Tropical Weather By Rick Garuckas and Andrew Calvi BFB Tropical Weather By Rick Garuckas and Andrew Calvi

Areas where tropical weather occurs Occur from the 23 ½ ˚ latitude north line down to the equator to the 23 ½ ˚ latitude line south of the equator in the North Atlantic, East Pacific, West Pacific, Caribbean, and Indian Ocean. Tropical activity is common along the ITCZ located off the Mexican and South American Coast lines.

Hurricane Season Atlantic Hurricane Season runs from June 1st to November 30th. Eastern Pacific Hurricane Season runs from May 15th through November 30th. Tropical cyclones have been observed outside of this period. Example: Dec 29th 2005- Jan 6th 2006, Tropical Storm Zeta formed, last named storm of 05-06 season.

Saffir-Simpson Scale Category 1: sustained winds of 74-95 mph Category 3: MAJOR-sustained winds of 111-129 mph Category 4: DEVASTATING-sustained winds of 130-156 mph Category 5: CATASTROPHIC-sustained winds >157 mph

Stages of Tropical Development Tropical Wave- a disturbance of tropical origin or broad area of low pressure. Can originate anywhere in the tropics . waves can be vigorous off the west coast of Africa near the Cape Verde Islands. Tropical Depression- a closed area of low pressure that has sustained winds of <39 mph. TD’s are issued a number. Tropical Storm- a tropical system with sustained winds between 39-73 mph. A name will be issued(names are recycled every 6 years.) Hurricane- A tropical system with sustained winds >74 mph.

Favorable Conditions Must have light winds and deep moisture/high humidity through a deep layer of the troposphere Important to have very low upper level wind shear Ocean temperatures are often > 80°F Helps to have converging surface winds, hence ITCZ

Structure of a Hurricane Warm core system(center of the storm is warmer than the air around it) Thermally direct circulation. No frontal boundaries Eye wall- most intense part of a hurricane. Eye- area of relative calm and even breaks in the cloud cover may occur. Strongest winds and greatest storm surge typically found in east and northeast quadrant of eye wall. The larger the size, the greater the storm surge Size does not determine strength

Tropical vs. Non-tropical systems Non-tropical systems have a larger wind field than tropical systems. Non-tropical systems can affect a larger population than tropical systems. Tropical systems tend to weaken over land due to friction unlike non-tropical systems that are not affected by land and can strengthen over land. Non –tropical systems are cold core. Tropical systems can transition to non-tropical systems(extratropical systems) as they hit the mid-latitudes and gain fronts.

Dvorak Method Invented between 1969 and 1984 by Vernon Dvorak. Method uses satellite imagery to estimate storm strength. Rankings are based on a T-scale determined by structure of tropical system. Tropical waves can be assigned a T number.

Dvorak Method

Famous Hurricanes Hurricane Katrina Formed on August 23rd 2005, first made landfall in South FL. as a Category 1 storm before rapidly intensifying and making multiple landfalls in Louisiana as a Category 3.(Was a Category 5 at one point.)

Famous Hurricanes LAST Category 5 to STRIKE the U.S. Formed August 16th 1992 and remained fairly weak and disorganized until rapidly beginning to intensify August 22 striking the Bahama Island of Eleuthera as a Category 5 on August 23. After weakening slightly over the Bahamas, Andrew regained category 5 strength just prior to landfall south of Miami, Florida before dawn on August 24.

Famous Hurricanes Hurricane Sandy Formed Oct 22nd 2012 Made landfall in Cuba, Bahamas, and South-Central Jersey. Storm was considered extratropical when it made land fall in New Jersey. Controversy surrounding lack of hurricane warnings issued north of the Carolinas due to forecast of storm becoming extra-tropical. National Hurricane Center revised protocol on watch/warning issuance. 2nd costliest natural disaster in USA.

Some More Info on Tropical Systems Wind and rain from tropical systems span well inland. Water typically is the deadliest impact from tropical systems. Tropical systems that have transferred into extratropical systems can pack a similar punch as tropical systems can. Canadian Hurricane Centre formed in 1986 one year after Hurricane Gloria affected eastern Canada.