Monthly Weather Report

April 2021

Director General

Pakistan Meteorological Department

Prepared by: National Weather Forecasting Center

Islamabad

Contents

SUMMARY ....................................................................................................................................... 1

INTRODUCTION ............................................................................................................................... 2

FIRST DECADE ................................................................................................................................. 3

SECOND DECADE ............................................................................................................................. 6

THIRD DECADE ............................................................................................................................... 9

ACCUMULATIVE RAINFALL ......................................................................................................... 12

RAINFALL DEPARTURE ................................................................................................................ 13

FORECAST VALIDATION ............................................................................................................... 14

TEMPERATURE ............................................................................................................................. 15

DROUGHT CONDITION .................................................................................................................. 16

ACKNOWLEDGMENT .................................................................................................................... 17

REFERENCES ................................................................................................................................. 17

ANNEX I ........................................................................................................................................ 18

List of Figures Figure 1 Synoptic situation 1st to 10th April 2021. 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. ...................................................................................................... 4

Figure 2 Rainfall (mm) distribution on 1st to 10th April 2021 ........................................................ 5

Figure 3 Synoptic situation from 11th to 20th April 2021. 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 4 Rainfall (mm) distribution during 11th to 20th April 2021 ............................................... 8

Figure 5 Synoptic situation from 21st to 30th April 2021. 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. ................................................................................... 10

Figure 6 Rainfall (mm) distribution during 21st to 30th April 2021 ............................................. 11

Figure 7 Rainfall (mm) distribution during April 2021 ............................................................... 12

Figure 8 Rainfall departure in April 2021 .................................................................................... 13

Figure 9 Spatial distribution of rainfall (mm) departure in April 2021 ....................................... 13

Figure 10 Temperature comparison between normal and April 2021 maximum temperatures .. 15

Figure 11 Mean temperature anomaly in April 2021 w.r.t 1981-2010 ........................................ 15

Figure 12 Drought outlook during the month of April 2021 ....................................................... 16

List of Tables Table 1: Rainfall Departure............................................................................................................ 2

Table 2 Forecast verification contingency table .......................................................................... 14

Table 3 Percentage accuracy of decade ........................................................................................ 14

1

SUMMARY

1. In April 2021 area weighted rainfall of Pakistan remained below normal by -29%.

2. On regional basis rainfall was below normal in Sindh -47%, Punjab -35%, Gilgit Baltistan -

31%, Azad Jammu and Kashmir -30%, Balochistan -27%, and in Khyber Pakhtunkhwa -26%.

3. Highest accumulated precipitation during the whole month was recorded in Balakot 152 mm.

4. Highest amount of rainfall during 24 hours was recorded in Balakot 66 mm on 22nd April.

5. Highest maximum temperature of 45.5℃ was recorded in Shaheed Sh. Benazir Abad on 4th of

April.

2

INTRODUCTION

Normal area weighted rainfall in April for Pakistan is 22.5 mm. For Azad Jammu and Kashmir it

is 79.6, Balochistan 10.8 mm, Gilgit Baltistan 36.1 mm, Khyber Pakhtunkhwa 74.5 mm, Punjab

20.6 mm and Sindh 3.1 mm. In April 2021 area weighted rainfall of Pakistan remained below

normal by -29%. On regional basis rainfall was below normal in Sindh -47%, Punjab -35%, Gilgit

Baltistan -31%, Azad Jammu and Kashmir -30%, Balochistan -27%, and in Khyber Pakhtunkhwa

-26%.

In this month highest maximum temperature of 45.5℃ was recorded in Shaheed. Benazir Abad on

4th April. Highest accumulated precipitation during the whole month was recorded in Balakot 152

mm. While highest amount of rainfall during 24 hours was also recorded in Balakot 66 mm on

22nd of the month.

Table 1: Rainfall Departure

3

FIRST DECADE

Synoptic situation during first decade of April 2021 as obtained by NCEP/NCAR reanalysis

dataset (Kalnay 1996) is shown in figure 1. A shallow westerly wave remained on upper areas of

the country. During 5th to 7th April circulation was present at 850 hPa on central and northern parts

of the country that caused rainfall in upper areas.

4

Figure 1 Synoptic situation 1st to 10th April 2021. 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

Rainfall distribution during the first decade is shown in figure 2. During this period upper parts of

the country especially Khyber Pakhtunkwa, Gilgit Baltistan and Azad Jammu & Kashmir received

moderate to heavy rainfall. While in Punjab and parts of Balochistan light rainfall recorded.

However rest of the country remained dry.

Figure 2 Rainfall (mm) distribution on 1st to 10th April 2021

6

SECOND DECADE

Synoptic situation during the second decade of the month is shown in figure 3. Most upper parts

of the country remained in the grip of a westerly wave from 15th to 18th of April. Moisture supply

from Arabian Sea at 850 hPa caused light to moderate rainfall in the country.

7

Figure 3 Synoptic situation from 11th to 20th April 2021. 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.

8

Spatial distribution of rainfall from 11th to 20th April 2021 is shown in figure 4. It shows that most

of the upper parts of the country receive rainfall with few heavy spells recorded in Khyber

Pakhtunkwa. Parts of Azad Jammu & Kashmir and Punjab also received moderate rainfall. While

Gilgit Baltistan, Balochistan and Sindh received light rainfall during this decade.

Figure 4 Rainfall (mm) distribution during 11th to 20th April 2021

9

THIRD DECADE

The synoptic situation during the third decade is shown in figure 5. A westerly wave entered

western parts of the country on 21st of the month due to which upper parts received rainfall on 21st

to 23rd of April. Moisture availability at 850 hPa from Arabian Sea and southeastern winds

supported the system.

10

Figure 5 Synoptic situation from 21st to 30th April 2021. 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.

11

Figure 6 represents the spatial distribution of rainfall during the third decade. Most upper parts of

the country especially Khyber Pakhtunkwa, Azad Jammu & Kashmir received moderate to heavy

rainfall. While parts of Punjab received light to moderate rainfall. Balochistan and some areas of

Sindh received light rainfall.

Figure 6 Rainfall (mm) distribution during 21st to 30th April 2021

12

ACCUMULATIVE RAINFALL

In April most parts of the country received rainfall. Figure 7 represents the spatial distribution of

rainfall during the month of April. The center of maximum rainfall was in Upper Khyber-

Pakhtunkhwa and Azad Jammu & Kashmir. Details of rainfall are appended in annexure I.

Figure 7 Rainfall (mm) distribution during April 2021

13

RAINFALL DEPARTURE

During this month area weighted rainfall of the country remained below normal -29%. On regional

basis rainfall was below normal in Sindh -47%, Punjab -35%, Gilgit Baltistan -31%, Azad Jammu

and Kashmir -30%, Balochistan -27% and in Khyber Pakhtunkhwa -26% as represented in figure

8 (CDPC 2021). Spatial distribution of rainfall departure in the month of April with respect to the

base period of 1961-2010 is shown in figure 9.

Figure 8 Rainfall departure in April 2021

Figure 9 Spatial distribution of rainfall (mm) departure in April 2021

14

FORECAST VALIDATION

An attempt is made to substantiate the accuracy of precipitation forecasts issued in April. This is

done by using the contingency table 2, for each of the three decades. This table is used to find out

the level of agreement between forecast and actual observation. The difference between forecast

and observation is the error. The lower the errors, the greater the accuracy.

Table 2 Forecast verification contingency table

Observed

Yes No Total

Foreca

st

Yes Hits False Alarms Forecast Yes

No Misses Correct Negatives Forecast No

Total Observed Yes Observed No Total

Hits means when the precipitation was forecasted and it occurred. Miss is used when the

precipitation was not forecasted and it occurred. False alarm means when the precipitation was

forecasted and it did not occur. Correct negatives are when the precipitation was not forecasted

and also it did not happen. Accuracy of forecast is calculated by using formula in equation 1. Table

3 describes the accuracy in each of the spells.

𝐴𝑐𝑐𝑢𝑟𝑎𝑐𝑦 = 𝐻𝑖𝑡𝑠 + 𝑐𝑜𝑟𝑟𝑒𝑐𝑡 𝑛𝑒𝑔𝑎𝑡𝑖𝑣𝑒𝑠/𝑇𝑜𝑡𝑎𝑙 (1)

Table 3 Percentage accuracy of each decade

Rainfall spells Percentage accuracy

First Decade 94.5

Second Decade 79.8

Third Decade 85.1

Average 86.5

15

TEMPERATURE

During the month of April slightly above normal maximum temperatures were recorded in

Pakistan. Maximum temperatures in Sindh, Balochistan and Khyber Pakhtunkhwa remained above

normal. In Punjab temperatures remained near to normal. However in Gilgit Baltistan and Azad

Jammu Kashmir mean maximum temperature remained below normal. Figure 10 represents the

comparison of April 2021 and mean maximum temperatures over the country. Spatial distribution

of mean temperature anomaly is shown in figure 11.

Figure 10 Temperature comparison between normal and April 2021 maximum temperatures

Figure 11 Mean temperature anomaly in April 2021 w.r.t 1981-2010

16

DROUGHT CONDITION

According to the latest drought analysis done by National Drought Monitoring Center of PMD,

Wet conditions prevailed over most of the northern most parts of the country. During the month

of April, rains in the agricultural plains of Khyber Pakhtunkhwa and Punjab gave relief to the

crops. Some districts in Sindh are under Moderate drought conditions due to no or very less

precipitation and persistent dry conditions over there. Drought analysis results using different

indices is represented in figure 12.

Figure 12 Drought outlook during the month of April 2021

17

ACKNOWLEDGMENT

This work is produced by the combined efforts of Zaheer Babar (Director), Muhammad Irfan Virk

(Deputy Director) and Mehar Fatima (Assistant Meteorologist). Special thanks to Mr. Muhammad

Safdar, Sheeza Khan National Weather Forecasting Center (NWFC), Islamabad. Mr. Nadeem

Faisal, Climate Data Processing Center (CDPC), Karachi. Mr. Ibrar Qureshi, Flood Forecasting

Division (FFD), Lahore. Mr. Nassir Yaseen, National Drought Monitoring Centre (NDMC),

Islamabad.

REFERENCES

CDPC, Pakistan Meteorological Department. 2021. “Winter Rainfall Update.” 2021.

http://www.pmd.gov.pk/cdpc/winter2021_rainfall_update.htm.

Kalnay, E. 1996. “The NCEP/NCAR 40-Year Reanalysis Project.” Bull. Am. Meteorol. Soc. 77

(3): 437–71. https://doi.org/10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2.

18

ANNEX I

Accumulative rainfall (mm) in April 2021, and their deviation from the normal rainfall.

PUNJAB STATIONS APR-21 NORMAL DEVIATION

BAHAWALNAGAR 4.01 10.8 -6.8

BAHAWALPUR,CITY 2.71 10.5 -7.8

BAHAWALPUR,AIRPORT 2.83 ** **

BHAKKAR 11.6 ** **

CHAKWAL 31.5 ** **

D.G.KHAN 7.01 ** **

FAISALABAD 12.63 23.7 -11.1

CHAKLALA AIRBASE 39.43 63.2 -23.8

ISLAMABAD,ZEROPOINT 50.02 59.6 -9.6

ISLAMABAD, AIRPORT 36.53 **

JHANG 5.12 ** **

JOHARABAD 19.22 ** **

JHELUM 20.87 40.2 -19.3

KASUR 34.03 ** **

KHANPUR 3.6 4.3 -0.7

KOT ADDU 3.21 ** **

KAMRA 14.56 73 -58.4

LAHORE, AIRPORT 30.14 21.1 9

LAHORE,CITY 18.56 21.6 -3

LAYYAH 8.03 ** **

MANDIBAHAUDDIN 25.03 ** **

MIANWALI AIRBASE 34.06 52.8 -18.7

MULTAN AIRPORT 2.71 14.2 -11.5

MULTAN CITY 3.72 ** **

MANGLA 11.93 ** **

MURREE 75 131.8 -56.8

NOORPUR THAL 40.91 ** **

OKARA 5.53 ** **

RAHIM YAR KHAN 6.61 ** **

GUJRANWALA 18.53 ** **

GUJRAT 20 ** **

SAHIWAL 3.24 ** **

SHORKOT 3.04 21.8 -18.8

SARGODHA AIRPORT 5.55 33.7 -28.2

SARGODHA CITY 5.41 ** **

SIALKOT CANTT 14.54 33.5 -19

SIALKOT AIRPORT 48.31 ** **

T.T. SINGH 5.7 ** **

HAFIZABAD 27.21 ** **

KHANEWAL 2.02 ** **

NAROWAL 48.72 ** **

19

GILGIT BALTISTAN & AZAD KASHMIR

STATIONS APR-21 NORMAL DEVIATION

ASTORE 43.7 85.5 -41.8

BUNJI 23.25 26.8 -3.6

BAGROTE 42.81 ** **

CHILAS 17.43 38.2 -20.8

G.DOPATTA 85.6 119 -33.4

GILGIT 18.23 25.5 -7.3

GUPIS 14 51.6 -37.6

KOTLI 75 72.8 2.2

MUZAFFARABAD AIRPORT 126.6 107.1 19.5

MUZAFFARABAD CITY 105 ** **

RAWALAKOT 130.02 ** **

HUNZA 16.3 ** **

SKARDU 27.64 37.2 -9.6

KHYBER PAKHTUNKHWA

STATIONS APR-21 NORMAL DEVIATION

BALAKOT 152 117.6 34.4

BANNU 12.4 21.2 -8.8

CHERAT 21 66.4 -45.4

CHITRAL 40.2 78.7 -38.5

D.I.KHAN 37.02 23.9 13.1

DIR 64 166 -102

LOWER DIR 50 ** **

DROSH 49.2 97.7 -48.5

KAKUL 87.8 111.9 -24.1

KALAM 134.6 ** **

KOHAT 79.02 54.9 24.1

MALAMJABBA 116 ** **

MIRKHANI 66.02 ** **

PARACHINAR 71 87.8 -16.8

PESHAWAR AIRPORT 24.92 62.1 -37.2

PESHAWAR CITY 20.23 ** **

PATTAN 127.2 ** **

RISALPUR 11.06 54.3 -43.2

SAIDU SHARIF 59.5 125 -65.5 SINDH

STATIONS APR-21 NORMAL DEVIATION

BADIN 1.01 1.7 -0.7

CHHOR 0 2.3 -2.3

HYDERABAD 17 7 10

JACOBABAD 1 2.7 -1.7

KARACHI A/P 0 3 -3

LARKANA 3 4.5 -1.5

MITHI 0 ** **

SH.B.ABAD 1 2.8 -1.8

PADIDAN 2 2.1 -0.1

20

ROHRI 1 4.9 -3.9

SUKKUR 0.01 5.7 -5.7

M.JO.DARO 12 2.9 9.1

THATTA 0 ** **

DADU 11 ** **

MIRPUR KHAS 0 ** **

TANDO JAM 0.01 ** **

BALOCHISTAN

STATIONS APR-21 NORMAL DEVIATION

BARKHAN 25 31.3 -6.3

DALBANDIN 0.01 5.6 -5.6

GAWADAR 0 ** **

JIWANI 0 3.4 -3.4

KALAT 4.01 8.4 -4.4

KHUZDAR 8.2 16.2 -8

LASBELA 35.01 7.2 27.8

NOKKUNDI 0.51 1.7 -1.2

PANJGUR 0 7.2 -7.2

PASNI 0 1.8 -1.8

QUETTA. (SH MANDA) 4.01 ** **

QUETTA. (SAMUNGLI) 4.04 22.9 -18.9

SIBBI 1.02 7.1 -6.1

TURBAT 2.3 1.6 0.7

ORMARA 0 0 0

ZHOB 19 31.9 -12.9