An arctic front swings through today, bringing a blast of cold air behind it going into the weekend. Temperatures will rebound dramatically going into the start of next week with an approaching storm system turning winds to the south. We’ll see high temperatures going from the upper-30s to the mid-50s by Monday.
Rest of today – mostly cloudy with a high temperature in the upper-40s. Chance of rain this evening with the passage of an arctic front. Overnight lows cooling into the low-30s with clearing skies.
Weather Prediction Center surface forecast for 7AM Saturday
Saturday – high pressure builds behind the arctic front bringing sunny skies but a much colder polar airmass with high temperatures struggling to hit 40ºF. Overnight lows drop into the mid-20s.
Sunday – high pressure center moves off to the east, allowing for warmer return flow from the south. This should allow temperatures to be a touch warmer than Saturday, in the low-40s. Overnight lows are expected to bottom out around 40ºF before actually rising due to an incoming storm system turning winds to the south.
GFS model output for 1PM Monday, a low-level jet at 850 mb with winds in excess of 40 knots is evident, along with pretty high values of relative humidity.
Monday– high temperatures continue to climb into the mid-50s with deep layer south-southwesterly winds. Increasing chances for rain as a cold front approaches from the west. Heavy rain is possible given a possible tropical moisture connection. Overnight lows barely moving into the low-50s.
Thursday will probably end up being the best day of the week. High pressure will be in control from most of the period allowing for a sunny day with seasonable temperatures. Winds may be stiff overnight as well as late Thursday night into Friday. Rain associated with a low pressure system moving in will hold off until Friday.
My Forecast High: 50°F | Low: 38°F | Max sustained winds: 20 mph | Total precipitation: 0.00″ – verification will come from METAR data for the period between 1AM Thursday and 1AM Friday (06Z Thursday to 06Z Friday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.
Verification High: 53°F | Low: 39°F | Max sustained winds: 14 mph | Total precipitation: 0.00″ – high temperatures ended up being a bit warmer than expected, more towards the EKDMOS 90th percentile range. I think this had to do with the fact that overnight lows were warmer (did a good job edging up on that), and because northwesterly winds backing to the west introduced an element of downsloping. Compressional warming from this was not offset by any other temperature advection, and allowed for temperatures to hit exactly the average high for this time of year. The other aspect I missed on was max wind speed. Here, looking at surface analyses from yesterday compared to the forecast models, there was a larger distance between the center of high pressure and the departing coastal low, leading to a weaker than expected pressure gradient early. The fastest winds ended up being clocked from the southwest as a result, ahead of the approaching cold front.
Weather Prediction Surface forecast for 7AM Thursday
Synoptic Set Up The forecast period starts with a north-south elongated high pressure over much of the Eastern US, centered over the Ohio Valley. The coastal low that impacted the area Monday is still forecast to linger southeast of Nova Scotia. A decent pressure gradient will be in place at the beginning of the forecast period as a result (high pressure measuring ~1025 mb, low ~998 mb). An approaching low pressure center will travel northeast from the Midwest across the Great Lakes into Southwestern Quebec during the forecast period. The low will continue intensifying and will erode the northern part of the high pressure center. Precipitation associated with this low won’t reach NYC until Friday, though. The primary influence of this low for the forecast period will be in shifting winds from the northwest to the southwest.
Above the surface, at 850 mb winds are forecast to start off northerly, between 20-25 knots. Wind speeds ease as they continue backing from north to west, then pick up in intensity to 30 knots from the southwest. Dry air, though moistening, will prevail at the 850 mb level throughout the forecast period. At 500 mb, slight ridging takes place during the day, then increased vorticity starts to pivot through ahead of the primary shortwave axis associated with the maturing surface low over the Great Lakes. Finally, at 300 mb we’ll start in the entrance region of a jet streak, then followed by a period of calm before the exit region of another jet streak approaches from the west.
GFS 2-meter (surface temperatures) in contours, and 10-meter wind barbs, valid 1AM Thursday. This shows a decent environment for cold air advection with winds at almost perpendicular angles to the temperature contours, pointing from colder to warmer temperatures. However, wind speeds are modest so the strength of an CAA would not be strong.
By 1AM Friday, GFS 850 mb height, moisture, and winds show depict winds shifting to the southwest, but the air above the surface will still be quite dry.
High Temperatures Statistical models (GFS, NAM, NBM) are good agreement, within a degree or two of 50°F. EKDMOS at 12Z similarly showed a tight band around 50°F, though this widened a bit at 18Z. 50°F is just a touch below climatological norms. I’m not seeing too many surprises here. Moisture is lacking for clouds to form until late in the period after the sun goes down. As winds shift to the southwest later in the day, they will largely parallel local isotherms so there won’t be appreciable warm air advection to look at either. I think 50°F is a good bet here.
Low Temperatures Stiff winds from the northwest will offset relatively clear conditions in terms of radiational cooling. Cold air advection (CAA) is looking modest. While the wind direction is looking to cut at almost perpendicularly across temperature contours from cold to warmer temperatures, wind speeds aren’t going to be sustained at strong speeds for too long. I think 38°F is reasonable because statistical guidance is only a degree cooler or so, with EKDMOS showing this temperature at about the 50th percentile.
GFS MOS forecast
NAM MOS forecast
Max Sustained Winds 850 mb winds have two peaks and so do surface winds in EKDMOS: one early, then one late in the forecast period. I tend to concur the fastest winds will come early in the forecast period, since northwest winds are climatologically favored to produce fast high speeds. However, I also don’t see evidence to support mixing of strong winds aloft down to the surface. One wrinkle is if the pressure gradient ends up being tighter between the lows and the high pressure, as that would drive stronger than anticipated winds. 20 mph is above statistical guidance, but not that much higher.
NAM forecast sounding for KLGA valid 7PM Thursday. Distinct moistening of the mid and upper levels is evident with the dew points (green line) nearly overlapping the environmental temperature (red line). Lower levels are still markedly drier.
Total Precipitation This is the easiest part of the forecast as strong high pressure and dry air throughout most of the atmospheric column for most of the day makes it nearly impossible for precipitation to materialize.
Seasonable temperatures to start the weekend won’t last as a cold front dives through and Canadian high pressure builds behind it Saturday. Cooler flow from the northeast will set up as the high sets up north of us and moves east. Winds will increase in intensity as an approaching coastal storm from the south leads to a tighter pressure gradient. This storm is currently tracking well offshore. However, we may still see some rain from the outer bands of the storm Monday. Aside from Saturday, temperatures will largely range 10-15°F lower than normal during this period.
Rest of today – sunny with high temperatures in the low-50s. Overnight lows around 30°F with winds increasing.
Weather Prediction Center surface forecast for 7AM Saturday
Saturday – with high pressure in control, we should see sunny conditions, but temperatures will be cooler with steady northeast winds of 20-25 mph. High temperatures around 40°F. Overnight lows in the low-30s.
Sunday – increasing clouds with high temperatures in the low-40s. Chances for rain possibly going overnight into Monday. Low temperatures in the upper-30s.
GFS model output for 7PM Monday, depicting a glancing blow from a coastal storm moving northeast well offshore of the area.
Monday– chances for showers with high temperatures in the mid-40s. Mostly cloudy otherwise. Overnight lows around 40°F. Persistent northeast flow may lead to coastal flooding concerns.
Very cold temperatures kick off the weekend, followed by a return to milder temperatures. The reprieve is brief though, with the outlook for next week looking equally cold, especially on the heels of another storm system possibly impacting the region Monday night through Tuesday. Behind this, a reinforcing blast of cold air will reintroduce much below average temperatures to the region. High temperatures will start off ~15°F below normal for this time of year, the moderate to just a couple degrees below normal by Veterans Day.
Rest of today – mostly sunny, strong winds from the northwest ranging 25-35 mph with higher gusts. High temperatures only in the low-40s with this cold wind. Overnight lows may approach record lows, in the upper-20s. This will be aided by winds dying down and clearing skies as the high pressure center shown below continues to build and move closer to us. This should allow for potentially strong radiational cooling before dawn.
Weather Prediction Center surface forecast for 7AM Saturday
Saturday – very cold start to the day, temperatures will struggle to climb into the low-40s, close to the record coldest high temperatures for this time of year. The plus side will be calmer winds, eventually shifting to the southwest as the high pressure above moves off to the east. This should help “warm” things up a bit, with overnight lows recovering into the mid-30s.
Sunday – much warmer with high temperatures in the low-50s despite more cloud cover, both due the influence of southwesterly flow. Overnight lows warming into the mid-40s.
GFS model 2 meter above ground level temperature anomalies for 7AM Saturday
Corresponding GFS 500 mb heights, vorticity. Troughing at the mid-levels here will allow for the continued influx of cold air into the Eastern US. Note how the western US, which is under a 500 mb ridge is expected to experience above normal temperatures.
Climate Prediction Center temperature outlook for Nov 13-17, showing a very high probability for continued colder than average conditions for much of the Eastern US.
Monday(Veterans Day) – partly sunny with high temperatures in the mid-50s. Overnight, a system will approach from the west and could bring rain with lows bottoming out in the low-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 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.
NASA satellite Moderate Resolution Imaging Spectroradiometer (MODIS) image of the Getty Fire on October 28, 2019, shortly after the fire began. Smoke is visible billowing offshore to the south.
“Extremely critical” fire weather conditions are forecast to impact a large part of Southern California, with the strongest Santa Ana wind event of the year possibly occurring Wednesday before some improvement Friday. Affected areas include the entire Los Angeles metro area, where the Getty Fire continues to burn. Wind gusts at or above 70 mph in higher elevations coupled with very dry air (relative humidity less than 10%) will make it incredibly difficult to make any progress towards containing this fire, and presents a high risk for new fires to start.
Weather Prediction Center surface forecast for 5AM PDT Wednesday
Weather Prediction Center surface forecast for 5PM PDT Thursday
Synoptic Set Up Believe it or not, the strength of the Santa Ana winds will be tied directly to the very cold air mass moving into the Great Basin. A low along the leading edge of this cold air has caused a massive ongoing snowstorm across much of Colorado. Behind this, cold, stable air will move in along with a strong area of high pressure with surface pressures forecast above 1040 mb. At the same time, a coastal low will sweep south along the northern and central CA coast along the leading edge of the colder air accompanying this high pressure. This will set up a tight pressure gradient at the coast favoring strong offshore east-northeast winds, with local forecast offices citing model output of as much as 10-12 mb gradient from Barstow to LAX, over a distance of only 200 miles.
Impacts With the tight pressure gradient forecast above, forecasters are calling for the possibility of gusts in excess of 70 mph in the mountain ranges near the coast with, with lower wind gusts of 35-40 mph at lower elevations. The influx of cold air already less capable of holding moisture that will downslope off coastal ranges and towards the ocean will yield relative humidities of 3-8% (as the air dries further during downsloping due to compressional warming). Santa Ana winds of this magnitude along with such dry conditions easily warrant the Storm Prediction Center designation of extremely critical fire weather.
GFS model output forecast sounding for KLAX at 11AM PDT Wednesday. Note the huge gap between the green dew point line and red environmental temperature line at the surface (5°F dew point, 64°F temperature). This will result in extremely low relative humidity values.
Storm Prediction Center fire weather outlook for Wednesday
Timing Peak potential for winds appears to be during the overnight hours through morning and early afternoon Wednesday. This is the time when the pressure gradient will be maximized. The high pressure referenced above is forecast to weaken overnight into Thursday, while the coastal low should also dissipate. The high pressure is forecast to continue weakening into the weekend, thus ending the most dangerous period of fire weather.
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.
Soaking rains from Wednesday’s nor’easter have long since exited east, yet we will continue to feel the impact of this low with windy conditions to start the weekend. As the low continues moving east, an area of high pressure will build in and take its place. Winds will relax and we should enjoy a nice, sunny day for Saturday. Clouds are expected to build back in as a potential extratropical remnant low of what could become Subtropical Storm Nestor this weekend pass south of the region. Temperatures during this period are expected to be at or just below normal in the low-60s with a warm up going into next week.
Rest of today – windy conditions continue as the pressure gradient between a building area of high pressure to the west and the low that brought us rain Wednesday which is now over the Canadian Maritimes. High temperatures around 60°F with partly cloudy skies. Overnight lows expected to be quite cool, in the low-40s with skies looking to clear up and winds dying down – conditions that could lead to some strong radiational cooling.
Weather Prediction Center surface forecast for 8AM Saturday
Saturday – high pressure builds in and gives us a sparkling, sunny, fall day with high temperatures in the low-60s. Overnight lows milder around 50°F.
Sunday – although the extratropical remnants of what could be Subtropical Storm Nestor are forecast to pass well south of the area, this storm is expected to have a broad cloud shield to its north, and some outlying rain bands could even result in a couple scattered rain showers for the area. High temperatures should be similar to Saturday in the low-60s, because even with clouds, overall flow will be from the south. Overnight lows around 50°F again.
GOES satellite imagery of Potential Tropical Cyclone Sixteen
National Hurricane Center’s latest forecast track guidance for this storm
Monday – with this low exiting east, we’ll see more southerly flow ahead of the next incoming storm system. High temperatures should respond by warmingin into the upper-60s with mostly sunny skies. Overnight lows in the mid-50s with mostly cloudy skies.
The persistent storm off the Northeast US coast finally starts to move east. This storm has defied the odds, increasing in organization and intensity overnight, and has just been named Subtropical Storm Melissa. We will enjoy a spell of warming temperatures (from the low-60s into the low-70s) and dry weather leading into early next week as the region sits between the exiting storm and another strong low over the interior of North America. A couple of frontal boundaries will pass over, however, these will be starved of meaningful moisture and should not result in any rain.
Rest of today – mostly cloudy with high temperatures in the low-60s. Overnight lows in the low-50s as winds start to shift to the north due to Subtropical Storm Melissa continuing to move to the east.
Satellite imagery of the incipient Subtropical Storm Melissa
Saturday – mostly cloudy with high temperatures warming to around 70°F. Winds will diminish as Subtropical Storm Melissa finally starts moving east. Overnight lows in the low-50s.
NAM model output for 500 mb heights and wind at 2PM Saturday. A significant closed upper-low, largely cut off from westerly steering currents, will be over the Upper Midwest. A slow-moving, strong occluded low will accompany this upper low at the surface. East of this, there will be some slight ridging, keeping our weather fair.
Sunday – a weakening cold front moves through, but with lack of appreciable moisture, there shouldn’t be any rain. High temperatures will be similar to Saturday, around 70°F, with m ore sunshine expected. Overnight lows in the mid-60s.
Weather Prediction Center surface forecast for 8AM Sunday
Monday (Columbus Day) – the cold front that moves through overnight into Sunday is expected to stall and become stationary. A surface low is forecast to form and move along this boundary near the coast, leading to increasing clouds with high temperatures in the low-70s. Overnight with lows dropping into the upper-50s.
A distinct fall feel this week with grey skies the norm and spotty rain chances for many of the days. A coastal storm brewing off the Southeast coast is forecast to track north and then northeast. National Hurricane Center is tracking this system as it has some potential to acquire subtropical characteristics. This will be a slow moving storm that will bring a long period of northeasterly winds to the area.
Rest of today – mostly cloudy, with highs in the upper-60s. Overnight lows in the upper-50s.
Weather Prediction Center surface forecast for 8PM Wednesday
The developing coastal storm depicted above.
Showers and thunderstorms over the western Atlantic between the southeastern coast of the United States and Bermuda are associated with a broad, non-tropical area of low pressure. This system is forecast to move northward or northeastward and could acquire some subtropical characteristics off the east coast of the United States by the end of the week.
Wednesday – although the storm referenced is forecast to remain well offshore, outer rain bands from it could bring showers to the area along with persistent northeast winds. These wind are anticipated to be on the strong side, steadily in the mid-teens with gusts in the 25 mph range. Mostly cloudy with highs around 60°F. Overnight lows in the low-50s.
Thursday – rain chances continue as the storm develops and becomes a closed low. Mostly cloudy with highs in the low-60s. Winds will become blustery from the northeast around 15 mph with higher gusts. This will be due to the increasing pressure gradient between the deepening low and high pressure over eastern Quebec. Overnight lows in the low-50s.
GFS model output of 850 mb winds and relative humidity. The coastal storm continues to spin off the Northeast coast, although its center remains well offshore (just above the pivotalweather logo in this frame).
Friday – rain still lingers though the storm starts to finally make some eastward progress as a trough approaches from the west. High temperature remain in the low-60s with mostly cloudy skies. Overnight lows in the upper-50s as warmer southerly flow starts to work into the region.
