NOAA’s National Weather Service Heat Prediction Gregory Lundeen Science and Operations Officer Weather Forecast Office El Paso Area July 13, 2016 NOAA’s National Weather Service

Heat Prediction Heat Wave Defined Heat Climatology Heat Prediction Heat Advisory / Warning Addendum This presentation will come in four parts: Heat definition, heat climatology, heat prediction, and heat warnings/advisories. An addendum to the presentation will provide extra information on products that National Weather Service can provide but will not fit within the time limits of this presentation.

Heat Wave Definition: General – A prolonged period of abnormally hot weather relative to normal temperatures for that time of year. Technical – A period of 48 hours during which neither the overnight low nor the daytime heat index (or temperature) falls below NWS heat stress thresholds of 80F to 105 F. Definitions of a heat wave

Heat Wave Main meteorological signature of a heat wave Slow moving or nearly stationary high pressure aloft sets up conditions favorable for the development of heat waves due to sinking air under the high pressure dome. Main meteorological signature of a heat wave

Heat Wave Neccessary Conditions in the El Paso area: Subtropical high pressure aloft (Chihuahuan High) positioned just over or south the local area. If the high is too far east – Monsoonal Flow occurs and temperatures fall. Warmest Temperatures along the west side of the dome of high pressure. Dry atmospheric conditions (low humidity), sometimes with a southwest to west flow at the surface. Mostly likely occurrence June & July While some slight differences may occur from year to year, strong high pressure aloft and relatively drier conditions in the lower levels of the atmosphere are needed to generate a heat wave conditions in the El Paso area. These conditions are mostly likely to occur in the June and July time frame but could earlier in May or as late as September.

Heat & Heat Index For humidity values less than 40% the NWS heat index chart. Dangerous Heat conditions occur at around 105 degrees for either Heat Index or actual Temperatures. For the El Paso area low humidity values often accompany high temperatures. Therefore, temperatures are used in place of the heat index. For humidity values less than 40% the actual temperature replaces the heat index. Temperatures are used in the El Paso area.

Heat Climatology Months for 100 Degree Days: Month # Days Percent High Date May 63 3.3% 105 2005 June 875 45.3% 114 1994 July 708 36.7% 112 1979 August 257 13.3% 110 1884 September 27 1.4% 104 1982 Earliest - May 8th Latest - September 15th June and July are the peak months for high heat. The all time high temperature at El Paso was 114 degrees, set in 1994 on June 30th. Every year has had at least one 100 degree day. 1994 had the most 100 degree days at 62.

Heat Climatology Over the past 131 years the average number of 100 degree days is 15. The average number of 100 degree days have been increasing recently with an average 22 days of 100 or higher in the past 30 years. Possible factors in this increase may include climate change and increased urbanization of the El Paso metro area (heat island effect).

Heat Warning/Advisory Excessive Heat Warning—Take Action! issued within 12 hours of the onset of extremely dangerous heat conditions. Criteria - maximum temperature is expected to be 110° or higher for at least 2 days and night time air temperatures will not drop below 75°. Excessive Heat Watches—Be Prepared !Heat watches are issued when conditions are favorable for an excessive heat event in the next 24 to 72 hours. Heat Advisory—Take Action! issued within 12 hours of the onset of dangerous heat conditions. Criteria - maximum temperature is expected to be 105° or higher for at least 2 days, and night time air temperatures will stay above 75°. Excessive Heat Outlooks -issued when the potential exists for an excessive heat event in the next 3-7 days.

Heat Warning/Advisory Heat warning/advisory is not uniform across the country due to differences in the types of weather and general climatology across the country. This map indicates the thresholds for heat warnings/criteria for NWS Southern Region Offices.

Heat Prediction Forecast Tools: Climatology – mostly likely period June-July Climate Prediction Center (CPC) Provides Long Term Seasonal Outlooks out to 2 years. NCEP - NWS Numerical Models produce data out to as much as 16 days. Weather Prediction Center (WPC) issues national outlooks through 7 days. Local NWS forecast office issues area specific forecasts through 7 days. Climatology establishes the most likely period for heat waves which is June and July. The Climate Prediction Center uses long range models to predict long term trends in the weather which can be used in conjunction with climatology to get a general sense of whether warm seasons will be above or below normal. The NWS runs a variety of numerical models that can predict temperatures as well other weather effects out to as long as 16 days. The Weather Prediction Center and local Weather Offices use this information, experience and expertise to formulate forecasts out through 7 days and sometimes longer.

Climate Prediction Center Examples of the kind of information you can find on the Climate Prediction Center’s web site. CPC provides long term outlooks and trends. www.cpc.ncep.noaa.gov

Climate Prediction Center This 3 month outlook covers July, August, and September. It indicates the expected trends in temperatures and probability percentages. The El Paso area will have between a 40 and 50 percent chance of warmer than normal temperatures for the 3 month period. CPC 3 month outlook for temperature probability

Climate Prediction Center This 1 month outlook covers July. It indicates the expected trends in temperatures and probability percentages. The El Paso area will have between a 30 and 40 percent chance of warmer than normal temperatures for July. CPC 1 month outlook for temperature probability

Climate Prediction Center This is CPC’s shorter range outlook of 8 to 14 days. It uses a combination of climate model and weather model data to provide a trend, which indicates warmer than normal temperatures. CPC 8 to 14 day outlook for temperature probability

NWS Meteorological Models The NWS runs many forecast models to help predict trends in the weather. The GFS model is one of the NWS mainline models and provides detailed information on temperatures, moisture, precipitation, winds and a variety of other meteorological information. Global Forecast System (GFS) Model Temperature. Data provided out to 16 days with skill out to 8 days.

Weather Prediction Center WPC maximum heat index forecast www.wpc.ncep.noaa.gov/heat_index.shtml

Local Weather Office WFO El Paso Forecast Products (out to 7 Days) Area Forecast Discussion (AFD) Zone Forecast Discussion (ZFP) Hazardous Weather Outlook (HWO) Point Forecast Matrix (PFM) State Forecast Table (SFT) Graphical Forecasts (NDFD) (collaborated) Graphicasts (for Web Page, Facebook, etc) Weather Hazards Outlook & Matrix (for IDSS) Heat Advisory / Warning (NPW) A list of products the NWS WFO El Paso produces on a regular basis.

Local forecasts available on our webpage Forecast Products Most of our local forecast products are available on our web page as well as a variety of other products. Local forecasts available on our webpage weather.gov/epz

Forecast Products Gridded Forecast (NDFD) describes the Gridded forecast is locally updated and merged with a national digital forecast database from other weather offices which is accessible on the web. Gridded Forecast (NDFD) describes the weather in picture format out through 7 days

NWS Product Dissemination NOAA Weather Wire Service NOAA Weather Radio Web Pages Facebook Twitter TV, Radio and Print Media Decision Support to Core Partners The NWS will use a variety of outlets to get weather information to the public.

Wrap Up Questions to consider: What additional information do you need? Are the Advisory/Warning thresholds adequate? What lead times do you need? What resources would you like the NWS provide?

Thank You For Your Time! National Weather Service Forecast Office El Paso Area 7955 Airport Road Santa Teresa NM 88008 Phone: 575-589-4088 Fax: 575-589-4026 Web Page: weather.gov/epz Facebook: www.facebook.com/NWSElPaso

Addendum Useful Web Page Links More information on local forecast products NWS heat safety tips

Useful Web Page Links weather.gov weather.gov/epz www.ncep.noaa.gov www.cpc.ncep.noaa.gov www.wpc.ncep.noag.gov climate.gov www.srh.noaa.gov www.nws.noaa.gov/om/heat/index.shtml

Forecast Products Area Forecast Discussion Product that Describes current weather patterns and conditions. It discusses what to expect over the next seven days.

Forecast Products Point Forecast Matrices Product that lists specific Values for a Specific area Out through 7 days.

Forecast Products Hazardous Weather Outlook describes any expected hazardous weather (including heat) out through 7 days

Text based product that forecasts Forecast Products Zone Forecast Product Text based product that forecasts expected weather at specific regions within the area through 7 days.

Forecast Products Web Page Forecast on the local web page.

Graphicasts An example of WFO El Paso weather office graphicast emphasizing heat

Climate.gov A useful site that provides additional links to climate information and outlooks.

Heat Safety Tips Web Page Main page of NWS heat safety

Heat Safety Tips Heat Safety Tips

Heat Safety Tips Heat exhaustion and heat stroke information

Local Heat Safety Tips Locally produced graphicast emphasizing heat safety.