10 Years of U.S. Hazards Assessments –

Where do We Go from Here?

Edward O’LenicClimate Prediction Center-NCEP

32nd Climate Diagnostics and Prediction WorkshopOctober 22-25, 2007Tallahassee, Florida

“When you come to a fork in the road,

take it.”

- Yogi Berra

“When you come to a fork in the road,

take it.”

- Yogi Berra

The tools and technology now exist to move the Hazards Assessment to a new level, one of probabilistic

forecasts, which can eventually be used in objective decision-making.

Outline

o Description & History

o Criteria

o An example

o Frequency of Hazards

o ROC diagram of Extreme Precipitation

o Steps to the Future

U.S. Hazards Assessment

Schedule, Leads The U.S. Hazards Assessment is intended to provide advance warning of extreme weather events to emergency managers, weather forecasters, planners and citizens at all levels of government, the private sector and the public.

Issued each day from Monday through Friday and covers days 3-14. A preliminary version of the product is prepared and placed on a web site by 11:00 AM on Monday for examination by NCEP Centers, and NWS Field offices who provide input to the Hazards forecaster.

Comments from NCEP service centers and output from dynamical models, including the GFS, ECMWF, Canadian model, NOGAPS, etc…, are the primary inputs to the product.

Each Wednesday, CPC hosts a telephone conference call which is open to the public.

A Unique Product and Origin

The U.S. Hazards Assessment is unique among NWS Official products, being a weather- oriented product, produced by a climate entity. Also it required, first NCEP, then NWS to officially acknowledge the importance of weather-climate (C-W) links.

Ants Leetmaa conceived the idea of a C-W links-based NWS product early in 1997, when El Nino became a real possibility. He tirelessly, aggressively, and successfully sold the idea to NCEP and NWS HQ.

I was the lucky person who got to develop the actual product, with input from a lot of people.

September, 1997: As CPC’s first real El Nino forecast gets National attention, NCEP embraces the idea of weather impacts linked to a climate event.A series of coordination meetings were

held during September and late October, 1997. These secured buy-in from NWS and emergency management entities.

Ron McPherson was heavily involved

early-on. He emphasized the importance of gaining buy-in from the NWS Field, and from other outside entities. His support greatly facilitated NWS cooperation.

Coordination meetings were held each week in October. The basic form of the product was agreed upon by late October.

One of the first “Threats Assessment” maps, October, 1997. The product also featured numerous links to forecast information and a weekly telephone conference call.

The product became fully operational in September, 2001, at Jack Kelly’s urging.

Event Threshold Lower threshold if:

Precipitation

Rain, Snow

The greater of 95th Percentile, or

1” precipitation/day,

snow >= 4” per day

Pre-existing flooding, saturated soils,

Heavy mountain snow likely

Temperature, TMB, TMA Lower/upper 12.5% T distribution Wildfire in progress

Extreme Heat Index Upper 12.5% HI distribution

Freeze First freeze, or unusually early (fall), or Late (spring) min T<=32

Freezing Rain Model forecast and subjective

Wind >34 mph winds, 1 hr

>58 mph gusts

Wildfire in progress

Heavy snow or extreme cold predicted

Drought Drought Monitor D2

Flood OH, USGS criteria, at least 0-5’>flood stage

Saturated soils

Rapid snowpack melting

Wildfire SPC 3-8 day guidance Dry lightning, high winds

Extreme heat + low RH

Thunderstorms >=30% probability - SPC 4-8 day guidance

Waves Long fetch normal to coast. Strong cyclone predicted, subjective

Strong on-shore flow through several tidal cycles

CRITERIA

Event Threshold Lower threshold if:

Precipitation

Rain, Snow

The greater of 95th Percentile, or

1” precipitation/day,

snow >= 4” per day, higher in West

Pre-existing flooding, saturated soils,

Heavy mountain snow likely

Temperature, TMB, TMA Lower/upper 12.5% T distribution Wildfire in progress

Extreme Heat Index Upper 12.5% HI distribution

Freeze First freeze, or unusually early (fall), or Late (spring) min T<=32

Freezing Rain Model forecast and subjective

Wind >34 mph winds, 1 hr

>58 mph gusts

Wildfire in progress

Heavy snow or extreme cold predicted

Drought Drought Monitor D2

Flood OH, USGS criteria, at least 0-5’>flood stage

Saturated soils

Rapid snowpack melting

Wildfire SPC 3-8 day guidance Dry lightning, high winds

Extreme heat + low RH

Thunderstorms >=30% probability - SPC 4-8 day guidance

Waves Long fetch normal to coast. Strong cyclone predicted, subjective

Strong on-shore flow through several tidal cycles

CRITERIA

Extreme precipitation hazards are verified using a 10x10 grid over the CONUS (881 points).

Frequency of Hazards Categories 1997-2005

Hazards Relative Frequency for 1997-2000, 2001-02, 2005, no drought

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

1 2 3 4 5 6 7 8 9 10 11

HAZARDS CATEGORY

FR

AC

TIO

N O

F E

VE

NT

S

1997-2000

2001-2002

2005

RAIN

SNOW

WIND

FRZRAIN

TSTORMS

TMBTMA XHEAT

WFIREFLOOD

FREEZE

ROC for Extreme Precipitation Events 2003-2007

Extreme

precipitation

events were

subjectively

predicted with

modest skill.

a b

c d

False Alarm Rate, b/(b+d)Fraction of all non-events that were incorrect

Pro

ba

bili

ty o

f d

ete

ctio

n,

a/(

a+

c)fr

act

ion

of

ob

serv

ed

eve

nts

th

at

wa

s co

rre

ctly

fo

reca

st

Probabilistic Hazards: Getting There from Here

This will require:- Climatologies- Model forecasts- Real-time obsWe have these for P,T, Heat, Drought,Thunderstorms

Ken Pelman will report on his effort todo this for heavyprecipitation using GFSensemble members tocreate an automatedprobabilistic forecast tool. Results arepromising.

Summary• The U.S. Hazards Assessment is a categorical forecast of

extreme events for days 3-14.• It is intended to provide users forecasts based, in part, on

climate-weather links and heavily on model forecasts.• First experimental versions were released in October, 1997.

Operational in September, 2001.• Relative frequency of posted hazards has been stable, and is

dominated by drought, rain, flood, thunderstorms, wildfire and wind, in that order.

• ROC scores for extreme precipitation events indicate modest skill.

• Simple, uncalibrated ensemble probability forecasts show promise for precipitation forecasts.

• Other parameters, and automated forecast techniques will be explored using similar techniques.

Cumulative

Contingency

Table:

1940 a 6979 b

41911 c 307527 d

Scores for Hazards Extreme PrecipitationJanuary 2004-October 2007

Threat Score=a/(a+b+c)

Bias = (a+b)/(a+c)

Probability of detection=a/(a+c) False Alarm Ratio=b/(a+b)

Hit Rate = (a+d)/(a+b+c+d)

Sometimes there’s a lot of Information

A 3-panel

Decomposition

was adopted in

1999.