# Presentation: 356170

## Operational Tropical CycloneWind Speed Probabilities

**Operational Tropical Cyclone****Wind Speed Probabilities**

**Richard Knabb**
**NOAA/NWS/National Hurricane Center**
**2007 Interdepartmental Hurricane Conference**

## 	
Replaced strike probabilities in 2006
Describe chances of a weather event at any specific location
Convey chances of wind speeds of at least particular thresholds
34 kt (tropical storm force)
50 kt
64 kt (hurricane force)
Account for combined uncertainty in official track, intensity, and size forecasts
Extend to 5 days
Include inland locations

- Replaced strike probabilities in 2006
- Describe chances of a *weather event* at any specific location
- Convey chances of wind speeds of at least particular thresholds
- 34 kt (tropical storm force)
- 50 kt
- 64 kt (hurricane force)
- Account for combined uncertainty in official track, intensity, and size forecasts
- Extend to 5 days
- Include inland locations

**Overview of wind speed probabilities**

## What are the chances this wind event will happen to me at all?
Do I need to prepare?
Cumulative period probabilities
NHC and CPHC graphics and text products
Northern hemispheric grids sent via WMO headers
National Digital Forecast Database (NDFD) CONUS grids

When is the event most likely to start at my location?
How much time do I have left to prepare?
Individual period probabilities
NHC and CPHC text products

*Do I need to prepare?*
**Cumulative** period probabilities
- NHC and CPHC graphics and text products
- Northern hemispheric grids sent via WMO headers
- National Digital Forecast Database (NDFD) CONUS grids
**When is the event most likely to start at my location?**
*How much time do I have left to prepare?*
**Individual **period probabilities
- NHC and CPHC text products

**What questions do these products answer?**

## What are the chances the event will be occurring at my location during a specific period?
(example) Will hurricane-force winds occur in my city on Saturday night?
Incremental probabilities
NDFD
Might go out via WMO headers by 2008
Being incorporated into WFO products

*(example) Will hurricane-force winds occur in my city on Saturday night?*
**Incremental** probabilities
- NDFD
- Might go out via WMO headers by 2008
- Being incorporated into WFO products

**What questions do these products answer?**

## Probabilities Convey Uncertainties in Track, Intensity, and Size Forecasts

**Ernesto Advisory #11**

## Magnitudes of Cumulative Probabilities Vary Greatly But Realistically

**Magnitudes of Cumulative Probabilities Vary Greatly But Realistically**

**Katrina Advisory #5**

## Magnitudes of Cumulative Probabilities Vary Greatly But Realistically

**Katrina Advisory #18**

**Magnitudes of Cumulative Probabilities Vary Greatly But Realistically**

## Changes to Graphics for 2007

## 2006 Operational 120-h Graphic (64 kt)

## 2007 Final 120-h Graphic (64 kt)

## 2007 Preliminary 120-h Graphic (64 kt)

**2007 Preliminary 120-h Graphic (64 kt)**

## Individual period probabilities help to understand timing uncertainty

**Individual period probabilities help to understand timing uncertainty**

**X**

## Dealing With Small Probabilities

## A Challenge During Ernesto

## A Challenge During Ernesto

**A Challenge During Ernesto**

## A Challenge During Ernesto

**Hurricane**
**Watch**

## A Challenge During Ernesto

**A Challenge During Ernesto**

## 	
Cumulative and incremental probabilities
Updated four times daily (00, 06, 12, 18 UTC)
6 hourly 0-120 h
34, 50, and 64 kt
CONUS domain only
5 km grid spacing
Experimental during 2006, declared operational for 2007 hurricane season

- Cumulative and incremental probabilities
- Updated four times daily (00, 06, 12, 18 UTC)
- 6 hourly 0-120 h
- 34, 50, and 64 kt
- CONUS domain only
- 5 km grid spacing
- Experimental during 2006, declared operational for 2007 hurricane season

**What is available via the NDFD****(National Digital Forecast Database)?**

## NDFD CONUS Domain

**NDFD CONUS Domain**

## Probabilities from NDFD Website

- www.weather.gov/forecasts/graphical/sectors/conusTropicalDay.php#tabs

## Probabilities in Hurrevac

## Graphics Widely Used in Emergency Management

**Graphics Widely Used in Emergency Management**

## Going forward

- Continue outreach and education
- Compare probabilities with watches/warnings
- Account for varying forecast confidence?
- Enhance Hurrevac capabilities
- Experimental storm surge probabilities

**For Additional Information...**

- www.nhc.noaa.gov/aboutnhcprobs.shtml

**For Additional Information...**

- www.nhc.noaa.gov/archive/2005/index.shtml

**For Additional Information...**

- Richard.Knabb@noaa.gov