Wind Chill: A Forward Approach

Kelly Balmes, Brian Adams, Justin McCoy

*Wind Chill: A Forward Approach

Statement of the Problem:• When cold temperatures already exist, wind can

make the situation much worse. • Dangerously low wind chill temperatures can cause

serious health concerns such as frostbite, hypothermia, breathing impediments for sensitive groups, and other health complications.

• It is for this reason that having timely forecasts is of the utmost importance for the protection of human life.

*Introduction

*Case Study: January 5-7, 2014

Cold Spell*Air mass of arctic origin draped across the Northern Midwest

*Wind gusts of 25 to 45 mph, wind chill values of -35 to -55 degrees

*Coldest stretch of weather since February of 1996

*Wind Chill Warnings issued 48 hours in advance,all of Iowa, Minnesota, and Wisconsin were under warnings

*All schools closed on Monday the 6th, most remained closed on the 7th.

*Also used data from January 24th-26th, anothersignificant cold spell

• Create plots of probabilities that determine the chance of temperatures exceeding the thresholds for either an advisory or a warning for two different lead times (24 and 48 hours).

• Determine the likelihood of an advisory or warning being issued for the inputted latitude and longitude.

*Objectives

• Collection of SREF ensemble files – provided by Dr. Greybush.• Data from January 4th, 6th, 24th, and 26th, 2014• Actual wind chill advisory and warning events.

*Description of Input Data

• Defined threshold temperatures values for wind chill advisories and warnings.• Wind Chill = 35.74 + 0.6215T - 35.75(V0.16) +

0.4275T(V0.16) • Advisory threshold = -26.111 degrees C• Warning Threshold = -31.667 degrees C

• Calculated probabilities of thresholds being exceeded.

• Calculated how many ensemble members had exceeded the threshold at each grid point.

*Decision Support

Algorithm

• Inputted latitude and longitude read in from the terminal.

• Probabilities were calculated using data from all the ensemble members and thresholds.

• Detailed maps were created, showing which areas were experiencing conditions that were conducive to significantly low wind chill temperatures.

*Implementation Details

• Output came in the form of plotted maps, like the one shown below, for wind chill temperatures.

* Description of Output

• The output also delivers probabilities of advisories and warnings at each grid point.

* Description of Output

• The output also delivers probabilities of advisories and warnings at each grid point.

* Description of Output

*Comparison of Output to Actual Event

• The output also displays to the terminal the likeliness (over or under 50% probability) of a warning or advisory being issued for an inputted latitude and longitude, which can physically be entered by a user of the program.

* Description of Output

• Two cities were chosen in order to test the validity of our program’s ability to determine wind chill advisories and warnings.

• First Test: Madison, WI (43.0667N, 89.4W) – test results yielded likely wind chill advisory and warnings.

* Test Plan and Examples

• Second Test: Dallas, Tx (32.7758N, 96.7967W) – test results yielded unlikely wind chill advisories and warnings.

* Test Plan and Examples

• Can be used as a forecasting tool for forecasters determining wind chill advisory and warnings for particular locations.

• Forecasters will be able to input SREF data for a particular day to enhance their forecasts.

• Emergency management could use it for event cancellations if wind chill advisories or warnings were likely to be issued for the inputted latitude and longitude of an event venue.

*Potential Uses of this Product

• Different categories of likeliness for advisories/warnings (i.e. slight risks, moderate risks, high risks)

• Filtering out temperatures not conducive to significant wind chill conditions (i.e. 80 degrees in Florida)

• Taking different wind chill thresholds into account for each state

• Specifying the forecast lead times via terminal input, instead of just having 24- and 48-hour forecasts

*Future Improvements

• SREF ensemble files used to help determine wind chill advisories and warnings.

• Calculated probabilities of the likelihood of wind chill advisory and warnings.• Program output generates maps of wind chill

advisory/warning probabilities, as well as wind chill temperatures.

• Users of the program may input a specified latitude and longitude value.• Terminal prints to the screen the likelihood of a wind

chill advisory/warning for the desired location.

*In Summary