Category Archives: Noreaster

NYC Weekend Weather – Nor’easter Update – Jan 23, 2015

January 23, 2015Freezing Rain, Noreaster, NYC, Precipitation Type, Rain, Snow, Storms, Weather Update, Weekend40 70 benchmark, freezing rain, high pressure, low pressure, mixed precipitation, noreaster, nyc weather, nyc weekend weather, nyc weekend wx, nyc wx, rain, sleet, snow, weatherLei Zhao

The details are starting to come together for tomorrow’s Nor’easter. Over the past day, forecast models have been pointing to a faster moving system, such that the onset of precipitation is expected to begin overnight tonight, with the bulk of the precipitation ending by early afternoon tomorrow. This storm is expected to throw a little bit of everything our way tomorrow, making for a nasty day overall, with snow changing over to freezing rain or sleet, then perhaps a period of plain rain, followed by a possibility of a rain snow mix.

What to Expect

Snow, moderate to heavy at times, beginning overnight tonight. Winds picking up from southeast, then eventually moving to the northeast and north during the day Saturday. Snow transitioning to a period of possibly freezing rain or sleet during the morning hours, then a period of rain around midday and a possible rain/snow mix towards late afternoon before precipitation gradually tapers off later in the evening. High temperature right around or slightly above freezing.

Forecast Storm Track

Forecast models are in generally good agreement that the center of this Nor’easter will be passing just inside the 40ºN 70ºW benchmark sometime in the late afternoon Saturday (approx 4-5PM).

Without a high pressure center to the north supplying cold air to the area, this setup will allow for enough warm, moist air to circulate around the eastern side of the low pressure center to give us a mix of precipitation throughout the day. The extent to which snow can be sustained will be strongly dependent on dynamical cooling, and how quickly cold air can be pulled in on the western side of the low pressure center.

Storm track forecast from the Weather Prediction Center, with clusters indicating forecast positions of individual ensemble members.

Snowfall Forecast

As you can see below, the probability of more than 4″ of snow is quite low for coastal areas, especially Eastern Long Island, where mainly rain is forecast. The heaviest totals (no more than 5″, most likely) will be concentrated well north and east of NYC where temperatures are expected to be cold enough to sustain all snow for longer. Because the forward speed of the storm is now predicted to be faster, the chances of NYC getting any significant snowfall (even 2″) is considerably lower. Most of the city is in a swath of between 30-40% chance of getting more than 2″ of snow.

Probability of greater than 2" of snowfall — Probability of greater than 2″ of snowfall

Probability of greater than 4" of snowfall — Probability of greater than 4″ of snowfall

Ice Accumulation

The probability of us receiving a trace, but a measurable amount of ice from freezing rain is quite a bit higher than the probability of receiving snow, with most of the city in the 40-60% range.

Sunday – the storm will be long gone by Sunday, and we’re expecting to hit highs in the mid-upper 30s.

Monday – there is some potential for a round of all snow on Monday, but forecast models have not been in good consensus on how this will play out. A clipper system is expected to pass through, though it is unclear whether this system will spawn a secondary low offshore. In the latter case, we could see some significant snow, while if it’s just a clipper, we probably won’t see more than a couple inches.

NYC Weekend Weather – Jan 22, 2015 – Nor’easter Coming

January 22, 2015Freezing Rain, Noreaster, NYC, Rain, Snow, Weather Update, Weekend40 70 benchmark, freezing rain, low pressure, new york city weather, noreaster, nyc weather, nyc weekend weather, nyc weekend wx, nyc wx, rain, snow, winter, winter wx, wintry mixLei Zhao

All eyes turn towards the imminent Nor’easter that will be bringing significant winter weather impacts to the NYC metro region. Many variables remain unresolved that could affect the eventual outcome, but at this time, it looks like we’re in for a nasty combination of freezing rain, rain, and snow during the day Saturday. At present, forecasts call for somewhere between 2-4″ of snow in the city along with some ice accumulation. Precipitation should fall as all snow north and west of NYC, however, overall accumulation should be slightly less than in the city itself since the most intense precipitation will remain near coastal areas.

Friday – we get a pleasant, sunny, and slightly above average day with high temperatures in the mid-upper 30s.

Saturday – a tricky forecast for Saturday. What we know for sure, with different forecast models in relatively close agreement, is that an area of low pressure now forming over the Texas Gulf Coast will track over the Southeast, and then offshore of North Carolina by Friday night/early Saturday. Once the low moves offshore, it will rapidly intensify, and then track right on or very close to the 40ºN 70ºW benchmark by Saturday afternoon/early evening.

The uncertain part about this scenario has to do with the thermal profiles in place. With no high pressure over us or to the north pumping in cold Canadian air, the depth of cold (sub-freezing) air will be relatively shallow.

As the Nor’easter approaches us, the cyclonic flow around its center will wrap in some relatively warmer air in from the ocean and points south. This makes for a complicated picture – with warmer air aloft (see animation below) during parts of the day, and below freezing air nearer to the surface throughout points in the day, the recipe is set for at least some periods of freezing rain – precipitation that falls as rain, and then freezes on contact with a sub-freezing surface.

During the middle portion of the day, temperatures should be warm enough at the surface to support plain rain for some time, before transitioning back into freezing rain, rain/snow mix, perhaps with a period of all snow before tapering off Saturday evening.

output_QGEuaq — NAM output of temperature profiles at about 4,800 feet between 10AM and 7PM Saturday. Notice the light pink indicating temperatures between 0ºC and 10ºC, which only gives way to below freezing temperatures (light blue, indicating 0ºC to -10ºC) later in the time frame. The center of the Nor’easter is located within the middle of the set of concentric rings you see near NYC.

Deviations in the storm track to the east would result in more cold air being pulled in from the action of northerly winds on the western side of the low pressure center’s cyclonic flow (less freezing rain/rain, more snow), while deviations of the track west would result in warmer air being in place (less snow, more rain). So, even a slight adjustment in the storm track could alter the thermal profiles, and subsequently what kind of precipitation we see.

Sunday – temperatures overnight Saturday will be below freezing, which would allow anything that fell and melted to refreeze. Things do clear up Sunday, with highs about average in the mid-30s, and with clouds diminishing.

Monday – there is a chance for yet another round of mainly snow, potentially heavy, as another coastal storm is possible. Highs will be close to the freezing mark, making this an all snow event if it should pan out.

NYC Weekend Weather & West Coast Storm – Dec 2, 2014

December 4, 2014Climate, Cool Images, Drought, Flooding, Noreaster, NYC, Outside of NYC, Rain, Storms, Weather Update, Weekend, Western UScalifornia drought, california storm, climate, drought, flooding, heavy rain, meteorology, nyc weather, nyc wx, pac energy, pacific storm, rain, weather, west coastLei Zhao

It’s been a up and down week for weather in NYC, with Monday starting out in the mid-60s, then a colder mid-week that featured some mixed precipitation and rain. The end of this week will feature rain and slightly warmer temperatures by Saturday, then a return to colder conditions Sunday into next week. I’m also going to point out some of the spectacular weather brought on by a huge Pacific storm that hit California this week.

Thursday – the remainder of today will be pleasant and sunny, though cold with high temps only in the low 40s.

Friday – clouds will begin to build overnight tonight ahead of the a storm system moving in from the Southern Plains to the Ohio Valley. There is a small chance for scattered showers, otherwise expecting a cloudy day with highs in the mid-40s.

Saturday – rain should overspread the area by Friday night into Saturday. This storm system will be drawing on energy and moisture from the Pacific storm that slammed California earlier this week (discussed below). Combined with influx of Gulf moisture, this setup favors a moderate to at times heavy rain event for Saturday. Temperatures will rise steadily ahead of this storm system as it pushes warm air up. High temperatures Saturday should reach into the mid-50s despite rain and clouds.

gfs_namer_042_1000_850_thick — GFS model output for overnight Friday into Saturday

Sunday – rain should end overnight Saturday, and high pressure from Canada should quickly build in behind this storm system. The positioning of this high pressure, along with the exiting low, will make for a tight pressure gradient, which should allow for stiff northwest winds perhaps in the 15-25mph range. Temperatures will drop back into the low 40s with the arrival the colder Canadian air.

gfs_namer_084_1000_850_thick — GFS model output for Sunday night

Monday – the storm system from Saturday will move offshore, but it appears from model runs that there’s some chance the storm lingers. As the high pressure from Sunday moves off to the northeast, the clockwise flow behind it may draw this offshore area of low pressure back into the area. This could lead to some rain on Monday. It’ll be a mostly cloudy day otherwise with highs in the low 40s.

Pacific Storm Slams California

Earlier this week, California got slammed by a very strong Pacific low. This storm brought on furious rains that dropped 1″+ in many areas of Northern California, with totals as high as 3-4″ in spots near the Coast Range and Sierra, as well as further south in the mountains east of San Diego. These totals represent more rainfall than had fallen in many of these areas all of last year.

You can see from the map below which overlays drought conditions (the deeper the red, the more extreme the drought, with the darkest red representing extreme/record-breaking drought) with rainfall totals from yesterday. You’ll see that much of the heaviest rain did fall over regions worst affected by drought. Sadly, though this is a case of too much of a good thing, as much of this desperately needed rainfall occurred so quickly, it will simply runoff back into the ocean.

Screen Shot 2014-12-04 at 12.08.35 PM — Map of California with drought condition layer (reds/oranges), and rainfall totals from yesterday

NYC Weekend Weather – Nov 14, 2014

November 14, 2014Noreaster, NYC, Rain, Snow, Storms, Weather Update, Weekendcold, fall, new york city weather, noreasters, nyc, nyc weather, nyc weekend weather, nyc weekend wx, nyc wx, rain, snow, weekend weather, winter, winter weatherLei Zhao

You can feel the chill in the air now. This cold will continue Saturday, but we’ll get a slight warmup Sunday and Monday ahead of a low pressure system moving in from the southwest. Behind that low pressure system, we get a reinforcing blast of arctic air that will be entrenched through the rest of next week. I’m also monitoring the potential for a Nor’easter just in time for the busy travel day Wednesday and through Thanksgiving.

Saturday – a cold day on tap despite ample sunshine. High temperatures will be generally in the lower 40s. There’ll be a noticeable northwest wind making it feel like it’s in the 30s.

Sunday – a milder day with warm air flowing in ahead of a low pressure system, but by warm, I mean highs only around 50. Clouds will increase throughout the day and there could be some rain Sunday night.

Monday – rain will be falling for the majority of the day, with highs in the city in the mid-40s. Monday night gets interesting with the potential for a rain/snow mix in the city, and all snow in interior regions north and west. Depending on the timing of the main slug of precipitation with this system, we could actually get some accumulating snow in the city also (the later in the night the main body of precipitation falls, the colder it will be, and the better the conditions for snow).Tuesday – cold air rushes back in behind this storm on Monday and we drop back into high temperatures hovering in the low 40s.

Potential Thanksgiving Nor’easter?

In looking ahead at the long-term GFS model output, I’m noting the possibility for a possible high-impact Nor’easter that would be timed to coincide with the busiest travel day right before and then during Thanksgiving. Of course, this far out, there’s still considerable uncertainty to the forecast, so this scenario could not pan out, or the storm track could be nowhere close to where it needs to be to produce a high-impact Nor’easter. Still, it’s worth watching, as it could be a major headache for folks if it does materialize.

NYC Weekend Weather – Oct 24, 2014

October 24, 2014Noreaster, NYC, Storms, Weather Update, Weekendhigh pressure, new york city weather, noreaster, nyc weather, nyc wx, rain, weather, wx, wx forecastLei Zhao

We are still feeling the impacts of that Nor’easter that passed through Wednesday and Thursday. There will be some lingering showers east of NYC this morning, before gradual things begin to dry out and skies gradually clear from west to east. High temperatures will be in the mid-60s, but with a north wind blowing, it will still feel quite cool. We’ve got an excellent, fall weekend on tap.

Saturday – we’ll get sunny skies again, and high temperatures will remain in the mid-60s.

Sunday – much the same as Saturday.

Monday – high pressure will continue to build to our south. This will mean a shift in winds to the south and southwest, which will open the door for warmer air to stream in from the south. High temperatures in the mid-upper 60s, under sunny skies.

Tuesday – as that high pressure strengthens, we’ll get another day of even warmer temperatures Tuesday with highs near 70. We’ll be watching for another storm system approaching from the west that could bring us a chance of rain Wednesday.

NYC Weather Update – Oct 20, 2014

October 20, 2014Noreaster, NYC, Rain, Thunderstorms, Weather Updatecoastal low, cold, gfs, nam, new england, noreaster, northeast, rain, rainfall, storms, thunderstorms, vorticity, windLei Zhao

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.

gfs_namer_054_1000_850_thick — GFS model output for Wednesday, Oct 22, 2014 @ 8PM EDT

gfs_namer_069_500_vort_ht — 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

October 18, 2014Climate, Noreaster, NYC, Rain, Weather Update, Weekendautumn, climate, coastal low, cold front, fall, gusty, high pressure, wind gusts, windy, winter outlookLei Zhao

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 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.

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.

NYC Weather Update – Sept 23, 2014

September 23, 2014Noreaster, NYC, Rain, Weather Update, Weekendautumn, coastal low, cold front, fall, noreaster, nyc weather, nyc wx, rain, rosh hashanah, weatherLei Zhao

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.

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.

Screen Shot 2014-09-23 at 6.40.40 PM — 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 Weather Update – March Snowstorm? Mar 21, 2014

March 21, 2014Climate, Noreaster, NYC, Snow, Storms, Weather Update, Weekendcold, nyc, snow, snowstorm, spring, storms, weather, weekendLei Zhao

This is not the news any of us want to hear, but confidence is increasing for a potential late-March snowstorm to impact the NYC area next Tuesday-Wednesday. First, the weekend forecast:

Saturday

A warm front will push through early Saturday followed by a cold front later in the day, with a slim chance for precipitation. After the passage of the warm front, gusty winds will increase from the south and southwest, ushering in some much anticipated spring-like warm air. High temperatures may top 60, but with mostly cloudy skies and the influence of the wind it will feel cooler.

Sunday

Clouds will diminish Sunday, but in the wake of the cold front, temperatures will struggle to hit the low-mid 40s. Polar high pressure continues to build overnight, with low temperatures much below average only in the mid-20s!

Monday

Fair conditions with the polar high in control, temperatures will only be in the mid-30s, nearly 15 degrees below normal for this time of year.

Tuesday and into Wednesday

An area of low pressure forecast to form offshore of the Carolinas will track into our area. Forecast models are pointing to this system rapidly strengthening with a sharp decrease in central pressure as it progresses into the waters off of Long Island. Recent model show a track closer to the 40N/70W benchmark, which increases the potential for a significant snowstorm. However, 5 days out, there’s still a good deal of uncertainty as to final track, positioning of precipitation bands, and available moisture. A track slightly further north will mean increased odds for a significant snow event, while a track too far north or south will diminish these chances.

GFS model showing a strong low pressure center consolidating southeast of Long Island around 1AM Wednesday morning.

GEFS model (spaghetti strings show upper air circulation 552mb and 564mb). The two main bunches of the strings represent the polar and subtropical jet streams respectively. Notice the loops connecting the two streams over the our region. This is converging of energy from both streams will feed the rapidly deepening low pressure center.

NYC Weather – Spring Climate Outlook – Mar 20, 2014

March 20, 2014Climate, Noreaster, NYC, Outside of NYC, Western UScalifornia, climate, drought, equinox, nyc, spring, west coastLei Zhao

Today is the vernal equinox and marks the first day of astronomical spring (because as next week will show, even though it is technically ‘spring’, it won’t feel that way from a weather or climatological perspective).

The equinox denotes the precise date when the sun is directly overhead of the equator at noon. Although it is popularly stated that the equinox is also the date when the length of day and night are equal, this is not necessarily true depending on where you are on the planet. For example, the exact length of daylight for NYC today is 12 hours and 8 minutes, according to astronomical data from Weather Underground. That means the actual equinox for NYC occurred a couple of days ago.

Spring Climate Outlook

This is a good time for us to look ahead towards the forecast climate trends for the United States. Below you’ll see a map showing the Climate Prediction Center’s three-month outlook for both temperature and precipitation. Note that the northern tier of the US is forecast to have anywhere between 33% and 40% chances of a cooler than average spring, while much of the southern and western US is forecast to have between 33% and 50% chances of a warmer than average spring. California in particular is forecast to have 50% chance of warmer than average spring, combined with 33%-40% chance of below normal precipitation, which will be conducive for the persistence of the severe drought in the region.

NYC and the surrounding region is in a zone of equal chances, meaning there’s no strong indication as to whether we’ll have an above, below, or normal spring in terms of both temperature and precipitation.

LZ | Weather

Weather updates & posts for NYC region