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SN | Parameters | Case 1: 21 Jun, 2004 | Case 2: 11 Jul, 2004 |
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1 | Representative location of high impact rainfall events | Rangamati and neighbourhoods (southeast region) | Rangamati and neighbourhoods (southeast region) |
2 | Position of monsoon trough (i.e., pressure at m.s.l.) | Northerly positioned compared to normal which runs towards the northeast India through the north of Bangladesh | Northerly positioned compared to normal and runs towards the northeast India through the extreme north of Bangladesh |
3 | Intensity of heat low | 996 hPa | 996 hPa |
4 | Pressure at the southern part of India | 1011 hPa | 1008 hPa |
5 | North-south pressure difference | 15 hPa | 12 hPa |
6 | Winds at 850 hPa | Cyclonic circulation with centre over the northwest Bangladesh and convergence over the southeast region of Bangladesh | Convergence and trough over the northwest region of Bangladesh |
7 | Winds at 200 hPa | Divergence over the southeast region (Rangamati) | Divergence over the southeast and northwest region |
8 | Jet streak at low level | About 30 ms−1 (58 knots) over Rangamati and neighbourhoods | More than 10 ms−1 (19 knots) over the southeast region |
9 | Wind shear of the u component of wind between 500 and 925 hPa level | Maximum over the southeastern boundary of Bangladesh of the order of 15–18 ms−1 | ~6–9 ms−1 over Rangamati and neighbourhoods |
10 | Low level (925 hPa) relative vorticity | Maximum over the southeast region of the order of 30–40 × 10−5 s−1 | Maximum of the order of 10–20 × 10−5 s−1 across the southeast region |
11 | Low level (925 hPa) convergence | Maximum over Rangamati region of the order of −20 to −25 × 10−5 s−1 | Maximum over the southeast region of the order of −15 to −20 × 10−5 s−1 |
12 | Upper level (200 hPa) divergence | Maximum over the southeast region of the order of 20–25 × 10−5 s−1 | Maximum over the southeast region of the order of 20–25 × 10−5 s−1 |
13 | Relative humidity (925 hPa) | ~90–100% over the southeast region | ~90–100% over the southeast region |
14 | Vertical extends of humidity | Up to 350 hPa level of troposphere | Upto 300 hPa level of troposphere in a narrow column |
15 | Amount of BMD observed rainfall in 24 h | 304 mm at Rangamati | 337 mm at Rangamati |
16 | Time of peak observed rainfall | 06 UTC | 03 UTC |
17 | Type of the rain producing system | Interaction of monsoon systems with trough in upper level westerlies | Active monsoon condition |
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