# Presentation: 920181

## Application of T382 CFS Forecasts for Dynamic Hurricane Season Prediction

- J. Schemm, L. Long, S. Saha and
- S. Moorthi
- NOAA/NWS/NCEP
- October 21, 2008
- The 33rd Climate Diagnostics and Prediction Workshop, Lincoln, NE

## Outline

- Description of the CFS experiment
- Datasets Used
- IRI Detection and Tracking Method
- Analysis of storm activity statistics
- Focus on the Atlantic Basin
- Statistics
- A look at CFS predictions for 2008
- Future plan

## CFS T382  hurricane season experiments

- One of the FY07/08 CTB internal projects
- AGCM - 2007 operational NCEP GFS in T382/L64 resolution
- 	LSM - Noah LSM
- 	OGCM - GFDL MOM3
- 3.   All runs initialized with NCEP/DOE R2 and NCEP GODAS.
- 	Initial conditions at 0Z, Apr. 19, 20, (21) and May 15(FY07)
- 	for 1981-2007.  Forecasts extended to December 1.
- 4.	For May 15 cases, runs in T62 and T126 resolutions also performed.

## Datasets

- CFS hindcasts at T382
- May 15th Initial Condition
- Output at every 3 hours
- 1981-2007, 27 years
- April 19th and April 20th Initial Condition
- Output at every 6 hours
- 1981-2008, 28 years
- More appropriate ICs for CPC Operational Hurricane Season Outlook
- Observations from the HURDAT and JTWC Best Track Dataset
- -Tropical depressions and subtropical storms
-   are not included in storm counts.

## Tropical Cyclone Detection Method

- Based on method devised by Camargo and Zebiak (2002) at IRI
- Detection algorithm uses basin-dependent threshold criteria for three variables
- Vorticity, thresh
- thresh = 2
- 10-m Wind Speed, thresh
- thresh = gl + gl = wind speed averaged over
-                                                      all global basins
- Vertically integrated temp anomaly, Tthresh
- Tthresh = T/2
- Calculated using only warm-core systems

## 1.	850-hPa relative vorticity > thresh
2.	Maximum 10-m wind speed in a 7x7 box > thresh
3.	SLP is the minimum in the centered 7x7 box
4.	Temp anomaly averaged over the 7x7 box and three pressure levels (300, 500, & 700 mb) > Tthresh
5. 	Temperature anomaly averaged over the 7x7 box is positive at all levels (300, 500, & 700 mb) *
6.	Temperature anomaly averaged over the 7x7 box at 300mb > 850mb *
7.	Wind speed averaged over the 7x7 box at 850mb > 300mb
8.	The storm must last for at least 6 hours.
           * Criteria 5 & 6 define a warm core system.

- 2.	Maximum 10-m wind speed in a 7x7 box > thresh
- 3.	SLP is the minimum in the centered 7x7 box
- 4.	Temp anomaly averaged over the 7x7 box and three pressure levels (300, 500, & 700 mb) > Tthresh
- 5. 	Temperature anomaly averaged over the 7x7 box is positive at all levels (300, 500, & 700 mb) *
- 6.	Temperature anomaly averaged over the 7x7 box at 300mb > 850mb *
- 7.	Wind speed averaged over the 7x7 box at 850mb > 300mb
- 8.	The storm must last for at least 6 hours.
-            * Criteria 5 & 6 define a warm core system.

- Eight conditions must be met for a point to be considered a tropical cyclone

## Storm Tracking

- Once a point is designated as a tropical cyclone, the cyclone is tracked forward and backward in time to create a full storm track.
- The maximum vorticity in a 5x5 grid around the cyclone is found and a new 3x3 box is formed around it.
- At the next time step, if the maximum vorticity in this new box is greater than 3.5 x 10-5 s-1, the procedure is repeated.
- This point has become part of the storm track.
- If two storm tracks are the same, they are considered the same cyclone and counted as one.

## Four NH Ocean Basins

## Examples of Storm Tracks for 4 NH Basins

## Atlantic

- Basin

- Atlantic Tropical Storms

## Eastern

- Pacific
- Basin

- Eastern Pacific Tropical Storms

## JJA Nino 3.4 SST Index

## JJA Atlantic MDR SST Index

## Tropical Storm Origins, 1981-2007 ASO

**OBS**

**IC=0515**

**IC=0419**

**IC=0420**

## Atlantic Basin Correlations

-    N=27     N=13      N=13        N=8          N=5          N=14

**Red** = Statistically Significant at 0.95

- Correlations based on
- 27-year anomaly

- 0.79

- Anomalies of Atlantic Storms

## Red = Statistically Significant at 0.95

**Red** = Statistically Significant at 0.95

**0.90**

## 2008 Atlantic Season Summary

|  | 
Obs | NOAA
Outlook | Outlook Update | CFS-Stat
May | CFS-Stat
Update |
| --- | --- | --- | --- | --- | --- |
| Named Storm | 
15 | 
12-16 | 
14-18 | 
9-16 | 
13-16 |
| 
Hurricane | 
7 | 
6-9 | 
7-10 | 
5-9 | 
7-10 |
| Major Hurricane | 
4 | 
2-5 | 
3-6 | 
2-4 | 
3-5 |

- As of October 17, 2008

## Atlantic Basin Prediction for 2008

- Two additional runs were made using July 15th and 16th initial conditions for 2008 only
- Used as a trial run for the CPC Hurricane Outlook Update

## Atlantic BasinCFS 2008 Monthly Storm Count

- Atlantic BasinCFS 2008 Monthly Storm Count

- 3

## Large number of storms over the Gulf of Mexico this year

- (Courtesy of Unisys)

- 2008 Atlantic Storm Tracks

## Resemble Bertha and Cristobal

**Resemble Bertha and Cristobal**

## .Summary

-   CFS in T382 resolution exhibits robust climatological
-     seasonal cycle of tropical cyclone over four NH basins.
-   Warming trend and intensification of hurricane activity in
-       the Atlantic basin captured in the CFS hindcasts.
-   Fair level of skill in predicting interannual variability of seasonal
-      storm activities based on the limited number of forecast runs.
-   Continue to increase number of ensemble members for better
-      climatology and storm statistics. Hope to provide input for 2009
-      Hurricane Season Outlook with real time prediction runs.
-   Prospect of multi-model ensemble approach for dynamical
-      hurricane season prediction