mid-50s.

Friday – partly sunny with highs in the mid-60s. Chance for rain with another cold front forecast to move through. Overnight lows in the low-50s as temperatures start to cool off behind this frontal passage.

Looking ahead, behind this cold front, a period of below normal temperatures is forecast to hit much of the Eastern US next week.

NYC Weather Update – Aug 17, 2020

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This week we will see a possibility of an extended period of cloudy weather, punctuated by periodic storms. This regime will bring cooler than normal temperatures mostly in the low-80s. Good news: Labor Day weekend looks to be dry and cool so far! Looking to the tropics, we’re about to enter the peak of hurricane season, and it’s no surprise in this very active season to date to see that National Hurricane Center is monitoring four disturbances that could become tropical storms.

Rest of today – cool, generally cloudy with possible peaks of sun, high temperatures in the upper-70s. Temperatures will be cool due to a persistent onshore flow with an area of high pressure over the Canadian Maritimes and a slow-moving warm front/stationary front to our south. This latter frontal boundary may also spark some showers overnight, with temperatures dropping into the mid-60s.

Weather Prediction Center surface forecast for 8AM Tuesday

Tuesday – the cool, cloudy trend continues with high temperatures again topping out in the upper-70s. Showers may occur periodically during the day. Overnight lows in the upper-60s with chances of showers continuing.

Wednesday – the cloudy, rainy weather continues, though temperatures may be a touch warmer around 80ºF. Chance for showers and thunderstorms. Overnight lows in the low-70s as the warm front finally pushes through.

Thursday – cloudy, with a chance for showers, and warmer temperatures in the mid-80s. Overnight lows in the mid-70s. Shower chances persist overnight.

Watching the tropics

Keeping eyes on the tropics, given that we’re about to enter the peak of the season (September) when oceanic heat content tends to be the highest, providing the greatest potential fuel for storms. There are four disturbances in the Atlantic that could become tropical systems, however, none of them are an immediate threat to the US mainland.

National Hurricane Center 5 day graphical tropical weather outlook.

NYC Weekend Weather – Aug 28, 2020

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Moisture associated with the remnants of Laura are set to bring soaking rain starting the weekend. A cold front eventually clears things out by Sunday, which will bring a markedly drier air mass into the region. Temperatures during this period will be generally cooler than at most points this week, in the low-80s. Next week, we could see a return to hotter weather towards mid-week.

Rest of today – increasing clouds with high temperatures in the upper-80s. Chances for rain and thunderstorms later in the day along a warm front that’s forecast to lift through during the day. Overnight lows in the low-70s with rain chances continuing.

Weather Prediction Center surface forecast for 8AM Saturday. By this time, a warm front will have lifted through and the remnants of Laura will be contributing moisture to rains over the region.

Saturday – Laura, which wrought serious devastation over the Gulf Coast, will make itself felt on Saturday, contributing tropical moisture to rain that will impact the area. This moisture will contribute to very high precipitable water content > 2″, which could lead to localized flooding. Mostly cloudy with rain possible throughout the day. Stronger storms are possible in the afternoon. High temperatures in the low-80s. Overnight lows in the upper-60s with rain chances diminishing as a cold front sweeps through.

  • GFS model precipitable water content valid 8AM Saturday. Very moist values of > 2.00″ are possible.
  • Weather Prediction Center’s analysis of possible rainfall totals Saturday. Parts of the region could see easily see 0.75-1.00″.

Sunday – by the morning, the trailing cold front associated with the primary low bringing this rain should’ve already pushed through. This will lead to a much drier, cooler day, with high temperatures peaking around 80ºF and plenty of sun. Winds may be gusty at times from the northwest. Overnight lows in the low-60s due to good radiational cooling with clear skies and winds calming.

Monday – even cooler than Sunday with high temperatures in the upper-70s, and sunny skies. Overnight lows in the mid-60s.

NYC Weekend Weather – Aug 21, 2020

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A week of refreshing, mostly dry, and seasonable weather gives way to a warming trend this weekend. There will be chances of isolated, diurnally driven thunderstorms both weekend days. By the end of the period, temperatures will be climbing into the upper-80s and low-90s across the region, and the warmer temps look set to carry over into the first half of next week.

Rest of today – mostly sunny with high temperatures in the mid-80s. Overnight lows in the low-70s.

Weather Prediction Center surface forecast for 8AM Saturday. The warm front and weak surface low pictured over the Delmarva is forecast to move north during the day.

Saturday – a weak warm front pushes north during the day. As a result, low clouds should be on the increase. Slight chance of showers and thunderstorms in the afternoon, coverage is likely to not be widespread. Overnight lows in the mid-70s with rain chances continuing.

Sunday – warm and more humid with high temperatures in the upper-80s. Another day where there will be chances for scattered showers and thunderstorms in the afternoon. Overnight lows in the low-70s.

Monday – the warm temperatures continue with high temperatures again in the upper-80s, approaching 90ºF under mostly sunny skies. Overnight lows in the low-70s.

GFS 850 mb temperature anomalies valid at 2PM Monday. The deeper the red hues, the more warmer the anomaly. This shows us on the northern side of an 850 mb high, with slightly above normal temperatures at this level as a result. 850 mb temperatures are often a good proxy for surface temperatures.

NYC Weather Update – Aug 17, 2020

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After a rainy, cool weekend, temperatures will rebound into the low-80s as high pressure takes over. This will bring about a week of pleasant, mostly dry weather, with plenty of sun all the way through end of the week. Further afield, we’re watching the tropics for 2 possible tropical storms brewing.

Rest of today – sunny with high temperatures in the low-80s. Overnight lows in the upper-60s with some potential for a scattered showers and thunderstorms as a cold front pushes through the region later this evening. Timing of these storms hitting the area appears to be around 8-10PM.

  • Weather Prediction Center surface forecast for 2AM Tuesday
  • High resolution rapid refresh simulated radar valid at 9:30PM tonight

Tuesday – behind this cold front, westerly downsloping winds will actually help temperatures rebound into the mid-80s under mostly sunny skies. Overnight lows in the mid-60s.

Wednesday – mostly sunny with highs in the low-80s. Overnight lows continue in the upper-60s.

Thursday – another great day with lots of sun and highs in the low-80s. Overnight lows in the upper-60s.

Watching the tropics

Way out in the tropical Atlantic, we have two tropical waves that the National Hurricane Center is keeping tabs on. These two waves could develop into the 12th and 13th named storms of the 2020 Atlantic Hurricane season, which thus far has been breaking records for the fastest forming named storms, beating out the horrific 2005 season that produced Katrina, Wilma, and some storms that had Greek alphabet names.

National Hurricane Center 5 day graphical tropical weather outlook.

NYC Weather Update – Jul 27, 2020

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Possibly record-breaking heat to start off the week with highs in the upper-90s Monday. Tuesday will have slightly cooler temps but similar heat index due to high humidity. This could allow for some strong thunderstorms with the weak cold front passage. This frontal boundary stalls out and becomes stationary. Cooler, drier air finally arrives later this week past.

Rest of today – sunny and hot with high temperatures in the upper-90s. Record breaking highs are possible across the region with strong 850 mb temperature anomalies above the surface. Overnight lows in the upper-70s could break some records for highest minimum temperatures.

  • GFS 850 mb temperature anomalies for 2PM Monday
  • Weather Prediction Center surface forecast for 8PM Tuesday.

Tuesday – although temperatures are overall expected to be cooler in the low-90s with more clouds, an increase in humidity will result in a heat index similar to Monday at or above 100ºF. A weak cold front moves through the region Tuesday evening and this could bring about a few strong to severe thunderstorms. Widespread severe weather is not expected at this time. Overnight lows in the mid-70s.

Wednesday – a bit cooler with high temperatures around 90ºF. Overnight lows continue to be uncomfortable in the mid-70s.

Thursday – high temperatures remain warm in the low-90s and mostly sunny skies. Overnight lows in the mid-70s. Looking ahead, above average warmth is still possible next week, even though we are expecting a break from the heat during the weekend.

National Hurricane Center 5 day graphical tropical weather outlook.

NYC Weekend, Tropical Storm Fay Weather – Jul 10, 2020

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Tropical Storm Fay will bring heavy rain, strong winds, flash flooding to start the weekend. A Tropical Storm Warning is in effect for all of NYC as well as coastal New Jersey and Connecticut, including all of Long Island. Conditions should start to improve Saturday as Fay continues tracking north and inland. We may even see some sun by Sunday. Temperatures start in the low-80s with the rain and clouds from Fay, but should be warming up upper-80s later on this weekend.

Rest of today – cooler with high temperatures in the low-80s. Windy and rain, with bouts of heavy, tropical downpours. 2-4″ of rain are possible with this storm. Sustained winds could approach tropical storm force (30-40 mph) near Fay’s core if it tracks over us. Otherwise, gusts up to 50 mph are possible. The main threat from Fay is from the heavy rains that could produce flash flooding. Overnight lows in the low-70s with tropical storm conditions still possible as Fay lifts north.

  • National Hurricane Center forecast for Tropical Storm Fay.
  • Weather Prediction Center rainfall forecast for Tropical Storm Fay. Note the widespread totals of 2-4″ possible in our region.

Saturday – as Fay lifts north and inland, it will weaken rapidly. Conditions should improve with a spell of dry weather possible before another non-tropical frontal system impacts the area with thunderstorms possible. Temperatures should be warm, in the upper-80s. Overnight lows in the mid-70s with rain chances diminishing behind the passage of this cold front.

Sunday – we may start off dry with some sun, which could allow temperatures to climb to the low-90s. However, scattered thunderstorms are possible later in the day. Overnight lows in the mid-70s.

Monday – similar day to Sunday, with high temperatures in the upper-80s. Partly sunny skies to start and isolated thunderstorms possible later in the day. Overnight lows in the mid-70s.

Weather Prediction Center surface forecast for 8AM Sunday

NYC Weather Update – Jul 5, 2020

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A hot, humid, and stormy start to the week with highs in the low-90s. A backdoor cold front moves through, granting a reprieve from heat mid-week with highs cooling off to the mid-80s Tuesday. The heat comes back after this. Later this week, and into the weekend, a storm with possible tropical characteristics could bring heavy rain to the region.

Rest of today – sunny to start with highs quickly climbing into the low-90s. Clouds increase later this afternoon. A shortwave trough will spark the potential for some showers and thunderstorms later this afternoon, around 4PM. These storms could bring heavy rain and gusty winds. Overnight lows in the low-70s with rain chances quickly dying off.

Weather Prediction Center surface forecast for 8PM Monday.

Tuesday – a backdoor cold front will push through overnight. The onshore flow from the northeast behind this front should result in mostly cloudy skies and cooler temperatures in the mid-80s. Showers and thunderstorms could still impact the area in the afternoon. Overnight lows in the low-70s.

Wednesday – the backdoor cold front will return north as a warm front Wednesday. Temperatures will remain stable with high temperatures in the mid-80s with mostly cloudy skies. Isolated showers and thunderstorms will again be possible in the afternoon hours. Overnight lows in the mid-70s.

Thursday – high temperatures rebound into the upper-80s and low-90s possibly with fewer clouds as high pressure briefly builds in. Overnight lows in the mid-70s. Looking towards the end of the week, we’ll be monitoring the progress of a low pressure center that the National Hurricane Center has identified as having the potential to develop tropical characteristics. This storm could bring some heavy rain this weekend.

National Hurricane Center 5 day graphical tropical weather outlook.

NYC Weather Update – Jun 29, 2020

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An upper low lingering over the Northeast results in unsettled weather to start this week. With the dynamics brought on by this upper low, there will be chances for isolated showers and thunderstorms each day esp. in the afternoon. High temperatures during this period should be generally in the low-80s. Luckily, this pattern should break in time for the Independence Day holiday weekend.

Rest of today – sunny with highs in the upper-80s to start. Chance for isolated showers and thunderstorms in the afternoon. Some of these thunderstorms could approach severe limits though we aren’t anticipating widespread severe weather today. Overnight lows around 70ºF.

Weather Prediction Center surface forecast for 8PM Monday.

Tuesday – more clouds resulting in cooler highs in the low-80s. Closed upper and surface lows over the northeast will provide for ongoing chances of showers and thunderstorms through the day. Coverage should again be scattered in nature. Overnight lows in the upper-60s.

Wednesday – similar day to Tuesday with highs in the low-80s, mostly cloudy with chances for showers and thunderstorms yet again. The closed upper low referenced above and visible in the graphic below will provide for a cold pool that should enhance lapse rates and increase chances for isolated severe thunderstorms. Overnight lows around 70ºF.

GFS model 500 mb temperature, height, and winds, valid for 2PM Wednesday.

Thursday – the nagging upper and surface lows will finally move off to the east. This should result in better conditions with sunny skies and no tangible risk for rain and thunderstorms. High temperatures should rebound into the upper-80s. Overnight lows in the low-70s.

NYC Weekend Weather – Jun 26, 2020

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A warm and potentially stormy start to the weekend on tap with Storm Prediction Center placing the area under slight risk for severe weather Saturday. Temperatures during this period in the upper-80s. Weather improves on Sunday behind a cold front. Next week, a lingering upper low may bring daily chances for rain in the afternoons.

This afternoon – mostly sunny with a high in the mid-80s. Overnight lows in the low-70s with increasing clouds towards daybreak.

  • Weather Prediction Center surface forecast for 8PM Saturday
  • Storm Prediction Center convective outlook for Saturday, showing the region under slight risk for severe weather.

Saturday – a warm front pushes through early in the morning and some showers could accompany this. Mostly cloudy with high temperatures in the upper-80s. A cold front is forecast to push through later, with a prefrontal trough ahead of it. These will serve as the loci for more organized convective activity. Thunderstorms forming in the warm sector behind the early warm front passage may be able to attain severe limits. The main threat is from damaging winds. Overnight lows in the mid-70s with rain chances diminishing early.

Sunday – despite the cold front passage, temperatures stay largely similar to Saturday in the upper-80s due to downsloping winds from the west. With an upper low lingering, isolated, diurnally driven thunderstorms may pop up in the late afternoon, mostly sunny otherwise. Overnight lows in the low-70s.

Monday – mostly sunny though a chance for afternoon pop up showers or thunderstorms persists. High temperatures remain warm in the upper-80s. Overnight lows in the low-70s. Below, you’ll see GFS forecasts for this upper low continuing to influence our weather going into next week. The tangible impacts for this will be continued chances of scattered showers and thunderstorms for much of the week until this upper low finally gets picked back up by primary westerly steering currents and moves offshore.

GFS model 500 mb height and wind. You can see evidence of a persistent upper low that drifts south, then gets cutoff from main steering currents, and remains largely stationary, even retrograding west during next week over the Northeast.