Excessive Heat Episode, Monday-Wednesday August 1-3, 2006

A dome of very hot air had developed under a strong upper level ridge of high pressure over the western half of the United States a week prior to the excessive heat event that developed over the Northeast. This western heat dome slowly migrated to the central Plains states, then to the Midwest, causing daytime temperatures to surge into the upper 90s and the low 100s in those parts of the country. As the air mass migrated east, a typical summer flow up from the Gulf of Mexico around surface high pressure located over the Appalachians, caused the moisture to increase in the hot air mass resulting in some of the highest dewpoint temperatures of the season throughout the middle part of the nation in the days before the heat arrived in New York and New England. The excessively high humidity along with the high temperatures resulted in heat index values (the combination of temperature and humidity to estimate an "Apparent" temperature of what it feels like to the human body) to surge to 115° in parts of the Midwest.

With the main branch of the jet lifting north of New York and New England by Tuesday, August 1, and the passage of a surface warm front, the flood gates opened for the super heated air to blast into the Northeast on a deeply layered northwest flow in the atmosphere.

And it was the deep layered northwest flow which was key to producing excessive heat in the Northeast. A northwest flow is a downslope flow for much of the region. The downsloping, off of higher terrain to the west, has the effect of compressing the air, which causes further warming. So an already hot air mass can become even hotter in the Northeast when the flow is deeply layered and out of the northwest. This air mass was also extraordinarily humid through a deep layer, which supported the exceptionally high dewpoints that occurred in the region. Additionally, due to fairly wet soil conditions throughout the Northeast some evaporation of that moisture added a degree or two to the dewpoint temperatures and also likely subtracted a degree or two off of the maximum temperatures. Despite part of the sun's energy going into evaporating soil moisture rather than heating the air, temperatures still climbed into the middle and upper 90s, a true testament to just how exceptionally hot this air mass was.

The very high dewpoint temperatures, ranging from the middle to upper 70s on the 1st through the 2nd, combined with the middle and upper 90 degree temperatures to produce the very rare for upstate New York and western New England peak heat index values ranging from 105° to 110°. And yet despite the excessively hot temperatures, no records were tied or broken @ Albany.

The excessive heat lead to record power usage throughout the local region as well as the entire state of New York. Record statewide power usage occurred on the 1st with NISO reporting a total usage of 33,879 megawatts. The record usage was then broken on the 2nd with a new statewide record usage of 33,939 megawatts being set. National Grid reported an all time record power usage on the 2nd of 6,692 megawatts breaking the old record of 6,618 megawatts set on August 4, 2005

And the heat also caused NYRA officials to cancel all races at the Saratoga Flat Track for the first time in modern times. Officials report that never in the past has an entire race card been cancelled at Saratoga due to heat.

A cold front and its associated cloud band slowly migrating south through northern New York and northern New England on the 3rd broke the heat for much of the region with temperatures dropping into the more tolerable but still very warm middle and upper 80s. The humidity, however, did not break as the dewpoint temperatures region wide remained in the oppressive low 70s with the cold front itself still north of the region. Farther from the front and the cloud zone the searing heat continued on the 3rd across the southern portions of the area, generally confined to the mid Hudson valley and southern New England, where temperatures for the third consecutive day under full sunshine and downslope compressional warming soared into the mid to upper 90s across Ulster, Dutchess, and Litchfield counties with heat indices up to 110°.

With the stretch of excessive heat lasting only two days at Albany with temperatures rising above 90°, the period cannot be considered a heat wave for the Capital Region, as in the Northeast, three consecutive days much reach 90° to establish a heat wave. However, the temperatures reached or exceeded 90° for four consecutive days at Poughkeepsie, establishing a heat wave for that location.

The cold front slowly moved through the region Thursday night and Friday (3rd-4th) bringing a round of showers during the overnight period which was followed by a gradual drop in the humidity that lead to a pleasant weekend with mild temperatures in the low to mid 80s and comfortable conditions.

This chart lists the high temperatures and peak Heat Index values for some of the National Weather Service reporting stations in the local area for the 1st through the 3rd.

Tuesday August 1, 2006

City High Temperature and Time of Occurrence Peak Heat Index
Albany Airport, NY 96° @ 4:20pm 108°
Poughkeepsie Airport, NY 98° @ 3:27pm 109°
Glens Falls Airport, NY 96° @ 4:27pm 110°
Bennington Airport, VT 92° @ 4:15pm 104°
North Adams Airport, MA 92° @ 3:46pm 104°
Pittsfield Airport, MA 90° @ 2:29pm 94°

Wednesday August 2, 2006

City High Temperature and Time of Occurrence Peak Heat Index
Albany Airport, NY 95° @ 1:16pm 104°
Poughkeepsie Airport, NY 99° @ 4:21pm 108°
Glens Falls Airport, NY 95° @ 1:16pm 104°
Bennington Airport, VT 92° @ 3:31pm 104°
North Adams Airport, MA 94° @ 2:35pm 106°
Pittsfield Airport, MA 91° @ 3:19pm 99°

Thursday August 3, 2006

City High Temperature and Time of Occurrence Peak Heat Index
Albany Airport, NY 87° @ 11:51am 94°
Poughkeepsie Airport, NY 97° 106°
Glens Falls Airport, NY 86° 89°

The following two charts list selected hourly conditions @ Albany on both the 1st and the 2nd. Note the long duration of the remarkably high dewpoint temperatures which created the sustained oppressive conditions across the region. And also note the peak dewpoint temperature reported at 4:00pm on August 1 @ Albany of 77°. It is quite rare in the Northeast for dewpoint temperatures to rise to such levels and to be sustained at those levels for an extended period of time.

Tuesday August 1, 2006, Hourly Conditions @ Albany, NY

Time Temperature Dewpoint Heat Index Wind (mph)
1:00pm 89° 76° 99° Calm
2:00pm 91° 76° 102° Calm
3:00pm 95° 76° 107° W 9 Gust: 20
4:00pm 93° 77° 106° SW 10
5:00pm 96° 73° 107° NW 14
6:00pm 95° 74° 105° W 9
7:00pm 91° 76° 102° SW 7
8:00pm 87° 75° 97° S 7
9:00pm 83° 74° 88° SSE 6

Wednesday August 2, 2006, Hourly Conditions @ Albany, NY
Note: A very small and weakening thundershower passed over the Albany Airport at approximately 2:30pm which significantly cooled the air. Sprinkles and light showers near the airport between 4pm and 5pm again caused a large drop in temperatures at the reporting station.

Time Temperature Dewpoint Heat Index Wind (mph)
10:00am 88° 75° 97° WNW 7
11:00am 90° 76° 99° W 9
12:00pm 91° 76° 102° WNW 8
1:00pm 92° 76° 102° NW 7
2:00pm 93° 74° 102° WNW 8
3:00pm 82° 76° 90° W 8
4:00pm 91° 74° 100° W 13
5:00pm 81° 70° 84° W 8
6:00pm 81° 71° 85° NW 9

Because of a very persistent warm layer in the mid levels of the atmosphere, the atmosphere remained fairly capped through the heat episode which prevented a widespread outbreak of severe thunderstorms. Had the atmosphere not been so capped (cooler aloft), widespread very damaging thunderstorms would likely have occurred due to moderately strong mid level wind fields that existed over the entire Northeast during the hot spell. Instead, rather isolated t-storms, forced by local boundaries, terrain, and the extreme heat of the day, produced localized damaging downburst winds on the 1st, with an even fewer number on the 2nd. Thunderstorm activity on the 3rd was squelched across much of the region due to the passage of a wind shift line during the morning, well in advance of the cold front slowly dropping in from the north. Convergence on the wind shift line in the super-heated air lead to a series of organized damaging thunderstorms across New York's southern tier and northeast Pennsylvania. These storms did move through southern Ulster, Dutchess, and Litchfield counties producing pockets of wind damage late in the afternoon on the 3rd.

The table is a listing of the Severe Weather Reports from the 1st through the 3rd from the isolated to widely scattered t-storms that occurred.

Town County Severe Weather Report Time and Date
Coxsackie Greene Tents blown over at farmers market at New Baltimore rest area on Thruway I-87, tree tops sheared off 2:10pm/August 1
Ghent Columbia Tree down blocking one lane of Route 66 2:31pm/August 1
Ghent Columbia Additional trees blown down 2:45pm/August 1
Copake Columbia Wind damage, trees and wires down at Four Corners Road and Pennsylvania Avenue 3:08pm/August 1
Salisbury, CT Litchfield Trees and wires down 3:45pm/August 1
Amenia Dutchess Trees and wires down on Depot Road 3:55pm/August 1
Sharon, CT Litchfield Trees and wires down 4:00pm/August 1
Greenville Center Greene Trees and wires blown down 4:45pm/August 1
Earlton Greene Tree down on County Route 45 5:20pm/August 1
Ghent Columbia Wires down at 123 Water Street 5:20pm/August 1
Dolgeville Herkimer Trees down from a localized downburst 2:50pm/August 2
Cheshire, MA Berkshire Significant downburst downing many large trees and wires 3:40pm/August 2
Old Forge Herkimer Trees down from weakening squall line 11:37pm/August 2
Ellenville Ulster Trees and wires down 4:29pm/August 3
Beacon Dutchess Trees down throughout the town 5:13pm/August 3
Woodbury, CT Litchfield Trees down 6:20pm/August 3