We have a stormy start to the forecast period with the Storm Prediction Center putting us under a slight risk for severe weather this afternoon. Behind this storm, windy conditions will prevail Friday with the pressure gradient tightening between an incoming high pressure and the departing low. This pressure gradient eases Saturday as high pressure moves more directly overhead. Decent weather continues Sunday before another storm rolls in Monday. Above normal temperatures for Thursday in the low-60s. Temperatures drop below normal in low-50s this weekend before picking up Monday into the upper-60s.
Rest of today – lighter stratiform rain in the morning hours with a warm front moving through. This will be followed up by a possible round of strong to severe thunderstorms in the afternoon hours (most likely around 1-2PM). The primary risk for severe weather comes from the potential for damaging wind gusts, with very fast winds aloft potentially mixing down to the surface. High temperatures in the low-60s. Overnight lows around 40ºF as gusty winds bring in strong cold air advection. See this detailed forecast for more info about today.
Storm Prediction Center convective outlook for Thursday, showing us in a slight risk area for severe weather later today.
Friday – despite a high in the low-50s, strong winds around a deepening low will make it feel significantly cooler. Clouds should gradually diminish during the day. Overnight lows cool, in the upper-30s.
Weather Prediction center surface forecast for 8AM Friday. A strong low pressure cetner is indicated tracking northeast out of Maine.
Saturday – winds ease as an area of high pressure moves more directly over us. High temperatures should range in the mid-50s with plenty of sun. Overnight lows will be in the mid-40s.
Sunday– clouds increasing with high temperatures in the upper-50s. Overnight lows will warm into the low-50s.
It’s been nearly three months since my last detailed forecast, so forgive me if I’m a bit rusty. Thursday in NYC will be an active weather day. A rather complex picture will unfold, with a warm front passing early, then a triple point passing nearby, followed by a trailing cold front that could bring the potential for thunderstorms later in the afternoon. Strong winds will be in the picture, and these winds will persist (if not increasing in intensity) into Friday.
My Forecast High: 61°F | Low: 49°F | Max sustained winds: 33 mph | Total precipitation: 0.24″ – verification will come from METAR data for the period between 2AM Thursday and 2AM Friday (06Z Thursday to 06Z Friday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.
Verification High: 58°F | Low: 44°F | Max sustained winds: 44 mph | Total precipitation: 0.26″ – this ended up being a decent forecast for the high temperature. The cooler scenario depicted by NAM ended up being correct, and siding with a more conservative high was the right call. Amazingly, I was only 0.02″ off from the precipitation total! However, in my focus on that aspect of the forecast, I neglected some basic signs about the winds and low temperatures. These two ended up being connected. Winds in the wake of the cold front were likely boosted by subsidence (sinking cold air), and these provided a boost to cold air advection, leading to the low actually occurring around midnight, as opposed to the overnight hours going into the day. This was actually apparent in the statistical guidance, but was something I failed to spot. Lesson learned: never forget to check the entire data set – and when cold fronts with convective activity swing through, consider being aggressive about the winds associated both with the storms themselves, and behind the front.
Weather Prediction Center surface forecast for 2AM Thursday
Weather Prediction Center surface forecast for 8AM Thursday
Weather Prediction Center surface forecast for 2PM Thursday
Weather Prediction Center surface forecast for 8PM Thursday
Synoptic Setup At the surface, two lows will be influencing the picture, one centered further north over Ontario, and another tracking closer to the area. Early in the forecast period, a warm front associated with secondary low pushes through. This could lead to some lighter stratiform rain due to isentropic (overrunning) lift. After this, a triple point passes just north of the area in the afternoon, and this should provide a locus for some some enhanced lift. This will be followed shortly thereafter by a trailing cold front passing through in the late afternoon hours. This cold front could trigger some thunderstorms with NAM showing some instability, though GFS isn’t as aggressive.
GFS is less bullish on showing a saturated layer at 850 mb. NAM does have wetter conditions which explains why the QPF totals are higher with this model. One thing both models agree on is the presence of strong winds at this level, anywhere from 35-50 knots. Should moisture content be better upstream, we should see effective moisture transport from this low-leve jet.
Further up in the atmosphere at 500mb, a shortwave trough attached to a closed 500 mb low over Ontario/Quebec border is forecast pivot through the region. Models are suggesting very strong positive relative vorticity associated with this feature. This should lead to ample divergence aloft and enhanced lift potentially supportive of organized convective activity. Low-mid level lapse rates due to the presence of the closed low could also be decent enough to support convection.
Finally, at the 300 mb level, a jet streak with very fast core winds in excess of 140 knots looks to set up over the Ohio Valley. We will be in the favorable left exit region of this jet streak, a set up that further favors enhanced divergence aloft. This should likewise increase lift in the atmosphere. This is reflected by SREF that shows a decent probability of moderate to strong omega over the region during the passage of this storm.
NAM model 850 mb relative humidity and winds valid 2PM Thursday
GFS model 500 mb height and relative vorticity valid 2PM Thursday
GFS model 300 mb height and winds valid 2PM Thursday
High Temperatures There was a large spread between NAM and GFS statistical guidance, with NAM much cooler and coming in only in the mid-50s, while GFS came in with low-60s. Given that there should be some warm air advection with southerly winds ahead of the cold front, I tend to buy more into the warmer end of the guidance envelope. However, both sets of statistical guidance also show a period of winds backing to the ESE in the afternoon which would bring a characteristically onshore flow and introduce a marine air mass. That might cut into overall high temperatures. Some limited evaporational cooling and clouds could also keep a cap on temperatures warming too much. With all this in mind, I’m going with a high temperature of 61ºF.
Low Temperatures There is likewise a big spread between GFS and NAM on low temperatures. NAM is close to climatological averages for low temperatures in the low-40s while GFS is a full 10ºF warmer. Southerly winds are indicated during most of the overnight hours seem to suggest erring on the warmer end of guidance. I think that EKDMOS 50th percentile of 49ºF seems reasonable.
GFS MOS guidance for KLGA
NAM MOS guidance for KLGA
Max Sustained Winds Both GFS and NAM indicate that a well-mixed layer will form by the late afternoon. As referenced above, winds aloft at 850 mb will be quite strong. This mixed layer should enable these strong winds to work their way down to the surface. This will be aided by any downward momentum transfer effected by falling rain. Layer mean wind analysis shows max wind speeds well above statistical guidance, and I few reasons to disagree with this, so I’m calling for max sustained winds of 29 knots, or 33 mph.
GFS forecast sounding for KLGA valid 2PM Thursday. The presence of a well mixed layer is apparent from the surface up to just above 850 mb. This should allow for strong winds at this layer to mix down to the surface, something that would be enhanced by precipitation drag effects from rain falling.
Total Precipitation There is high bust potential for total precipitation forecasts here with convective precipitation in the picture. The earlier light stratiform precipitation with the warm front probably will not result in too much overall precipitation. However, just one strong thunderstorm/heavy downpour could wreck any forecast here. The blended GFS/NAM mean is about 0.25″ and SREF probabilities for precipitation greater than this are not a lock, despite the overall synoptic picture showing decent support for good lift. SREF gradients are quite sharp going south. In addition, onshore winds that are possible could help stabilize the area by bringing in a cooler marine layer. I don’t feel confident that we’d see more than 0.25″ unless a convective burst hits KLGA head on, so I am going with 0.24″ as a conservative play.
A retrograding low will bring increasing clouds, wind and rain to end the week. This low will be blocked from moving east until late Friday. High pressure will move in Saturday and should dry things out, and bring more sun. A weak cold front is forecast to pass through Sunday. Some rain will be possible with this frontal passage. Temperatures during this period should remain at or above normal for this period in the mid-50s.
Rest of today – increasing clouds with a low retrograding west towards the area. High temperatures in the mid-50s. Winds will pick up also as the pressure gradient builds between the retrograding low and high pressure to the west. Overnight lows should be around the mid-40s.
Friday – chances for rain, mostly in the morning hours, with high temperatures in the mid-50s under mostly cloudy skies. Rain chances will diminish as this low finally pulls off to the south. Overnight lows again in the mid-40s.
Weather Prediction center surface forecast for 2AM Friday
GFS model 500 mb height, vorticity and wind forecast valid 10AM Thursday. Note the presence of the closed upper low offshore of the Northeast, with an omega blocking pattern over the eastern Atlantic (two lows, with a ridge in between, literally looks like the Greek letter for omega)
Saturday – as high pressure moves in, we’ll see a better day with partly to perhaps mostly sunny skies and high temperatures in the upper-50s. Overnight lows will be in the mid-40s.
Sunday– a weakening cold front may bring a chance for showers, but ahead of this, temperatures will be mild in the upper-50s. Overnight lows will warm into the mid-40s.
The active weather pattern we’ve seen so far this week with alternating days of sun and rain continues with two more storms coming for the end of the week into the weekend. This time around, the rainy days will outnumber the sunny ones. We will start off with a beautiful Thursday before a weaker storm impacts the area tomorrow. A more significant system will move through later Saturday into Sunday. Temperatures during this time will range around normal to above normal in the 50s.
Rest of today – high pressure will be in control of the weather today, yielding a sunny day with temperatures steadily rising into the upper-50s. Overnight lows should be around the mid-40s.
Weather Prediction Center surface forecast for 8AM Friday
Friday – clouds will build overnight into the day and by the morning hours a weak area of low pressure will be moving through the area. We can expect some light rain with this system in the morning, rather than a full day washout. Clouds will remain through the rest of the day even after the system clears and rain stops. High temperatures around 60°F. Overnight lows will be in the low-40s as a result of radiational cooling as high pressure briefly builds.
Saturday – with high pressure positioned to our north to start, northeasterly flow will keep temperatures cool in the low-50s. A stronger storm system with origins in the lee of the Rockies will be moving towards us throughout the day. A warm front will slowly move up from the south bringing a steady rain ahead of it. Overnight lows will be in the mid-40s as rain continues.
GFS 500 mb height and relative vorticity valid 8PM Sunday. Note the presence of a closed 500 mb low over Michigan and southern Ontario generating lots of positive voriticity around it. This will provide divergence and lift at the upper levels to support the storm hitting us Sunday.
Sunday– With the warm front making its way through and flow turning towards the south/southwest, temperatures should rise to around 60°F. However, rain chances are expected to continue throughout the course of the day before tapering off overnight. Overnight lows will warm into the upper-40s.
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.
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.
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.
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.
NAM 500 mb heights and vorticity valid 4PM Saturday
NAM forecast 300 mb heights and wind valid 1PM Saturday
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.
NAM MOS forecast for KLGA
GFS MOS forecast for KLGA
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.
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.
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.
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.
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.
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.
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.
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 November.
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.
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 (12%).
Directions that are most and least common: Other most common wind directions include west-northwest (10%), due west (8.5%), and due southwest (8.25%). Least common wind directions are east-southeast (1.5%), due southeast (1.75%), and south-southeast (2.75%).
Direction(s) most likely to produce the fastest winds: Winds in excess of 21.4 knots (~25 mph) are most frequently found coming from due northwest. West-northwest, north-northwest, due northeast, east-northeast, and due south directions can also see less frequent winds over 21.4 knots.
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: November wind patterns are a marked shift from the prior two months. Winds coming from the northwestern quadrant become prominent. Meanwhile, winds from the south and southwest decline in frequency.
In general, northwesterly winds bring cooler, drier Canadian air into the region following cold fronts. Northwesterly winds will tend to warm slightly because of compressional warming as they 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. Northeasterly winds, on the other hand, are often 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.
The pattern of winds in November suggests the prevalence of classic frontal systems moving through, where warmer southwesterly winds precede the passage of a cold front, behind which strong, gusty westerly and northwesterly winds pick up. Northeasterly winds are, as pointed out above, a sign of passing coastal storms.
Maximum observed two-minute wind speed for the month: 41 knots (47 mph).
Temperature and Precipitation Averages/Records
Temperature units are in Fahrenheit and precipitation is in inches.
Worth noting: Average high temperatures in November start falling into the 50s, while lows fall into the upper-30s. November is the first fall month in which no record high temperature exceed the 90°F.
This weekend starts off with fair and dry weather. A storm developing along the Gulf Coast of Texas, tracking north along the Mississippi and Ohio Valleys into the Great Lakes, then east towards our area will bring a prolonged period of steady rain on Sunday. As of 11AM today, National Hurricane Center has designated this storm as Tropical Depression Seventeen. This storm should pull out of the area before the start of next week. Temperatures during this period should be at or above average for this time of the year in the low-mid 60s.
Rest of today – partly sunny to mostly cloudy with a cold front weakening, then stalling and returning north as a warm front. High temperatures in the mid-60s. Overnight lows in the low-50s with decreasing clouds as high pressure builds in.
Weather Prediction Center surface forecast for 8AM Saturday
Saturday – high pressure builds briefly and should give us mostly sunny skies with high temperatures in the mid-60s. Overnight lows in the low-50s with increasing clouds and chances for rain.
Sunday – much like last weekend, a storm with tropical origins will bring rain and lots of moisture to the area. The extratropical remnants of Tropical Depression Seventeen will track north towards the Great Lakes during this period. A warm front attached to it will bring a shield of steady stratiform rain over the area. Mostly cloudy with highs in the upper-60s as winds turn to the south. Steady rain continuing into the early overnight hours until the storm’s trailing cold front finally sweeps through and drier air works in. Lows in the mid-50s.
NAM model output for relative humidity and wind at 850 mb for 5PM Sunday. Note the nearly saturated nature of the lower levels of the atmosphere.
NAM model output for wind at 850 mb for 5PM Sunday. Note the high wind speeds at this level, indicating the presence of an 850 mb low-level jet (LLJ)
NAM model output for precipitable water at 2PM Sunday. Note the high values above 1.50″. This makes sense, given the tropical origins of the storm that will impact us Sunday.
Projected track of Tropical Depression Seventeen
Monday – high pressure and calmer conditions return with highs in the mid-60s and mostly sunny skies. Overnight lows in the mid-50s with mostly cloudy skies.
