Kelly Godsey and Jeffry Evans National Weather Service Tallahassee, Florida

Basic Tropical Definitions Tropical Depression: A tropical cyclone that has maximum sustained winds 38 mph or less. Tropical Storm: A tropical cyclone that has maximum sustained winds between 39 mph and 73 mph. Hurricane: A tropical cyclone that has maximum sustained winds of 74 mph or greater. Major Hurricane: A tropical cyclone that has maximum stained winds of 111 mph or greater. Saffir-Simpson Hurricane Scale: The rating system for hurricanes based on maximum wind speed.

Saffir-Simpson Hurricane Wind Scale CategoryWind Speed Range (peak 1-minute wind) ??

Extratropical storm (1993) Subtropical Storm Gustav (2002) Hurricane Rita (2005) Three types of Cyclones

Tropical and Extratropical Storms

Structure of a Tropical Cyclone Feeder Bands Central Dense Overcast Eye

Cross Section of a Hurricane

What the Hurricane Hunters Saw in Katrina

What drives tropical cyclones? Tropical systems are steered by the upper level winds Typically, the Bermuda High and it’s location will determine how large hurricanes move across the Atlantic. An approaching trough of low pressure can cause a system to “recurve” before reaching the United States Simulation

What is required for tropical cyclones to form? Lots of moisture Low wind shear Sufficently deep warm ocean water

Where do we look for tropical cyclone formation It all depends on the time of the year and if the ingredients for development exist Tropical systems typically form in the Caribbean or Gulf of Mexico at the beginning and end of the season. Development shifts to the Central and Eastern Atlantic in the middle of the season.

Development in June

Development in July

Development in August

Development in September

Development in October

Development in November

Climatology Compared to the rest of Florida, hurricane landfalls in the Florida Big Bend are rare. Landfalls in the Florida Panhandle are higher over the last 100 years.

Storm Names – Where did they come from? Prior to 1953 meteorologists informally named tropical systems to keep track of multiple active storms. Starting in 1953, a list using only female names was introduced. In 1970, Grandpa Jones explains why only female names were used at first.

Storm Names – Continued Men’s names joined the list in 1979 Six lists are used and rotate each season Storms that are especially deadly or cause significant damage are permanently retired from the active list. Katrina, Hugo, and Andrew are notable examples. In the event all storm names are used for a single hurricane season, the Greek Alphabet is used: Alpha, Beta, Gamma, Delta, etc.

2010 Storm Names AlexBonnie ColinDanielle EarlFiona GastonHermine IgorJulia KarlLisa MatthewNicole OttoPaula RichardShary TomasVirginie Walter Replacement name (2004)

Important changes for the 2010 Hurricane Season Hurricane/Tropical Storm Watches now mean conditions are possible within 48 hours. Hurricane/Tropical Storm Warnings now mean conditions are expected within 36 hours. The Public Advisory format has changed. Saffir-Simpson Scale no longer tied to storm surge New Coastal Zones for Tallahassee Forecast Area Our pre-season hurricane guide, complete with these changes and more will be available by the last week of April.

Why change the watch/warning times Track errors at 48 hours are now similar to those years ago at 36 hours. Greater lead time is needed to evacuate some coastal counties. What does this mean? Watches may be posted as much as 3 days prior to arrival of the predicted condition, especially for larger storms.

New Public Advisory Instead of paragraph format, product divided into five sections to provide better access to information Summary of storm location Watches and Warning Summary New watches and warning changes first Summary to follow Discussion and 48 hour outlook Hazards affecting land (surge, wind, rainfall etc.) Next advisory time

Observed Storm Surge Different from that Advertised by Saffir-Simpson Hurricane Scale  storm surge is modulated by more than just the peak wind IKE (2) CHARLEY (4)

New Coastal Zones for NWS Tallahassee

Coastal Zones and Hurricanes Coastal zones were designed based on storm surge climatology and other coastal effects. Coastal zones will carry any tropical storm or hurricane watches and warnings Inland zones in coastal counties and inland counties will carry tropical storm or hurricane wind watches and warnings.

Seasonal Forecast Factors Status of El Nino Southern Oscillation Atlantic Sea Surface Temperature observations relative to normal. Rainfall occurring over Sub-Saharan Africa Prevailing atmospheric conditions over North America

El Nino Status

Latest forecasts for the 2010 Season OrganizationTropical Storms HurricanesMajor Hurricanes Colorado State (Dec ‘09) Colorado State (Apr ‘10)1584 NOAA (due May ‘10)?? Normal Values ( ) Hurricane Season932 **Seasonal forecasts are to be considered only as a guide began a period of above normal activity. Only three seasons since 1995 have featured below normal activity in the Atlantic Basin.

Watching for a storm to develop The National Hurricane Center continually monitors the tropical Atlantic for signs of development. Four times a day, NHC issues a text and graphical tropical weather outlook. Issued at 8 am, 2 pm, 8 am, and 2 am Eastern Time. This outlook highlights areas at increased risk for development. The graphical map includes a “mouse over” ability Active tropical systems are indicated on the map.

A storm Develops in the Atlantic The initial development is called a tropical depression. When winds reach 39 mph, the depression will receive a name and be called a tropical storm. When winds reach 74 mph, the storm becomes a hurricane

NHC Website for active storms NHC is responsible for issuing advisories on tropical systems. Website includes sections devoted to each active storm. Text products include: Public Advisory Forecast/Advisory Forecast Discussion Wind Speed Probabilities Graphics are provided in the section below. Sample

What are the wind speed probability graphics? Display the percentage 34 knot, 50 knot, or 64 knot winds are possible in your location over the next five days, or 120 hours. Corresponds with a text version that provides details for the onset of 34 knot, 50 knot, or 64 knot winds. Example

Text Probability Table Issued by NHC with each advisory package Details probability of 34kt, 50kt, and 64kt winds during a particular interval and throughout the entire 5 day forecast period. Well known locations chosen in the projected area of impact

Sample Interval and Cumulative Probability Product

Terms of Uncertainty Utilizes the probability data provided by the National Hurricane Center in conjunction with the forecast prepared by local meteorologists. Available through the point and click forecast accessible from the Tallahassee main page. Includes both graphics and text

Terms of Uncertainty (Con’t) Wednesday Wednesday Night Thursday There are six phrases that can be used: Tropical Storm (Hurricane) conditions possible: This phrase will be used most often. Tropical Storm (Hurricane) conditions expected: This phrase requires a watch or warning to be in effect with a high degree of confidence Tropical Storm (Hurricane) Conditions: This phrase is only used in the first 24 hours of the forecast.

Storm Impacts for our Region

Storm Surge Defined STORM SURGE is an abnormal rise of water generated by a storm, over and above the predicted astronomical tide. STORM TIDE is the total water level during a storm (i.e astronomical tide + storm surge)

Storm Surge/Storm Tide

DEEP WATER b. Side view of Cross Section “ABC”a. Top view of Sea Surface 0’ 5O’ 100’ 150’ 200’ Wind Current A B C MSL A B Eye C Wind

LANDFALL b. Side view of Cross Section “ABC”a. Top view of sea surface and land Wind A BC 0’ 50’ 100’ 150’ 200’ Continental Shelf Barrier Island Mainland A B C Eye Current MSL STORM SURGE Wind STORM SURGE

Width and Slope of Shelf Wide shelf/ gentle slope Narrow shelf/ sharp slope

Start of shelf trapped wave up the Florida Coast

180 miles

Storm Surge and the NWS National Hurricane Center provides forecasts for all tropical cyclones in the Atlantic Basin. When a hurricane watch is issued for any portion of the U.S. Coast, NHC begins operational runs for the active system based on the latest forecast track. Probabilistic surge runs are also available, which take into account forecast uncertainty.

Alternative to Single Runs Atlas of pre-computed surge maps based on: Different directions of motion Different landfall locations Different intensities Different storm sizes Different forward speeds

Available Ensemble Products MEOWs MOMs Probabilistic

Maximum Envelope of Water Composite of maximum storm surge heights at each grid cell using hypothetical hurricanes run with the same: –Category (Intensity) –Forward Speed –Landfall Direction –Initial Tide Levels Composite achieved by reviewing parallel tracks that make landfall at different locations Over 80 MEOWs have been generated for some basins MEOW

Maximum of MEOWs Composite of the maximum storm surge height for all hurricanes of a given category Disregards forward speed, landfall direction, landfall location, etc. Only 5 MOMs per basin, i.e. one per storm category MOM

Probabilistic Storm Surge Use an ensemble of SLOSH runs to create probabilistic storm surge(p-surge) Intended to be used operationally so it is based on NHC’s official advisory P-surge’s ensemble perturbations are determined by statistics of past performance of the advisories P-surge uses a representative storm for each portion of the error distribution space rather than a random sampling

Errors Used by P-surge The ensemble is based on distributions of the following: Cross track error (impacts Location) Along track error (impacts Forward Speed, Timing) Intensity error (impacts Pressure) Rmax error (impacts Size)

Example: Cross Track Error

Understanding/Using Probability The number one argument against using probability is that users do not understand how to interpret low probabilities of an extreme event The odds of winning the Mega Millions lottery are 1 in 135,145,920, yet ~1/2 of Americans play the lottery (AP)

Surge Guidance Timeframe Day 5: MOMs Day 4: MEOWs/MOMs Day 3: MEOWs/MOMs Day 2: MEOWs/P-Surge/Operational Runs Day 1: MEOWs/P-Surge/Operational Runs Given current NHC intensity errors, always allow for one category higher on the Saffir-Simpson scale

Don’t forget about the Tornadoes! Tornadoes are possible with any landfalling tropical system. Tornadoes are likely in the right front quadrant of the storm. It is difficult to predict how great the risk of tornadoes will be with an individual tropical system. Hurricane Ivan (at right), produced a considerable number of tornadoes. Hurricane Dennis was not a prolific tornado producer Right front quadrant

Tornadoes with hurricanes Just over ½ of land-falling hurricanes produce tornadoes. These are generally EF 0 -EF 2. Occur without hail and often with no lightning. Develop anytime, day or night Some factors found favorable: ‘Dry’ air at the mid levels of atmosphere drawn into system. Accelerating and/or strengthening systems at land-fall. Tornado threat can linger for days and can both increase and become more associated with aftn heating 12+ hrs post-land. Could see an extended period under tornado watches. 9/15/04 9/16/04 9/17/04 IVAN

Ivan (2004) tornadoes 24 tornadoes were reported in our forecast area 117 tornadoes were reported across the Southeast Six fatalities occurred in our region

In addition to numerous hazards with major hurricane!

Tools Available Locally Hurricane Local Statement Text description of storm surge impacts Graphical Hurricane Local Statement Images detailing storm surge impact for each county.

Overview section of the Hurricane Local Statement

Hurricane Local Statement Segments Segment 1 is focusing on threats for portions of South Central Georgia Segment 2 is focusing on the Southeast Florida Big Bend. Specific information regarding storm surge will be included here.

Graphical Hurricane Local Statement Designed to provide a quick look at the risk level from all hazards in a tropical system. NWS Tallahassee uses five tiered ranking system for assigning risk. (None, Low, Moderate, High, Extreme) Maps available for Wind, Inland Flooding, Surge, and Tornadoes. Product is only active when Tropical Storm or Hurricane watches or warnings are in effect for our region.

Mouse over capability to display HLS text Can show higher impacts at the coast. GHLS-NWS Tallahassee GHLS-NWS Tallahassee

Webinars NWS Tallahassee conducts webinars when a tropical system will potentially pose a threat to our area. Webinars are designed for the emergency management community. Emergency management groups may invite media partners to their EOCs to view the presentation as a method of increasing public awareness of significant weather events. Webinars for tropical events will typically be held at 930 am ET or 230 pm ET

Feedback from you We are interested in your thoughts on our performance. What is one area that we can improve? What is something we aren’t doing that you’d like us to do?

Questions? Comments? Thank you for coming to our emergency management training day. We are having an afternoon session on Hurrevac 2010 that you are more than welcome to stay for.