Tag Archives: nyc wx

NYC Weather Update – Feb 11, 2020

Light rain today will fall today. This will be followed by a brief spell of sunny skies and calm weather Wednesday. Another storm system impacts the area Thursday, bringing some mixed precipitation and rain. On the back side of this system, a drastic drop in temperatures will take place going into the weekend. This will be the coldest air mass we’ve seen in many weeks with lows in the teens.

Rest of today – Light rain in the morning and cloudy. High temperatures in the upper-40s. Overnight lows in the mid-30s with gradual clearing.

Weather Prediction Center surface forecast for 7AM Wednesday

Wednesday – high pressure briefly builds in with high temperatures in the mid-40s. Mixed precipitation could begin later in the day as the next storm system approaches. Overnight lows in the upper-30s with increasing mixed precipitation then transitions to rain.

Thursday – A warm up takes place with a warm front and southerly flow overnight. High temperatures reach into the mid-50s with rain ending in the morning/early afternoon. Much cooler temperatures overnight with lows around 30°F once the cold front of this storm system moves through.

GFS model 1000-500 mb precipitation and thickness valid 5PM Friday. Note the large area of Canadian high pressure centered over Indiana.

Friday strong Canadian high pressure builds behind the cold front mentioned above. A much colder air mass will accompany this high, with temperatures Friday only in the low-30s. The real chill takes place overnight, with lows dropping into the mid-teens as Arctic air keeps pumping in!

NYC Weather Update – Feb 3, 2020

The groundhogs were unanimous in their proclamation of an early spring, but do their predictions jive with climate forecasts? Either way, the first week of February will be an active one with multiple storms impacting the area. Temperatures are forecast to start much above normal in the mid-50s, then taper down to being a touch above normal in the low-40s. Most of the precipitation that falls should be in the form of rain, though overnight periods could produce mixed precipitation.

Rest of today – Early clouds should give way to more sunny skies later in the day. High temperatures will be mild, in the mid-50s as a stationary front slowly lifts north as a warm front into the overnight hours. Overnight lows in the low-40s.

Tuesday – High temperatures in the low-50s. The warm front mentioned above stalls out, then returns as a cold front. This pattern brings the potential for some light rain showers. Overnight lows in the low-40s.

Wednesday – high pressure builds in briefly, and should give us some reprieve from rain, however, north winds will cool things off with highs in the low-40s. Overnight lows drop into the low-30s as a second, stronger storm system takes aim at the area. This one could start off as wintry mix and sleet overnight for NYC.

Thursday any accumulation of wintry mix should get washed away as this second storm system lingers and produces rain during the course of the day Thursday. Mostly cloudy otherwise as highs climb into the low-40s. Temperatures currently forecast to remain steady for the most part overnight with onshore flow.

Are the Groundhogs Right?
Climate Prediction Center’s temperature outlooks for the second half of February and the entire month suggest that the groundhogs might be on to something – at least for the eastern part of the US (especially the southeast), where above normal temperatures are being forecast. That isn’t as much the case for the western US, as you can see below.

NYC (KLGA) Climatology for February

During my time taking classes as part of Penn State University’s Undergraduate Certificate in Weather Forecasting, we were taught that understanding the climatology of the location you are interested in is an important prerequisite for making accurate forecasts. This post continues on this theme, adding a climatology for February.

Other Month’s Climatologies

January
March
April
May
June
July
August
September
October
November
December

Station Basic Information

City Name / Station ID: New York, NY (LaGuardia Airport – KLGA)

Local Geography and Topography

Station Elevation: 10 feet above sea level.

Station Location: LaGuardia Airport (KLGA) is situated on the north shore of Queens along the East River, approximately 6 miles east-northeast of Midtown Manhattan.

KLGA’s location within the broader NYC area, as seen in a Google Maps terrain view

Important Topographical Features: New York City is located in the extreme southeastern corner of New York State, bordering suburban New Jersey and Connecticut. These suburban regions combined with those in Long Island comprise the Greater New York City Metropolitan Area, which is the most populous urban agglomeration in the United States and one of the populous urbanized areas in the world with an estimated population of 18 million. New York City itself sprawls across the coastal plain around the Hudson River estuary. The terminal moraine formed by glaciers of the last Ice Age result in a ridge of higher terrain that cuts a swath from southwest to northeast across the boroughs from northern Staten Island, northern Brooklyn, southwestern through central and northeastern Queens. Otherwise, the city itself is low lying. This ridge varies in height between 200-400 feet, rising sharply from south to north, but tapering more gently north. North and west of the city (about 30-50 miles away), lie significant elevations of the Catskills (north), Poconos (west), Taconics that are part of the broader Appalachian Mountain Range. The elevations of the lower foothills can range from 1000-1500 feet. Some of the elevations in the Poconos and Catskills, west and north of KLGA respectively, peak between 2000-3000 feet. The open expanse of the Atlantic Ocean lies south of KLGA and New York City. Long Island Sound also lies east-northeast. The vast urbanized area of the NYC metropolitan region has significant effects on local microclimates via differential heating (urban heat island effect). KLGA is in a low-lying area sensitive to UHI effects and marine influences.

Topographical map of New York State

Per the Local Climatological Data report from the National Weather Service:

On winter mornings, ocean temperatures which are warm relative to the land reinforce the effect of the city heat island and low temperatures are often 10-20 degrees lower in the inland suburbs than in the central city. The relatively warm water temperatures also delay the advent of winter snows. Conversely, the lag in warming of water temperatures keeps spring temperatures relatively cool. One year-round measure of the ocean influence is the small average daily variation in temperature.

National Weather Service – NYC Office

Wind Patterns

Below is a wind rose – you can read more about how to interpret this chart here.

Frequency (percentage) of the single most common wind direction: Due northwest (14.25%), same as with January.

Directions that are most and least common: Other most common wind directions include west-northwest (11.25%), due northeast (10.5%), and north-northeast (9.5%). Least common wind directions are east-southeast (0.5%), due east (1%), and south-southeast (1.25%).

Direction(s) most likely to produce the fastest winds: As is the case with other cold weather months, winds in excess of 21.4 knots (~25 mph) are most frequently found coming from due northwest. West-northwest, north-northwest, and due northeast winds can also produce winds over 21.4 knots though less frequently.

Direction(s) least likely to produce the fastest winds: As is the case with several other months, the least common wind directions of due east, east-southeast, and due southeast also rarely seen winds in excess of 16.4 knots.

Impacts of wind direction on local weather: February wind patterns are remarkably similar to January. Winds from the northwestern quadrant remain prominent. These directions also continue to produce the strongest winds. Interestingly, due northeast winds pick up in frequency in February compared to January.

Northwesterly winds bring cooler, drier Canadian air into the region following cold fronts. Winds from this direction also occur on the backside of departing coastal lows. Winds from these directions downslope coming off the higher terrain of the Catskills, and Poconos outside of the city. This can sometimes lead to warmer temperatures than would normally be expected for this wind direction as well as faster wind speeds. As with other months, northeasterly winds are usually related to backdoor cold fronts sweeping from the Canadian Maritimes, the onshore flow ahead of an advancing warm front, or a passing coastal storm to the south.

Maximum observed two-minute wind speed for the month: 39 knots (46 mph).

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth noting: February average high and low temperatures start the a slow upward trend that will carry through to the spring and summer. Amazingly, record high temperatures in February can top 70°F, even nearing 80°F.

DateNormal HighNormal LowRecord HighRecord LowRecord Lowest MaxRecord Highest MinNormal PrecipRecord Precip
1402766314500.101.59
2402759-118400.091.75
3402764116450.101.08
44027681018480.101.72
5402770617490.091.18
6412769420410.101.51
7412758520410.092.89
8412862-221470.100.80
9412862719420.091.82
10412860417420.091.67
11412863213450.101.32
12422863415450.091.59
13422865815400.092.19
14422860115430.091.00
15422974-717470.101.57
16422969217450.101.02
17432966211460.100.94
18432967014480.101.67
19432966925530.101.70
20432970320470.091.50
21432979620500.101.65
22443070919450.111.60
23443066826540.100.90
24443073625510.111.70
254430681222490.111.49
26453062922470.101.04
27453073921500.111.79
284531661024470.111.56
29671223420.64
Range40-4527-3152-79-7-1211-2640-540.09-0.110.80-2.89



NYC Detailed Forecast for January 25, 2020 (Lunar New Year)

Lunar New Year day in New York city will see the passage of a relatively robust storm system. Ahead of this storm, persistently easterly onshore winds could result in some minor coastal flooding. A band of moderate to heavy rain looks like it will sweep through in the afternoon hours. Rain should clear up quickly by the early evening. Temperatures should be above normal with some warm air advection.

My Forecast
High: 49°F | Low: 38°F | Max sustained winds: 26 mph | Total precipitation: 0.85″ – verification will come from METAR data for the period between 1AM Saturday and 1AM Sunday (06Z Saturday to 06Z Sunday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.

Verification
High: 52°F | Low: 38°F | Max sustained winds: 30 mph | Total precipitation: 0.78″ – all around this wasn’t too bad of a forecast. Wind speeds were slightly higher, and coming from the southeast. This could help explain why temperatures broke into the low-50s as this set up would have produced better warm air advection. Got the low temperature spot on. As for precipitation, at first I thought this was going to be a bust because the storm seemed to be moving faster than model data suggested. However, even with rain stopping by around 4pm, enough moderate to heavy rain fell that we went above 0.75″, though not too much over. I’m glad I didn’t buy into a higher precipitation total than 0.85″!

Weather Prediction Center surface forecast for 7AM Saturday

Synoptic Set Up
A primary occluded low tracking over the Great Lakes will spawn a secondary coastal low at the triple point between its occluded, warm and cold fronts. The primary low should weaken as it becomes vertically stacked with a 500 mb closed low (depicted below) and slowly consolidate with the secondary low. During the day, the secondary low is forecast to track northeast with the triple point tracking almost directly over NYC by around 7PM.

Ahead of this, we could see some light rain due to isentropic lift north of the surface warm front. Strong lift is expected as the low/triple point tracks closer, and lift will be enhanced by favorable conditions at 300 mb and 500 mb levels. At the 500 mb level, the aforementioned closed low is forecast to cause ample downstream positive vorticity resulting in increased divergence. Further up at the 300 mb level, it appears the left exit region of a powerful jet streak over the Southeastern US will lie south of us, and we’ll be under the right entrance region of a smaller, weaker jet streak. Both these regions will produce increased divergence and enhance lift. SREF probabilities for moderate to strong omega > -6 mb/sec were in the 50%-70% range.

High resolution models suggest a narrow band of moderate to heavy rain during the afternoon hours. A significant low-level jet at 850 mb with winds 45-55 knots and will aid with transporting subtropical moisture northwards. A dry slot works in quickly behind the primary slug of moisture by 7PM – this should cut off precipitation for the most part.

High Temperatures
Statistical models were in decent agreement, with NAM being the coolest coming in at 46°F. GFS was closer to 50°F and EKDMOS 50th percnetile was 49°F. Erring on the side of being cautious about going warmer than 50°F because of of the proximity of the triple point. If that tracks offshore more, we’d see a switch to westerly winds sooner and would end up being in a cooler airmass. Rain and clouds will also keep things in check. There’s some warm air advection indicated, but also need to keep in mind that sea surface temperatures are only in low-40s offshore around NYC. For these reasons, went the EKDMOS 50th percentile at 49°F.

Low Temperatures
The surface and near surface layer start off pretty dry. Evaporational cooling as the column saturates could have potential to keep temps on the cool side. EKDMOS 50th percentile was steady across two runs at 39°F. Statistical models had a spread from NBM at 36°F to GFS with 42°F. I’m going with 38°F because I think evaporational cooling will be a factor overnight.

Max Sustained Winds
Seems like winds will mostly driven by synoptic factors, since I don’t see signs of a well-mixed surface layer. However, downard momentum transfer with heavy rains could help bring some of the very fast 850 mb winds to the surface. It’s not hard to imagine sustained winds in excess of 20 knots. Winds coming from the east-northeast and east will be off the water towards LGA, with decent fetch over open water, so edging towards a higher max wind of 26 mph. This matches EKDMOS 50th percentile and is higher than GFS and NAM statistical guidance of 16 and 19 knots respectively.

NAM forecast sounding for KLGA valid 1PM Saturday. The atmospheric column is saturated throughout by this point (dew point temperature in green and environmental temperature in red overlap), meaning precipitation is ongoing. Also note how strong winds are throughout the column.

Total Precipitation
Strong lift will accompany the triple point as stated above. A low-level jet is also forecast to set up, creating conditions conducive for heavy rain. However, development of a dry slot is apparent in the early evening – this would put the brakes on precipitation. If that dry slot moves through earlier, bust potential for higher end total precipitation amounts is there. Statistical guidance ranges 0.60″-0.75″ on the low end, up to 1.23″-1.48″ (which would be record-breaking) on the high end. Various ensemble means range from 0.77″-0.94″, which is on the low end of the statistical guidance. Ensembles also showed a fairly tight spread, indicating decent confidence. The ensemble plume mean is close to the average mean of statistical guidance around 0.85″. This seems reasonable as it allows for possibility of heavy rain while still falling squarely within predicted ranges for both statistical and ensemble guidance. SREF probabilities for > 1.00″ of total precipitation aren’t a lock (10%-50%) with a very tight gradient southeast.

NYC Weather Update – Jan 7, 2020

A quick hitting storm system brings possible light snow to the region overnight into Wednesday. High pressure builds behind this storm, with winds shifting to the northwest bringing a cool down midweek. Another storm approaches towards the end of the week. Ahead of this, temperatures surge back above normal, approaching 60°F, as southwesterly winds instigate warm air advection.

Rest of today – increasing clouds with high temperatures in the mid-40s. A coastal low passes east of the area, bringing some potential for light snow accumulations (1″ or so). Precipitation will start off as rain, though, then transition to snow briefly overnight. Overnight lows drop to around 30°F.

Weather Prediction Center surface forecast for 7PM Tuesday

Wednesday – snowfall may be enhanced by a second fast-moving arctic front. Behind this front, high pressure builds. Decreasing clouds, with winds picking up from the west then veering northwest towards overnight hours. High temperatures in the low-40s. Overnight lows will plummet quickly into the upper-20s with an Arctic air mass and northwesterly flow. Winds may gust above 30 mph during the overnight hours.

Thursday – expecting a calm, bright, sunny day with high temperatures in the low-30s, below normal for this time of year. High pressure will be moving right over us during this time. Overnight lows in the low-30s.

GFS model 500 mb height anomalies for 1AM Friday. Note the strong positive height anomaly over the Northeast, with a corresponding strong negative height anomaly over the Rockies.

Friday – high pressure will move offshore to the east, setting up warm southwesterly return flow between the western periphery of the high and an incoming storm system. High temperatures expected in the upper-40s. Temperatures should in fact warm up overnight, through the upper-40s.

NYC (KLGA) Climatology for January

During my time taking classes as part of Penn State University’s Undergraduate Certificate in Weather Forecasting, we were taught that understanding the climatology of the location you are interested in is an important prerequisite for making accurate forecasts. This post continues on this theme, adding a climatology for January.

Other Month’s Climatologies

February
March
April
May
June
July
August
September
October
November
December

Station Basic Information

City Name / Station ID: New York, NY (LaGuardia Airport – KLGA)

Local Geography and Topography

Station Elevation: 10 feet above sea level.

Station Location: LaGuardia Airport (KLGA) is situated on the north shore of Queens along the East River, approximately 6 miles east-northeast of Midtown Manhattan.

KLGA’s location within the broader NYC area, as seen in a Google Maps terrain view

Important Topographical Features: New York City is located in the extreme southeastern corner of New York State, bordering suburban New Jersey and Connecticut. These suburban regions combined with those in Long Island comprise the Greater New York City Metropolitan Area, which is the most populous urban agglomeration in the United States and one of the populous urbanized areas in the world with an estimated population of 18 million. New York City itself sprawls across the coastal plain around the Hudson River estuary. The terminal moraine formed by glaciers of the last Ice Age result in a ridge of higher terrain that cuts a swath from southwest to northeast across the boroughs from northern Staten Island, northern Brooklyn, southwestern through central and northeastern Queens. Otherwise, the city itself is low lying. This ridge varies in height between 200-400 feet, rising sharply from south to north, but tapering more gently north. North and west of the city (about 30-50 miles away), lie significant elevations of the Catskills (north), Poconos (west), Taconics that are part of the broader Appalachian Mountain Range. The elevations of the lower foothills can range from 1000-1500 feet. Some of the elevations in the Poconos and Catskills, west and north of KLGA respectively, peak between 2000-3000 feet. The open expanse of the Atlantic Ocean lies south of KLGA and New York City. Long Island Sound also lies east-northeast. The vast urbanized area of the NYC metropolitan region has significant effects on local microclimates via differential heating (urban heat island effect). KLGA is in a low-lying area sensitive to UHI effects and marine influences.

Topographical map of New York State

Per the Local Climatological Data report from the National Weather Service:

On winter mornings, ocean temperatures which are warm relative to the land reinforce the effect of the city heat island and low temperatures are often 10-20 degrees lower in the inland suburbs than in the central city. The relatively warm water temperatures also delay the advent of winter snows. Conversely, the lag in warming of water temperatures keeps spring temperatures relatively cool. One year-round measure of the ocean influence is the small average daily variation in temperature.

National Weather Service – NYC Office

Wind Patterns

Below is a wind rose – you can read more about how to interpret this chart here.

Frequency (percentage) of the single most common wind direction: Due northwest (14.25%).

Directions that are most and least common: Other most common wind directions include west-northwest (13.5%), due west (11%), and due northeast (8.25%). Least common wind directions are east-southeast and due southeast (0.5%), and south-southeast (1.5%).

Direction(s) most likely to produce the fastest winds: As is the case with other cold weather months, winds in excess of 21.4 knots (~25 mph) are most frequently found coming from due northwest. Due west, west-northwest, north-northwest, and due northeast winds can also produce winds over 21.4 knots though less frequently.

Direction(s) least likely to produce the fastest winds: As is the case with several other months, the least common wind directions of due east, east-southeast, and due southeast also rarely seen winds in excess of 16.4 knots.

Impacts of wind direction on local weather: January’s winds build on a pattern first seen in November, where winds from the northwestern quadrant become prominent. January wind patterns are nearly identical to December, with winds from due west to northwest being very common. These wind directions also continue to produce the fastest winds most often.

Northwesterly winds bring cooler, drier Canadian air into the region following cold fronts. Winds from this direction also occur on the backside of departing coastal lows. Winds from these directions downslope coming off the higher terrain of the Catskills, and Poconos outside of the city. This can sometimes lead to warmer temperatures than would normally be expected for this wind direction as well as faster wind speeds. As with other months, northeasterly winds are usually related to backdoor cold fronts sweeping from the Canadian Maritimes, the onshore flow ahead of an advancing warm front, or a passing coastal storm to the south.

Maximum observed two-minute wind speed for the month: 39 knots (46 mph).

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth noting: January average temperatures for both high and lows start to bottom out, and there’s only a small range in these figures.

DateNormal HighNormal LowRecord HighRecord LowRecord Lowest MaxRecord Highest MinNormal PrecipRecord Precip
1402860819520.101.33
2402860923430.101.52
34028631017470.112.53
4402766413570.102.02
5402764920510.101.25
6402772815550.111.56
7392762418490.101.13
8392764313520.101.19
9392766114490.110.79
10392759216430.101.42
11392662415440.111.34
12392668112480.110.97
13392663418460.101.23
14392664718450.112.04
15392662014550.110.88
16392659214520.101.74
17392659-19450.111.20
18392664012440.101.98
19392664-39410.100.76
20392661014420.101.41
21392664-38420.103.13
22392657516430.101.25
23392662315470.102.60
24392668318540.101.48
25392657215470.101.43
26392672518450.092.40
27392666018440.101.93
28402760720450.091.55
29402768213500.110.80
30402763419440.100.79
31402761217410.100.88
Range39-4026-2857-72-3-108-2341-570.09-0.110.76-3.13



NYC Weather Update – Dec 17, 2019

A soggy and messy start to the week will give way to a blast of Arctic air, leading to an extended period of below normal high temperatures only in the 30s for the most part. Temperatures do look to rebound over the weekend towards more seasonable levels. The next chance for precipitation happens Wednesday as an arctic front, harbinger of these much colder temperatures, crosses the area and brings possible snow squalls.

Rest of today – periods of rain during the day with high temperatures in the mid-30s. Rain tapers off and ends early this evening as the low pressure responsible for the stormy conditions moves off to the east. Overnight lows drop to around 30°F.

GFS model 500 mb height anomalies for Wednesday at 7PM, note the strong negative height anomaly over the Northeastern US and St. Lawrence Valley

Wednesday – should be a mostly sunny day, though as an arctic front hits us late in the day and in the early evening, a few snow squalls/snow bands could hit. These would be brief in nature but could impinge on visibility, making travel difficult. High temperatures should be similar to today in the mid-30s. Overnight lows will plummet quickly into the upper-teens with an Arctic air mass and northwesterly flow.

Thursday – northwesterly flow continues as strong Arctic high pressure builds. This will keep temperatures only in the upper-20s for highs under mostly sunny skies. Overnight lows in the low-20s.

Weather Prediction Center surface forecast for 7AM Friday

Friday – temperatures moderate a little bit, with highs in the low-30s as the high starts moving east. Overnight lows in the low-20s.

NYC Weather Update – Dec 10, 2019

Very mild air at the start of the week gives way to a much colder air mass as a cold front finally sweeps through later today. Drenching rains from yesterday should give way to lighter precipitation today, however, with temperatures dropping we could see some light accumulating snow by Wednesday morning. Temperatures will rebound into normal to above normal ranges after a dip into high temperatures in the 30s mid-week.

Rest of today – mostly cloudy with high temperatures peaking in the upper-50s. Long duration southerly flow ahead of an slow moving cold front has brought in a much warmer air mass to the region. Rain chances pick up in the afternoon with the front nearing and continues into the overnight hours with a couple breaks. Behind this front, much colder air rushes in with overnight lows dropping to near freezing. With precipitation continuing, this should allow for a transition to all snow. Light accumulation of around 1″ is possible, though not a lock since the ground has been quite warm for a couple days now with all the rain.

Weather Prediction Center probabilistic forecast for 1″+ accumulation of snow by 7AM Wednesday

Wednesday – snow winding down in the morning. High temperatures in the upper-30s, about 10°F below normal for this time of year. Skies clearing later in the day with overnight lows in the mid-20s.

Thursday – with a chilly start to the day, high temperatures will have a tough time getting out of the low-30s. Mostly sunny otherwise. Overnight lows in the upper-20s.

Friday – high pressure that fills in behind the cold front passing Tuesday and giving us the sunny weather Thursday eventually moves off to the northeast. Onshore flow should help moderate highs into the upper-40s. Rain chances increase with the next storm system – a possible coastal low – moving up overnight. Overnight lows in the mid-40s.

NYC (KLGA) Climatology for December

During my time taking classes as part of Penn State University’s Undergraduate Certificate in Weather Forecasting, we were taught that understanding the climatology of the location you are interested in is an important prerequisite for making accurate forecasts. This post continues on this theme, adding a climatology for December.

Other Month’s Climatologies

January
February
March
April
May
June
July
August
September
November

Station Basic Information

City Name / Station ID: New York, NY (LaGuardia Airport – KLGA)

Local Geography and Topography

Station Elevation: 10 feet above sea level.

Station Location: LaGuardia Airport (KLGA) is situated on the north shore of Queens along the East River, approximately 6 miles east-northeast of Midtown Manhattan.

KLGA’s location within the broader NYC area, as seen in a Google Maps terrain view

Important Topographical Features: New York City is located in the extreme southeastern corner of New York State, bordering suburban New Jersey and Connecticut. These suburban regions combined with those in Long Island comprise the Greater New York City Metropolitan Area, which is the most populous urban agglomeration in the United States and one of the populous urbanized areas in the world with an estimated population of 18 million. New York City itself sprawls across the coastal plain around the Hudson River estuary. The terminal moraine formed by glaciers of the last Ice Age result in a ridge of higher terrain that cuts a swath from southwest to northeast across the boroughs from northern Staten Island, northern Brooklyn, southwestern through central and northeastern Queens. Otherwise, the city itself is low lying. This ridge varies in height between 200-400 feet, rising sharply from south to north, but tapering more gently north. North and west of the city (about 30-50 miles away), lie significant elevations of the Catskills (north), Poconos (west), Taconics that are part of the broader Appalachian Mountain Range. The elevations of the lower foothills can range from 1000-1500 feet. Some of the elevations in the Poconos and Catskills, west and north of KLGA respectively, peak between 2000-3000 feet. The open expanse of the Atlantic Ocean lies south of KLGA and New York City. Long Island Sound also lies east-northeast. The vast urbanized area of the NYC metropolitan region has significant effects on local microclimates via differential heating (urban heat island effect). KLGA is in a low-lying area sensitive to UHI effects and marine influences.

Topographical map of New York State

Per the Local Climatological Data report from the National Weather Service:

On winter mornings, ocean temperatures which are warm relative to the land reinforce the effect of the city heat island and low temperatures are often 10-20 degrees lower in the inland suburbs than in the central city. The relatively warm water temperatures also delay the advent of winter snows. Conversely, the lag in warming of water temperatures keeps spring temperatures relatively cool. One year-round measure of the ocean influence is the small average daily variation in temperature.

National Weather Service – NYC Office

Wind Patterns

Below is a wind rose – you can read more about how to interpret this chart here.

Frequency (percentage) of the single most common wind direction: West-northwest (13.75%).

Directions that are most and least common: Other most common wind directions include due northwest (13.5%), due west (11%), and due southwest (8%). Least common wind directions are east-southeast (1%), due southeast (1.25%), and south-southeast (1.5%).

Direction(s) most likely to produce the fastest winds: As is the case with November, winds in excess of 21.4 knots (~25 mph) are most frequently found coming from due northwest. West-northwest, north-northwest, due northeast winds can also produce winds over 21.4 knots though less frequently.

Direction(s) least likely to produce the fastest winds: As is the case with several other months, the least common wind directions of due east, east-southeast, and due southeast also rarely seen winds in excess of 16.4 knots.

Impacts of wind direction on local weather: December’s winds build on a pattern first seen in November, where winds from the northwestern quadrant become prominent. In December, winds from due west to northwest become markedly more common, while the frequency of winds from the southwesterly quadrant continues to decrease. In addition, the frequency of winds in excess of ~25 mph (21.4 knots) from the northwesterly quadrant also increases.

Northwesterly winds bring cooler, drier Canadian air into the region following cold fronts. Winds from this direction also occur on the backside of departing coastal lows. Winds from these directions downslope coming off the higher terrain of the Catskills, and Poconos outside of the city. This can sometimes lead to warmer temperatures than would normally be expected for this wind direction as well as faster wind speeds. As with other months, northeasterly winds are usually related to backdoor cold fronts sweeping from the Canadian Maritimes, the onshore flow ahead of an advancing warm front, or a passing coastal storm to the south.

Maximum observed two-minute wind speed for the month: 38 knots (44 mph).

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth noting: December average high temperatures drop into the 40s. It’s the first month of the winter where record lows have historically dipped below 0°F at times.

DateNormal HighNormal LowRecord HighRecord LowRecord Lowest MaxRecord Highest MinNormal PrecipRecord Precip
14937711929540.121.29
24937661732510.132.22
34836691123540.131.48
44836741227590.121.76
54836692132560.131.38
64735721825580.121.29
74735751728500.121.39
84735641826520.120.94
94634661327520.132.68
10463470922530.120.96
114634671424490.122.74
12453366819530.121.32
13453363820530.123.65
144533641224510.111.75
154432671526520.121.18
164432621321470.112.39
17443261921500.111.29
184331621625470.111.29
194331571423470.111.31
20433161-216540.111.07
21433062-117500.111.92
22423069817560.111.59
23423066719540.111.45
24423072421590.121.27
25422964-110540.111.27
26412962517470.112.62
27412963920540.111.17
284129651219470.101.25
294128681222540.101.26
30412863321480.101.56
31402863313500.101.31
Range41-4928-3757-75-2-2110-3247-590.10-0.130.94-3.65



NYC Weather Update – Dec 3, 2019

A quiet, though colder than normal week lies ahead after the departure of Monday’s storm. This storm ended up not bringing the city much of any accumulating snow, though the story was quite different further north. High pressure settles in briefly before a weaker disturbance affects the area later in the week. An arctic front passes Friday, bringing a reinforcing shot of cold. Temperatures during this time will range in the low-40s.

Rest of today – mostly sunny with high temperatures in the low-40s. Winds diminishing as the low that hit us yesterday continues to pull away to the northeast. Overnight lows around the freezing mark.

Weather Prediction Center surface forecast for 7PM Wednesday

Wednesday – partly sunny with high temperatures in the low-40s. Overnight lows in the mid-30s.

Thursday – mostly sunny with high temperatures in the low-40s, and overnight lows in the low-30s.

Climate Prediction Center temperature outlook for next week. A warm up is coming after this week of below normal cold.

Friday – mostly sunny with high temperatures in the low-40s and overnight lows in the mid-20s behind the passage of a dry Arctic front.