Category Archives: Rain

NYC Weather Update – Oct 28, 2014

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Summary

This week will be archetypical of autumn weather, with large temperature swings in store for the region. We’ll start off with highs more characteristic of late summer near 70, though with clouds overhead, we may not top that number. A weak cold front will push through tomorrow with some chance of showers. Behind this front, temperatures will drop to more seasonable highs around 60 with dry conditions. The week ends like winter with an arctic airmass invading the region, leading to the possibility of snow and high temperatures only in the upper 40s.

Wednesday – clouds build in and showers will be possible for most of the day. Most rain should conclude by the evening hours. High temperatures will remain warm ahead of the passage of the cold front with winds from west pushing warm air ahead of the front.

Weak cold front passing through Wednesday, scattered showers possible.
Weak cold front passing through Wednesday, scattered showers possible.

Thursday – clear and sunny skies behind the cold front passing Wednesday, high temperatures cooler near 60. Overnight lows will be quite cool in the lower 40s with good conditions for radiational cooling.

Friday – clouds will increase ahead of the next storm system, and high temperatures will remain near 60.

Saturday – an intrusion of arctic air accompanying a strong, deep trough (cold front) will set the stage for what should be a raw, chilly, winter-like day. With the arctic air pumping in, high temperatures will struggle to even hit 50. In the chart below, you’ll see a height of 540 near us. Without going into too much detail, low heights generally correspond to colder temperatures, as colder air is more dense, it takes up less volume than the same mass of warmer air. A height of 540 is considered by forecasters to be important when determining precipitation type, as it indicates temperatures cold enough to support snow. That’s right – we will probably see some snow north and west of the city, and depending on the track of a secondary low that forms Saturday along the coast, we could even get some of the white stuff in NYC. This is a complex system, so it will bear watching over the next couple days.

 

gfs_namer_099_500_vort_ht

 

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 18, 2014

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We get one last day of late summer-like temperatures today before autumn comes back with a vengeance. A cold front has already passed through the city and you can already notice the winds beginning to shift to the northwest. This will herald a much cooler temperature trend. For the remainder of today, we can expect temperatures near 70 with some clouds building behind the front. There could be a sprinkle or two but nothing serious.

Sunday forecast map
Sunday forecast map

Sunday will be noticeably more cold with high temperatures struggling to hit the mid-50s and with a gusty northwest wind. Gusts could top 30mph at times with sustained winds 15-25mph. Overnight lows into Sunday and Sunday night will be downright chilly in the 40s. Some interior areas could see frost Sunday night.

Monday the winds will abate as the pressure gradient between the departing cold front and high pressure to the west eases. Temperatures will remain cool at only around 60.

Tuesday and into later this week we will see the impact of a frontal system that moves through from the Great Lakes and develops as a coastal low off the Mid-Atlantic. Current models seem to suggest that this low will linger for a few days offshore, so we could see multiple rounds of rain as bands rotate around the storm center.

gfs_namer_078_1000_850_thick

 

Winter Climate Outlook

The Climate Prediction Center has released its 3 month temperature and precipitation long range outlooks for the months ahead. As you will see, CPC has the NYC area in a zone of 33% chance of seeing a wetter and warmer than average winter. Call it a hunch, but I still think we’ll get a couple nasty Nor’easter type blizzards. Warmer than average of course doesn’t imply we won’t get freezing temperatures. A slightly warmer atmosphere would allow for more moisture and energy for coastal storms to feed off.

temp precip

NYC Weather Update – Oct 14, 2014

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Apologies for the lapse in posts last week. There was plenty to talk about with the formation and dissipation of Hurricane Fay, and with Hurricane Gonzalo developing. Gonzalo won’t be a threat to the U.S. mainland, but may wreak havoc in the vicinity of Bermuda as a low end Category 3 storm with 115-120mph sustained winds. This storm has the potential to hit Category 4.

Back to our region:

Today – we get to enjoy a very warm day for this time of the year with highs in the mid-upper 70s and sunny skies! Unfortunately, clouds will begin spreading over the area in a few hours time ahead of a system described in detail below.

Wednesday – there will be a chance of light rain in the morning, with the chance for more substantial rainfall increasing in the afternoon. Temperatures will remain mild in the mid-70s with persistent southeasterly flow channeling in warm, moist air from the south ahead of the cold front and storm system that was responsible for a severe weather outbreak in parts of the Midwest and Southeast earlier this week.

Thursday – will be the main event. Lucky for us, the storm system coming at us won’t be bringing severe weather, however, a thunderstorm or two is not out of the question. The main issue for us will be the risk of flooding from this slow moving system. Forecast models show training of storm cells, meaning the same areas will get hit repeatedly or continuously with moderate rain showers. Rain will likely be falling throughout the entirety of the day Thursday with little or no breaks. Rainfall totals of nearly 2″+ could lead to some minor flooding. However, the rain is welcome since we are nearly 3″ below average for rainfall. Temperatures should again remain on the warm side with highs in the mid-70s.

NAM high resolution model output for Thursday, Oct 16 @5PM
NAM high resolution model output for Thursday, Oct 16 @5PM – note the bright blue and purples stretched over the area, indicating bands of heavier rain
Precipitation total forecast for 8PM Wednesday-8PM Thursday. Nearly 2" for the NYC area.
Precipitation total forecast for 8PM Wednesday-8PM Thursday. Nearly 2″ for the NYC area.

Friday – things settle down quickly as a brief window of calm weather enters the picture. Temperatures will be cooler in the wake of the cold front with west winds and highs in the lower 70s.

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 30, 2014

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The skies look gloomy today, but there’s not a high chance of precipitation as the best dynamics for showers remain mostly offshore and to the east. High temperatures will be a bit above average with high temperatures in the low 70s.

Wednesday the chance for scattered showers will remain with a stationary frontal boundary slow to push south through our region. The best chance for precipitation will again lie to the east, likely well away from the city. High temperatures will be somewhat cooler around 70 with mostly cloudy skies.

Thursday – following the passage of the frontal boundary above, high pressure will build in from the north. Cloud cover should decrease gradually though not entirely clearing, but northeast and easterly wind will lead to cooler temperatures with highs only nudging the 70 degree mark.

Friday should be much the same as Thursday, with high temperatures right around 70 and clouds & sun.

GFS model output for Saturday, Oct 4, 2014
GFS model output for Saturday, Oct 4, 2014

Saturday – the forecast models are unambiguous in anticipating the passage of a negatively tilted cold front through the region (negative tilt in the northern hemisphere would correspond to a frontal boundary where the northern end lies to the west of southern end of the boundary, these types of fronts are often associated with higher levels of instability). Temperatures will be cool in the upper 60s to around 70, with a period of steady showers likely at some point during the day, right now it’s looking like this will be during the morning hours.

NYC Weather Update – Sept 23, 2014

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Today marks the first day of astronomical autumn, and it has been feeling ever more fall-like the past few days.

Wednesday – the day should start off partly cloudy, and high temperatures will sit at right about 70. However, with a coastal low forming off the Mid-Atlantic, cloud cover will increase especially later in the day.

NAM high resolution model output for Thursday, 9/25 @ 11AM EDT.
NAM high resolution model output for Thursday, 9/25 @ 11AM EDT.

Thursday – a slow moving coastal low (technically a Nor’easter) will be moving over the NYC region during the early morning hours Thursday and throughout the course of the day itself. With the low pressure center just to our south or southeast, we should see a cool northeast wind off the ocean. This will limit high temperatures to only the upper 60s under cloudy skies and periods of rain.

Friday – with this coastal low out of the way, high pressure will take control again and clear the way for a superb start to the Rosh Hashanah weekend. Highs on Friday should bounce back nicely into the mid 70s under clearing skies.

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GFS model output for Saturday, 9/26

Saturday – high temperatures will continue climbing to nearly 80 on Saturday under clear skies.

Sunday – pretty much a carbon copy of Saturday. High near 80.

The next chance at rain will be next Tuesday with a cold front approaching us from Canada.

 

NYC Weekend Weather – Sept 12, 2014

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Although the passage of a cold front yesterday didn’t bring any precipitation with it, you can definitely feel its impact in the form of much cooler and drier air today. Temperatures will be in the low 70s today with crisp, clear skies above.

Saturday – cloud cover will build tonight as an area of low pressure originating from the Tennessee Valley area slides along the frontal boundary that’s now located offshore to our east. This low pressure system will bring a solid chance at rain tomorrow especially later in the day into the evening hours. High temperatures will be cool, around 70, under cloudy skies.

NAM high resolution model output for Saturday evening at 8PM
NAM high resolution model output for Saturday evening at 8PM

Sunday – luckily, this storm system will exit rather quickly to our east, making Sunday an excellent day for outdoor activity of all varieties. Temperatures will be on the cool side, with highs in the low 70s under partly cloudy skies.

Monday – this week begins a trend towards cooler, fall-like temperatures as an upper air pattern favoring the intrusion of a cool, Canadian airmass takes hold. Highs on Monday will again only be in the low-70s, about 5 degrees cooler than average for this time of the year.

Tuesday – brings us our next shot at rain, as a weak impulse of energy passes through. The rest of the week after Tuesday looks like it will be uneventful, albeit on the cool side with the aforementioned arrival of a Canadian airmass and high pressure.

GFS 500mb vorticity and height model output. Note the two areas of very strong vorticity and closed heights in the Atlantic and Eastern Pacific corresponding to two tropical systems.
GFS 500mb vorticity and height model output. Note the two areas of very strong vorticity and closed heights in the Atlantic and Eastern Pacific corresponding to two tropical systems.

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 Weather Update – Sept 2, 2014

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Despite the unofficial end of summer, today may very well turn out to be one of the hottest days of the summer! We’re looking at forecast high temperatures in the upper 80s into the lower 90s across urban areas. Some relief will be possible with afternoon thunderstorms, and then another round of showers and thunderstorms overnight. A few of these storms could be approach severe limits, however, despite the heat and humidity, atmospheric dynamics are not favorable for widespread severe weather.

Cold front passing through overnight could give some temporary relief to the heat
Cold front passing through overnight could give some temporary relief to the heat

Wednesday – despite the passage of the cold front above, temperatures will remain warm and humid with highs in the mid-upper 80s under sunny skies.

Thursday & Friday – essentially the same, hot, humid, sunny with highs in the mid-upper 80s. The culprit will be an area of high pressure that moves offshore and to the southeast Thursday. This setup will allow for hot, humid air from the Southeast of the country to pump into the area.

High pressure southeast of us allowing for hot, steamy air to enter the area.
High pressure southeast of us allowing for hot, steamy air to enter the area.

The Weekend – we’ll finally see the heat break later Saturday and into Sunday as a stronger cold front brings in a cooler, drier Canadian airmass.