Tropical Storms and Hurricanes

Super Hurricanes Motivation http://www.youtube.com/watch?v=ZXMj1yHgfPE&NR=1&feature=fvwp

This material was partially provided by the following sources: Prof This material was partially provided by the following sources: Prof. Jennifer Collins (Florida State University), Aguado and Burt: Understanding Weather and Climate Comet educational program - UCAR (see websites in the last slide) Mr. Forest Cannon (graduate student Dept. Geography)

Tropical Cyclones and Hurricanes Tropical cyclone and hurricane development, structure, and movement Hurricane damages, warning systems, and naming conventions

They are all considered tropical cyclones Regional Names Extremely strong tropical storms go by a number of different names, depending on where they occur. Over the Atlantic and eastern Pacific they are hurricanes. Those over the extreme western Pacific are called typhoons; those over the Indian Ocean and Australia are cyclones. They are all considered tropical cyclones

Hurricanes, Typhoons and tropical Cyclones around the globe. Seasonal Variability and local names Hurricanes Typhoons Cyclones Hurricanes Cyclones Cyclones Hurricanes, Typhoons and tropical Cyclones around the globe.

Some of the main characteristics of a Hurricane Hurricanes have sustained wind speeds of 120 km/hr (74 mph) and are typically about 600 kilometers (350 mi) wide. Sea level pressure near the center of a typical hurricane is around 950 mb, but pressures as low as 870 mb have been observed for extremely powerful hurricanes.

Hurricanes obtain most of their energy from the latent heat released by condensation and are most common where a deep layer of warm water fuels them. August and September are the prime hurricane months in the Northern Hemisphere, while January to March is the main season in the Southern Hemisphere.

Did you know… Hurricane numbers vary considerable each year with a maximum number in the North Atlantic ever recorded in a single year of 15. This of course occurred recently in the infamous 2005 season. A minimum number of 2 occurred in 1982 which was an El Nino year. There is a mean number of hurricanes in this basin of just under 6 a year.

Important questions: Why do hurricanes form? What causes their interannual variability? That is, why sometimes they are so frequent (as in 2005 – 15 hurricanes) and other times so rare (as in 1982 – 2 hurricanes – El Nino year)

Gray’s factors for tropical cyclone formation Geographic Coriolis Force sufficient to give initial cyclonic spin Dynamic Low vertical wind shear (shear is the vertical variation of the wind either in speed or direction) Thermodynamic High values of relative humidity Sea Surface Temperatures > 26-27 oC (~79-81oF) to a depth of 60 m (~200 ft) An unstable atmosphere To answer this one needs to refer to the pioneering work of Bill Gray whose seasonal tropical cyclone forecasts the news often quotes. When considering the N Atlantic Ocean, Gray noted the factors necessary for tropical cyclone formation. Coriolis force initiates the spin of the tropical cyclone. It occurs because we are on a rotating planet and causes a right deflection in the NH and a left deflection in the SH resulting in counter clockwise and clockwise flow of air in the NH and SH respectively. A geographic factor (influenced by latitude) Dynamic factors Thermodynamic factors

Coriolis effect and hurricanes Top view Low Low No Coriolis Effects With Coriolis Effects (Northern Hemisphere example)

Internal Dynamics Horizontal Pressure Gradient Coriolis Force L

No tropical cyclones, hurricanes or Typhoons: blame Coriolis: 5S-5N Negligible Coriolis Force near the Equator means there are no hurricanes there No tropical cyclones, hurricanes or Typhoons: blame Coriolis: 5S-5N The farther from the equator the greater the coriolis force, it is negligible along the equator. This is why hurricanes do not form on or within a few degrees of the equator.

2nd Inhibiting factor: wind shear Speed Shear Direction Shear With high vertical windshear the storm gets ripped apart. Directional wind shear is the change in wind direction with height. In the image (right), the view is looking north. The wind near the surface is blowing from the southeast to the northwest. Upper-level winds are blowing from the SW. Speed shear is the change in wind speed with height. In the illustration the wind speed is increasing with height as air moves away from the frictional influences. Strong vertical shear is the combination of directional shear and strong speed shear

The effect of Shear on the organization of the storm Heat and moisture spread out over a larger area Heat and moisture focused over a small area More efficient in organizing tropical cyclones

Let’s look at December climatology of the zonal wind profile with height between 20S-30N and 100W-30W Westerlies Easterlies

Example of the mean zonal winds between 100W and 30 W during December El Nino 1997 Example of the mean zonal winds between 100W and 30 W during December La Nina1988 Westerlies Westerlies Easterlies Easterlies

Example of the mean zonal winds between 100W and 30 W during December El Nino 1997 Example of the mean zonal winds between 100W and 30 W during December La Nina1988 Westerlies weaker Easterly anomalies Westerlies intensified Easterlies weaker Easterlies near normal Increase in the vertical wind shear during El Nino years

High relative humidity required: one of the most important ingredients to form hurricanes is the release of latent heat to the atmosphere Latent heat released due to condensation warms the atmosphere and cause the decrease of pressure at surface There must also be high enough relative humidity for significant condensation to occur, providing latent heat. Low pressure As sea level pressure decreases, more air converges at the center of the storm, more latent heat is released and the storm becomes stronger and more powerful, with increasing winds

Warm water through depth required: water vapor is the fuel of tropical storms Sea Surface 28 26 Temperature (°C) Depth High sea surface temperatures! This is key, and that’s why talk of global warming is so interesting for those interested in TC formation. According to Grey, the threshold for TC formation is 26C to a depth of at least 60 meters. The high temperatures have to reach a certain depth because otherwise as the winds of a storm stir up the waters beneath it the cooler waters will rise to the surface and inhibit formation. 24

Cyclogenesis NEGLIGIBLE CORIOLIS

Cyclogenesis: origin of cyclones APPROXIMATE AREA OF WARM SST

Ocean Temperature IKE Deadly Hurricanes http://www.youtube.com/watch?v=ZXMj1yHgfPE&NR=1&feature=fvwp IKE

Ocean Temperature IKE

Where do Hurricanes originate Hurricanes often originate as Tropical Disturbances Tropical disturbances are disorganized groups of thunderstorms having weak pressure gradients and little or no rotation. Most tropical disturbances that enter the western Atlantic and become hurricanes originate in easterly waves, large undulations or ripples in the normal trade wind pattern.

The importance of monitoring wave activity over west Africa Easterly waves have surface convergence and cloud cover east of the axis and divergence to the west.

Tropical Weather & Waves Tropical winds typically blow from the east, and when they encounter a slow moving trough of low pressure, called a tropical wave, the winds initially converge and lift to produce showers and thunderstorms.

Pre-Existing Disturbance BILL FRED For a tropical cyclone to form, a disturbance must already be present. The convergence at this low pressure system is what initiates the cyclonic development.

ORIGIN OF CYCLOGENESIS Wind Shear WESTERLIES EASTERLIES IDEAL FOR CYCLONES ORIGIN OF CYCLOGENESIS DOLDRUMS NCEP Reanalysis and TC data for composites: 1950-2003.

When a tropical disturbance develops to the point that there is at least one closed isobar on a weather map, the disturbance is classified as a tropical depression. If the depression intensifies further and maintains wind speeds above 60 km/hr, it becomes a tropical storm. A further increase in sustained wind speeds to 120 km/hr creates a true hurricane. PHASES OF DEVELOPMENT

Hurricane Lifecycle

A cross section of a typical hurricane.

Internal Dynamics

The hurricane eye is a region of relatively clear skies, slowly descending air, and light winds. Along the margin of the eye lies the eye wall, the zone of most intense storm activity with the strongest winds, thickest cloud cover, and most intense precipitation of the entire hurricane.

Structure of a Hurricane In this image of Hurricane Elena, the central area of broken clouds is the eye, surrounded by an eye wall cloud and spiral rain bands, with a total diameter nearing 500 kilometers.

http://www. nasa. gov/mission_pages/station/multimedia/hurr_ike091008 http://www.nasa.gov/mission_pages/station/multimedia/hurr_ike091008.html Hurricane Ike (September 10/2008): downlinked by the crew of the International Space Station, flying 220 statute miles above Earth. The center of the hurricane was near 23.8 degrees north latitude and 85.3 degrees west longitude, moving 300 degrees at 7 nautical miles per hour. The sustained winds were 80 nautical miles per hour with gusts to 100 nautical miles per hour and forecast to intensify. Photo Credit: NASA

IKE, September 9/2008

Cross-section of a hurricane showing cloud patterns and air flows (a), rainfall intensities (b), pressure distributions (c), and wind speed (d).

Hot towers (above) are embedded in some eye walls and last between 30 minutes and 2 hours. Hot towers are localized portions of eye walls that rise to greater heights (up to 12 km, or 7 mi) than the rest of the eye wall and may indicate that the hurricane will intensify within 6 hours.

A hypothetical hurricane moves northward at 50 km/hr. Along the right-hand side, the 200 km/hr winds are in the same direction as the movement of the storm, so there is a net-wind speed of 250 km/hr. On the left side, the net winds are southward at 150 km/hr.

Hurricanes and tropical storms have a tendency to move north or northeast out of the tropics along the southeast coast of North America and often move in wildly erratic ways. After making landfall, a tropical storm may die out completely within a few days.

Sources of destruction from a hurricane Winds Flooding Rain Storm Surge Waves Tornado Down-drafts

Effects of Tropical Cyclones Wind and Rain Storm Surge Hurricanes are among nature’s most destructive events and annually account for unparalleled environmental destruction and loss of life.

Precipitation Tropical Cyclones account for a large percentage of Annual precipitation in many regions Single events can be extremely destructive especially in mountainous regions Create Flooding and Landslides Influenced by geography

Storm Surge Created by barometric low in hurricane center as well as wind driven piling up of water Elevated sea level follows storm For every milibar of pressure decrease, the water level rises 1 cm. When cyclone makes landfall water surges inland When associated with high tide can be up to 25 feet Most destructive part of tropical cyclones Flooding can last for extended periods of time destroying local infrastructure (New Orleans, Bangladesh)

More on the hurricanes Revision of concepts: (second movie) http://www.youtube.com/watch?v=ZXMj1yHgfPE&NR=1&feature=fvwp Movie showing storm surges and impacts on coastal areas http://www.youtube.com/watch?v=HJydFJORWf4&feature=related

Comparison of hurricanes and mid-latitude cyclones Similarities: Type of low pressure system Wind direction Differences: Energy derivation Strongest winds Surface charts

Can you tell if they are tropical or extratropical cyclones?

Locations of hurricane landfalls from 1950 through 2004.

When forecasters predict that an approaching hurricane will reach land in more than 24 hours, they issue a hurricane watch. If it is expected to make landfall over the United States within 24 hours, they issue a hurricane warning. NOAA Official link for hurricane watch http://www.nhc.noaa.gov/

Hurricane Watch & Warning The National Hurricane Center in Florida issues a hurricane watch 24 to 48 hours before a threatening storm arrives, and if it appears that the storm will strike within 24 hours, a hurricane warning is issued. While some consider the warning area too large, causing unneeded evacuation, such evacuations have saved many lives. Hurricane Hugo, with peak winds near 174 knots, caused tremendous damage.

The Saffir-Simpson scale classifies hurricanes into five categories, with increasing numbers corresponding to lower central pressures, greater wind speeds, and larger storm surges.

Hurricane Names and Cost Category 5 Hurricane Andrew (1992) was the costliest US storm (prior to 2005 season!), but it ranks as less intense than 1935 and 1969 hurricanes. Hurricane names are chosen from an alphabetical list of male and female names for the Atlantic and Pacific, some of which are retired if the storm was especially damaging.

Tropical Cyclones names for the Atlantic sector 2009 2010 2011 2012 2013 2014 Ana Bill Claudette Danny Erika Fred Grace Henri Ida Joaquin Kate Larry Mindy Nicholas Odette Peter Rose Sam Teresa Victor Wanda Alex Bonnie Colin Danielle Earl Fiona Gaston Hermine Igor Julia Karl Lisa Matthew Nicole Otto Paula Richard Shary Tomas Virginie Walter Arlene Bret Cindy Don Emily Franklin Gert Harvey Irene Jose Katia Lee Maria Nate Ophelia Philippe Rina Sean Tammy Vince Whitney Alberto Beryl Chris Debby Ernesto Florence Gordon Helene Isaac Joyce Kirk Leslie Michael Nadine Oscar Patty Rafael Sandy Tony Valerie William Andrea Barry Chantal Dorian Erin Fernand Gabrielle Humberto Ingrid Jerry Karen Lorenzo Melissa Nestor Olga Pablo Rebekah Sebastien Tanya Van Wendy Arthur Bertha Cristobal Dolly Edouard Fay Gonzalo Hanna Isaias Josephine Kyle Laura Marco Nana Omar Paulette Rene Sally Teddy Vicky Wilfred http://www.nhc.noaa.gov/aboutnames.shtml

Hurricane Andrew In video, they added stuff about Andrew. Andrew happened whilst film was being produced. Andrew moved thru Homested, South of Miami Often a double wammy happens as a hurricane hits land, goes over gulf and hits another place. Camile CAT 5: 1969 Gilbert didn’t get much press as it didn’t kill many people Andrew Katrina: will go down in the record as most devastating storm Rita did damage but in a couple of years from now, she will be forgotten. Figure 5.41

Hurricane Andrew Devastation in Homestead, Florida August 24, 1992

Rita 9/23/05 Katrina 8/28/05 Wilma 10/21/05 Emily 7/21/05 The number of Atlantic tropical storms (purple), hurricanes (orange), and Category 3–5 hurricanes (green) by year, 1851–2004.

What was the deadliest hurricane in the USA history?

At the turn of the last century Galveston, Texas was a sophisticated seaport of 38,000 people, a city prosperous from the cotton trade and richer in millionaires than even Newport, R.I. It was the first city in Texas with phones and electricity, and its residents enjoyed a grand lifestyle: an opera house, 50 miles of streetcar track and foreign consulates for 19 countries. On Friday evening, Sept. 7, 1900, many of the residents of Galveston were settling down to dinner, few if any of them concerned about the steady 15 mph northerly wind rattling their windows. Within 48 hours, at least 8,000 of the townspeople --almost one in five Galvestonians -- would be dead, victims of the single worst natural disaster in U.S. history. The tragedy killed more Americans than the legendary Johnstown Flood, the San Francisco Earthquake, the 1938 New England Hurricane and the Great Chicago Fire combined.

The 15 deadliest Atlantic Hurricanes in history : 1742-2009 http://www.wunderground.com/hurricane/deadly.asp?MR=1 Rank: Name / Areas of Largest Loss: Dates: Deaths: 1. "Great Hurricane" Martinique, Barbados, St. Eustatius 10-16 Oct 1780 22000 2. Great Galveston Hurricane 8 Sep 1900 8000-12000 3. Mitch: Honduras, Nicaragua 10/22 - 11/5 1998 9086 4. Fifi: Honduras 14-19 Sep 1974 8000-10000 5. Dominican Republic 1-6 Sep 1930 8000 6. Flora: Haiti, Cuba 9/30-10/8 1963 7. Pointe-a-Pitre Bay, Guatemala 6 Sep 1776 6000 8. Newfoundland Banks 9-12 Sep 1775 4000 9. Puerto Rico, Carolinas 8-19 Aug 1899 3433 10. FL, PR, Martinique, Guadeloupe, Turks 12-17 Sep 1928 3411 11. Cuba, Cayman Islands, Jamaica 4-10 Nov 1932 3107 12. Jeanne: Haiti, Dominican Republic, Bahamas, Florida 13-29 Sep 2004 3000 13. Central Atlantic 16-17 Sep 1782 14. Martinique Aug 1813 15. El Salvador, Honduras 4-8 Jun 1934

*Very interesting material for consultation: (comet/ucar website) http://www.meted.ucar.edu/tropical/textbook/ch10/tropcyclone_visuals.html Video of Tropical Cyclone Ingrid (2005) making landfall in Australia: http://www.meted.ucar.edu/tropical/textbook/ch10/media/video/Ingrid_Cape_Don_Short.html Hurricane intensity scale: http://www.meted.ucar.edu/tropical/textbook/ch10/media/flash/hurricane_winddamage.html Access comet website Email: leila@geog.ucsb.edu Pass: victory http://www.ranker.com/list/10-biggest--deadliest--most-destructive-hurricane_s-ever--/jeff419

Work in groups: Summarize what you have learned regarding: 1) tropical cyclones names 2) tropical cyclones formation, development, propagation 3) Characteristics (rain, winds, pressure) 4) Inhibiting factors 5) Damages 6) Warning and watch 7) Role of El Nino/La Nina phenomenon for the frequency of hurricanes

Interpret the information provided in the next slide