Gulf States Hurricane Conference Mobile, AL

June 3, 2010

NWS Coastal Office Tropical Weather ProductsDavid McShane

NWS MobileFrank Revitte

NWS New Orleans/Baton Rouge Area

Topics

• Changes to National Hurricane Center Products for 2010

• Local National Weather Service Tropical Storm/Hurricane Products and Services for Coastal Area

• Discussion

Changes to Tropical Cyclone Watch/Warning Lead Times in 2010

• Lead time virtually unchanged while skill in track forecasting has improved

• NHC in fact frequently does issue watches and warnings at longer lead time than Directive indicates

• Key evacuation decisions now need to be made before 24 h and in some cases before 48 h

• Some jurisdictions, businesses, and schools still tag closure decisions to warning or watch

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Coastal County Population, Texas to Maine

53% of the U.S. population now lives within 50 miles of the coast

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Tropical Storm Watches and Warnings

Tropical Storm Watch tropical storm conditions (sustained winds

of 39 to 73 mph) are possible within the specified coastal area within 48 hours

Tropical Storm Warningtropical storm conditions (sustained winds

of 39 to 73 mph) are expected somewhere within the specified coastal area within 36 hours

Hurricane Watches and Warnings

Hurricane Watch hurricane conditions (sustained winds of 74 mph or

higher) are possible within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds

Hurricane Warning hurricane conditions (sustained winds of 74 mph or

higher) are expected somewhere within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds

In some cases, we were already doing it…

Hurricane Watch issued for Texas coast at 4PM CDT on Wed Sep. 10

Tropical storm force winds begin affecting Texas coast

about 48 hrs later

Saffir-Simpson Hurricane Wind Scale

IKE (2)KATRINA (3)

CHARLEY (4)

Surge, rainfall, and pressure fit the scale like a square peg in a round hole

http://www.nhc.noaa.gov/aboutsshs.shtml

NHC Forecast Cone

• Represents the probable track of the center of the tropical cyclone.

• Formed by connecting circles centered on each forecast point (at 12, 24, 36 h, etc.)

• Size of the circles determined so that, say, the actual storm position at 48 h will be within the 48-h circle 67% of the time.

New Public Advisory Format

Section headers added

Storm information first

Changes to watches and warnings in the current advisory are highlighted

Bulleted summary of all watches and warnings in effect

Section headers

Discussion of forecast motion and intensity and other pertinent information

Storm hazards and impacts, shown by type

New Public Advisory Format

Fatality from falling treeLafayette, LA

Water overtops Industrial CanalNew Orleans, LA

AP PhotosGustav Damage

Coastal Hurricane Hazards and NWS Weather Forecast Office Products

NWS – Weather Forecast Office Tropical Weather Products

• WFO has traditionally issued text products to complement NHC products and give additional detailed information for the local area

• Often lengthy and difficult to sort through the information.• Specific Tropical Weather Products

– Hurricane Local Action Statement– Inland Hurricane/Tropical Storm Watches and Warnings– Extreme Wind Warning

• Extreme winds associated with Category 3, 4 or 5 Hurricanes• Traditional NWS text products are also issued during tropical

events– Tornado Watches, Tornado Warnings, Flash Flood Warnings, etc.

HURRICANE KATRINA LOCAL STATEMENTNATIONAL WEATHER SERVICE NEW ORLEANS LA1015 AM CDT SUN AUG 28 2005

...HURRICANE KATRINA NOW A CATEGORY 5 HURRICANE PACKING SUSTAINEDWINDS OF 175 MPH...

...DIRECT STRIKE OF POTENTIALLY CATASTROPHIC AND LIFE THREATENING HURRICANE EXPECTED...

...RUSH PROTECTIVE MEASURES TO COMPLETION AND LEAVE THE AREA NOW!...

...MORE HEADLINES.....

...AREAS AFFECTED...IN SOUTHEAST LOUISIANA...THE FOLLOWING PARISHES ASSUMPTION...ST JAMES...MORE PARISHES...

IN COASTAL MISSISSIPPI...THE FOLLOWING COUNTIES HANCOCK...HARRISON...JACKSON

...WATCHES AND WARNINGS...A HURRICANE WARNING IS IN EFFECT FROM EAST OF MORGAN CITY EAST TO THE ALABAMA-FLORIDA BORDER AREA. THIS INCLUDES THE METRO NEW ORLEANS AREA...AND

THE MISSISSIPPI COAST.

...STORM INFORMATION...AT 10 AM CDT...THE CENTER OF HURRICANE KATRINA WAS LOCATED NEAR LATITUDE 26.0 NORTH...LONGITUDE 88.1 WEST OR ABOUT 225 MILESSOUTHEAST OF THE MOUTH OF THE MISSISSIPPI RIVER.

MAXIMUM SUSTAINED WINDS ARE NEAR 175 MPH...WITH HIGHER GUSTS. HURRICANE KATRINA IS A CATEGORY FIVE HURRICANE ON THE SAFFIRSIMPSON SCALE. MORE INFORMATION.

...PRECAUTIONARY/PREPAREDNESS ACTIONS...PROTECT YOU AND YOUR FAMILYS LIVES. FOLLOW LOCAL EMERGENCY MANAGERS RECOMMENDATIONS AND LEAVE HURRICANE WARNING AREA NOW BEFORE WEATHER

CONDITIONS WORSEN. MORE INFORMATION.

MANDATORY EVACUATION ORDERS ARE IN EFFECT FOR MOST SOUTHEAST LOUISIANA PARISHES AND COASTAL MISSISSIPPI COUNTIES. RESIDENTS SHOULD FOLLOW EVACUATION RECOMMENDATIONS FROM LOCAL PARISH OFFICIALS.

...STORM SURGE FLOOD AND STORM TIDE IMPACTS...KATRINA IS EXPECTED TO MAKE LANDFALL ALONG THE NORTHERN GULF OF MEXICO COAST AS A CATASTROPHIC LIFE THREATENING HURRICANE. WHILE EXACT LOCATION LANDFALL IS UNCERTAIN AT THIS TIME...SIGNIFICANT AND LIFE THREATENING STORM SURGE 18 TO 22 FEET ABOVE NORMAL IS POSSIBLENEAR AND TO THE RIGHT OF THE LANDFALL AREA. MORE INFORMATION....

...WIND IMPACTS...EAST TO NORTHEAST WIND OF 20 TO 25 MPH SHOULD CONTINUE OVER THE REGION TODAY...THEN INCREASE LATE THIS AFTERNOON AND CONTINUINGTONIGHT. TROPICAL STORM FORCE WINDS ARE LIKELY TO OVERSPREAD THE COASTAL AREAS THIS EVENING MORE INFORMATION.

KATRINA IS FORECAST TO MOVE ASHORE AS CATEGORY FIVE HURRICANE...SIMILAR IN STRENGTH TO HURRICANE CAMILLE IN 1969. MORE INFORMATION...

...RAINFALL...RAINFALL TOTALS OF 8 TO 10 INCHES...MORE INFORMATION....

...NEXT UPDATE...THE NEXT LOCAL STATEMENT WILL BE ISSUED AROUND 130 PM CDT.

$$

Extreme Wind Warning -Example• BULLETIN - EAS ACTIVATION REQUESTED• EXTREME WIND WARNING • NATIONAL WEATHER SERVICE NEW ORLEANS-BATON ROUGE LA• 943 AM CDT MON SEP 15 2008

• THE NATIONAL WEATHER SERVICE HAS ISSUED An

• * EXTREME WIND WARNING FOR THE ONSET OF SUSTAINED WINDS OF 115 MPH OR GREATER FOR...

• WASHINGTON PARISH IN SOUTHEAST LOUISIANA• ST. TAMMANY PARISH IN SOUTHEAST LOUISIANA• PEARL RIVER COUNTY IN SOUTHERN MISSISSIPPI• HANCOCK COUNTY IN SOUTHERN MISSISSIPPI

• * UNTIL 1130 AM CDT

• * AT 940 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED THE LEADING EDGE OFINTENSE EYEWALL WINDS ASSOCIATED WITH VERY DANGEROUS HURRICANE ALPHA MOVING THROUGH SOUTHEAST LOUISIANA AND SOUTH MISSISSIPPI. NORTHERN PORTION OF THE INTENSE EYEWALL PRODUCING EXTENSIVE DAMAGING WINDS FROM NEAR SLIDELL TO 15 MILES EAST OF PICAYUNE ...MOVING NORTH AT 18 MPH.

• * EXTREME WINDS ARE EXPECTED TO AFFECT...• ST TAMMANY AND WASHINGTON PARISHES IN SOUTHEAST LOUISIANA• HANCOCK AND PEARL RIVER COUNTIES IN SOUTH MISSISSIPPI

• THE ONSET OF DESTRUCTIVE WINDS WITH GUSTS OF 100 TO 120 MPH CAN BE • EXPECTED SHORTLY. THESE DESTRUCTIVE WINDS WILL PRODUCE WIND • DAMAGE SIMILAR TO A TORNADO OVER LARGE AREAS. SEEK SHELTER ON THE LOWEST • FLOOR OF THE BUILDING IN AN INTERIOR HALLWAY OR ROOM SUCH AS A • CLOSET. STAY AWAY FROM WINDOWS AND REMAIN IN YOUR SAFE SHELTER UNTIL • THE EYEWALL PASSES.

• LAT...LON 3042 8935 3045 8958 3034 8975 3023 8984•

• Event driven product

• Sustained winds of 115 mph or greater (Cat 3,4,or 5)

• Duration- 2 hr or less

• Several parishes/counties

• Wording similar to a tornado warning.

Graphical Hurricane Local Statement • Graphics depicting hazard is

automatically generated on NWS Office work station sent to web site.

• Pre-set risk levels – low, medium high

TS Ida – Storm Surge Hazard

Webinars, and Conference Calls

• Positive Step Forward –• Ability to display graphics depicting

hazards and • Interact, explain and clarify critical

information with emergency managers and decision makers.

Challenges • Tropical Cyclone

Forecasts Have Errors – location, intensity, etc

• Risk Associated with those errors may range from minor to catastrophic and life threatening.

• How do we effectively communicate hazard and risk to aid decision process?

NHC Forecast Cone

• Represents the probable track of the center of the tropical cyclone.

• Formed by connecting circles centered on each forecast point (at 12, 24, 36 h, etc.)

• Size of the circles determined so that, say, the actual storm position at 48 h will be within the 48-h circle 67% of the time.

3- and 5-Day Error Conesslight reduction in size due to lower track errors

Forecast Period

(h)

2009 Circle Radius (n mi)

(‘04 – ’08 errors)

2010 Circle Radius (n mi)

(‘05 – ’09 errors)

12 36 36

24 62 62

36 89 85

48 111 108

72 167 161

96 230 220

120 302 285

Remember - Forecast Error Can Occur “Along” The

Predicted Tack

• Hurricane Gustav– Excellent forecast of

pinpointing area of coast impacted

– Hurricane moved onshore earlier than suggested by the 72 hour forecast

– Tropical storm conditions arrived ~12 hours earlier.

Tropical Storm/Hurricane Wind Probability

• Wind Probability data is available both in tabular data and graphical format.

• Graphical depiction of areas with greatest wind threat.

Hurricane Ivan: A case study

Suppose this 48 H forecast – 115 knots – deterministic SLOSH forecast

10 feet

30 miles further west

6 feet

30 miles further east

17 feet

Gustav Surge Based on Advisory 31 – Storm surge concentrated near track over Terrebonne Parish.

Radius of Max Wind 30 mi

Gustav SLOSH estimate using a larger wind field (50 nm Radius of Max Wind)

SLOSH MEOW developed to account for uncertainty in track and intensity forecasts

Storm Surge Probabilitiesbased on Gustav Advisory 28

Heights which have a 10% chance of being exceeded

Probability of Storm Surge Exceeding 8 Feet

Storm Surge Probabilities “Ida” Advisory 28

Heights which have a 10% chance of being exceeded

Probability of Storm Surge Exceeding 8 Feet

google earth mapping- kml file

Storm Surge Probability InfoAvailable on NHC Web Site

• Initiated whenever a hurricane watch or warning is in effect (~ 36 hours before the arrival of tropical storm force winds)

• Available ~20-30 minutes after advisory release

• Questions / Comments

• Contact Information– Frank Revitte – New Orleans/Baton

Rouge Area• 985-649-0357 x223

– David McShane – Mobile• 251-633-6443

NWS Web Sites– www.weather.gov

• Select area on map.