Objective Nowcasting Development

What is our goal?

Forecasters now use GOES imagery andDerived Product Imagery (DPI) to monitor weather – and makesubjective forecasts into the future

We are developing tools to allow forecasters to:

- Project detailed satellite products into the near future – objectively- Preserve observed gradients and max/min features- Retain earlier IR information in areas where clouds later grow- Provide rapid and timely updates to NWP guidance- Focus on identifying extreme weather events- Mix multiple data sources- Minimal forecast model influence

Why are we proposing to use a LaGrangian Approach for Objective Nowcasting?

Background: Nowcasting Task Description •A new objective nowcasting tool has been formulated which:

•Preserves and takes full advantage of both:

•Horizontal and vertical detail (discontinuities) inherent in future hyper-spectral satellite products and

•Frequent information updates available from current and future geostationary instruments.

•The technique:

•must be fast (required due to the perishability of information regarding severe weather development),

•preserves observed data to the fullest extent (retains data extremes)

•integrates GOES data with data from other data sources in a timely and faithful manner.

•can be used to update conventional NWP guidance

•uses minimal computing resources, a necessity for forecast office application.

Task Progress this past year:

 1 - Formulate basis for LaGrangian Nowcasting approach 

The conceptual and dynamical basis for the LaGrangian Nowcasting approach was documented and presented at the GOES Users’ Conference in May 2004. Preparation of a journal article continues.

 

2 - Performed analytical accuracy and performance tests 

Additional analytical tests of advantage of LaGrangian techniques to different dynamical processes especially relevant to nowcasting have been built emphasizing the Jet Streak. The goals are two-fold: 1) To provide evidence of the advantage of the LaGrangian approach in a

manner relevant to forecasters and 2) To provide a tools for teaching:

1) A more thorough understanding of the dynamical processes involved in mesoscale systems – especially those related to creating an environment conducive to severe storm development – and

2) How the result of these dynamics is shown in rapidly changing GOES satellite data

3. Initial Nowcasting Model Prototype Developed

Testing of the initial prototype LaGrangian nowcasting model updating system began last year and is continuing under the guidance of Bob Aune (NESDIS at CIMSS).

The Initial LaGrangian Nowcasting model is being upgraded to use 10 km RUC grids as a basis. This change will allow:

Better compatibility with full resolution GOES DPIs Higher resolution initial winds

Integration of other data sources.

Results are being produced in “DPI look alike formats”

Daily results will be posted on a web page.

Case of convection on 20 July 2005 which was initially moved over Central Wisconsin, Decayed and then Redeveloping past Chicago

Why did initial convection decay and why did it reform where it did?

1545 UTC

1715 UTC

1915 UTC

Lower-tropospheric GOES Sounder Derived Product Imagery (DPI)

3 layers of Precipitable Water

Sfc-900 hPa900-700 hPa700-300 hPa

0700 UTC

GOES 900-700 hPa Precipitable Water - 20 July 2005

1000 UTC

1300 UTC

1800 UTC

However, after initial storm has developed, cirrus blow-off masks lower-level moisture maximum in

subsequent IR satellite observations

Small cumulus developing in boundary layer later in morning

also mask retrievals in second area.

MoistureMaximum

0700 UTC

1000 UTC

1300 UTC

1800 UTC

Mid-tropospheric GOES Sounder Derived Product Imagery (DPI)

3 layers of Precipitable Water

Sfc-900 hPa900-700 hPa700-300 hPa

Over time, cirrus blow-off also masks the presence of an extended

area of mid-level dryness.

(Differential motion of lower-tropospheric moisture

under upper-tropospheric dryness creates convective instability)

GOES 700-300 hPa Precipitable Water - 20 July 2005

Maximum Dryness

Returning to 20 July 2005 case

Question: Can GOES Sounder Derived Product Imagery (DPI) be projected forward in time to

provide forecasters more information about second storm

development south of Chicago at ~ 1800 UTC?

0700 UTC

GOES 900-700 hPa Precipitable Water - 20 July 2005

1000 UTC

1300 UTC

1800 UTC

However, after initial storm has developed, cirrus blow-off masks lower-level moisture maximum in

subsequent IR satellite observations

Small cumulus developing in boundary layer also mask retrievals

in second moist area.

MoistureMaximum

0.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

20 July 2005 Case StudyNowcasting the Lower-Tropospheric Moisture Source1200 UTC data projected forward to 1800 UTC

Blue = MoistureMaximum

White =Cloudy

0.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

0.50 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

1.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

1.50 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

2.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

2.50 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

3.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

3.50 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

4.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

4.50 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

5.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

5.50 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

6.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

6.00 Hr LaGrangian Nowcast900-700 GOES Precipitable Water

0-10 mm – Red, 10-20 mm – Green >20 mm - Blue

Important Lower-Level MoistureInformation about Storm Formation Obscured

by Clouds from Storm in Observations

4. Initial testing Initial tests of the previous prototype system were discontinued during at mid-yearin order to concentrate on the development of the new model.

Once the new model passes checkout, the tests will continue. The objective of these tests is to provide forecasters continuous updates of 3 to 6 hour forecasts of the DPI fields.

Initial tests are focusing on the ability of the technique to preserve observed gradients without developing biases.

5. Visualization Visualization tools must be incorporated to allow forecasts to see the predicted DPIs in formats identical to the current observational products.

There must be no impediments to implementation of the newest GOES forward models with the new nowcasting model.

Postprocessing procedures have been tested and are in place for converting the new nowcasting model outputs into synthetic forecast DPIs.  We have also responded positively to requests from EMC to assist in their efforts to develop ‘satellite like’ images of clouds and other variables from NCEP’s operational mesoscale models (WRF).

GOES-12 single field-of-view Level 2 precipitable water (mm) valid at 15, 16, 17 and 18 UTC, August 18, 2005

GOES-12 single field-of-view Level 2 precipitable water (mm) valid at August 18, 2005 at 15, 16, 17 and 18 UTC,

advanced forward to 18 UTC

6. Incorporation of other data sources  Aircraft, Wind Profiler and cloud tracked wind data will be integrated

to provide observed wind as well as moisture data updates.

Offline test of the LaGrangian approach using observed Wind Profiler data [and in the near future AERI data (used to emulate GOES-R) and current GOES data]have begun using data from the May 1999 Oklahoma City tornado case.

The sample shown next illustrates how parcels (initialized at any location and any level) can be projected forward in time to identify:

• Air Parcel Source Regions• Projected paths• Future development of Divergence/Convergence• Multiple level combinations• Development of Convective Instabilities• CAPE / CINH

DIV=(-1294/1624)/7200 = -1.1x10-4 s-1

262o

255o

237o

218o

262o

268o

10.9

12.4

16.7

17.2

Vorticityx 10-5 s -1

With the LaGrangian approach,

d/dt (ξ + f) = - (ξ + f) DIVergence or DIV = - d/dt (ξ + f) / (ξ + f)

(6/57)/3600=2.92x10-5+8x10-5=1.092x10-4(7/57)/3600=3.41x10-5+8x10-5=1.241x10-4

(18/57)/3600=8.77x10-5+8x10-5=1.677x10-4(19/57)/3600=9.26x10-5+8x10-5=1.726x10-4

Change in Vorticity at 1900 GMT yields 1.04x10-4 CONVERGENCE

This rapid localized development Low-level Convergence

was coincident with drying andGrowth of Divergence in the

Exit of the Jet Streak Aloft

Last Year we showed a Sample of a LaGrangian Diagnostic Study of

The development of a Pre-Convective Environmentusing 3-hourly Analyses of

Radiosonde DataFrom the SESAME Literature

From Kocin et al., 1986.

An example from this years efforts uses trajectory procedure in both a Forward (forecast) and Backward (diagnosis) mode.

-Wind Profiler data take at 2100UTC (shortly prior to the first severe thunderstorm development) are both traced backward (to trace the origins of the air parcels) and forward (to project their future paths and indicate potential divergence) for 3 hours.

Note:1- the increase in convergence between 2100 and 0000 UTC and 2- the increased cyclonic curvature during the period of storm development, an area which 3 hours earlier had show divergence.

These results are consistent with diagnostic calculation of divergence and moisture flux divergence made using the Wind Profile and AERI data reported previously.

7. Incorporate existing hyper-spectral Products AIRS soundings will be used to begin assessing the impact of higher vertical resolution on resolving the pre-convective environment.

Task under development.

These data are available now for testing.

8. Development of supporting algorithms The process of recombining the ‘forecast parcels’ onto a regular grid for visualization will ultimately require improvements in ‘aging algorithms’ used to combine the influence of recent and past forecast parcels based on expected forecast confidence and data density.

Activity in this area is planned for early 2006.

9. Data Level Matching The level of the atmosphere which is represented in GOES water vapor products varies as a function of the atmospheric water vapor content itself,

As such, techniques are needed to assure that the winds and geopotential fields used to translate air parcels are representative of the level of the maximum weighting function for each piece of moisture information.

This, for example, will prevent ‘upper level dry slots’ from being moved with winds from too high in the atmosphere – since the peak of the weighting function for these features is lower in the

atmosphere than in most ‘moist’ cases

10. Product Testing and Evaluation Thorough and systematic testing of the next generation of nowcasting products is essential to for the successful introduction and use of these new products.

Much of this responsibility will be placed on the new graduate student who will be joining the project in the coming fall.

Evaluations will be done based on the full sets of observed data available at CIMSS, include comparisons with:

-observed satellite products, -vertical profiles from rawinsondes and aircraft, -wind profilers, -surface observations, and-model analyses and short-range forecasts.

The objective is:-to assess major sources of error in the models and -to validate the hypothesis that short-range projections of data provide

improvements on already available longer-range NWP products

11. User Interactions and Involvement Relationships will be established with several WFOs, NSSL and NCEP/SPC to serve as focal points for evaluating and critiquing the new objective nowcasting products.

Initial data availability will be via web pages.

Overview seminars and training visits will be made to assess the optimal means of accessing and using these new forecasting tools- Will include several WFOs and Norman, OK

A goal will be to integrate additional nowcasting technique assessment into the annual NSSL Spring Storm Experiment in 2006.

 

12. Operational Integration Discussion will begin with FSL as to the best approaches to consider for integrating the objective nowcasting tools into the AWIPS environment.

Although the actual integration wouldn’t be expected for several years, early planning is essential.

Likewise, COMET will be briefed on the benefits of the approach so that training programs can be developed as needed.