Monthly Weather Report April 2019 Director General Pakistan Meteorological Department Prepared by: National Weather Forecasting Center Islamabad Contents SUMMARY ....................................................................................................................................... 1 INTRODUCTION ............................................................................................................................... 2 FIRST SPELL ................................................................................................................................... 3 SECOND SPELL ................................................................................................................................ 5 THIRD SPELL .................................................................................................................................. 7 FOURTH SPELL ............................................................................................................................... 9 ACCUMULATIVE RAINFALL ......................................................................................................... 11 FORECAST VALIDATION ............................................................................................................... 13 TEMPERATURE ............................................................................................................................. 14 DROUGHT CONDITION .................................................................................................................. 15 WEATHER OUTLOOK FOR MAY ................................................................................................... 16 ACKNOWLEDGMENT .................................................................................................................... 17 REFERENCES ................................................................................................................................. 17 ANNEX I ........................................................................................................................................ 18 List of Figures Figure 1 Synoptic situation on 10th April 2019. Shaded portion represents the geopotential height pattern at 500 hPa, solid line represents the geopotential height pattern at 850 hPa, while arrows indicate 850 hPa winds. ...................................................................................................... 3 Figure 2 Rainfall (mm) distribution on 10th April 2019. ............................................................... 4 Figure 3 Synoptic situation on 12th April 2019. Shaded portion represents the geopotential height pattern at 500 hPa, solid line represents the geopotential height pattern at 850 hPa, while arrows indicate 850 hPa winds. ...................................................................................................... 5 Figure 4 Rainfall (mm) distribution on 12th April 2019. ............................................................... 6 Figure 5 Synoptic situation from 16th to 18th April 2019. Shaded portion represents the geopotential height pattern at 500 hPa, solid line represents the geopotential height pattern at 850 hPa, while arrows indicate 850 hPa winds. ..................................................................................... 7 Figure 6 Rainfall (mm) distribution during 15th to 18th April 2019. .............................................. 8 Figure 7 Synoptic situation from 24th to 26th April 2019. Shaded portion represents the geopotential height pattern at 500 hPa, solid line represents the geopotential height pattern at 850 hPa, while arrows indicate 850 hPa winds. ..................................................................................... 9 Figure 8 Rainfall (mm) distribution during 24th to 26th April 2019. ............................................ 10 Figure 9 Rainfall (mm) distribution during April 2019. .............................................................. 11 Figure 10 Rainfall departure in April 2019 .................................................................................. 12 Figure 11 Spatial distribution of rainfall (mm) departure in April 2019 ..................................... 12 Figure 12 Temperature comparison between normal and April 2019 maximum temperatures. 14 Figure 13 Temperature anomaly in April w.r.t 1981-2010 .......................................................... 14 Figure 14 Drought outlook during the month of April. ............................................................... 15 List of Tables Table 1 Forecast verification contingency table .......................................................................... 13 Table 2 Percentage accuracy of each spell ................................................................................... 13 SUMMARY 1. In April 2019 area weighted rainfall of the country remained above normal +58 %. 2. On regional basis rainfall was above normal in Balochistan +184%, Punjab +146%, Khyber Pakhtunkhwa +10%, and below normal in Gilgit Baltistan -68%, Azad Jammu and Kashmir -20% and Sindh -4%. 3. Highest accumulated precipitation during the whole month was recorded in Dir, Khyber Pakhtunkhwa, 190 mm. 4. Highest amount of rainfall during 24 hours was recoded in Jiwani, Balochistan, 89.0 mm. 5. Highest Maximum Temperature was recorded in Shaheed Benazirabad, 46.5℃. 1 INTRODUCTION April is the first month in which summer conditions are settling in over most parts of the country. During April mean minimum temperature varies from 4.0℃ in Kalam to 23.0℃ in Karachi. While mean maximum temperature varies from 15.2℃ in Astore to 40.2℃ in Shaheed Benazirabad. Normal area weighted rainfall in April for Pakistan is 22.5 mm. For Khyber Pakhtunkhwa 73.9 mm, Punjab 20.6 mm, Balochistan 10.9 mm, Sindh 3.1 mm, Azad Jammu and Kashmir it is 45.2 mm and Gilgit Baltistan 38.8 mm. In April 2019 area weighted rainfall of Pakistan remained above normal +58%. On regional basis rainfall was above normal in Balochistan +184%, Punjab +146% and Khyber Pakhtunkhwa +10% below normal in Gilgit Baltistan -68%, Azad Jammu and Kashmir -20% and Sindh -4%. In this month highest maximum temperature was recorded in Shaheed Benazirabad (46.5℃). Highest accumulated precipitation during the whole month was reported from Dir, Khyber Pakhtunkhwa (190 mm). While highest amount of rainfall during 24 hours was recoded in Jiwani, Balochistan (89.0 mm). Pakistan experienced four rainfall spells during this month. Their detail is appended below. 2 FIRST SPELL First rainfall spell in April was on 10th of the month. Synoptic situation during this day as obtained by NCEP/NCAR reanalysis dataset (Kalnay 1996) is shown in figure 1. A westerly wave is present over the central parts of the country and a trough of low pressure can also be seen at 850 hPa. Figure 1 Synoptic situation on 10th April 2019. Shaded portion represents the geopotential height pattern at 500 hPa, solid line represents the geopotential height pattern at 850 hPa, while arrows indicate 850 hPa winds. 3 Rainfall distribution during the first spell is shown in figure 2. This spell produced rainfall in upper and central parts of the country. Most of the southern parts of the country remained dry during this spell. Figure 2 Rainfall (mm) distribution on 10th April 2019. 4 SECOND SPELL Second wet spell of the month was on 12th April. The synoptic situation on this day was very similar to the previous wet spell. A westerly wave in upper air and a trough at lower level is present. An anticyclonic circulation is also present in South Arabian Sea Figure 3 Synoptic situation on 12th April 2019. Shaded portion represents the geopotential height pattern at 500 hPa, solid line represents the geopotential height pattern at 850 hPa, while arrows indicate 850 hPa winds. Spatial distribution of rainfall on 12th April is shown in figure 4. It shows northern parts of the country received rainfall, while most of the southern parts of the country remained dry. 5 Figure 4 Rainfall (mm) distribution on 12th April 2019. 6 THIRD SPELL Third wet spell of April was during 15th to 18th. The synoptic situation during these days is shown in figure 5. A strong cyclonic circulation on 16th April is seen gripping most of the central parts of the country. 850 hPa wind direction is also predominantly southwesterly transporting moisture from the Arabian Sea to upper parts of the country. This weather system latter on 17th and 18th April moved to upper parts of the country. Figure 5 Synoptic situation from 16th to 18th April 2019. Shaded portion represents the geopotential height pattern at 500 hPa, solid line represents the geopotential height pattern at 850 hPa, while arrows indicate 850 hPa winds. Figure 6 represents the spatial distribution of rainfall during the spell. In this spell most parts of the country received rainfall. Upper parts of the country received more rainfall than rest of the country. 7 Figure 6 Rainfall (mm) distribution during 15th to 18th April 2019. 8 FOURTH SPELL Third wet spell of April was during 24th to 26th. The synoptic situation during these days is shown in figure 7. A shallow cyclonic circulation gripped the country on 24th April and persisted for next two days producing rainfall in different parts of the country. Figure 7 Synoptic situation from 24th to 26th April 2019. Shaded portion represents the geopotential height pattern at 500 hPa, solid line represents the geopotential height pattern at 850 hPa, while arrows indicate 850 hPa winds. 9 Figure