Modeling the April 19, 1996 outbreak
We are using the
Penn. State/NCAR MM5 model to simulate the severe
thunderstorms on this day.
The high temporal and spatial resolution in
the model fields will allow us to better analyze and understand the
convective initiation and evolution in the mid-to-late- afternoon
on April 19.
Our simulations are being carried out on the Origin2000 at
NCSA.
We have completed simulations at 3 km horizontal
resolution and have recently begun modeling at 1 km.
66 vertical layers are used, with
vertical resolution
of approximately 60 m near the ground increasing to 600 m aloft.
Key characteristics:
- Simple ice (Dudhia) microphysics
- Blackadar PBL (also testing other PBLs)
- Grell cumulus parameterization (on outer grids;
only explicit microphysics are used on the inner domains).
- FDDA: on outermost (81 km) grid for entire 27-hour run, and
on 2nd (27 km) grid for first 12 hours, only. No nudging
is performed on the innermost 3 nested grids.
Simulation layout
| Grid | is... | Resolution |
Domain | Start | Comments |
All domains |
| 1 | Outer | 81 km | 45x30 |
00z |
Init. w/data (most of U.S.) |
b&w / color |
| 2 | Nest | 27 km | 61x46 |
00z |
Init. w/data (Plains-midwest) |
| 3 | Nest | 9 km | 115x94 |
00z |
IA/MO/IL, init. from grid 2 |
| 4 | Nest | 3 km | 211x181 |
18z |
se IA, ne MO, most of IL |
| 5 | Nest | 1 km | 250x250 |
20z |
ne MO/sw IL, moved w/storms |
Grid layout
is shown here;
upper-air station
locations are plotted here.
Recent results
- Current MM5 research results
are here
(access restricted)
1-km MM5 fields valid 22:36 UTC 19 April, looking north
Click on image for animation
The 3- and 1-km results reproduce many aspects of the
actual convective behavior
on this day, in particular cell formation in eastern MO, splitting
and merging, and (in the 3-km runs; 1 km is incomplete) emergence of
long-lived rotating cells which move into central IL, as actually occurred.
The modeled convection also moves off the drytrough boundary.
We are examining animated cross-section fields to study the initiation
and movement relative to the cold front aloft (CFA) in the simulation, and
have begun idealized studies to further study cell interaction.
A conference paper on this work
appears here.
Simulations were carried out on the
NCSA Origin2000 system.
This work supported by the
National Science Foundation
under grants ATM 96-33228 and ATM 99-86672. Computing, visualization
and other support provided by NCSA.
Brian F. Jewett
| bjewett@ncsa.uiuc.edu
| homepage
| NCSA convective storms group
