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.
This Saturday will likely start off with the coldest overnight low temperatures so far this season for NYC. Strong high pressure will be moving in from the west overnight and during the day, the center of this high pressure will be passing almost directly overhead. As a result, we should see a sunny day with diminishing winds, though high temperatures will be much below normal (69°F) with the day starting off pretty chilly. Quite a contrast between this past Wednesday when we set a new daily record high across the city with temperatures peaking at 92-93°F! Autumn is certainly in the air.
My Forecast High: 61°F | Low: 48°F | Max sustained winds: 14 mph | Total precipitation: 0.00″ – verification will come from METAR data for the period between 2AM Saturday and 2AM Sunday (06Z Saturday to 06Z Sunday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.
Verification High: 60°F | Low: 46°F | Max sustained winds: 20 mph | Total precipitation: 0.00″ – Temperature forecast turned out to be pretty good, especially high temperatures. Off by 2°F on low temperatures, which ended up 1°F colder than statistical guidance. I believe this was due to slightly stronger cold air advection than expected leading into the forecast period. Off by 6 mph for max sustained winds, which qualifies as a minor bust. The highest wind speed direction was northeast. Judging by METAR data, winds were coming form this direction sometime between 7-8AM Saturday. I think it’s possible that the pressure gradient was tighter than forecast the day before, which would have resulted in the potential for faster winds like these.
Weather Prediction Center surface forecast for 2PM Saturday
Synoptic Set Up A strong area of high pressure is forecast to be the dominant feature at the surface for much of the Northeast, Mid-Atlantic, and Ohio Valley during the forecast period. The center of this high pressure will be moving east during this time and will be nearly overhead for the hours of peak solar heating tomorrow. This high pressure will be accompanied by a dry airmass throughout nearly the entire atmospheric column. Reference the images below, which show NAM model output of relative humidity and winds at 300 mb, 500 mb, and 850 mb respectively. The brown hues shown indicate very dry conditions.
High Temperatures GFS, NAM, and NBM are in good agreement that tomorrow will be a much below average day in terms of high temperatures. These forecast sources depict high temperatures ranging from 58-62°F, which is 7-11ºF below normal for this time of year. They also show winds that are veering from northerly to east-southeast, which makes sense given the forecast position and track of the high pressure center. Although northeasterly and easterly are onshore wind directions, the near surface layer of the atmosphere is forecast to start off so dry that it would take quite a while for moisture off the ocean to make an impact and produce clouds that could eat into high temperatures. Furthermore, sea surface temperatures at this time are actually ranging in the upper-60s, so onshore flow should actually serve to bring warmer air in. EKDMOS 50th percentile for high temperatures is about 60°F. NAM is a touch cooler at 58°F while GFS and NBM call for 62°F. NAM seems to suggest slightly more cloudiness than GFS. I’m going with a high of 61°F, which I think is a reasonable balance that incorporates the data points above.
Low Temperatures Just as is the case with high temperatures, statistical guidance similarly shows that low temperatures could be as much as 8°F below normal for this time of year. These temperatures are more typical of the end of October. This is a result of decent cold air advection leading into the beginning of the forecast period. Clear and dry conditions should carry though the overnight hours. However, winds should be strong enough so as to limit radiational cooling. EKDMOS has 47°F as the 10th percentile, and 50°F as 50th percentile so going with 48°F seems plausible when considering that statistical guidance is nearly unanimous calling for 47°F as the low.
NAM MOS forecast, initialized at 8AM Friday
GFS MOS forecast, initialized at 2PM Friday
Max Sustained Winds Climatologically, winds during October can be quite strong from the northeast, but easterly to southeasterly winds are typically the weakest. Since the center of the high pressure should be moving overhead during the forecast period, the pressure gradient should be decreasing, leading to diminishing winds. Statistical guidance looks on point calling for peak winds at the beginning of forecast period. Even with a well-mixed layer forecast to form during the afternoon tomorrow, winds aloft will be weak, so wind speeds should be subdued. NBM came in with max wind speeds well below the other statistical guidance at only 6 knots. EKDMOS 50th percentile is about 10 knots, thus a forecast of 12 knots here should be OK.
GFS model forecast sounding for 2PM Saturday
Total Precipitation This is the easiest part of the forecast as strong high pressure and very dry air throughout most of the atmospheric column makes it nearly impossible for precipitation to materialize.
Strong high pressure and sunny weather will be the main theme this weekend. Despite the sun, we do have a chance to see the coldest overnight temperatures so far this season tonight into Saturday. High temperatures start to warm from the 60s to the low-70s by the second half of the weekend and to start next week as the high pressure progresses east and we get warmer southerly return flow before the next storm system approaches Monday.
Rest of today – sunny with high temperatures in the mid-60s. Breezy with a refreshing northerly wind, 15-20 mph with higher gusts due to the relatively tight pressure gradient between the high pressure building moving in from the west and the low that brought us rain yesterday continuing to move offshore. Cold overnight, with lows in the upper-40s. Frost advisories and freeze warnings are up for many areas of upstate New York not too far from us.
850 mb winds as indicated by GFS model for 8AM today, indicating the presence of strong winds of 30-40 knots just above the surface.As the day progresses, the near-surface layer up to 850 mb is forecast to become well-mixed, and this will allow the faster winds above to reach the surface.
Saturday – a sparkling, sunny fall day with high temperatures in the low-60s. Wins will calm also. Overnight lows in the mid-50s with increasing clouds.
Weather Prediction Center surface forecast for 8AM Sunday
Sunday – the cloud shield preceding an incoming storm system will continue moving in Sunday resulting in partly sunny skies. High temperatures will warm to around 70°F as winds turn to the south. This is due to the high pressure exiting east (clockwise flow around this) as well as winds ahead of an approaching cold front. Overnight lows in the low-60s.
Monday – mostly cloudy with chances for rain increasing later in the day. High temperatures in the mid-70s. Heavier rain accompanying the passage of a cold front overnight with lows dropping into the upper-50s.
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 October.
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 southwest (9%). Note: due northeast is basically co-equal most common wind direction, perhaps only off by a fraction of a percentage point.
Directions that are most and least common: Other most common wind directions include due northeast (9%), due northwest (8.75%), and west-northwest (8.25%). Least common wind directions are east-southeast (1.8%), due southeast (2.75%), and due east (3%).
Direction(s) most likely to produce the fastest winds: Winds of 16.5-21.4 knots 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: October’s wind profile is a continuation on the trend established in September where wind frequencies begin to be distributed more evenly across the compass and less focused in the south. Winds from the northwest quadrant continue to increase in frequency, along with the frequency of the fastest winds coming from these directions. Northeasterly winds still figure prominently, though slightly less so than in September. Curiously, while southerly winds generally decreased in frequency, due southwest winds tick up slightly compared to September.
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. Southwesterly winds are still capable of bringing in oppressive heat, as seen in the temperature section below.
Maximum observed two-minute wind speed for the month: 56 knots (64 mph) – this is the fastest recorded two-minute wind speed for any calendar month.
Temperature and Precipitation Averages/Records
Temperature units are in Fahrenheit and precipitation is in inches.
Worth noting: Even though average high temperatures in October fall into the 60s, it’s still possible to see summer-like warmth – you can see this from the record high of 95°F, set anew in 2019, and that record highs can reach into the mid-80s until late in the month. Overnight lows start to fall into the 50s and end up in the 40s by the end of the month!
This week will see a wild temperature swing that will take us into the upper-80s, giving us a last taste of summer, followed up by a plunge into decidedly fall-like temperatures barely in the upper-60s. Friday night in particular looks like it could be the coldest yet this season, with overnight lows possibly dipping below 50°F. Temperatures start to recover over the weekend to around normal for this time of year around 70°F.
Rest of today – partly sunny with high temperatures warming into the upper-70s, near 80°F. A warm front is forecast to push through and winds will be coming from the southwest, ushering in some renewed warmth. Overnight lows around 70°F.
Weather Prediction Center surface forecast for 8AM Wednesday
Wednesday – with a warm front passing Tuesday, and high pressure setting up over the Southeast US, warm air will be surging from the southwest towards the region. This should allow high temperatures to rise well into the upper-80s and possibly close to 90°F. A cold front will be approaching from the north Wednesday night, bringing along rain and thunderstorms. Temperatures will cool off quickly with the rain and the cold front, dropping into the upper-50s.
Thursday – much cooler with high temperatures only reaching into the low-60s. Rain chances linger during the day with the cold front stalling out south of us and another low pressure center pushing east. Overnight lows not much cooler than daytime highs, around 60°F as rain chances continue.
GFS model output for precipitation, 1000-500 mb thickness, valid for 10AM Friday. Note the relatively closely packed black lines (isobars) between the high pressure centered over Wisconsin and the Low off the coast of Nova Scotia. This pressure gradient will deliver some windy conditions Friday.
Friday – conditions should clear up as the low pressure responsible for rain on Thursday moves off to the east. A tight pressure gradient is forecast to form between this low and a high pressure center building over the Great Lakes. This should result in a windy day, with high temperatures bouncing back into the mid-60s. Overnight lows are forecast to drop to around 50°F with the influence of the much cooler continental polar airmass and north/northwesterly winds.
High pressure and fair weather will get punctuated with the passage of a cold front scheduled to push through overnight into Sunday. This front could touch off a few thunderstorms. Temperatures during this time will be slightly above average in the upper-70s. A cooler airmass should finally move in Monday with more easterly onshore flow.
Rest of today – sunny with high temperatures in the upper-70s. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8PM Saturday
Saturday – warmer, with high temperatures around 80°F and sunny skies. Overnight lows in the upper-60s. Scattered thunderstorms are possible overnight as a cold front pushes through
Sunday – sunny again with high temperatures in the upper-70s. Despite the cold front, we should see some warmth from downsloping northerly winds and subsidence in the wake of the frontal boundary causing compressional warming. Overnight lows in the low-60s.
NAM model output for 2PM Monday, mean sea level pressure and 10 m above ground level winds. Note the easterly flow in NYC imparted by the high pressure to our east-northeast
Monday – another sunny day with cooler high temperatures in the low-70s, overnight lows in the low-60s.
A warm start to fall yesterday gives way to cooler, drier weather that will actually feel like fall. Much as was the case last week, high pressure will be in control over the area. This should lead to generally fair weather. However, there is some chance for rain Thursday as a cold front pushes through.
Rest of today – mostly sunny with high temperatures in the upper-70s. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8AM Wednesday
Wednesday – high temperatures again mild in the upper-70s with warming influence of downsloping northwest winds. Overnight lows in the mid-60s.
Thursday – increasing clouds with high temperatures in the low-80s and overnight lows in the upper-50s. A chance of showers later in the day as a cold front approaches.
GFS model output for 2 meter above ground level temperature and 10 meter above ground level winds at 8PM Friday
Friday – high temperatures in the mid-70s with sunny skies and overnight lows in the low-60s behind the cold front.
The story of the weekend will be a continued stretch of fair weather with high pressure remaining in control. The positioning and movement of the high pressure center will result in a gradual warming pattern as winds turn to the south with high temperatures returning to summer-like levels in the low-mid 80s by the end of the weekend. A cold front scheduled to move through beginning next week will bring cooler weather back but warmer temperatures could make another return later next week, despite the autumnal equinox taking place Monday and fall formally starting.
Rest of today – sunny with high temperatures around 80°F. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8PM Saturday
Saturday – warmer, with high temperatures in the low-80s and sunny skies. Overnight lows in the mid-60s.
Sunday – sunny with high temperatures in the mid-80s. Overnight lows in the upper-60s.
Monday – another sunny day with high temperatures in the mid-80s, overnight lows in the mid-60s.
Climate Prediction Center short-range outlook for temperatures the second half of next week.
A weak frontal boundary passes through today. Behind this, high pressure will build and extend into the weekend. This persistent high pressure will result in mostly sunny conditions. Below normal temperatures in the low-70s will accompany northeasterly flow but a warming trend is forecast for the weekend as the center of high pressure shifts to the east.
Rest of today – mostly cloudy with a cold front pushing south then stalling out. Chances for light rain linger through the day. High temperatures in the upper-70s. Overnight lows in the low-60s.
High resolution rapid refresh simulated radar for 5PM today, showing some scattered light showers
Tuesday – high temperatures cool off into the low-70s behind the front. Winds turn to the northeast as high pressure builds over central Quebec. Overnight lows around 60°F but could dip into the upper-50s.
Wednesday – mostly sunny with high temperatures in the low-70s and overnight lows in the upper-50s.
GFS model output for surface pressure and winds valid at 2PM Thursday. The area of high pressure over the Northeast will serve to keep our weather fair, while pushing Hurricane Humberto safely out to sea.
Thursday – high temperatures remain in the low-70s, overnight lows in the upper-50s. It will definitely feel like autumn has arrived a few days early!
