# Presentation: 502361

## Editing Methodology

**Using Work Grids in GFE**
**Tim Barker, SOO Boise**

**Choosing model grids is one thing,**
**but making changes to model**
**(or existing) grids, is where we **
**can add meteorological value.**

## Most Objective Analysis schemes

**use a "first guess" grid and make **
**small adjustments to the original **
**grid based on some data**

**For example...**

## ADAS starts with this...

**ADAS starts with this...**

## Adds this...

## And gets this...

**And gets this...**

## This is the essence of what we are 

**trying to do in GFE, too...**
**Taking a first guess grid, and making**
**adjustments to create a new grid.**

## I believe a methodology strongly

**emphasizing *****adjustments***** or *****changes***
**can help us keep our focus on **
**the meteorological value we**
**are adding to the grids.**

## For example, say the AVN model gives

**you this MaxT grid:**

## You like the basic spatial pattern, 

**but you think southerly winds will be **
**stronger than the model suggests, and **
**that will make temperatures a little **
**warmer in the western part of the CWA.**
**How do you proceed?**

## You could define an edit area:

## And adjust_up with edge:

**the final grid looks OK**

## But the adjustment looks a little "cartoonish"

## Go a little further, define an area where downslope will

**be particularly strong.**

## And do more adjust_up with edge effects...

**Result still "looks" OK**

## But the total changes still look "cartoonish"

## To keep changes:

**	****	****less "cartoonish"**
**	****	****well bounded**
**	****	****and meteorologically sound**
**Why not concentrate on the changes we are**
**trying to make rather than on the final field?**

## Start with a blank "change grid"

## make and upslope/downslope field (WindEffects tool):

## change the sign to get warming/cooling right

**(multiply/divide tool)**

## Make it mostly warming (AdjustUp)

## Set change to zero outside the area where we think

**southerly winds will develop...**

## Smooth it around the edges a little, use the pencil tool

**to clean up a few areas that seem overdone...**

## Add this to the original field - and it still "looks good",

**but the modifications are very meteorologically based**

## The point is...

**Doing most of the editing in the **
**"change grid" can help you keep**
**your mental focus on**
**	****	****the reason,**
**	****	****the magnitude, **
**	****	****and the spatial distribution**
**of the modifications you are making**

## "change grids" dont have to start 

**from scratch or be totally "freehand"**
**Models contain a rich set of information**
**about temporal changes**

## Eta model 24-hour change in MaxT

**(via change_over_time tool):**

**Cooling aloft**

**Warming below**

## We could simply add this temporal

**change onto the forecast grid we**
**already have**

## But lets say we want to do more.

**Lets say we like the spatial pattern of cooling**
**and warming, but we want to make *****structural***
***changes***** to the pattern of adjustment**
**Say, for example, the model has been**
**consistently making lapse rates too steep**
**over the past few days...**

## Reduce the magnitude of the changes by multiplying

**by 0.75 (Multiply/Divide tool)**

## Or we could make other, simple, structural 

***changes *****to grids:**
**Chop off cooling,  only allow warming in valleys**
**by using the LimitValues tool:**

## The resulting change grid:

## Rather than chopping off cooling,  lets keep the

**pattern, but modify the range of changes using**
**the ShrinkStretch tool:**

## The resulting change grid:

## Finally, just add our 24-hour adjustment 

**to our current forecast grids (using the ****Add_Change_over_Time tool):**

## And complex adjustments have been

**made very quickly, without creating**
**unusual gradients, etc.**

## We need to be a little careful.

**We don't want our changes to get us**
**too far away from the current forecast**
**or from the model solutions.**
**We can see how different our field is**
**from the same model field using the**
**Change_over_Model tool.**

## The difference between our grid and the

**MRF model grid:**

## Once again, we may want to modify how

**much our grid will deviate from the model's**
**grid, using a variety of tools:**

## Then we can make sure our field differs

**from the model by that amount by using**
**the Add_Change_over_Model tool:**

## With the result:

## There are other ways you might want to

**make your adjustment grids.**
**Perhaps you have some idea of the**
**adjustments you want to make at some**
**points, and you want to *****spread that out***
**over the rest of the grid. **
**This is the typical objective analysis**
**problem.**

## But Don't Forget...

**Concentrate on the "changes" you**
**are making.**
**	****Why you are making them**
**	****Where you are making them**
**	****How big they should be**
**The American People are paying for**
**meteorologists to do this job!**

## Tools Shown in This Presentation

- AdjustUp with edge
- WindEffects
- multiply/divide
- Change_over_Time
- LimitValues
- ShrinkStretch
- Add_Change_over_Time
- Change_over_Model
- Add_Change_over_Model