Category Archives: Flooding

NYC Weekend Weather – Aug 20, 2015

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Unsettled weather will be a trend for the end of this week and into the weekend as a cold front pushes through the region. Friday is shaping up to be the worst day with heavy rain with a risk for flash flooding. Conditions improve somewhat Saturday and Sunday, although a chance for showers and thunderstorms cannot be ruled out either day.

Rest of today – slight chance of showers or thunderstorms persists through this afternoon, though the best chances remain west of the Hudson, as was the case yesterday. We’ve hit a humid highin the mid-80s with a mix of sun and clouds above.

Friday – a cold front will be pushing through during the course of the day Friday. As the frontal boundary approaches overnight and into the early morning hours Friday, a slow moving band of heavy rain is expected to form and track from north to south across the area. It appears likely that the heaviest rain will fall in a narrow band during the early morning hours, and that things may already be drying out by the AM rush. High temperatures will be cooler than average with the cloud cover and rain, near 80.

Satellite image of the storm that will be bringing us some heavy rain Friday
Satellite image of the storm that will be bringing us some heavy rain Friday
High resolution rapid refresh simulated radar for 3AM EDT Friday
High resolution rapid refresh simulated radar for 3AM EDT Friday

A chance for showers and thunderstorms continues through Friday. By the end of the day, some areas could pick up between 1-2″ of rain, raising the risk of some flash flooding.

Saturday – although high pressure will be building once the cold front passes on Friday, a chance of showers and thunderstorms continues on the backside of this front. Temperatures will again be below normal with mostly cloudy skies and a high in the low-80s.

 

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Sunday – showers and thunderstorms cannot be ruled out for Sunday, which will end up being nearly identical to Saturday in sensible weather with high temperatures in the low-80s and mostly cloudy skies.

NYC Weather Update

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The weather story for the first part of this week will be a prolonged heavy rain event occurring Tuesday, delivering parts of the region some much needed precipitation. Temperatures will remain slightly below normal through Thursday, first because of the rain and clouds and then due to the influence of high pressure to our west.

Rest of today – NYC remains under mostly sunny skies, however, cloud cover is building to our west, so we could end up with more clouds later this afternoon. It will be a noticeably more humid day, although temperatures will still only top out in the low-80s.

Tuesday – rain should begin falling in the early overnight hours, and looks to persist through the morning and into the early afternoon hours. The heaviest rain seems likely to fall during the morning hours. Thunderstorms cannot be ruled out, and while the atmospheric conditions will not be very favorable (timing of the strongest lift will occur early in the day before any substantial daytime heating, which will be diminished due to cloud cover anyway), a few strong storms could still pop up in the morning. Some areas could see some isolated flash flooding if storm cells end up training over the same spots. Under the cloud cover and rain, high temperatures should be limited again to the low-80s.

North American Model High Resolution simulated radar for 11AM EDT Tuesday
North American Model High Resolution simulated radar for 11AM EDT Tuesday

Wednesday – rain will have cleared out after the passage of the cold front responsible for Tuesday’s storms. Behind this cold front, high pressure will set up over the Ohio Valley, bringing in cool, dry air. Temperatures will be quite comfortable in the low-mid 80s with low humidity.

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Thursday – the pattern of cool, dry weather continues with another day of sunny skies and high temperatures slightly below normal in the low-80s.

Drought Relief

A slight/moderate drought continues to cling to areas of Long Island and costal Connecticut, as you can see from the map below. It does appear that this upcoming Tuesday storm will bring some much needed rain to these particular areas. As you’ll also note from the map of forecast precipitation totals for Tuesday, some of the highest totals are expected precisely in the areas that need them the most.

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Weather Prediction Center's Quantitative Precipitation Forecast for total precipitation between 8AM EDT Tuesday and 8AM EDT Wednesday
Weather Prediction Center’s Quantitative Precipitation Forecast for total precipitation between 8AM EDT Tuesday and 8AM EDT Wednesday

NYC Weather Update & TS Bill – Jun 16, 2015

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We’ve certainly seen plenty of rain during the month of June, yet the NYC region remains in an area of moderate drought as of last Thursday. However, this does not reflect the rain that fell overnight Sunday into Monday. After a gloomy start to the week, we get a break of decent weather tomorrow, before another possible round of rain Thursday. The week ends with some drying out and improving conditions.

Rest of today – highs should top out in the upper-70s to around 80 today, with the potential for showers and thunderstorms later this afternoon. Storms have already formed to our west over northeastern Pennsylvania, but there is a stabilizing marine air layer over NYC and points east, so these storms may yet break apart before reaching us.

 

High Resolution Rapid Refresh model simulated radar for 1PM today.
High Resolution Rapid Refresh model simulated radar for 1PM today.

Wednesday – skies will clear rapidly overnight and lead to a sunny, dry, and pleasant day on Wednesday. Highs should be near 80. The high pressure creating these pleasant conditions will not stay around long, as another warm front approaches from the west.

Thursday – will look a lot like today, with mostly cloudy skies, and a potential for showers and thunderstorms in the afternoon as a warm front nears the region. Highs will be a bit cooler in the mid-70s with the influence of clouds and a southeasterly flow off the ocean ahead of the warm front.

Friday – the warm front from Thursday is followed quickly by a cold front passing Friday morning. Behind this, high pressure takes control and brings decent weather for the first half of the weekend. Highs Friday should be in the low-80s with clouds and sun.

 

Tropical Storm Bill

Over the weekend, a disturbance organized over the western Gulf of Mexico, and by last night it had consolidated and intensified enough to be designated the 2015 Atlantic Hurricane Season’s second named tropical cyclone – Tropical Storm Bill. Bill will be making landfall imminently in Texas as a moderate strength tropical storm with maximum sustained winds of 60mph.

Satellite image of Tropical Storm Bill about to make landfall on the central Texas Gulf Coast
Satellite image of Tropical Storm Bill about to make landfall on the central Texas Gulf Coast

However, for people living in the path of Bill, it is not the wind but rather the potential for dangerous flash flooding that is the primary concern with this storm. Bill is forecast to bring as much as 10″ of rain over the next few days to parts of Texas, and upwards of 6″ for a wide swath of Oklahoma and Missouri. As you may recall, some of these areas were the scene of deadly flooding just a few weeks back, and the arrival of a rainmaker like Bill is most unwelcome for these areas that are still in the midst of recovering. Moisture from Bill will eventually work its way into our region, but in a much less intense way.

Forecast rainfall totals for TS Bill
Forecast rainfall totals for TS Bill

NYC Weekend Weather – Jun 4, 2015

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We have struggled to reach normal temperatures this week, with plenty of rain and Wednesday as the only sunny break. We end this week with more cool, damp weather, before transitioning to warmer, drier conditions this weekend. Portions of the area received anywhere between 2-4″ of rain between Sunday night and Tuesday night, which will help improve drought conditions, however, these rainfall totals also led to flash flooding across large portions of the area.

Rest of today – cloudy, with a small chance for isolated light showers, cool with temperatures topping out only in the low-mid 60s, about 10ºF below normal for this time of year.

Atmospheric setup favoring the cool, cloudy, damp weather
Atmospheric setup favoring the cool, cloudy, damp weather

Friday – more clouds and cool weather, with this easterly onshore flow regime sticking around for one more day. High temperatures will again be only in the mid-60s, much below normal. There is a slightly higher chance Friday for scattered showers, but nothing like the soaking we got earlier this week.

Saturday – some improvement in conditions will take place Saturday as high pressure starts building from the west. Partly sunny skies may give way to more sun, with high temperatures warmer near 80.

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Sunday – high pressure moves to our east, allowing us to enjoy another pleasant, dry day, with high temperatures in the mid-70s.

Monday – a frontal system approaches the area. Ahead of the front, warmer air will flow in from the southwest, giving us temperatures at or above normal near 80ºF. As the front nears, thunderstorms and showers are possible across the region.

 

Arctic Jet Stream Slowing Leading to Increased Incidence and Duration of Extreme Weather? 

The massive quantities of snow that fell over the Northeast this past winter, the flooding rains over Texas last month, the enduring drought over California, and the asphalt-melting heatwave in India have all raised the question of what is causing this apparently increased incidence of long-duration extreme weather events. One possible explanation offered by researchers at Rutgers University is that the polar jet stream circling the Arctic has been slowing.

Jet streams are generated by two factors: the rotational energy of the Earth spinning on its axis, and the pressure gradient between two airmasses of varying temperatures. In the case of the polar jet circling the Arctic, rapid warming of the Arctic over the last couple decades has led to a decreased thermal and pressure gradient between air over the Arctic and air directly to the south. Researchers posit that this effect has led to a slowing of the polar jet stream. Since the jet stream is responsible for moving large (synoptic) scale weather patterns, any affect on its speed and orientation can have dramatic impacts for widespread regions of the world. In this case, the slowing polar jet stream is theorized as the mechanism behind the prolonged effects of the weather events mentioned above.

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

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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.

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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.

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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.

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Map of California with drought condition layer (reds/oranges), and rainfall totals from yesterday

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 Weather Update – Jul 14, 2014

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The Storm Prediction Center has placed the entire NYC metro area in an area for a slight risk of severe weather today. A strong low pressure center over the Great Lakes and its associated cold front are slowly making their way towards the Eastern Seaboard. Despite the cloudiness today, forecasters are still fairly confident that atmospheric conditions will be favorable for the formation of severe thunderstorms in the region. Based on current radar trends, these storms would most likely not be arriving in the NYC area until later this afternoon. The primary threat to our area will be damaging winds and torrential rain capable of triggering flash floods.
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Tuesday will feature a similar set up for weather over the region, though there is less risk for severe weather tomorrow. However, strong storms are possible throughout the day and the risk of flash flooding is a distinct possibility. High temperatures will be in the mid 80s despite cloud cover, due to the influence of warm, humid air rushing in between the cold front and high pressure offshore over the Atlantic. This same warm, humid air mass is what will feed the storms for today and tomorrow. As you see below, the forecast rainfall total for today and tomorrow is as high as 3.6″ over Northeastern New Jersey, and ranges between 2.5-3″ for most parts of the Tri-State area.Untitled2

Wednesday – we get a reprieve from the stormy weather as the cold front and storm system finally move east of NYC. Expect a cloudy start to the day with gradual clearing and conditions improving markedly. The next weather story for Wednesday through the end of the week is the cool, polar air mass that will be a dominant feature. High pressure will build in behind this storm system and usher in much cooler temperatures, with highs in the low 80s Wednesday-Friday, and overnight lows in the low-mid 60s in the city, and in the 50s north and west!

Thursday & Friday – expecting these two days to be essentially the same weather-wise, with high temperatures in the low 80s in the city (and upper 70s further north). Sunny to mostly clear skies for both days.

NYC Weekend Weather Update – May 16, 2014

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First for weather headline that will be dominating today: the storm system that is set to bring us heavy, potentially flooding rain later today and into the overnight hours. Currently, temperatures in our area are generally in the mid-upper 60s with a strong south to southeasterly wind. This is leading to an influx deep moisture ahead of the approaching cold front. We are firmly entrenched in what meteorologists refer to as a warm sector. This will provide the necessary conditions for heavy rain and some possible embedded thunderstorms to form later.

NOAA NCEP surface analysis as of 9AM EDT. Note the cold front sitting just off to our west with an elongated area of moderate to heavy rain.
NOAA NCEP surface analysis as of 9AM EDT. Note the cold front sitting just off to our west with an elongated area of moderate to heavy rain.

Based on the latest output from GFS and NAM models, it would appear the heaviest of the rain will arrive in our area during the PM rush and last through the evening into the early morning hours. So, if you’re going to be heading out this evening, grab an umbrella and appropriate rain gear.

NCEP's forecast for quantitative precipitation totals over the next 24 hours.
NCEP’s forecast for quantitative precipitation totals over the next 24 hours.

One of the major hazards with this storm is flash flooding and flooding in general. Because a high amount of precipitation is anticipated to fall in a relatively short time window, flash flooding is a real concern especially in urban areas and small streams. This will make for a sloppy and slow evening commute. The flip side of the fast moving nature of this storm system is that it should clear the area fairly quickly, meaning that you runners out there should have slightly better conditions than previously forecast for the start and duration of the Brooklyn Half Marathon.

NAM high resolution model output showing the cold front and storm system to have pushed through our area by about 5AM EDT
NAM high resolution model output showing the cold front and storm system to have pushed through our area by about 5AM EDT

Saturday after the cold front passes through and the rains subside, we should be looking at gradually clearing skies and slightly above average temperatures in the low 70s.

Sunday through Tuesday – we will be compensated for this rainy Friday by a string of days with fair conditions and seasonable temperatures. A high pressure center will form and camp out over our area, preventing any bad weather from impacting us. As such, temperatures should be nearly steady each day during this period in the upper 60s to low 70s with mostly sunny skies.

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NYC Weather Update & BK Half Marathon – May 14, 2014

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We’ve been fortunate that a persistent high pressure off of Nova Scotia has been stalling the arrive of a storm system earlier forecast to bring showers during the midweek period.

Our luck is about to run out, however, as the low pressure center and associated frontal boundaries will finally make their approach over the NYC area.

Thursday – overnight, a warm front is projected to pass through our area, bringing along a chance of drizzle, and the possibility for dense fog tomorrow morning as lower levels of the atmosphere become saturated with the coming southerly flow. Once the warm front passes over us, we will see a noticeable increase in temperatures, with highs forecast to be in the mid-upper 70s and possibly low 80s in interior portions of the region. Although the probability is low, there could be a couple showers and stray thunderstorms as well.

Friday – as the cold front associated with the low pressure center below draws closer, chance of precipitation will increase steadily during the course of the day. To start off, lighter showery precipitation should move in during the morning and early afternoon hours. Thereafter, heavier precipitation, and possibly thunderstorms, will move in especially during the evening and overnight hours. Due to the ground being somewhat saturated from the last round of rain we got, there could be some flash flooding in the heaviest down pours. Temperatures will be a bit cooler than Thursday in the upper 60s to around 70.

L and H correspond to approximate locations of surface low and high pressure centers. Notice the strength (high amplitude) of the associated upper trough and ridge
L and H correspond to approximate locations of surface low and high pressure centers. Notice the strength (high amplitude) of the associated upper trough and ridge

Saturday (BK Half Marathon Race Day) – good news for you runners out there as it appears the weather will cooperate for race day. The pesky slow-moving frontal boundary responsible for the rain on Friday will finally clear the area early Saturday morning, just in time for the start of the race. There may be some light showers early, but once the front clears conditions should start to improve. I would estimate start time temperature to be in the low 60s, with a high temperature forecast to be in the low 70s.

Simulated radar image from the North American Model (NAM)
Simulated radar image from the North American Model (NAM) for Saturday at 8AM EDT

Sunday – a return to nice weather as the cold front has passed through and high pressure builds in temporarily. Partly cloudy with a high in the low 70s.

NYC Weather Update – Apr 30, 2014

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Are you wondering why today is so cool with highs barely touching 50, but tomorrow is forecast to have high temperatures in the low 70s? It’s because there’s a warm front currently situated to our south. Let me clarify the two most common types of frontal boundaries:

  1. A warm front delineates a boundary where the airmass behind the front is significantly warmer than the airmass ahead of it.
  2. A cold front, not surprisingly, applies to the reverse situation and delineates a boundary where the airmass behind the front is significantly colder than the airmass ahead of it.

Currently, a warm front sits south of us, causing an onshore flow (easterly winds) off the frigid Atlantic Ocean. Why the easterly winds? Looking at the image below, you’ll see yellow contour lines that demarcate isobars of pressure. In the Northern Hemisphere, air flows counterclockwise around a low pressure center and clockwise around a high pressure center. The counterclockwise flow also applies to the frontal boundaries attached to a low pressure center.

In our present situation, the air flows towards the east (counterclockwise) south of the west-east oriented warm front (in red), and then from the east to west north of it. Hence, we are experience very cool conditions, and the moisture being funneled off the Atlantic Ocean into our region is fueling these steady showers.

Current surface analysis from the WPC with my overlay showing movement of the warm front to our south.
Current surface analysis from the WPC with my overlay showing movement of the warm front to our south.

We should actually see temperatures begin to rise overnight as the warm front pushes through the area. Once this occurs, we will be in what is referred to as the “warm sector”, which is an area that sits behind a warm front and ahead of an advancing cold front. This type of setup is favorable for the development of thunderstorms.

Therefore, Thursday will be a warm, cloudy day with high temperatures in the low 70s and a chance of showers and thunderstorms in the morning.

Friday, with the cold front having passed through, conditions will clear up and we’ll have a nice, sunny day, with temperatures near 70. There will be a chance for afternoon showers.

Saturday continues the trend of nice weather with another day in the upper 60s and mostly sunny skies. Again, there will be a chance for afternoon showers, especially inland where daytime heating can produce enough energy (and instability) to induce those showers.

One other note about today and tomorrow, and that’s the whopping headline numbers for how much rain is forecast to fall, with totals ranging from as high as 3″+ in the western portions of the Tristate to 1.5″+ in the east. This could easily cause flooding in poor drainage areas, small streams, and urban areas.Screen Shot 2014-04-30 at 1.50.54 PM