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Paper No: 3a.2 AMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NCNortheast United States heat index climatology: 1981 2010Mary Stampone New Hampshire State Climate OfficeDepartment of Geography, University of New Hampshire, Durham, NH

and David A. GlennNOAA/NWSFO Newport/Morehead City, North Carolina, Newport, NCExtreme heat is one of the deadliest weather hazard, second only to excessive cold. Each year, hundreds, possibly thousands, of people worldwide suffer heat-related illnesses. In US, there was an estimated average of 237* heat-related fatalities per year from 1994-2003.

* 10-year average of heat related fatalities from 1994-2003. U.S. Natural Hazard Statistics. http://www.crh.noaa.gov/pub/heat.php 11Heat Hazards

3a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC

In 2010, a heat wave killed thousands in Russia, China, Japan and India. A record heat wave struck the Northeastern US in July of 2010, stressing power grids and sickening hundreds in Philadelpia, NYC, Providence and Boston.23a.2: Stampone & Glenn

AMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC2Apparent Temperature

Steadman (1979) developed an index to measure the combined effects of heat and humidity on the human body.Source: Steadman, RG (1979) The assessment of sultriness. Part1: A temperature-humidity index based on human physiology and clothing science. J. Appl. Meteor., 18, 861-873.Biometerological Assumptions:Vapor pressure & wind speedDimensions, heat & moisture characteristics of skin & clothingActivity & perspiration rateFrom the Central Plains to the East Coast, hot summer temperatures often coincide with high atmospheric humidity. High humidity reduces the bodys perspiration rate and its ability to cool itself making it feel hotter during warm periods with high humidity. Steadman (1979) proposed a temperature-humidity index as a measure of how hot it feels often referred to as apparent temperature - considering the combined effects of heat and humidity on the human body. 33a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC3The NWS Heat Index

NWS Taunton, MA (BOX) Heat Warning (105 F)Heat Advisory (101-104 F)The NWS developed the Heat Index equation based on Steadmans work that estimates the apparent temperature as the Heat Index. 4

DfbBskHAwBwhCsaCfbCfaHHBskBskDfaUS Climate Zones(Kppens Classification)3a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC4ClimateDfaDfbHumid Continental (Cool Summer)Humid Continental (Warm Summer)In the summer, the boundary between cool and warm air masses is to the north of the region, allowing inflow of warm, humid air.New England and New York are located within the Humid Continental climate zone, split between warm summers to the south and cool summers north. Compared the more oppressive summer conditions that characterize the Mid-Atlantic region of the NE, New England and northern NY are relatively more comfortable during the summer months.However, temperature and humidity are highly variable over short distances due to the diverse topography and distribution of urban and rural areas.Southern areas are highly urbanized and include the NYC, Boston & Providence Metropolitan areas as well as the densely populated Connecticut and Hudson River Valleys. Northern areas are much less densely populated with scattered small cities and urban centers. The north is also characterized by rugged terrain with several mountain ranges separated by large river valleys including the Hudson, Connecticut, & Merrimack. 53a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC

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NHMENYVTMACTRI39 stations with hourly temperature and dew point observations for 1981-2010http://cdo.ncdc.noaa.gov/pls/plclimprod/poemain.accessrouterData Source: NCDC US Integrated Hourly Surface ObservationsUrban/SuburbanCoastalNorthernInterior Mountains, Valleys and PlainsHeat Index ClimatologyHourly station data from NCDC US Integrated hourly surface observations with 140 (NYC, Providence & Boston) Coast east of Long Island < 140Cape Cod < 100

3a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC6Heat Index ClimatologyTotal number of days with a heat index of 95 F (1981-2010)

(/) Significant trends (95 % c.l.)Total number of days with a heat index value of 95F or above over the climate normal period 1981-2010 .Significant decrease in number of HI days >95 of 5.2 days (+/- 1.6) at Floyd Bennett NY due to high totals in 1983 & 1988. No trend from 1990-2010.Significant increase in number of HI day >95 of 1.3 at Block Island RI due to occurrence after 1999 with no days prior.7Fewest northern tier (cool summers)Northern NH, VT, & NY < 15Most of ME, northern Green Mountains and Adirondacks < 10Highest southern tier (warm summers)Urban areas > 30 (NYC, Providence & Boston) Coast east of Long Island < 20Cape Cod < 15

3a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC7Heat Index ClimatologyAverage hours per year with a heat index of 95 F (1981-2010)

(/) Significant trends (95 % c.l.)Average number of hours per year from 1981-2010 with a heat index value of 95F or above.Significant increases in total number of hours per year at NYC Central Park (16.7) and Block Island due increase in occurrence after 1999Block Island RI had no hours prior 1999.8Fewest northern tier (cool summers)Northern NH, VT, & NY < 35Most of ME, northern VT & NY < 25

Highest southern tier (warm summers)Urban areas > 65(NYC, Providence & Boston) Coast east of Long Island < 50Cape Cod < 35

3a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC8Heat Index ClimatologyTotal number of days with a heat index of 100 F (1981-2010)

(/) Significant trends (95 % c.l.)Total number of days with a heat index value of 100F or above over the climate normal period 1981-2010 .Five significant decrease at Houton ME, Montpelier VT, Floyd Bennett, Albany and Elmira NYHoulton and Montpelier due to a few days in the 80s & early 90s but nothing after 1995Elmira & Floyd Bennett Significantly above average count in 1983 (and lesser so in 1988 for all and Albany) and no trend since 1995Significant increase at Block Island RI due to occurrence of days in 2006 and 2010 none prior.9Fewest northern tier (cool summers)Northern NH, VT, & NY < 5Most of ME, northern NH, VT, & NY < 10

Highest southern tier (warm summers)Urban areas > 10 (NYC, Providence & Boston) Coast east of Long Island < 5Cape Cod < 2

3a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC9Heat Index ClimatologyAverage hours per year with a heat index of 100 F (1981-2010)

Highest southern tier (warm summers)

(/) Significant trends (95 % c.l.)Average number of hours per year from 1981-2010 with a heat index value of 100F or above.Significant decreases at four stations and 1 increaseSignificant decreases in total number of hours per year at Barnes MA (15.6 +- 4.7), houlton ME (0.6 +- 0.2), Elmira (5.5 +- 1.7) and Montpelier (1.9 +- 0.6)Houlton and Montpelier had few hours overall with all occurring prior to 1995Barnes high total hours in 1981-1983 (61 in 1983) and a smaller peak in early 90s. All annual total hours less than each of first three yearsElmira pattern was similar to Barnes but with high total in 1983 and early 90s then dropping off Significant increases in total number of hours per year at Block Island (4.8 +- 1.5) due to occurrence in 2006 and 2010 none prior.10Extreme heat index values ( 95 F) occurred: most frequently over the densely populated, urban areas of southern New York, Connecticut, Rhode Island, and eastern Massachusetts. much less frequently across Maine, northern New Hampshire and Vermont, and northern and western portions of New York.infrequently over most of Maine and the higher elevations of the Green Mountains of Vermont and New Yorks Adirondacks.

Despite the southern location and proximity to large urban centers, coastal areas of southern New England, particularly Cape Cod, had a low occurrence of extreme and dangerous heat and humidity.3a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC10SummaryDespite the northern location, uncomfortable and even dangerous atmospheric conditions due to the combined effects of high heat and humidity occur throughout New England and New York. 113a.2: Stampone & GlennAMS 19th Conference on Applied Climatology 18-20 July 2011 Asheville, NC11Acknowledgements Support for this work was provided by:

New Hampshire State Climate OfficeUniversity of New Hampshire

and

National Oceanic and Atmospheric AdministrationNational Weather Service Forecast OfficeNewport/Morehead City, NC & Gray, ME