Hydrology and Meteorology Nagpokhari, Kathmandu, Nepal

Government of Nepal Ministry of Energy, Water Resources and Irrigation D epartment of Hydrology and Meteorology Nagpokhari, Kathmandu, Nepal.

PRELIMINARY WEATHER SUMMARY OF NEPAL May 2018

Note: This weather summary is based on daily data of 38 meteorological stations established by Department of Hydrology and Meteorology.

MAIN HIGHLIGHT Most parts of the country recorded normal to above normal rainfall and normal to below normal temperature (Fig.2 and Fig.4).

SYNOPTIC SEQUENCES An east-west trough extending up to 1.5 km above mean sea level ran from northwest Rajasthan to Manipur across the cyclonic circulations (CC) over Haryana, Uttar Pradesh, Gangetic West Bengal and Assam and Meghalaya on 2nd May 2018 and a western disturbance (WD) spurred wide spread rainfall covering whole Nepal on 3rd May. The trough became less marked on 3rd May however these circulation continued to bring significant amount of rainfall during 1st week.

North-south trough roughly along Long. 88°E to the north of Lat.24°N and CC over Bihar with trough at 1.5km from Bihar to Odisha along with a WD contributed well distributed rainfall over Nepal during 9th, 10th and 11th May. These systems became less marked by 11th May.

A trough ran from the cyclonic circulation over south Haryana to Nagaland across north Madhya Pradesh, Bihar, West Bengal and Meghalaya and extended up to 1.5 km above sea level on 13th and became less marked on 14th. The trough and a WD as CC over Jammu and Kashmir and trough aloft with its axis at 5.8km above sea level influenced rainfall that covered whole Nepal on 14th May and eastern Nepal on 15th. Another WD as a trough in mid-tropospheric westerlies with its axis at 5.8 km ran roughly along long. 82°E to the north of lat. 34°N, CC over Rajasthan and Madhya Pradesh and north-south trough along long. 92°E to the north of 24°N between 5.8 km & 7.6 km above mean sea level on 16th brought wide spread rainfall over the country on 17th.

CC over Bihar, Madhya Pradesh brought rain mostly to the eastern half of Nepal throughout the 4th week.CC over Punjab, Pakistan and Rajasthan as well as trough running from CC over northwest Madhya Pradesh to east Assam across Uttar Pradesh, Bihar, West Bengal and a low pressure area that formed over Bay of Bengal on 28th May and intensified into depression and crossed the Myanmar Coast on 30th May supported during last three days of the month.

PRECIPITATION DISTRIBUTION Normal to above normal rainfall occurred over most of the country except for southeastern parts of the country and few isolated patches over of the rest of the country where below normal rainfall was received (Fig.2). Among 38 stations, the highest 24 hour rainfall of 108.0 mm was recorded on 3rd May at Lumle while Pokhara Airport recorded the highest monthly total rainfall of 438.0mm (121.9% of normal rainfall) (Fig.2) Similarly, Taulihawa recorded the highest monthly total rainfall above normal in percentage (291.9%, 167.1mm)(see Fig.2 and Table 2). In terms of weekly distribution, highest amount of the rainfall was received during 2nd week of the month (Table 1).

TEMPERATURE PATTERN Except for southern part of Province 7, northern parts of Province 6 and small patches over northern Mustang (Province 4), and Taplejung (Province 1), rest of the country recorded normal to below normal temperature (Fig.3). Regarding mean temperature departure, highest negative anomaly of -2.2°C was recorded in Darchula whereas the highest positive anomaly of 1.0°C was recorded over Jumla. Among the 38 stations, the mean temperature varied from below 12.0°C in the northern parts to above 30.0°C in southern parts (Fig. 3). Nepalgunj Airport recorded the highest maximum temperature of 42.2°C on 26th May while Thakmarpha recorded the lowest minimum temperature of 0.0°C on 10th May (Table 2).

[The viewers of this site need to consider this difference that due to the interpolation of the data into (1kmx1km) grid to produce the figure listed below there is variability in the real data in the table and the color legends in the figure. ]

Table 1: Temporal distribution of average rainfall in May, 2018

Week Total rainfall (mm) Percentage (%) of Daily rainfall (arithmetic average of monthly total Intensity (mm) station rainfall)

1st 30.9 24.7 4.4

2nd 38.4 30.8 5.5

3rd 20.3 16.3 2.9

4th 20.5 16.5 2.9

Remaining 3 days 14.7 11.8 4.9

Total 124.8 100.0

30 Fig.1: Total Precipitation (mm) May 2018

Dadeldhura Jumla Dipayal 29 Dhangadhi Jomsom Surkhet Lumle Nepalgunj Dang Pokhara 28 Kathmandu Jiri Bhairahawa Okhaldhunga Taplejung Simara 27 Dhankuta Dharan Janakpur 25 50 75 100 150 200 250 300 400 Biratnagar

30 Fig.2: Percentage of Normal Precipitation(%) May 2018

30 Fig.3: MeanTemperature(°C) May 2018

Dadeldhura Jumla Dipayal 29 Dhangadhi Jomsom Surkhet Lumle Nepalgunj Dang Pokhara 28 Kathmandu Jiri Bhairahawa Okhaldhunga Taplejung Simara 27 Dhankuta Dharan Janakpur

4 8 12 18 24 30 Biratnagar

Fig.4:Departure of Mean Temperature from Normal(°C) May 2018 30 Province 6

Dadeldhura Jumla

Dipayal Province 4 29 Dhangadhi Jomsom Surkhet Province 3 Province 7 Lumle Province 1 Nepalgunj Dang Pokhara 28 Kathmandu Jiri Bhairahawa Province 5 Okhaldhunga Taplejung Simara 27 Dhankuta Dharan Janakpur

Province 2 Biratnagar -1.5 -1 -0.5 -0.2 0.2 0.5 0.8 80 81 82 83 84 85 86 87 88 Remarks: Normal Rainfall (Gray colour) = 100 ± 10 % Normal Temperature (Gray colour) = 0 ± 0.2 °C

Table: 2 PRELIMINARY MONTHLY WEATHER DATA May 2018 PRECIPITATION TEMPERATURE No. of Rainy Days Maximum ( °C ) Minimum ( °C ) Mean ( °C )

Stations

Total(mm)

%of Normal

≥ 1.0 mm 1.0 ≥

≥ 10.0 mm 10.0 ≥ mm 25.0 ≥ mm 50.0 ≥

Average Max Average Min Average

temperature>30°C

MonthlyMean

LowestDate&Min

HighestDate& Max

No.ofwith Days maximum

24hrs Extreme Rainfall Date& Extreme 24hrs

Departure from Departure the normal from Departure the normal from Departure the normal DADELDHURA 81.6 88.5 11 2 1 0 33/10 26.4 0.32 29.6/21 14.5 0.0 9.5/10 20.5 0.1 0 DARCHULA 153.6 118.2 13 4 2 0 43.1/2 31.2 -2.7 36/26 17.2 -1.7 13/9 24.2 -2.2 26 DHANGADHI 48.7 61.7 5 2 0 0 16/14 37.6 0.4 41.2/26 23.6 1.1 19/10 30.6 0.7 31 DIPAYAL 84.8 97.9 10 5 0 0 17/3 36.1 0.0 41/21 19.2 -0.3 15.3/10 27.7 -0.1 31 JUMLA 62.8 109.4 11 2 1 0 25/9 25.2 1.1 29.4/22 8.6 0.9 3.5/9 16.9 1.0 0 SURKHET 165.1 180.9 10 8 2 0 37/14 33.3 -0.6 36.7/27 19.7 -0.7 16.5/9 26.5 -0.6 30 NEPALGUNJ AIRPORT 89.0 147.2 6 4 1 0 39/14 37.3 -0.7 42.2/26 23.3 0.3 19.2/3 30.3 -0.2 31 CHAURJHARITAR 11.0 19.0 2 0 0 0 7/9 35.2 0.7 39.5/27 18.2 -0.7 14/9 26.7 0.0 31 GHORAI ( DANG ) 81.0 86.5 6 3 1 0 35/14 33.4 -0.4 37.4/26 21.4 -0.1 13.7/14 27.4 -0.3 30 JOMSOM 32.8 166.3 5 1 0 0 15/10 20.1 -1.1 24.5/11 9.0 1.4 1.5/10 14.5 0.2 0 THAKMARPHA 41.6 123.3 5 2 0 0 19.5/9 19.3 -0.1 23/22 5.5 -2.1 0/10 12.4 -1.1 0 TANSEN 121.3 134.3 10 4 2 0 43/3 28.3 -1.1 32/8 18.6 0.6 13.8/14 23.4 -0.3 7 BHAIRHAWA AIRPORT 146.1 177.6 8 4 2 1 65/3 34.9 -1.5 38.6/8 22.3 -1.3 16.9/14 28.6 -1.4 31 KHANCHIKOT 151.5 136.8 8 5 3 0 45.8/3 23.3 -0.4 26/27 15.2 -0.5 10.7/3 19.2 -0.4 0 TAULIHAWA 167.1 291.9 6 5 2 1 95.2/3 34.6 -2.6 38.6/22 23.5 1.8 14.7/16 29.1 -0.4 30 POKHARA AIRPORT 438.0 121.9 22 14 7 1 74/31 29.4 -0.7 32.1/26 19.4 1.0 14.5/9 24.4 0.1 15 LUMLE 243.5 76.3 18 6 2 1 108/3 21.9 -1.3 25/26 14.3 0.0 10/3 18.1 -0.7 0 RAMPUR 133.9 76.5 9 5 1 0 35/3 34.3 -1.3 37.2/8 22.5 0.3 19/11 28.4 -0.5 30 SIMARA AIRPORT 94.5 72.2 9 3 1 0 32/14 34.3 -0.6 37/8 23.2 0.1 19/28 28.8 -0.3 31 GODAVARI 70.1 52.7 9 3 0 0 22/11 27.5 1.7 32.6/25 13.6 -1.2 11/16 20.5 0.2 8 KATHMANDU AIRPORT 155.7 125.9 12 7 1 0 42/30 27.7 -1.0 31.5/26 16.3 0.6 13/1 22.0 -0.2 6 PANCHKHAL 124.1 124.8 13 6 1 0 29.7/14 30.8 -1.1 35/27 18.3 0.5 12/2 24.5 -0.3 21 DHUNIBESI 99.4 79.1 13 3 1 0 37.6/17 30.5 -0.7 34.3/27 19.3 0.1 16/1 24.9 -0.3 23 JIRI 232.8 128.5 18 7 2 1 58.6/14 22.8 -0.5 26.8/27 12.0 0.9 6.3/11 17.4 0.2 0 JANAKPUR AIRPORT 100.2 78.1 7 3 2 0 36.4/9 33.8 -0.8 36.8/8 24.2 0.3 18.5/9 29.0 -0.3 31 JALESORE 111.7 123.9 5 4 3 0 36.5/14 34.0 -1.3 37.3/24 24.4 0.3 19/14 29.2 -0.5 31 KABRE 176.4 158.7 14 6 4 0 35.5/14 25.4 -1.1 29/19 16.1 1.1 11.5/1 20.7 0.0 0 OKHALDHUNGA 194.7 126.6 13 7 2 0 35/18 24.3 -0.4 29.7/25 14.4 -1.1 9.6/9 19.4 -0.7 0 UDAYPURGADHI 64.8 39.9 7 3 1 0 27.8/9 33.1 0.7 35/8 22.2 -0.3 17.7/9 27.6 0.2 29 LAHAN 58.6 55.2 3 2 1 0 38.5/9 33.0 -1.4 35/21 24.1 -0.1 19/9 28.5 -0.8 31 RAJBIRAJ 123.4 97.2 7 6 1 0 44.2/24 32.5 -1.9 35/21 24.5 1.2 20.5/9 28.5 -0.4 28 DHANKUTA 86.6 80.0 16 2 0 0 19/14 26.5 -0.4 29.1/27 17.9 0.0 14.9/11 22.2 -0.2 0 DHARAN 89.5 48.6 9 4 1 0 26/4 32.7 -0.1 35.3/30 23.2 -0.4 19/9 27.9 -0.3 28 BIRATNAGAR AIRPORT 149.0 80.1 14 5 1 1 61/9 32.0 -1.3 35/9 22.9 -0.4 19/9 27.4 -0.8 28 TARAHARA 32.8 17.6 5 2 0 0 14/9 32.7 -0.3 35.5/9 22.4 -0.3 18/9 27.5 -0.3 29 KHADBARI 94.0 61.0 14 2 0 0 18.1/11 26.9 -1.7 30/26 18.3 -0.6 14.4/9 22.6 -1.1 1 TAPLEJUNG 236.2 100.4 22 8 2 0 35/18 23.9 0.4 26.7/26 14.7 0.2 11/11 19.3 0.3 0 KANKAI 194.9 92.0 13 6 4 0 40.7/23 32.5 -0.8 35/30 20.9 -0.7 17.5/4 26.7 -0.7 31

Max 438.0 291.9 22.0 14.0 7.0 1.0 108.0/3 37.6 1.7 42.2/26 24.5 1.8 20.5/9 30.6 1.0 31.0 Min 11.0 17.6 2.0 0.0 0.0 0.0 7.0/9 19.3 -2.7 23.0/22 5.5 -2.1 0.0/10 12.4 -2.2 0.0 Remarks: Rainfall recorded on a day is the total 24 hour rainfall from the previous day 8:45 am till 8:45 am of that day.