# Presentation: 424546

## Improving the Validation and Prediction of Tropical Cyclone Rainfall

**Timothy P. Marchok**
- NOAA/GFDL  Princeton, NJ
**Robert F. Rogers**
- NOAA/AOML/HRD  Miami, FL
**Robert E. Tuleya**
- NOAA/NCEP/EMC/SAIC  Camp Springs, MD
*58**th** Interdepartmental Hurricane Conference, Charleston, SC*
- March 1-5, 2004
*** This project is being funded by the Joint Hurricane Testbed (JHT)**

## Goals

- Goal: *Develop a set of rainfall validation schemes **	**	**  more suited specifically for TCs*
- Motivation: Conventional precip skill scores are often difficult to interpret in the context of tropical cyclones
- Goal: *Produce model QPF error statistics for historic **	**  U.S. landfalling storms.*
- Motivation:  No systematic QPF verification has been done on NWS operational models for the specific subset of landfalling U.S. tropical cyclones
- Goal: *Develop a modified R-CLIPER that incorporates **	**  vertical shear & storm track data.*
- Motivation: Recent research has shown that including vertical shear information can add structure to R-CLIPER's currently symmetric rainfall distribution

## Outline

- Standard QPF verifications
- GFDL model: 1995-2002 storms; rain gauge data
- NWS operational suite: 1998-2003 storms; Stage IV gridded rainfall analyses
- Application of a new verification technique to Hurricane Isabel’s landfall
- Future work

## GFDL Model QPF Verification, 1995-2002

- Verification data: Hourly & daily rain gauges
- Gauge data within 800 km of storm track was summed over model forecast interval
- Interpolated model storm total rainfall to gauge location
- Average of 211 hourly gauges per storm
- Nearly 1200 daily gauges per storm
- Only used forecasts initialized at 12 UTC, to coincide with daily rain gauge network
- All storms within ~24h of landfall

## U.S. Landfalling Cases for Model Evaluation

| 1995 | 1996 | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Allison 
60  | Bertha 
90 | Danny 
65 | Bonnie 
95 | Bret 
100 | Gordon 55 | Allison 
45 | Bertha
35 | Bill 
50 |
| Dean 
40 | Fran 
100 |  | Charley 40 | Dennis 
60 | Helene 
65 | Barry 
60 | Edouard
35 | Claudette
75 |
| Erin 
75 | Josephine
60 |  | Earl 
70 | Floyd 
90 |  | Gabrielle 60 | Fay 
50 | Grace
35 |
| Opal 
100 |  |  | Frances 
45 | Harvey 
50 |  |  | Hanna 
45 | Henri
30 |
|  |  |  | Georges
90 | Irene 
70 |  |  | Isidore
55 | Isabel
90 |
|  |  |  | Hermine
35 |  |  |  | Kyle 
35 |  |
|  |  |  |  |  |  |  | Lili 
85 |  |

-  NWS Operational Suite

- GFDL, R-CLIPER

## QPF Bias Scores: GFDL vs. R-CLIPER

## Equitable Threat Scores

## Model vs. obs correlation: A first guess at pattern matching

## Track error <-> QPF error

## Storm Intensity <-> QPF Error

## QPF verification for NWS model suite: 28 storms from 1998-2003

- GFDL, NCEP/GFS, NCEP/Eta, R-CLIPER, 2xR-CLIPER
- GFDL 2003 version used for all 28 cases
- Obs data:  Hourly multi-sensor (radar, gauge) gridded data available online from NCAR
- 2002-2003: NCEP/EMC Stage IV data
- 1998-2001: NCEP/EMC Stage II data

## QPF Bias Scores

## QPF Equitable Threat Scores

## Slide 14

## GFS:    0.65

- Eta:      0.56
- GFDL:  0.52
- RCLIP: 0.47

## GFS:    0.65

- Eta:      0.56
- GFDL:  0.52
- RCLIP: 0.47

## Stage 

- Stage

- GFS

- Eta

- GFDL

- IV

## Stage 

- GFS

- Eta

- GFDL

- IV

## Rainfall statistics for observations and forecasts of 24-h rain

**from 12 UTC 18 to 12 UTC 19 September for Isabel (2003)**

|  | Total areal coverage of rain (x 106 km2) | Total rain flux (x 106  in-km2) | Mean R (in) |
| --- | --- | --- | --- |
| Stage IV | 1.201 | 1.536 | 1.28 |
| R-CLIPER | 1.936 | 2.191 | 1.13 |
| GFDL | 1.933 | 2.453 | 1.27 |
| GFS | 1.877 | 1.485 | 0.79 |
| Eta | 1.404 | 2.528 | 1.80 |

## Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September

**Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September**
**for Isabel (2003) for NPVU and R-CLIPER**

**Stage IV**

**R-CLIPER**

## Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and GFDL

**Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and GFDL**

**Stage IV**

**GFDL**

## Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and GFS

**Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and GFS**

**Stage IV**

**GFS**

## Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and Eta

**Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC 19 September for Isabel (2003) for NPVU and Eta**

**Stage IV**

**Eta**

## Probability-matched 24-h rain estimates from Stage IV data vs. 

**Probability-matched 24-h rain estimates from Stage IV data vs. **
**R-CLIPER, GFDL, GFS, and Eta models for Hurricane Isabel****  **

**90%**

**90%**

**90%**

**10%**

**10%**

**10%**

**10%**

## Summary & Future Plans

- QPF error stats for landfalling TCs:
- GFDL only: 1995-2002 vs. rain gauge data
- NWS suite: 1998-2003 vs. gridded Stage IV data
- Compare operational GFDL vs. 2003 GFDL for all storms, 1995-2003
- Development of a set of QPF verification schemes more suited to TCs
- Apply a PDF/CDF method to TC rain flux
- Use PDF/CDF method on NWS suite, 1998-2003
- Investigate other spatial-based methods?
- Develop a modified R-CLIPER that incorporates 	  vertical shear & storm track data (Year 2)