International Journal of Atmospheric Sciences

Research Article

Simulation of High Impact Rainfall Events Over Southeastern Hilly Region of Bangladesh Using MM5 Model

Table 1

Synthesized results of the synoptic analysis of the high impact rainfall events.


SN	Parameters	Case 1: 21 Jun, 2004	Case 2: 11 Jul, 2004

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