An Lpa in last week of July formed over Mp (India). It intensified into a deep depression during westward movement, over south Rajhistan and caused extremely heavy falls over Gujrat, Rajhistan and adj Se Sindh. Imd in its morning forecast of that very day expected Dd to stay their for 48 hours, Gfs was also consistent with this forecast and jet stream was also not favorable for the system to track northward. Only a less reliable model Cmc had been showing heavy rains over Kpk and adjoining Punjab. At the same time a weak wave of Mjo had just moved into tropical Indian ocean , which helped another system over Bob to gain strength of deep depression. Strong easterly jet was such that it was split into 2 branches, the weak one had been moving Nw from Rajhistan to Kpk and the strong one had been penetrating Sindh from Rajhistan and further downward to lower Sindh. But 24 to 36 hours of continues heavy rains over Se Sindh dropped Se Sindh temperature quite sharply relative to Baluchistan, this horizontal Temperature gradient allowed a south jet to form over western Sindh, which gradually pushed the system upward and system started moving Ne initially and then N and at later stage Nw. In subsequent 3 to 4 days this southerly jet continued pushing the system upward, on the meantime system weaken into Wml and then into Lpa and was located over Nw Rajhistan and and adjoining south Punjab roughly at 3.5 Km above Msl with moderate easterly jet over it and weak southerly jet west of the system. The westerly jet over Afghanistan didn’t changed much and remain almost stalled over there and didn’t influence much on this system. The system which was Lpa on 31 July in lower level also caused scattered rains over south Punjab and very heavy falls over Dg khan and Di khan for couple of days. The Dd over Bob also moved along coastal Bangladesh and moved westward thereafter. The Lpa over Nw Rajhistan in low level with Dd over Bob and reversal of Mjo the Lpa was highly likely to merge into monsoon trough, but on the very day easterly jet intensified a bit and had been traveling toward Wnw over Lpa and had been penetrating into Kpk and Nw Punjab, somehow Lpa managed to servive. The cloud and rain movement toward north during this whole northward movement from Sindh to Sakesar was very slow.
Odd lightning appeared on 31 july 2015 near sunset over Sakesar hill roughly 33 km Sw of Dhurnal Nw punjab, and reached Dhurnal around 11 PM of night and till 12 PM 50 mm rain had occurred. The on off heavy rain continued till 11 PM of 1st August. This first 24 hour span of rain was so heavy that, it caused 238 mm of rain. After that rain intensity eased up and ended on 3rd of August morning. The 60 hours spell caused 408 mm of rain, same time the Paf Base Mianwali , Sw of Dhurnal measured 385 mm, though Pmd reported 340 mm. The Ne and east as well as north side of Dhurnal received just light to moderate rain during the period. Almost no rain in Chakwal 60 Km Ne, and light rain at Dhok Pathan observatory 40 km Ne, and Talagang got moderate rain 30 Km Ne. But Isolated extremely heavy with scattered heavy falls reported from Kpk during the spell. A very strong easterly jet over Ne Punjab in the meantime didn’t allow clouds to move there and continued pushing clouds from western Himalyan region to Nw of Lpa. The Moderate easterly jet over Lpa pushed clouds and rain much west of it, where Kpk hills didn’t allowed cloud movement further west and, jet was also eased up there. Continues feeding of moisture from Arabian sea in low level, 500 Mb and above triggers from Bob, with high mountains in the west, along with 3 days static position and long life of Lpa, were the key contributers of this record breaking extreme event at regional level.
Fahim Malik Dhurnal