HEAT WAVES AND EFFETCS IN THE INDIAN SUB CONTINENT

heat waves

1. Data from 1293 weather stations in the country have been received from the new_csv7d_latlong.csv file. Of these, 350 are observed stations, while the remaining stations are forecast stations and city weather stations. Observed stations provide data for today as well as seven days of forecast data, while forecast stations only provide seven days of forecast data. Station Data

2. To accurately interpolate maximum temperature we use the observed 12:00 UTC maximum temperature from yesterday for the morning and the 12:00 UTC maximum temperature from today for the evening, along with the next five days of forecast data. We calculate the maximum temperature departure using pentad normal data from 1991-2020 from CRS Pune and the observed 12:00 UTC maximum temperature for observed stations and also forecast stations. The resulting spatial map is also used on the heat wave web-GIS page. Additionally, the observed maximum temperature and its departure for the past five days are also available on the web-GIS page . Maximum Temperature & Departure

3. Pentad Normal (1991-2020) In ISSD script, taking Normals of 28 february for 29 february . CRS Pune has provided pentad normal data with 73 columns for each 5 days. It will consist of 365 days so when leap year occurs then we have 366 days so for this leap year we take 28 feb data normal for calculating departure for 29 feb . 12 th column of pentad will use for 25 th feb to 1 st mar (5days). During leap year, it is 25 th feb to 1 st mar (6days).

4. Similarly, to determine the minimum temperature, we use the observed 03:00 UTC station data for today's data and combine it with observed and forecast stations for the next five days of forecast data . We also calculate the minimum temperature departure using pentad normal data from 1991-2020 from CRS Pune and the observed 03:00 UTC minimum temperature for observed stations and forecast stations. The resulting spatial map is used on the heat wave web-GIS page. Additionally, the observed minimum temperature and its departure for the past five days are also available on the web-GIS page. Minimum Temperature and its Departure

5. To interpolate relative humidity, we use the observed relative humidity at 12:00 UTC from yesterday and the observed relative humidity at 03:00 UTC from today for the morning, and the relative humidity at 12:00 UTC from today for the evening. The resulting spatial map is then utilized on the heatwave web-GIS page. Additionally, the observed relative humidity for the past five days is also available on the web-GIS page. Relative Humidity (RH)

6. The data collected from 0900UTC synoptic data includes the dry bulb temperature, wind speed, wind direction, and relative humidity. Similarly , the forecast data are used for the next five days. These products are one of the inputs for the generation of heat wave bulletin including heat index. 09:00UTC Temperature , wind speed, wind direction and Relative Humidity

7. The observed max temperature and its departure are used to calculate the heat wave / Severe Heat Wave for today and the forecast max temperature and its departure are used for the next five days' heat wave / Severe Heat Wave. (Reference: Forecasting Circular No. 5/2015 (3.7). Heat wave is considered if maximum temperature of a station reaches at least 40°C or more for Plains and at least 30°C or more for Hilly regions. a) Based on Departure from Normal Heat Wave: Departure from normal is 4.5°C to 6.4°C Severe Heat Wave: Departure from normal is >6.4°C b) Based on Actual Maximum Temperature Heat Wave: When actual maximum temperature ≥ 45°C Severe Heat Wave: When actual maximum temperature ≥47°C Criteria for describing Heat Wave for coastal stations When maximum temperature departure is 4.5°C or more from normal, Heat Wave may be described provided actual maximum temperature is 37°C or more. Heat Wave

8. The observed max temperature and minimum departure are used to calculate the warm night/severe warm night for today and the forecast max temperature and minimum departure are used to calculate the warm night/severe warm night for the next five days . It should be considered only when maximum temperature remains 40°C or more. It may be defined based on departures or actual minimum temperatures as follows: Warm night: minimum temperature departure is 4.5°C to 6.4°C Very warm night: minimum temperature departure is >6.4°C Warm Night

9. The heat index for today is calculated using the dry bulb temperature and relative humidity from 0900UTC synoptic data. For the next five days, the heat index is calculated using the forecast temperature and relative humidity. Heat index formula : https:// www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml The computation of the heat index is a refinement of a result obtained by multiple regression analysis carried out by Lans P. Rothfusz and described in a 1990 National Weather Service (NWS) Technical Attachment (SR 90-23). The regression equation of Rothfusz is HI = -42.379 + 2.04901523*T + 10.14333127*RH - .22475541*T*RH - . 00683783*T*T - .05481717*RH*RH + .00122874*T*T*RH + .00085282*T*RH*RH - . 00000199*T*T*RH*RH Where , T is temperature in degrees F and RH is relative humidity in percent. HI is the heat index expressed as an apparent temperature in degrees F. Heat Index

10. If the RH is less than 13% and the temperature is between 80 and 112 degrees F, then the following adjustment is subtracted from HI: ADJUSTMENT = [(13-RH)/4]*SQRT{[17-ABS(T-95.)]/17} Where, ABS and SQRT are the absolute value and square root functions, respectively. On the other hand, if the RH is greater than 85% and the temperature is between 80 and 87 degrees F, then the following adjustment is added to HI: ADJUSTMENT = [(RH-85)/10] * [(87-T)/5 ] Heat Index

11. The Rothfusz regression is not appropriate when conditions of temperature and humidity warrant a heat index value below about 80 degrees F. In those cases, a simpler formula is applied to calculate values consistent with Steadman's results: HI = 0.5 * {T + 61.0 + [(T-68.0)*1.2] + (RH*0.094)} In practice, the simple formula is computed first and the result averaged with the temperature. If this heat index value is 80 degrees F or higher, the full regression equation along with any adjustment as described above is applied . The Rothfusz regression is not valid for extreme temperature and relative humidity conditions beyond the range of data considered by Steadman. Heat Index

12. The maximum temperature percentile of a station refers to the ranking of the maximum temperature of any particular day with respect to all the maximum temperatures recorded for all the days of that months in record. For example, if there were 100 maximum temperature value records and these are arranged in ascending order, then the highest 90th value will be called 90th percentile, 95th value will be called 95th percentile and 98th value will be termed as 98th percentile. Statistically, the percentile values convey the information that 90th percentile temperature indicate that the 90 percent of times the maximum temperatures will be cooler than this temperature or in other words the maximum temperature above 90th /95th/98th percentile indicate the unseasonably warm day of any month. By subtracting the temperature value from the 98th, 95th, and 90th percentile marks, creating a departure map for the 98th, 95th, and 90th percentiles. This applies to both the maximum and minimum temperatures. Temperature Percentile Map & Departures

13. GIS based important Heat Wave Products (Completed) Forecast Max Temp ( up to 5 days) Forecast Min Temp (up to 5 days) Forecast Severe / Heat Wave (up to 5 days) Forecast Warm/very Warm Night 90/95/98 Percentile of Max & Min Temp Forecast Temp, RH& Wind Speed & direction Forecast of Heat Index Observed Max Temperatures & Dep Observed Min Temperatures & Dep Observed Severe/Heat Wave Observed Warm/Very Warm Night 90/95/98 Percentile of Max and Min Temp Observed Relative Humidity Observed Temp, Wind Speed & Direction Observed Heat Index 12 UTC Today and Past 5days 03 UTC Today and Past 5days 12 UTC Today and Past 5days 12 UTC Today and Past 5days 03 & 12 UTC Today and Past 5days 03, 09 & 12 UTC Today and Past 5days 09 UTC Today and Past 5days 09 UTC Today and Past 5days 00 UTC MME for next 5days 00 UTC MME for next 5days 00 UTC MME for next 5days 00 UTC MME for next 5days 00 UTC MME for next 5days 09 UTC for next 5days 09 UTC for next 5days

14. The products are to be added in the heat wave GIS WEB Page (Ongoing) Climatology Spatial Patterns of Maximum and Minimum normal for March – June Heat Wave Days in March – June (1961-2020 or 1991-2020) Average HW days during a) the El Nino years and b) La Nina years during the period 1961-2020 Monthly mean Relative Humidity (%) Monthly mean Wind Speed (Knots) Vulnerability due to heat wave 1969 to 2019 Vulnerable Zones due to heat wave (MAMJJ ) Monthly mean Hot Weather Hazard Scores Heat Wave IBF Heat Hazard Analysis

15. Thank you for your kind attention. Any queries or suggestions