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Nearcasting Severe Convection Using the GOES Sounder

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Title: Nearcasting Severe Convection Using the GOES Sounder


1
Nearcasting Severe Convection Using the GOES
Sounder
  • Presented by
  • Robert Aune

2
Requirement, Science, and Benefit
  • Requirement/Objective
  • Mission Goal Weather and water
  • Increase lead time and accuracy for weather and
    water warnings and forecasts
  • Improve predictability of the onset, duration,
    and impact of hazardous and severe weather and
    water events
  • Increase development, application, and transition
    of advanced science and technology to operations
    and services
  • Science
  • Can observations from a geostationary IR sounder
    be used to predict severe weather outbreaks 1 to
    6 hours in advance, filling the gap between radar
    nowcasts and NWP models?
  • Benefits
  • Reduce loss of life, injury and damage to the
    economy
  • Better, quicker, and more valuable weather and
    water information to support improved decisions
  • Increased customer satisfaction with weather and
    water information and services

3
Challenges and Path Forward
  • Science challenges
  • Current GOES sounders cannot see low-level
    temperature inversions and dryness which leads to
    false alarms
  • Accurate mesoscale wind information is needed to
    initialize trajectories
  • Next steps
  • Assimilate additional products from the GOES
    sounder to determine which is the best indicator
    of de-stabilization
  • Perform Observing System Simulation Experiments
    (OSSEs) to determine the impact of using a
    hyperspectral sounder
  • Transition Path
  • Evaluation at NWS forecast office has commenced
    (AWIPS, webpage)
  • Evaluation at Storm Prediction Center Severe
    Weather Test Bed to commence May, 2010 (supported
    by GOES-R Risk Reduction)
  • Convert system to run at local forecast offices

4
Nearcasting Severe Convection Using the GOES
Sounder
  • Research description
  • The GOES sounder can provide hourly snapshots of
    layer-averaged stability parameters. These
    observations can be assimilated at multiple
    levels using a simple approach to provide fast,
    short-term projections of atmospheric stability.
  • Recent science accomplishments (FY08 to present)
  • In collaboration with CIMSS, a Lagrangian
    approach was selected that moves the GOES
    observations along forward trajectories.
    Observation error growth remains small to 4 hours
    and beyond.
  • GOES sounder retrieved parameters such as
    equivalent potential temperature (Theta-E) at
    750hPa and 500hPa are projected forward 6 hours.
    Destabilization is indicated when Theta-E500
    (5800m) minus Theta-E750 (2500m) becomes
    negative.
  • The nearcasting model has been tested in real
    time at CIMSS using the GOES-12 sounder.
    Products are displayed on the internet
    (http//cimss.ssec.wisc.edu/model/nrc).
  • Hourly nearcasts are currently being transmitted
    to NWS Central Region AWIPS for evaluation.
  • Product will be evaluated at the NWS Storm
    Prediction Centers Spring Experiment in May 2010.

5
Filling the Guidance Gap and Atmospheric
Stability Basics
The GOES sounder can detect water vapor at 2-3
layers in a clear atmosphere. Gradients of water
vapor can be tracked using multiple GOES sounder
scans. Upper level drying over lower level
moistening conditions lead to autoconvection.
  • The Guidance Gap
  • Very-short-range NWP
  • precipitation forecasts often
  • either
  • 1) miss significant moisture
  • features
  • 2) have difficulty with exact
  • position and timing of
  • events / phenomena

Max Precipitation Axis
When the layer is lifted the inversion bottom
cools less than top and it becomes absolutely
unstable
3hr Model Forecast Valid 1700 UTC 7/2/08
Max Precipitation Axis
If moisture is present in the stable layer and
the entire layer is lifted, it can become
unstable.
2hr Model Forecast Valid 1700 UTC 7/2/08
Fill the Gap Between Nowcasting NWP
To detect the development of areas becoming
convectively unstable, we need to monitor not
only the increase of low level moisture, but
areas where low-level moistening and upper-level
drying overlap
Verification 7/2/08 1700 UTC Radar
0 2 4 10
12 hours
6
Lagrangian Nearcasting Approach
GOES-12 900-700 hPa precipitable water analysis
valid 21 UTC 13 April 2006
GOES-12 900-700 hPa precipitable water retrievals
valid 00 UTC 14 April 2006
Dry Moist
Dry Moist
0-hour Nearcast
3-hour Nearcast
O
O
Starting location
New location
  • How it works
  • NWP models use randomly spaced moisture
    observations interpolated on to a fixed grid, and
    use gridded wind data to advect the moisture
    information forward in time at fixed grid points.
    This process smooths horizontal gradients.

The Lagrangian approach interpolates wind data
to each observation location (10km spacing)
which is then projected forward to a new
location forced by dynamically changing wind
forecasts. A relatively long time step (10 min)
can be used. The new data locations are then
transferred back to a regular grid.
7
Nearcasts of Severe Weather
6-hour NearCast for 2100 UTC Low level Theta-E
Low-level Theta-E nearcasts shows warm moist air
band moving into far NW Iowa by 2100 UTC.
Oklahoma City tornado
6-hour NearCast for 2100 UTC Mid - Low level
Theta-E Differences
Vertical Theta-E Differences predict complete
convective instability by 2100 UTC.
De-stabilization predicted by nearcast
Radar indicates rapid development of convection
over NW Iowa between 2000 and 2100 UTC, 9 July
2009. Correct shape is indicated.
4-hour nearcast of precipitable water lapse rate
(mm differences) near Oklahoma City valid 22UTC
Feb 10, 2009. De-stabilization potential is
indicated.
8
Evaluation by NWS Forecast Office, Sullivan,
Wisconsin
NWS Milwaukee is evaluating the CIMSS
precipitable water nearcasting product. The
example below shows a good relationship between
amount of convective clouds (or lack of them) and
strong vertical gradients of PW.
CIMSS nearcast products are currently being
inserted into the operational AWIPS data stream
for NWS evaluation.
CIMSS precipitable water lapse rate product
valid 15UTC April 13, 2009.
1-hour nearcast of vertical precipitable water
differences (mm) valid 19 UTC, July 2, 2009.
Same CIMSS nearcast product displayed on an
AWIPS workstation.
Visible image for 19 UTC, July 2, 2009. Red
indicates where convection is likely. Black
indicates areas where convection is not likely.
9
Improved Nearcasting of Severe Weather using a
Hyperspectral Environmental Sounder (HES)
Strong low-level Theta-E gradients are indicated
by HES which has the ability to detect low-level
moisture.
Weak gradients of low-level Theta-E are indicated
by ABI which has only two water vapor channels.
The nearcasting model was tested using simulated
observations from the Advanced Baseline Imager
(ABI), and a proposed geostationary
Hyper-spectral Environmental Sounder
(HES). Temperature and moisture profiles were
retrieved from the radiance datasets and
assimilated by the CIMSS Nearcasting Model and
compared. Detailed Theta-E gradients were
resolved by HES.
Simulated ABI
Simulated HES
5-hour NearCast for 2000 UTC Low level Theta-E
5-hour NearCast for 2000 UTC Low level Theta-E
Simulated composite reflectivity from nature run
indication the formation of convection.
Simulated ABI
Simulated HES
5-hour NearCast for 2000 UTC Low to Mid level
Theta-E Differences
5-hour NearCast for 2000 UTC Low to Mid level
Theta-E Differences
Rapid Development of Convection over Texas and
Nebraska between 2000 and 2100 UTC 12 June 2002
10
Challenges and Path Forward
  • Science challenges
  • Current GOES sounders cannot see low-level
    temperature inversions and dryness which leads to
    false alarms
  • Accurate mesoscale wind information is needed to
    initialize trajectories
  • Next steps
  • Assimilate additional products from the GOES
    sounder to determine which is the best indicator
    of de-stabilization
  • Perform Observing System Simulation Experiments
    (OSSEs) to determine the impact of using a
    hyperspectral sounder
  • Transition Path
  • Evaluation at NWS forecast office has commenced
    (AWIPS, webpage)
  • Evaluation at Storm Prediction Center Severe
    Weather Test Bed to commence May, 2010 (supported
    by GOES-R Risk Reduction)
  • Convert system to run at local forecast offices
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