Category Archives: Climate

NYC (KLGA) Climatology for September

September 3, 2019Climate, NYCclimatology, cold front, high pressure, new york city climate, new york city weather, new york city wx, nyc climate, nyc weather, nyc wx, sea breeze, warm front, wind roseLei Zhao

Other Month’s Climatologies

January
February
March
April
May
June
July
August
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 northeast (9.5%).

Directions that are most and least common: Most common wind directions include due south (9%), due southwest (8.5%), and northwest (8%). Least common wind directions are east-southeast (1.5%), due southeast (2.5%), and due east (3.5%).

Direction(s) most likely to produce the fastest winds: Winds of 16.5-21.4 knots are most frequently found coming from due northeast, and due northeast. North-northwest, 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: September’s wind profile sees a shift away from the general pattern of the summer months preceding it (June, July, August) during which southerly winds are predominant, and during which due south is the single most common wind direction. April is the last calendar month when due south isn’t the single most common wind direction, so it takes quite a bit of time in order for winds to shift off this summer pattern.

The most common wind directions in September are almost evenly split between northeasterly and northwesterly and southerly and southwesterly winds in percentage terms of frequency. Northwesterly winds are notably more frequent, and faster northeasterly and northwesterly winds start to appear in September as opposed to the summer months. Northwesterly winds in general will bring cooler, drier Canadian air into the region following cold fronts. Northeasterly winds, on the other hand, are related to backdoor cold fronts sweeping from the Canadian Maritimes, the onshore flow ahead of an advancing warm front, or a passing coastal storm.

The continued downward trend in southerly winds is likely a reflection of the diminishing influence of sea breezes as average land temperatures cool while average sea surface temperatures are still close to their peak (though also cooling). The narrowing gap between these two will tend to reduce the potential for sea breeze circulations to set up. However, these sea breezes can still exert an influence on local temperature and can still provide boundaries for convection. Southwesterly winds are also similarly capable of bringing in oppressive heat, as seen in the temperature section below.

Maximum observed two-minute wind speed for the month: 44 knots (51 mph)

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth noting: September can still offer up oppressive heat, especially in the first half of the month. The monthly all-time record high of 102°F is also the second highest record temperature recorded for the year at KLGA (August has the hottest record high: 104°F). September’s monthly precipitation record of 4.63″ in one day is also has the 3rd highest single-day precipitation record after April and August. While it can get quite hot in September, it’s also possible for temperatures to get cold too, with the record low for the month in the low-40s! Average high temperatures dip back below 80°F and average lows drop below 60°F again in September after the summer months, marking a definite fall feel.

‘Date	Normal High	Normal Low	Record High	Record Low	Record Lowest Max	Record Highest Min	Normal Precip	Record Precip
1	81	67	96	55	67	78	0.11	1.20
2	81	66	102	56	65	81	0.12	2.88
3	80	66	95	54	68	77	0.12	2.33
4	80	66	93	54	66	80	0.12	3.12
5	80	66	93	54	67	79	0.12	1.00
6	80	65	96	53	62	79	0.12	3.21
7	79	65	90	53	66	74	0.12	2.37
8	79	65	95	54	65	76	0.12	3.85
9	79	64	93	53	65	77	0.11	0.56
10	78	64	95	50	67	76	0.12	1.47
11	78	64	96	51	64	78	0.12	2.93
12	78	63	94	52	68	75	0.12	3.63
13	77	63	93	50	61	75	0.13	2.93
14	77	63	92	48	63	74	0.13	2.93
15	77	62	91	49	59	76	0.13	0.82
16	76	62	95	48	62	73	0.12	4.63
17	76	62	95	48	61	79	0.12	1.65
18	76	61	89	48	64	72	0.13	1.99
19	75	61	92	49	61	72	0.13	1.62
20	75	60	90	46	61	74	0.13	1.72
21	75	60	89	43	59	73	0.13	3.02
22	74	60	93	47	56	73	0.12	1.00
23	74	59	93	42	57	77	0.12	2.14
24	73	59	91	44	52	73	0.12	1.34
25	73	59	90	42	57	72	0.13	2.84
26	73	58	90	44	57	72	0.12	3.19
27	72	58	90	43	56	73	0.13	2.72
28	72	57	84	42	56	72	0.14	3.27
29	71	57	86	43	58	72	0.14	1.85
30	71	57	88	43	56	71	0.14	1.80
Range	71-81	57-67	84-102	42-56	52-68	71-81	0.11-0.14	0.56-4.63

NYC (KLGA) Climatology for August

August 7, 2019Climate, NYCclimatology, cold front, high pressure, new york city climate, new york city weather, new york city wx, nyc climate, nyc weather, nyc wx, sea breeze, warm front, wind roseLei Zhao

Other Month’s Climatologies

January
February
March
April
May
June
July
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 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 south (12.25%).

Directions that are most and least common: Most common wind directions include due southwest (10%), due northeast (9.75%), and south-southwest (8.75%). Least common wind directions are east-southeast (1%), due southeast (2.5%), and due east (2%).

Direction(s) most likely to produce the fastest winds: Winds of 16.5-21.4 knots are most frequently found coming from due northeast, and due south. It appears that due northeast also has some probability of exceeding 21.4 knots.

Impacts of wind direction on local weather: August winds continue to exhibit a distinctive summer pattern, and share many of the characteristics of the wind profiles for June and July. Southerly and southwesterly winds are a touch less common in August versus July, while northwesterly winds increase in frequency slightly. Like in July, heat waves can accompany the clockwise return flow from the southwest when subtropical Bermuda highs set up southeast of the area. A slight down tick in the frequency of southerly winds may point to a decline in sea breezes, with sea surface temperatures continuing to warm and narrowing the gap with average air temperatures. Increases in northwesterly winds could be an indication of a stronger influence from Canadian high pressure.

Maximum observed two-minute wind speed for the month: 45 (52 mph)

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Date	Normal High	Normal Low	Record High	Record Low	Record Lowest Max	Record Highest Min	Normal Precip	Record Precip
1	85	70	100	62	69	83	0.15	2.03
2	85	70	102	59	73	86	0.15	1.31
3	85	70	100	59	70	82	0.16	2.80
4	85	70	99	62	75	80	0.15	2.78
5	85	70	100	57	69	81	0.15	2.08
6	85	70	95	57	69	81	0.15	2.34
7	85	70	99	61	65	81	0.13	1.31
8	85	70	98	59	72	81	0.14	2.54
9	85	70	104	61	71	82	0.14	2.97
10	85	70	99	57	62	81	0.14	1.91
11	85	70	99	57	68	79	0.12	2.03
12	84	70	98	56	64	82	0.13	6.40
13	84	70	100	56	67	84	0.13	4.12
14	84	69	98	59	72	81	0.14	6.60
15	84	69	97	59	67	82	0.13	0.98
16	84	69	96	58	67	79	0.14	2.48
17	84	69	94	58	70	79	0.13	3.54
18	84	69	95	59	69	81	0.13	1.18
19	84	69	94	59	71	77	0.13	2.74
20	83	69	98	58	70	77	0.14	1.31
21	83	69	97	57	62	78	0.13	1.24
22	83	68	93	55	69	78	0.13	2.34
23	83	68	92	56	70	75	0.14	1.96
24	83	68	93	55	65	77	0.13	1.40
25	83	68	96	53	67	80	0.13	2.09
26	82	68	103	53	61	80	0.12	2.58
27	82	68	99	55	70	78	0.12	4.73
28	82	67	99	54	61	81	0.11	3.62
29	82	67	100	51	66	84	0.11	2.57
30	81	67	99	54	70	81	0.11	1.89
31	81	67	100	52	68	79	0.11	1.60
Range	81-85	67-70	92-104	51-62	61-75	75-86	0.11-0.16	0.98-6.60

NYC (KLGA) Climatology for July

July 1, 2019Climate, NYCclimatology, cold front, high pressure, new york city climate, new york city weather, new york city wx, nyc climate, nyc weather, nyc wx, sea breeze, warm front, warm sector, wind roseLei Zhao

Other Month’s Climatologies

January
February
March
April
May
June
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.

Frequency (percentage) of the single most common wind direction: Due south (13.5%).

Directions that are most and least common: Most common wind directions include due southwest (9.5%), due northeast (9.25%), and due northwest (8.5%). Least common wind directions are east-southeast (1%), due east (2%), and due southeast (2.5%).

Direction(s) most likely to produce the fastest winds: Winds of 16.5-21.4 knots are most frequently found coming from due northwest, and due south.

Impacts of wind direction on local weather: July winds are remarkably similar to June. Southerly and southwesterly winds are a bit more common in July than in June, and northwesterly winds a little less so. This pattern of winds continues to suggest the influence of mid-latitude lows tracking inland north of the area, bringing more southerly warm sector flow. As with June, persistent, subtropical high pressures continue to be a factor at times in July over the western North Atlantic. The clockwise flow around these high pressure centers would result in more southerly and southwesterly winds, which can lead to the onset and maintenance of heat waves. Southerly winds (along with easterly and some northeasterly winds) would bring cooler, and more stable marine air, sometimes in the form of sea breezes. Sea breezes can become commonplace during this month whenever there’s light synoptic winds. At this point in the year, the average max temperatures well exceed the threshold of 5-7°F warmer than sea surface temperatures (which are slowly climbing through the mid-60s) required for sea breezes.

Maximum observed two-minute wind speed for the month: 46 (53 mph)

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth Noting

July is the month when average temperatures peak at 86ºF. However, sweltering heat is possible well beyond this point, and record highs in this month are frequently in the upper-90s. Meanwhile, record highest low temperatures can easily be in the upper-70s and low-80s – making for very uncomfortable nights. July is also on average the wettest month of the year, which makes sense given the possibility for thunderstorms and a connection to tropical moisture.

Date	Normal High	Normal Low	Record High	Record Low	Record Lowest Max	Record Highest Min	Normal Precip	Record Precip
1	84	68	97	56	68	79	0.12	1.12
2	84	68	101	58	69	78	0.13	1.59
3	85	68	107	57	67	81	0.12	1.77
4	85	69	100	57	62	82	0.12	2.13
5	85	69	100	56	65	86	0.13	1.75
6	85	69	103	56	62	85	0.13	2.15
7	85	69	101	59	71	81	0.13	2.14
8	85	69	99	60	66	78	0.13	1.24
9	85	69	98	57	65	82	0.14	1.81
10	85	69	99	60	71	80	0.15	2.46
11	85	69	98	62	73	80	0.14	1.68
12	85	70	98	58	68	81	0.15	1.84
13	86	70	99	58	69	84	0.16	2.01
14	86	70	99	59	73	79	0.16	1.02
15	86	70	103	62	67	83	0.16	3.53
16	86	70	97	58	70	80	0.15	1.19
17	86	70	98	60	71	79	0.15	2.74
18	86	70	101	62	68	83	0.15	2.67
19	86	70	100	62	71	86	0.15	1.02
20	86	70	101	61	70	83	0.14	2.61
21	86	70	100	62	70	83	0.15	2.06
22	86	70	104	62	70	85	0.15	3.02
23	86	70	100	59	69	82	0.14	3.51
24	86	70	98	59	68	84	0.15	3.07
25	86	70	97	59	70	82	0.15	1.60
26	86	70	98	62	71	80	0.15	2.89
27	86	70	100	59	71	81	0.15	2.77
28	86	70	98	60	72	83	0.16	1.97
29	86	70	97	62	75	82	0.17	3.45
30	85	70	99	61	74	81	0.15	3.46
31	85	70	97	62	69	78	0.17	1.23
Range	84-86	68-70	97-107	56-62	62-75	78-86	0.12-0.17	1.02-3.53

NYC (KLGA) Climatology for June

June 1, 2019Climate, NYCclimatology, cold front, new york city climate, new york city weather, new york city wx, nyc climate, nyc weather, nyc wx, sea breeze, warm front, warm sector, wind roseLei Zhao

Other Month’s Climatologies

January
February
March
April
May
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.

Frequency (percentage) of the single most common wind direction: Due south (13.5%).

Directions that are most and least common: Most common wind directions include due northwest (9.5%), due northeast (9.25%), and due southwest (just below 9%). Least common wind directions are east-southeast (1%), due east (1.5%), and due southeast (2.5%).

Direction(s) most likely to produce the fastest winds: Winds of 16.5-21.4 knots are most frequently found coming from due northwest, north-northwest, and due south.

Direction(s) least likely to produce the fastest winds: As is the case with several other spring 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: Wind patterns in June present a similar pattern to those in May, but with a notable increase in the frequency of winds from the southwestern quadrant, and a decrease in winds from the northeastern quadrant. This could be a reflection of shifting storm patterns, with coastal storms and backdoor cold fronts from the northeast becoming less common while more mid-latitude lows track inland north of the area, bringing more southerly warm sector flow. Persistent Bermuda highs can sometimes also develop in June over the western North Atlantic. The clockwise flow around these high pressure centers would result in more southerly and southwesterly winds. During this time of year, southwesterly winds should generally advect warmer, more humid air from the Southeastern US into the region. When this pattern becomes persistent, it can cause oppressive heat waves. Meanwhile, southerly winds (along with easterly and some northeasterly winds) would bring cooler, and more stable marine air, sometimes in the form of sea breezes. In the wake of passing cold fronts associated with mid-latitude storms, northwesterly and northerly winds, though decreasing in frequency compared to May, should still be effective at transporting cooler, drier Canadian (continential Arctic) airmasses into the area.

Maximum observed two-minute wind speed for the month: 36 (41 mph)

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth Noting
June is the first month of summer, and not surprisingly is also the first month of the season where record highs have exceeded 100ºF.

Date	Normal High	Normal Low	Record High	Record Low	Record Lowest Max	Record Highest Min	Normal Precip	Record Precip
1	76	59	94	46	58	75	0.14	1.90
2	77	59	94	48	53	75	0.14	2.85
3	77	60	93	49	53	75	0.14	2.47
4	77	60	96	51	54	80	0.14	2.69
5	78	61	91	49	54	78	0.14	1.78
6	78	61	93	49	59	72	0.14	2.56
7	78	61	97	50	60	72	0.14	3.33
8	79	62	97	50	56	78	0.15	0.94
9	79	62	99	49	59	78	0.14	1.93
10	79	62	100	48	64	77	0.14	1.25
11	79	63	96	46	62	76	0.15	1.07
12	80	63	96	49	64	76	0.14	2.20
13	80	63	101	51	55	80	0.14	1.64
14	80	64	99	51	61	80	0.13	1.72
15	81	64	96	54	59	78	0.14	0.55
16	81	64	96	55	64	79	0.13	1.33
17	81	65	96	53	62	77	0.13	2.30
18	81	65	95	49	65	75	0.13	1.84
19	82	65	97	56	65	77	0.13	1.46
20	82	65	98	55	60	74	0.12	0.91
21	82	66	98	53	63	79	0.12	4.00
22	82	66	99	53	62	76	0.11	3.43
23	83	66	95	53	63	77	0.12	1.33
24	83	66	96	53	59	77	0.12	1.51
25	83	67	99	53	63	76	0.13	1.00
26	83	67	101	55	65	84	0.12	0.82
27	84	67	97	56	61	77	0.12	1.06
28	84	67	96	56	63	78	0.11	1.48
29	84	68	98	59	73	81	0.12	0.98
30	84	68	97	57	66	80	0.12	3.73
Range	76-84	59-68	91-101	46-59	53-73	72-84	0.11-0.15	0.41-4.00

NYC (KLGA) Climatology for May

May 9, 2019Climate, NYCclimatology, cold front, new york city climate, new york city weather, new york city wx, nyc climate, nyc weather, nyc wx, sea breeze, warm front, warm sector, wind roseLei Zhao

Other Month’s Climatologies

January
February
March
April
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.

Frequency (percentage) of the single most common wind direction: The most common wind direction for this month by frequency of occurrence is due south (~13%).

Directions that are most and least common: Due northeast (11.5%) winds present a second maximum of most frequent winds. The least common wind direction is east-southeast (~2%), followed by due east (~2.25%).

Direction(s) most likely to produce the fastest winds: Due northwest winds have a slim possibility of generating winds over 21.5 knots. No other wind direction seems to have a measurable occurrence of winds exceeding this speed. This is a marked difference from the previous two months when wind speeds of this magnitude were much more common. Winds of 16.5-21.4 knots are most frequently found coming from the west-northwest, due northwest, north-northwest, and due south.

Direction(s) least likely to produce the fastest winds: Due east, east-southeast, and due southeast winds rarely exceed 16.4 knots.

Impacts of wind direction on local weather: The most common wind directions in May differ from the previous two months, with northwesterly winds becoming less frequent, while southerly and northeasterly winds become more prominent. In fact, winds from the southern semicircle are generally more common than previous months. Cold air advection from northwest winds continue to influence temperatures in the wake of cold fronts approaching from the west, however, the effect should be dramatic than in prior spring months. Winds from the northeast can be associated to backdoor cold fronts arriving from the Canadian Maritimes, bringing a moist, cool maritime polar air mass; the advance of coastal Nor’easter type storms; or a warm front approaching from the south. The difference between sea surface temperatures and temperatures over land widens during May as daily normal highs increase. This increases the chances for sea breezes during periods of overall weak synoptic winds, though generally, southerly winds would allow for advection of warmer, more moist airmasses into the area. This would often be the case when the NYC region is in the warm sector of mid-latitude lows, preceding the passage of a typical cold front attached such lows.

Maximum observed two-minute wind speed for the month: 36 (41 mph)

Temperature and Precipitation Averages/Records

Temperature units are in Fahrenheit and precipitation is in inches.

Worth Noting: Average temperatures climb above 70ºF in May for the first time during the spring months. In 2019, new record lows were set for the 13th and 14th of May, at 42ºF and 44ºF respectively. In 2020, an all-time monthly record low of 36ºF was set on May 9th. In 2021, record lowest max temperatures were set for the 29th and 30th (52ºF, brrr), and record lows were set for the 29th-31st (48ºF, 48ºF, and 50ºF respectively)!

Date	Normal High	Normal Low	Record High	Record Low	Record Lowest Max	Record Highest Min	Normal Precip	Record Precip
1	67	49	85	38	50	62	0.10	2.18
2	67	50	90	40	47	67	0.12	0.83
3	67	50	93	40	50	70	0.11	1.45
4	67	50	92	41	49	72	0.12	0.89
5	68	51	90	42	46	65	0.12	2.27
6	68	51	93	41	47	61	0.11	1.28
7	68	51	93	40	44	60	0.12	1.11
8	69	51	89	37	49	68	0.11	2.28
9	69	52	92	36	46	76	0.12	1.21
10	69	52	91	38	53	71	0.11	1.44
11	70	52	96	42	51	68	0.11	1.77
12	70	53	88	43	50	68	0.11	1.30
13	70	53	89	42	55	67	0.11	1.74
14	71	53	84	44	54	64	0.11	2.82
15	71	54	92	43	53	65	0.11	0.89
16	71	54	90	41	53	63	0.12	2.57
17	72	54	94	38	56	68	0.12	1.03
18	72	54	97	44	54	80	0.12	1.44
19	72	55	96	43	50	68	0.12	2.00
20	72	55	97	44	52	77	0.14	1.79
21	73	55	93	45	51	71	0.13	1.60
22	73	56	94	47	57	70	0.14	0.95
23	73	56	94	45	55	69	0.14	1.72
24	74	56	91	41	54	72	0.13	1.82
25	74	57	95	44	47	74	0.14	1.64
26	74	57	94	45	55	75	0.13	1.59
27	75	57	92	41	48	73	0.13	1.84
28	75	58	92	44	58	73	0.13	1.41
29	75	58	95	48	52	71	0.14	2.41
30	76	58	96	48	52	74	0.14	2.19
31	76	59	96	50	60	78	0.14	2.23
Range	67-76	49-59	84-97	37-50	44-60	60-80	0.10-0.14	0.83-2.82

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.

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

NYC Weekend Weather – Mar 1, 2019

March 1, 2019Climate, NYC, Rain, Snow, Weather Update, Weekendclimate prediction center, coastal storm, new york city weather, new york city wx, nyc weather, nyc wx, polar jet stream, rain, snowLei Zhao

Although the calendar has flipped to March and we’re less than 3 weeks from the official start of spring, the weather has taken a decidedly winter-like turn as of late. This pattern will continue over the weekend and into next week. Initially, we’ll contend with 2 coastal storms that will bring chances for snow, and then enter next week with temperatures well below normal for this time of year. Sadly, this colder than normal pattern looks locked in for the next week or more

Rest of today – overcast conditions with temperatures hovering in the mid-30s. Precipitation will move back into the area by later this evening. Thermal profiles overnight point to a mix of snow/sleet at the coast with lows just around freezing. The local forecast office calls for an accumulation of 1-2″ of this wintry mess.

Weather Prediction Center surface forecast for 7AM Saturday

Saturday – the wintry precipitation continues the first half of the day as the first of two coastal storms continues to impact the region. High temperatures should warm up to around 40ºF with mostly cloudy skies, and precipitation should die off later in the day. Overnight lows should be around freezing.

Sunday – starts off as a decent enough day, but a second storm will be brewing and moving offshore, impacting the area overnight into Monday. High temperatures should be similar to Saturday in the low-40s with partly sunny skies. At this point, the primary precipitation modes at the coast appears to be a rain/snow mix. Thermal profiles don’t appear cold enough to support all snow with overnight lows expected to be above freezing around 35ºF.

Global Forecast System 1000 mb – 500 mb height, pressure, thickness foreast for 6AM Monday

Monday – precipitation tapering off early in the morning as this storm is a fast-mover. Temperatures topping out in the upper-30s with mostly cloudy skies.

Colder than Normal Temperatures Ahead

Climate Prediction Center has a 6-10 day temperature outlook suggesting a colder than normal pattern for much of the country, including our area. During this time, the polar jet stream is expected to dip further south allowing colder air to penetrate into the Continental US.

January 20, 2019 KLGA Forecast Post-Mortem

January 28, 2019Climate, NYC, Post Mortem, Rain, Snow, Stormsfrontogenesis, isentropic lift, metar, new york city weather, nyc wx, post-mortem, snowLei Zhao

For reference, here’s the post that triggered the following forecast post-mortem analysis. To start, here’s my forecast and the verified totals.

My Forecast
High: 48°F | Low: 17°F | Max sustained winds: 35 mph | Total QPF: 1.40″ | Total snow accumulation: 1.00″

Verification
High: 40°F | Low: 15°F | Max sustained wind: 38 mph | Total precipitation: 0.80″ | Total snow: 0.00″

Since I did decently at forecasting maximum sustained winds and the low temperature, this analysis will focus primarily on why I missed the mark on both total precipitation and the high temperature.

How I Verify Forecasts
I haven’t explained in previous posts like this how I go about verifying the results of my own forecasts, though I do talk about METARs (hourly weather reports) and daily climate summaries from the National Weather Service as sources for verification data. There’s a reason why I choose to use the 06Z Day 1 to 06Z Day 2 (1AM/2AM Day 1 to 1AM/2AM Day 2 depending on Daylight Saving Time) time window to forecast, and that’s because this lines up well with METAR synoptic reports that occur every 6 hours (00Z, 06Z, 12Z, 18Z). This is something I picked up from my Weather Forecasting Certificate Program at Penn State World Campus. So, when I’m looking at the METAR data, I’m looking for specific data points at these synoptic times:

KLGA 210551Z 32023G36KT 10SM SCT037 M09/M16 A2980 RMK AO2 PK WND 31037/0500 SLP091 T10941161 11067 21094 51032 $
KLGA 202351Z 32027G35KT 10SM SCT035 M07/M13 A2960 RMK AO2 PK WND 31041/2323 SLP024 T10671133 10033 21067 51063 $
KLGA 201751Z 34012G22KT 10SM FEW008 SCT012 BKN024 BKN190 03/00 A2927 RMK AO2 RAE09 SLP911 P0000 60020 T00280000 10044 20022 55002 $
KLGA 201151Z 06016KT 6SM RA BR BKN006 BKN010 OVC028 02/01 A2944 RMK AO2 PK WND 05028/1102 WSHFT 1059 PRESFR SLP970 P0003 60060 70114 T00220011 10028 20017 56055 $

I won’t bore you with details of how to read METARs, which you can learn about here, but from these entries, I can get the maximum temperature from the highest value 1 group, low temperature from the lowest 2 group, and total precipitation from summing up the 6 groups for these synoptic times. So in this case, “10044” indicates a maximum temperature of 4.4C, which is converted from 40F. “21094” shows a minimum temperature of -9.4C, converted from -15F. “60060” translates to 0.60″ and “60020” likewise is 0.20″, and the sum gives us 0.80″ total precipitation.

Last, with max sustained wind, and in this case snow, I checked the NWS daily climate reports for LGA (see red outlined boxes).

Post-Mortem Analysis
On this forecast, I ended up handling the low temperature and max sustained winds well, however, I was much too high on both the high temperature and total precipitation. So what happened here?

High Temperature
In my forecast, I had confidence based on various model data that NYC would spend a decent amount of time in the warm sector of the low that would be responsible for the storm. Unfortunately, this simply just did not happen, and as a result, we never got into that warm southerly/southwesterly flow that would have propelled temperatures into the upper-40s. Instead, looking at the METARs for that day reveals that winds stayed consistently east-northeast to north-northeast overnight into the early morning hours before almost immediately shifting to the northwest by 11AM. This makes sense, given the orientation and location of the warm front just to our south to start.

Click the images below to see the Weather Prediction Center’s surface analyses at 7AM, 10AM, 1PM respectively for Sunday, January 20.

In the end, I should have heeded some signals that there was enough uncertainty in the storm track even on Saturday that we could miss the warm sector. The local forecast office for the NWS also indicated that there was a potential for this, which would keep temperatures suppressed due to persistent, cool, northeasterly flow. Their forecast high, which I believe was 42°F, factored this in, and ended up being a lot more accurate. The takeaway here for me is to not completely buy into model consensus even if there’s good agreement, when there’s a possibility of storm tracks shifting. I don’t think I would have gone as low as 40°F even with this in mind, but I might have forecast something like 44°F, which would have been closer.

Total Precipitation
I missed the total precipitation forecast by more than 0.50″ – objectively a bad outcome. In this case, I think there were a couple reasons behind my own forecast bust. First, the storm progressed faster than data on Saturday suggested, resulting in heavier precipitation earlier in the overnight period, also meaning that the strongest frontogenesis/isentropic lift moved through quicker than anticipated. Secondly, the best moisture convergence stayed just offshore, leading us to miss out on some of the heavier rain.

Click the images below for enlarged versions of the archived radar image for 8AM Sunday, January 20, and the Storm Prediction Center’s moisture convergence analysis for the same time.

The fact that we never ended up in the warm sector for too long during the day Sunday also meant that the best moisture didn’t quite make it up to NYC. Note how the areas of strongest moisture convergence are also coincide well with the most intense radar echos. For precipitation with strong storms like this, it can always be a hit-or-miss proposition to pinpoint precipitation totals for one spot. My own personal forecast bias leads me to over forecast precipitation quite often. I should have consulted the daily average for precipitation to factor climatology into this as well before doing the forecast. For reference, the record precipitation total for KLGA on January 20th was 1.41″ – so I was, in essence, forecasting a near record-breaking precipitation event. That usually doesn’t pan out, as you see.

NYC Climate Update: Possible 2019 El Niño – Jan 7, 2019

January 7, 2019Climate, Cool Images, NYC, Outside of NYCnyc climate, subtropical jetLei Zhao

The latest seasonal forecast from the Climate Prediction Center suggests a 90% chance of an El Niño forming during this winter. Because El Niño (and its opposite, La Niña) occurs when there are sea surface temperature anomalies over large portions of the equatorial Pacific, it can affect sensible weather across the world. However, even if an El Niño does form, and is potentially strong, it doesn’t mean it’s the only determining factor for climate outlooks in our region.

Climate Predicition Center’s latest ENSO Outlook as of December 13, 2018. The CPC’s forecast probability that El Niño will form and persist through April 2019 exceeds 80%.

Definition: What is El Niño?

The term El Niño refers to the large-scale ocean-atmosphere climate phenomenon linked to a periodic warming in sea-surface temperatures across the central and east-central equatorial Pacific (between approximately the date line and 120^oW)… [CPC] declares the onset of an El Niño episode when the 3-month average sea-surface temperature departure exceeds 0.5^oC in the east-central equatorial Pacific [between 5^oN-5^oS and 170^oW-120^oW].
Climate prediction center

There are links between a pattern of weakening trade winds and the onset of El Niño, though there’s no conclusive understanding of the mechanics that lead to the formation of this effect. Either way, this post will focus more on possible effects of El Niño. The key lies in the geographic extent of El Niño, impacting much of the central and east-central Pacific. Since the oceans play a pivotal role in governing global atmospheric patterns, it’s no surprise that El Niño can have global weather impacts.

General Impacts of El Niño

El Niño global impacts from The Weather Network

As you can see, impacts from a classic El Niño bring warmer than normal weather to the northern part of the western US, and cooler and wetter conditions to the Gulf Coast/Deep South. Though not official yet, it does appear an El Niño was already in progress September-November, and possibly into December. This has already brought copious rains to the Southeastern US.

Green and blue hues indicate areas that received above normal precipitation.

One of the primary ways that El Niño affects global weather is by altering the intensity, orientation, and physical extent of the subtropical jet at the 200 mb level. Over the southeastern US, El Niño promotes a stronger subtropical jet streak – this can lead to the formation of stronger than usual storms over this portion of the country, bringing above normal precipitation patterns we see above.

CPC’s analysis of atmospheric anomalies, in this sequence of images, you can see the elongation of the subtropical jet (area of yellows, oranges, reds) flowing east from Asia. Similarly, a stronger subtropical jet streak is seen over parts of the US.

El Niño doesn’t have particularly strong impacts on our area, and this is borne out by the CPC’s seasonal 3-month outlook for this winter. It appears we may see slight chances for above normal precipitation here, but about equal chances of temperature anomalies.

CPC 3-month temperature outlook
CPC 3-month precipitation outlook

Notice, however, that some of the areas forecast to experience above normal temperatures do map well with a classic El Niño’s impacts (Alaska, parts of the Pacific Northwest, extreme Northern Plains), as do parts of the southern tier (Texas, Gulf Coast).