# Presentation: 066107

## Historic Look at the Tropical Cyclone Track

**Forecasting Skill of Operational NWP**
** ****Models and their Consensus**
**James S. Goerss and Charles R. Sampson**
**NRL  Monterey**
**James M. Gross**
**TPC/NHC/NOAA/NWS Miami**

## NWP Model Availability

** ****at NHC and JTWC**

_**NHC**_
**1998-1999 ****– NOGAPS, UK Met Office global model, and the ****	****GFDL model**
**2000-2002**** – Addition of NCEP global forecast system, GFDL ****	****model run by FNMOC, and COAMPS****TM****.**
_**JTWC**_
**1992-1995 ****– NOGAPS, UK Met Office global model, and JMA ****	****typhoon model (JMA typhoon model out to 48h)**
**1996-1999 ****– Addition of JMA global spectral model, GFDL ****	****model run by FNMOC, and JMA typhoon model out to 72h**
**2000**** – Addition of COAMPS****TM**** and MM5 run by AFWA**
**2001-2002**** – Addition of NCEP global forecast system**

## NOGAPS Upgrades

**1990 ****– Assimilation of synthetic TC observations into NOGAPS ****	****T79L18, Arakawa-Schubert cumulus parameterization**
**1994 ****– NOGAPS T159L18**
**1995**** – TC motion and proximity incorporated into synthetic TC ****	****observations**
**1996**** – Assimilation of feature-track winds from geostationary ****	****satellites**
**1998**** – NOGAPS T159L24**
**2001**** – Emanuel cumulus parameterization**
**2002**** – NOGAPS T239L30, upgrades to Emanuel cumulus ****	****parameterization, NOGAPS run 4 times per day**
**	**

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Interpolated Model Forecast Error (nm)**

**12h**

**24h**

**Jim Goerss:**
- 12 and 24 hour errors (km), NGPI  (blue), EGRI (red), and JTYI  (green)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Interpolated Model Forecast Error (nm)**

**48h**

**72h**

**Jim Goerss:**
- 48 and 72 hour errors (km), NGPI  (blue), EGRI (red), and JTYI  (green)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Interpolated Model 72-h Forecast Error (nm)**

**Jim Goerss:**
- 72 hour errors (km), JGSI  (green), GFNI (blue), COWI  (red), AFWI (brown), and JAVI (lavender)

## Atlantic – Historic Performance

**Atlantic – Historic Performance**
**Interpolated Model 24-h Forecast Error (nm)**

**Jim Goerss:**
- 72 hour errors (km), JGSI  (green), GFNI (blue), COWI  (red), AFWI (brown), and JAVI (lavender)

## Atlantic – Historic Performance

**Atlantic – Historic Performance**
**Interpolated Model 48-h Forecast Error (nm)**

**Jim Goerss:**
- 72 hour errors (km), JGSI  (green), GFNI (blue), COWI  (red), AFWI (brown), and JAVI (lavender)

## Atlantic – Historic Performance

**Atlantic – Historic Performance**
**Interpolated Model 72-h Forecast Error (nm)**

**Jim Goerss:**
- 72 hour errors (km), JGSI  (green), GFNI (blue), COWI  (red), AFWI (brown), and JAVI (lavender)

## Consensus Forecast Properties

**Consensus TC track forecast error is dependent upon two things (Goerss 2000):**
**The TC track forecast error of the individual NWP models that make up the consensus**
**The degree of independence (or effective degrees of freedom) of the TC track forecast errors of the individual NWP models that make up the consensus**

## 2002 Western North Pacific

**2002 Western North Pacific**
**72-h TC Forecast Error (nm)**

**The interpolated models available to JTWC for the western North Pacific are NOGAPS (NGPI), the NCEP global forecast system (AVNI), the UK Met Office global model (UKMI), the GFDL model run by FNMOC (GFNI), the Japanese global model (JGSI), the Japanese typhoon model (JTYI), COAMPS (COWI), and the MM5 run by AFWA (AFWI).  CONU is a consensus forecast that requires that forecasts from at least two of the aforementioned models are available.  As CONU has become JTWC’s primary guidance, the official JTWC forecast errors (not shown) were quite close to those for CONU.  The forecast errors for AFWI and COWI are not shown but are very similar to those for JTYI.**

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Model Consensus Forecast Error (nm)**

**24h**

**12h**

**Jim Goerss:**
- 24 hour errors (km), 3 model consensus (blue), 5 model consensus (red), 7 model consensus (green) and 8 model consensus (lavender)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Model Consensus Forecast Error (nm)**

**24h**

**12h**

**Jim Goerss:**
- 24 hour errors (km), 3 model consensus (blue), 5 model consensus (red), 7 model consensus (green) and 8 model consensus (lavender)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Model Consensus Forecast Error (nm)**

**72h**

**48h**

**Jim Goerss:**
- 72 hour errors (km), 3 model consensus (blue), 5 model consensus (red), 7 model consensus (green) and 8 model consensus (lavender)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Model Consensus Forecast Error (nm)**

**72h**

**48h**

**Jim Goerss:**
- 72 hour errors (km), 3 model consensus (blue), 5 model consensus (red), 7 model consensus (green) and 8 model consensus (lavender)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Model Consensus 12-h Forecast Skill**
**Percent Improvement Over Best Track CLIPER**

**  ****(443)    (397)    (636)    (359)    (605)    (649)     (281)    (305)   (559)    (554)    (485)**

**Jim Goerss:**
- 12 hour skill relative to best track CLIPER, 3 model consensus (blue), 5 model consensus (red), 7 model consensus (green) and 8 model consensus (lavender)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Model Consensus 24-h Forecast Skill**
**Percent Improvement Over Best Track CLIPER**

**  ****(498)    (386)    (629)    (348)    (595)    (639)     (261)    (281)   (509)    (508)    (451)**

**Jim Goerss:**
- 24 hour skill relative to best track CLIPER, 3 model consensus (blue), 5 model consensus (red), 7 model consensus (green) and 8 model consensus (lavender)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Model Consensus 48-h Forecast Skill**
**Percent Improvement Over Best Track CLIPER**

** ****(429)    (314)    (544)    (267)    (522)    (561)     (206)    (197)    (405)    (405)     (374)**

**Jim Goerss:**
- 48 hour skill relative to best track CLIPER, 3 model consensus (blue), 5 model consensus (red), 7 model consensus (green) and 8 model consensus (lavender)

## Western North Pacific – Historic Performance

**Western North Pacific – Historic Performance**
**Model Consensus 72-h Forecast Skill**
**Percent Improvement Over Best Track CLIPER**

** ****(177)     (87)     (236)    (114)    (322)    (385)     (115)     (96)     (253)    (283)    (270)**

**Jim Goerss:**
- 72 hour skill relative to best track CLIPER, 3 model consensus (blue), 5 model consensus (red), 7 model consensus (green) and 8 model consensus (lavender)

## Percent Improvement over CLIPER

**Percent Improvement over CLIPER**
**72-hour Forecast (3-yr Weighted Mean)**

## Atlantic – Historic Performance

**Atlantic – Historic Performance**
**Model Consensus 72-h Forecast Error (nm)**

**Jim Goerss:**
- 72 hour errors (km), JGSI  (green), GFNI (blue), COWI  (red), AFWI (brown), and JAVI (lavender)

## Atlantic – Historic Perspective

**Atlantic – Historic Perspective**
**72-h TC Forecast Error (nm)**

**The interpolated models available to JTWC for the western North Pacific are NOGAPS (NGPI), the NCEP global forecast system (AVNI), the UK Met Office global model (UKMI), the GFDL model run by FNMOC (GFNI), the Japanese global model (JGSI), the Japanese typhoon model (JTYI), COAMPS (COWI), and the MM5 run by AFWA (AFWI).  CONU is a consensus forecast that requires that forecasts from at least two of the aforementioned models are available.  As CONU has become JTWC’s primary guidance, the official JTWC forecast errors (not shown) were quite close to those for CONU.  The forecast errors for AFWI and COWI are not shown but are very similar to those for JTYI.**

## 2002 Western North Pacific

**2002 Western North Pacific**
**Consensus Forecast Availability Percentage**

**Availability Percentage for the 2002 Western North Pacific season**

## Atlantic – Historic Perspective

**Atlantic – Historic Perspective**
**Consensus Forecast Availability Percentage**

**Availability Percentage for the 2002 Western North Pacific season**

## Summary

**Over the past decade, there has been a steady improvement in the TC track forecast performance of the individual NWP models.  NWP model 72-h TC track forecasts today are as skillful as 48-h TC track forecasts were in the early 1990’s.**
**Over the past decade, there has also been a steady increase in the number of NWP models capable of making high-quality TC track forecasts.  Today, JTWC has eight NWP models available to make a consensus, compared with three models in the early 1990’s. NHC has six NWP models available, compared with three models in the late 1990’s. **
**Both of these factors have resulted in a dramatic improvement in consensus TC track forecasts over the decade.  Consensus 72-h TC track forecasts today are more skillful than consensus 48-h TC track forecasts were in the early 1990’s.  Due to the increase in the number of NWP models, consensus forecast availability today is greater than 95% for all forecast lengths out to 72 h.**