Tag Archives: climatology

NYC (KLGA) Climatology for April

April 2, 2019Climate, NYCclimatology, new york city climate, new york city weather, new york city wx, nyc climate, nyc weather, nyc wx, sea breeze, wind roseLei Zhao

Other Month’s Climatologies

January
February
March
May
June
July
August
September
October
November
December

Station Basic Information

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

Local Geography and Topography

Station Elevation: 10 feet above sea level.

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

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

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

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

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

Wind Patterns

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

Frequency (percentage) of the single most common wind direction: Due northwest occuring about 13% of the time.

Directions that are most and least common: Most common wind directions following due northwest are due south (10%), west-northwest (9%), and due northeast (8.75%). Least common wind directions are east-southeast (1.25%), due east (2.5%), and due southeast (2.75%).

Direction(s) most likely to produce the fastest winds: Winds from the northwest, west-northwest, and to some extent the northeast and east-northeast tend to produce the fastest winds.

Direction(s) least likely to produce the fastest winds: Winds from the east-southeast, due east, and south-southwest are least likely to produce the fastest winds.

Impacts of wind direction on local weather: Like March northwesterly winds during April are likely tied to the passage of cold fronts and coastal storms. Cold air advection from these winds will still be quite robust during the beginning of the month especially, as record lows for this month suggest. Winds from the northeast are still tied to backdoor cold fronts arriving from the Canadian Maritimes, bringing a moist, cool maritime polar air mass, or the advance of coastal Nor’easter type storms. During April, sea surface temperatures around NYC become markedly cooler than the air temperature as average highs continue climbing in response to more direct sun angle on longer spring days. On days approaching record warmth, in an overall environment of otherwise light winds, you could even see some sea breezes start forming along the coasts.

Maximum observed two-minute wind speed for the month: 48 knots (55 mph).

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth Noting

April is the first month in the spring when record high temperatures exceed 90ºF. Record lows still routinely dip into the 20s during this month, reflecting the variability that spring can bring. The most recent record low was set in 2021, at 29ºF for 4/2. April also has the second highest single day precipitation record with 6.69″ falling on 4/15.

Date	Normal High	Normal Low	Record High	Record Low	Record Lowest Max	Record Highest Min	Normal Precip	Record Precip
1	55	40	80	27	42	56	0.14	1.89
2	56	40	79	29	39	55	0.14	1.66
3	56	40	77	25	39	53	0.14	1.59
4	57	41	76	24	36	56	0.14	1.74
5	57	41	74	25	38	53	0.14	2.12
6	57	41	80	22	40	53	0.14	2.45
7	58	42	91	22	30	63	0.13	2.00
8	58	42	89	25	38	67	0.14	2.03
9	59	42	84	26	40	64	0.15	2.28
10	59	43	82	29	39	53	0.14	2.85
11	59	43	82	32	42	57	0.15	0.94
12	60	43	86	29	44	54	0.14	1.72
13	60	44	85	25	36	59	0.14	1.63
14	60	44	84	27	41	58	0.14	0.93
15	61	44	86	28	40	64	0.14	6.69
16	61	45	89	31	44	68	0.13	2.50
17	62	45	94	32	45	73	0.13	1.71
18	62	45	91	35	45	69	0.12	0.58
19	62	46	85	35	40	70	0.13	1.41
20	63	46	85	35	47	63	0.13	1.89
21	63	46	86	33	40	61	0.13	1.84
22	63	47	85	33	44	61	0.13	1.90
23	64	47	85	36	44	57	0.12	2.21
24	64	47	87	36	46	59	0.13	2.06
25	64	48	88	36	48	59	0.12	1.50
26	65	48	91	37	47	63	0.13	1.33
27	65	48	89	38	45	61	0.13	1.85
28	66	49	89	36	41	68	0.12	2.64
29	66	49	88	36	49	65	0.13	1.00
30	66	49	89	42	47	60	0.11	5.26
Range	55-66	40-49	74-94	22-42	30-49	53-73	0.11-0.15	0.58-6.69

NYC (KLGA) Climatology for March

March 3, 2019Climate, NYCclimatology, continental polar, maritime polar, new york city climate, new york city weather, new york city wx, nyc climate, nyc weather, nyc wx, wind roseLei Zhao

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. As such, I’ve decided to post some critical components of climatology for the closest station to me, LaGuardia Airport (KLGA). Below, I’ve posted some general climate data, and also specific data for the month of March.

Other Month’s Climatologies

January
February
April
May
June
July
August
September
October
November
December

Station Basic Information

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

Local Geography and Topography

Station Elevation: 10 feet above sea level.

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

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

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

Wind Patterns

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

March wind rose for KLGA, source: National Resource Conservation Service

Frequency (percentage) of the single most common wind direction: Due northwest occuring about 14% of the time.

Directions that are most and least common: Most common wind directions following due northwest are due northeast (11.75%), west-northwest (10.25%), north-northwest (8.5%). Least common wind directions are east-southeast (1%), due southeast (2%), and due east (2.25%).

Direction(s) most likely to produce the fastest winds: The most common wind directions are also the ones most likely to produce the fastest winds.

Direction(s) least likely to produce the fastest winds: Again, the least common wind directions are also least likely to produce the fastest winds.

Impacts of wind direction on local weather: Prevalent northwesterly winds during this month generally follow in the wake of cold fronts and coastal storms. These winds can lead to substantial cold air advection (transport of cold, dry continental polar air mass from interior Canada), often because of subsidence in the wake cold fronts mixing down very fast winds to the surface. These winds will downslope and warm slightly as they approach the coast though. A secondary maximum of winds from the northeast can be attributed to backdoor cold fronts arriving from the Canadian Maritimes, bringing a moist, cool maritime polar air mass, or in conjunction with the advance of coastal Nor’easter type storms. During March, sea surface temperatures in the vicinity of NYC are above freezing, but by no means warm. If a warmer air mass is in place prior to winds shifting to the northeast, cooler, more moist conditions will result. If a colder, below freezing air mass is present, northeasterly winds can exert moderating influence on temperatures. Persistent northeasterly winds can also lead to the potential for coastal flooding given the shape of local coastline.

Maximum observed two-minute wind speed for the month in knots: 40 knots (46 mph).

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth Noting: Average temperatures in March rise above 50°F for the first month since November. However, March can certainly still produce cold days – many of the record lowest max temperatures are below freezing, with record lows still in the teens and single digits. It is a month indicative of spring when large temperature swings are possible.

Date	Normal High	Normal Low	Record High	Record Low	Record Lowest Max	Record Highest Min	Normal Precip	Record Precip
1	45	31	71	8	25	53	0.12	2.23
2	46	31	67	13	25	50	0.11	2.44
3	46	31	65	10	25	49	0.12	2.26
4	46	31	69	7	25	46	0.11	1.53
5	46	32	72	9	25	48	0.12	0.72
6	47	32	64	14	24	48	0.12	2.47
7	47	32	69	14	25	49	0.13	1.90
8	47	32	74	14	28	54	0.12	1.20
9	47	33	75	14	26	49	0.12	2.18
10	48	33	78	12	27	62	0.12	1.52
11	48	33	70	15	30	49	0.12	1.40
12	48	33	69	15	28	49	0.12	1.83
13	49	34	83	19	33	53	0.12	3.15
14	49	34	75	18	34	50	0.12	1.41
15	49	34	74	14	29	48	0.13	1.61
16	50	34	77	19	32	51	0.13	1.12
17	50	35	74	15	26	54	0.13	1.39
18	50	35	75	13	19	51	0.14	2.05
19	51	35	72	10	26	53	0.13	1.38
20	51	36	82	19	31	53	0.14	1.18
21	51	36	70	18	34	53	0.14	2.00
22	52	36	76	19	33	54	0.13	3.15
23	52	37	74	19	26	56	0.14	1.44
24	52	37	74	17	30	50	0.14	1.63
25	53	37	77	18	32	50	0.13	1.55
26	53	38	72	20	34	51	0.14	1.26
27	54	38	83	23	36	54	0.14	1.20
28	54	38	83	23	36	58	0.13	2.83
29	54	39	86	25	34	59	0.14	1.90
30	55	39	79	23	34	59	0.13	2.65
31	55	39	82	24	36	59	0.14	2.10
Range	45-55	31-39	64-86	7-25	19-36	45-62	0.11-0.14	0.72-3.15

WxChallenge Philadelphia, PA Climatology – Nov 4, 2018

November 4, 2018Outside of NYCclimatology, cold air damming, downsloping, high pressure, low pressure, philadelphia weather, philadelphia wx, philly weather, philly wx, topograhy, wind rose, wxchallengeLei Zhao

As part of the WxChallenge competition and Penn State University World Campus’ METEO 410 capstone course on weather forecasting, we are required to write up climatologies for cities that we will be forecasting for during the competition. I thought I would share the latest one I put together for Philadelphia, PA, which will be our forecast city for the next 2 weeks in the competition.

Climatology for Philadelphia, PA (KPHL)

City Name / Station ID: Philadelphia, PA (Philadelphia International Airport, KPHL)

Time Period: November 6-November 16

Topography and Geography

Local Time Zone: Eastern Standard Time (UTC -5)

Station Elevation: 10 feet above sea level.

Station Location: Philadelphia International Airport (KPHL) lies on the north bank of the Delaware River, 6.75 miles southwest of City Hall in downtown Philadelphia.

Important Topographical Features: Philadelphia is located in the southeasternmost corner of Pennsylvania, along the border with New Jersey to the east defined by the Delaware River. Philadelphia lies along the Fall Line, and there are rolling hills oriented southwest-northeast immediately west and north of the city. These hills have elevations of 200-500 feet. The Appalachian Mountains are further north and west, though many of these can be characterized more as narrow ridges. The elevations of these ridges range from 1000-1500 feet. East of the city are lowlands of the coastal plain in New Jersey. Although KPHL isn’t directly on the coastline, there are significant bodies of water within 55 miles of the site, including Chesapeake Bay to the southwest, Delaware Bay to the south, and the Atlantic Ocean to the southeast and east. Lastly, although not technically a topographical feature, the city of Philadelphia is a sizable urban agglomeration that can have effects on local microclimates via differential heating (urban heat island effect).

Winds

Wind Roses:

Frequency (percentage) of the single most common wind direction: West-northwest, occurring around 11.5% of the time.

Directions that are most and least common: Most common wind directions: southwest (~10.25%), west (~10%), northwest (~9.5%), west-southwest (~8.75%). Least common wind directions: southeast (2.5%), east-southeast (~2.75%), south-southeast (3%).

Direction(s) most likely to produce the fastest winds: west-northwest, and northwest have the highest likelihood of producing winds in excess of 21.5 knots. Due west is not far behind either.

Direction(s) least likely to produce the fastest winds: The least common wind directions (east-southeast, southeast, and south-southeast) also are least likely to produce winds exceeding 16.5 knots. Among these, southeast winds have the lowest frequency of producing winds in excess of 16.5 knots.

Impacts of wind direction on local weather: Winds from the westerly-northerly directions flowing towards KPHL would all experience some degree of downsloping (not particularly strong), as they flow over and down the higher terrain in these regions as discussed in the section on topography. Southwesterly-easterly winds all have the potential to transport moisture into the KPHL area, as they would flow over Chesapeake Bay (southwest), Delaware Bay (south), and the Atlantic Ocean (southeast-east). Southwest winds are quite common – the southerly-easterly winds are significantly less common, but still occur collectively about 17% of the time. The LCD mentions both the Appalachian Mountains and the Atlantic Ocean as moderating influences, as winds from the former warm via downsloping; and winds from the advect cooler marine air in the warm season, and milder air in the cold season.

While northeasterly are generally uncommon, east-northeast winds are somewhat more frequent, occurring about 6.5% of the time. Winds from these directions are noteworthy for a couple impacts. First, when KPHL lies north of a deepening coastal low, these winds can enhance moisture transport from the Atlantic Ocean while also possibly bringing milder air from the ocean when the sea surface temperatures exceed surface temperatures during winter. Second, when a high pressure center approaches KPHL from the west, these winds can bring result in cold air damming as they would eventually pool cooler air at the base of higher terrain west of KPHL before turning south. This scenario would bring about cooler temperatures than otherwise expected. Though less of a concern during the cold season, there could be scenarios in which a strong enough sea breeze could penetrate far enough inland during the warm season to suppress temperatures at KPHL. On the other hand, the urban heat island effect induced by the city of Philadelphia should have year-round impacts in terms of generating an inbound wind from outlying suburbs towards the city center (which KPHL is very close to), while also resulting in warmer temperatures than surrounding areas.

Maximum observed two-minute wind speed for the month (or months) in knots: 40 knots (converted from 46 mph)

Temperatures

Date	Normal Maximum (ºF)	Normal Minimum (ºF)	Record Maximum (ºF)	Record Minimum (ºF)	Record Lowest *Maximum* (ºF)	Record Highest *Minimum* (ºF)
Tuesday 11/06	60	42	79	26	36	66
Wed. 11/07	59	42	75	20	38	56
Thursday 11/08	59	41	78	25	42	61
Friday 11/09	59	41	78	23	40	60
Tuesday 11/13	57	40	72	24	38	57
Wed. 11/14	57	40	76	19	35	56
Thursday 11/15	56	39	81	19	38	61
Friday 11/16	56	39	76	22	38	55
RANGE	56-60	39-42	72-81	19-26	35-42	55-66

Precipitation

Date	Normal (inches of liquid)	Record Maximum (inches of liquid)
Tuesday 11/06	0.09	1.41
Wednesday 11/07	0.10	3.99
Thursday 11/08	0.09	3.07
Friday 11/09	0.09	0.86
Tuesday 11/13	0.09	1.56
Wednesday 11/14	0.09	2.64
Thursday 11/15	0.10	1.95
Friday 11/16	0.09	1.46
RANGE	0.09-0.10	0.86-3.99

WxChallenge for Omaha, Nebraska (KOMA) | Oct 9-12

October 10, 2018Outside of NYC, Rain, Thunderstorms, Weather Update, WxChallengeclimatology, cold front, high pressure, low pressure, omaha weather, omaha wx, rain, snow, stationary front, wxchallengeLei Zhao

A couple days into the forecast period for the second WxChallenge city for this fall, and I’ve experienced my worst forecast bust (for yesterday). Highlights in the post-mortem section. It has been a week of transitions for Omaha, which started off with relatively mild conditions but will end the week with possibility for patchy frost!

Synoptic Set Up

A 500 mb longwave trough will with multiple attendant vorticity maxima will pivot through the KOMA region during the first half of the forecast period before flow becomes more zonal. At the 300 mb level, multiple jet streaks could boost divergence with these 500 mb vorticity maxima. This enhanced lift, and strong wind shear profile could lead to some isolated strong-severe thunderstorms. The 850 mb shows evidence of a decently robust LLJ that would should bring a continuous supply of Gulf moisture up the Missouri Valley into the area. At the surface, a warm front looks to lift through Monday, then stall as a cold front in the vicinity of KOMA through late Wednesday due to the deep unidirectional winds parallel to the front boundary.

Notes

The potential for flash flooding, and bouts of heavy rain, is duly noted in the AFD during the first half of the weak. The synoptic ingredients for a long duration rainfall event are certainly evident. Soils in the area are already quite moist, given that flood warnings were present for stretches of the Missouri last week. GFS MOS QPF range on Sunday for 06Z Tuesday to 06Z Wednesday was 1.75-4.46”. NAM MOS QPF range for this time was 1.35-2.71”, consensus was 1.55-3.59”. Records around this time of year for QPF show that 1-2” can easily occur, despite the normal being only a mere 0.07”. SREF probabilities of >= 0.50” were above 90% for this period, and >= 1.00” was 50-70%, but over 2.00” of QPF probabilities were less than 10%. SREF mean was 2.73”, with a pretty large spread, from 0.69-5.54”. GFS mean was 3.93” with spread of 1.82-5.16”. For now, going with a superblend of the low-end of the ranges of MOS and plumes: 1.40”.

As of Monday, SREF and GEFs means had become much better aligned, with SREF mean at 2.83” and GEFs mean 2.95”. SREF spread was 1.34-4.46”, GEFs was 1.43-4.43”. QPF forecast shows KOMA a pretty large QPF gradient, and that uncertainty seems borne out well in the ensemble forecasts. SREF probabilities of >= 2.00” increased to the 10-30% with KOMA lying right on the fringe of 30-50% probabilities of this amount. >= 1.00” probabilities increased to 70-90%. Official NWS forecast as of 10Z Monday called for 1.65” during the forecast period Tuesday. GFS MOS QPF range was 2.10-4.21”, NAM 1.01-2.06”, consensus here is 1.55-3.13”. Based on these updates, I’m increasing my forecast to 1.85” – I’m hedging down below the SREF and GEFS means because I’m still not sure where the stationary/slow-moving surface front will set up in relation to KOMA, and where the best lift will be for heavy rain/thunderstorms as a result. Also, if the 850 mb LLJ fails to materialize close to KOMA, we could be looking at lower overall totals. Low SREF probabilities of over 2.00” also help justify this call. Looking at Wednesday, rain chances diminish considerably after the front moves through, but the story then becomes strong winds possible, with MOS pointing at 17-20 knot synoptic winds.

Ensembles continue to trend upwards as of Monday afternoon with QPF, SREF mean now 2.96” and GEFS mean is 3.16”. SREF probabilities are close to placing KOMA in the 50% >= 2.00” QPF. Will take one more look at 18Z MOS guidance and some other factors before finalizing, but am leaning towards increasing the precip forecast again, this time to maybe 1.90” I’m wary of going for 3” of QPF or higher, given that the entire month’s single-day QPF record is 3.09”. Even beyond 2” still seems unlikely.

On Tuesday, looking ahead at Wednesday and Thursday, the passage of a cold front is quite evident. Temperatures are forecast to drop considerably compared with the beginning of the weak, and precipitation will end, too. The forecast for Wednesday still retains a slight chance for some measurable QPF on the tail end of the main precipitation event Tuesday. Models have backed down from up to 0.25” of precip to less than 0.10”. SREF and GEFS means show approximately 0.04” on Wednesday. SREF probabilities showed that KOMA had a greater than 90% chance of receiving precipitation >= 0.01”, but less than 10% of >= 0.10”, going to go straight up with the ensemble means here. The other story for Wednesday will be stiff winds from the northwest, with MOS synoptic winds of 17-18 knots. This suggests even stronger sustained winds, and will aid in cold advection, keeping high temperatures suppressed. These blustery conditions are forecast to gradually abate by late in the day Thursday, such that the strongest winds Thursday should occur early in the overnight hours. Cold temperatures overnight into Thursday should be somewhat tempered by decent vertical mixing and overcast skies.

Forecasts Submitted

This only reflects finalized forecasts, I’ve made small adjustments to the forecast based on checking MOS daily.

Forecast Day	Max Temp (°F)	Min Temp (°F)	Max Sustained Wind (kts)	Precipitation (inches)
10/09/2018	62	57	14	1.91
10/10/2018	48	44	20	0.02
10/11/2018	48	34	17	0.00
10/12/2018	48	35	9	0.10

Post-Mortem

Day 1: Major bust across the board. Was off by more 5 degrees or more on both the high and low. This made up about half of the error points. The rest came from being off on max precipitation by more than 1.20”. MOS was considerably off the mark with temperatures – though NAM was closer. This was all due to the fact that a stationary frontal boundary never made it close enough to KOMA to realize warmer temperatures, and heavier precip. The axis of the 850 mb LLJ stayed south and east, along with the best surface convergence. As a result, nearly all of the model guidance was horribly wrong. The closest forecast in the class was still nearly 0.50” too high. I put too much credence into the upwards trends on the models – there were some indications already that KOMA was trending to be on the drier side of this event. Still, even if I had nailed the precipitation forecast, I would have still busted hard on the temperatures. Need to be a lot more cautious going forward about situations where a frontal boundary and precipitation are around, and probably hedge down on temperatures during transitional season when a forecast site could be on the cold side of a front with rain.

LZ | Weather

Weather updates & posts for NYC region

Tag Archives: climatology

NYC (KLGA) Climatology for April

Other Month’s Climatologies

Station Basic Information

Local Geography and Topography

Wind Patterns

Temperature and Precipitation Averages/Records

NYC (KLGA) Climatology for March

Other Month’s Climatologies

Station Basic Information

Local Geography and Topography

Wind Patterns

Temperature and Precipitation Averages/Records

WxChallenge Philadelphia, PA Climatology – Nov 4, 2018

Climatology for Philadelphia, PA (KPHL)

Topography and Geography

Winds

Temperatures

Precipitation

WxChallenge for Omaha, Nebraska (KOMA) | Oct 9-12

Synoptic Set Up

Notes

Forecasts Submitted

Post-Mortem