# Presentation: 753300

## 2006 NHC Verification Report Interdepartmental Hurricane Conference5 March 2007

**James L. Franklin**
**NHC/TPC**

## Verification Rules

- System must be a tropical (or subtropical) cyclone at both the forecast time and verification time, includes depression stage (except as noted).
- Verification results are final (until we change something).
- Special advisories ignored; regular advisories verified.
- Skill baselines for track is revised CLIPER5 (updated developmental data to 1931-2004 [ATL] and 1949-2004 [EPAC]), run post-storm on operational compute data.
- Skill baseline for intensity is the new decay-SHIFOR5 model, run post-storm on operational compute data (OCS5).  Minimum D-SHIFOR5 forecast is 15 kt.
- New interpolated version of the GFDL: GHMI.  Previous GFDL intensity forecast is lagged 6 h as always, but the offset is not applied at or beyond 30 h.  Half the offset is applied at 24 h.  Full offset applied at 6-18 h.  ICON now  uses GHMI.

## Decay SHIFOR5 Model

- Begin by running regular SHIFOR5 model.
- Apply the DeMaria module to adjust intensity of tropical cyclones for decay over land.  This includes recent adjustments for less decay over skinny landmasses (estimates fraction of the circulation over land).
- Algorithm requires a forecast track.  For a skill baseline, CLIPER5 track is used.  (OFCI could be used if the intent was to provide guidance).

## 2006 Atlantic Verification

**VT      NT    TRACK     INT**
**(h)          (n mi)    (kt)**
**============================ **
**000     241     9.5     2.1**
**012     223    ****29.7****     6.5 **
**024     205    ****50.8****    10.0**
**036     187    ****71.9****    12.4**
**048     169    ****97.0****    14.3**
**072     132   ****148.7****    18.1**
**096     100   205.5    19.6**
**120      78   265.3    ****19.0****   **

- Values in green meet or exceed all-time records.
- *  48 h track error for TS and H only was  96.6 n mi.

## Track Errors by Storm

## Track Errors by Storm

## 2006 vs. 5-Year Mean

## New 5-Year Mean

**New 5-Year Mean**

- 55 n mi/day

## OFCL Error Distributions

## Errors cut in half since 1990

## Mixed Bag of Skill

## 2006 Track Guidance (Top Tier)

## 2nd Tier Early Models

## 2006 Late Models

## Experimental NASA Model (FV5)

## Guidance Trends

## Goerss Corrected Consensus

- CCON 120 h FSP: 36%

- CGUN 120 h FSP: 33%

- Small improvements of 1-3%, but benefit lost by 5 days.

## FSU Superensemble vs Goerss Corrected Consensus

## FSU Superensemble vs Other Consensus Models

## 2006 vs 5-Year Mean

## No progress with intensity

## Skill sinking faster than dry air over the Atlantic

## Intensity Guidance

## Intensity Guidance

## Dynamical Intensity Guidance Finally Surpasses Statistical Guidance

## Intensity Error Distribution

**When there are few rapid-intensifiers, OFCL forecasts have a substantial high bias.**

**GHMI had larger positive biases, but higher skill (i.e., smaller but one-sided errors).**

## FSU Superensemble vs Other Consensus Models

## 2006 East Pacific Verification

**VT     N      Trk    Int**
**(h)         (n mi)  (kt)**
**========================**
**000   379     8.8    1.7**
**012   341    ****30.2****    6.8**
**024   302    54.5   11.2**
**036   264    77.4   14.6**
**048   228    99.7   16.1**
**072   159   142.3   17.8**
**096   107   186.1   19.3**
**120    71   227.5   ****18.3**

- Values in green represent all-time lows.

## 2006 vs 5-Year Mean

## Errors cut by 1/3 since 1990

## OFCL Error Distributions

## Skill trend noisy but generally upward

## 2006 Track Guidance (1st tier)

**Larger separation between dynamical and consensus models (model errors more random, less systematic).**

## 2nd Tier

## FSU Superensemble vs Other Consensus Models

## Relative Power of Multi-model Consensus

*n**e* = 1.65				 *n**e* = 2.4

## 2006 vs Long-term Mean

## Same as it ever was...

## ...same as it ever was.

## 2006 Intensity Guidance

## FSU Superensemble vs Other Consensus Models

## Summary

- Atlantic Basin - Track
- OFCL track errors set records for accuracy from 12-72 h.  Mid-range skill appears to be trending upwards.
- OFCL track forecasts were better than all the dynamical guidance models, but trailed the consensus models slightly.
- GFDL, GFS, and NOGAPS provided best dynamical track guidance at various times.  UKMET trailed badly.  No (early) dynamical model had skill at 5 days!
- ECMWF performed extremely well, when it was available, especially at longer times.  Small improvement in arrival time would result in many more EMXI forecasts.
- FSU super-ensemble not as good as Goerss corrected consensus, and no better than GUNA in a three-year sample.

## Summary (2)

- Atlantic Basin - Intensity
- OFCL intensity errors were very close to the long-term mean, but skill levels dropped very sharply (i.e., even though Decay-SHIFOR errors were very low, OFCL errors did not decrease).  The OFCL errors also trailed the GFDL and ICON guidance.
- For the first time, dynamical intensity guidance beat statistical guidance.
- OFCL forecasts had a substantial high bias.  Even though the GFDL had smaller errors than OFCL, its bias was larger.
- FSU super-ensemble no better than a simple average of GFDL and DSHP (three-year sample).

## Summary (3)

- East Pacific Basin - Track
- OFCL track errors up, skill down in 2006, although errors were slightly better than the long-term mean.
- OFCL beat dynamical models, but not the consensus models. Much larger difference between dynamical models and the consensus in the EPAC (same as 2005).
- FSU super-ensemble no better than GUNA (two-year sample).

## Summary (4)

- East Pacific Basin - Intensity
- OFCL intensity errors/skill show little improvement.
- GFDL beat DSHP after 36 h, but ICON generally beat both.
- FSU super-ensemble slightly better than ICON at 24-48 h, but worse than ICON after that.