Microwaves

Microwaves are a type of wave in the electromagnetic spectrum (see here). Their wavelengths are longer than any type of wave except for radio waves (see here).

The wavelength of a microwave can range from 1 millimeter (.001 meter) to 1 meter. This range is actually within the broader term radio wave, but on some scales, they are separate. Accordingly, the frequency range of microwaves is 300 MHz to 300 GHz (300,000,000 to 300,000,000,000 Hz).

Microwaves are specifically used in areas such as communication, power, and radar. Before fiber-optic cables were adopted into the phone system, microwaves were used for the same purpose. Radar, or the ability to map objects by bouncing waves off them, lies predominantly within the microwave region, but perhaps the most famous of microwave uses is the microwave oven. Microwave ovens bombard non-radioactive radiation into food, installing energy into, and therefore heating, it.



The main component of the microwave oven is the magnetron. This is a cross-section of such a device which generates an electric field to produce microwaves. Magnetrons are generally for heating certain substances with microwaves, such as water, sugar, and fats in food, and sometimes, humans. Microwaves, however, are not specifically heat radiation.

Microwaves, just like all waves used for communication are divided into bands to organize their use. WIth microwaves, these bands are denoted by letter, (e.g. the L Band, ranging from 1 to 2 GHz) and each band has specific uses.

Yet another use of microwaves is in astronomy. There are many sources of microwaves in the heavens, but the most notable is the Cosmic Microwave Background Radiation. This radiation was emitted 379,000 years of the Big Bang, when the Universe became transparent due to the cessation of photon-plasma reactions. Plasma is ionized gas, and is therefore made of ionized atoms. When the temperature of the Universe had fallen enough to support complete atoms with electrons, the atoms became neutral, and the reactions stopped. The image of the Universe released at that moment was carried by gamma rays, but over time red shifting transferred these into microwaves, as they are today. More and less intense patches on the radiation indicate the density of different parts of the Universe. The differences were minute at the time, but gravity gradually increased the differences, and all of the structure in the large scale Universe was defined.



An image adjusted from the original Cosmic Microwave Background to show temperature differences in the early Universe.

Microwaves have a variety of uses, from communication to heating to discovering the origins of the Universe.

Sources: http://en.wikipedia.org/wiki/Microwave, http://www.gallawa.com/microtech/mwave.html, http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation, etc.

Radio Waves

Radio Waves are part of the electromagnetic spectrum (see here) and consist of photons in their wave form. Out of all of the electromagnetic waves, radio waves have the lowest frequency and highest wavelength.

The range of radio waves is approximately 3 Hz, meaning three wavelengths per second, to 300 GHz, or 300,000,000,000 Hz, although the boundary isn't clearly defined, and waves with frequencies even smaller than these exist. This range is equivalent to wavelengths from 1 millimeter (.001 meter) to 100,000 kilometers (100,000,000 meters).

Radio waves are both man-made, and occur from natural sources, and have many uses, due to the fact that most of the radio spectrum pass through Earth's atmosphere intact. The percentage of waves that pass through the atmosphere are shown on the picture below, along with the rest of the spectrum.



Since radio waves can pass through the atmosphere, they are invaluable for communication purposes and information propagation takes place mainly in the radio spectrum. This portion of the spectrum is further divided into powers of 10. For example, the area from 3-30 Hz is known as Extremely Low Frequency (ELF), the area from 30-300 Hz is known as Super Low Frequency (SLF), the area from 300-3,000 Hz (3 kHz) is known as Ultra Low Frequency (ULF) and so on. The chart of frequencies above ULF are shown below.



The first radio waves to be used for communication are AM radio waves, which extend from 148.5 kHz (148,500 Hz) to 30 MHz (30,000,000 Hz). These waves are in the Low, Medium, and High Frequency ranges. However, waves of these frequencies are produced naturally by the ionosphere and magnetic storms, causing interference. As a result, FM radio, falling entirely under the Very High Frequency range, is now used for long distance broad casts. This area of the spectrum is the busiest of all, as television, FM radio and mobile communications all resides within 30-300 MHz.

The very low frequencies, (VLF and lower) are used for military (submarine) communications as they are useful in subaquatic environments.

The higher frequencies also have uses. Super High Frequency (3-30 GHz, or 3,000,000,000-30,000,000,000 Hz) is used for radar, and Extremely High Frequency (30-300 GHz) is used for radio astronomy.



The Very Large Array, located in New Mexico, USA, is used for radio astronomy. Large, parabolic satellite dishes concentrate the signals on a specific sources in the center of each individual telescope. Since many radio waves picked up from space have very long wavelengths, a very large apparatus is needed to capture a reasonable image. The Very Large Area has 27 radio telescope receivers, each 82 feet in diameter, and the images produced by each are compiled into a single one in the center.



This is an optical (visible light) image of the M87 elliptical galaxy. The active center and jet of radiation from it are visible, but in visible light, most of the galaxy is a haze of stars.



However, by use of radio astronomy, a much more specific picture can be taken. Unlike visible light, radio waves are not produced to a great extent by any part of the galaxy except the active center, and it can therefore be identified better in radio astronomy. The above image is taken by the Very Large Array (VLA). However, the bottom image, which is magnified tens of thousands of times more than the above one, is taken by the Very Long Baseline Array (VLBA). Since M87 is over 50 million light years away, a resolution of this magnitude can only be created by use of a planet sized radio telescope, which is essentially what VLBA is. Satellite dishes all over the world are synced together by a central computer in Europe, and therefore at least a small number of radio waves coming in over a Earth-sized area can be put together to get a very precise view, even if all the incoming waves aren't picked up.

Notable sources of radio waves from space include the Sun (only due to its proximity to Earth, because stars do not emit a majority of their energy in radio waves), galactic centers, such as the Milky Way itself, and active ones like M87, neutron stars, and very distant powerfully emitted objects such as quasars. The redshift effect of the quasars' movement away from us causes the waves to lengthen in wavelength as they approach Earth. As a result, many waves that start higher in frequency are radio waves when they reach Earth. This effect is most notable at very long distances, billions of light years away. Among objects at this distance, only quasars are bright enough to be visible, and are therefore excellent subjects of radio astronomy.

Sources: http://www.google.com/imgres?imgurl=http://www.electronics-radio.com/, http://en.wikipedia.org/wiki/Radio_astronomy, etc.

Electromagnetic Spectrum

The Electromagnetic Spectrum, technically speaking, is the range of frequencies that a photon wave can assume. The photon is essentially the particle of light, and this particle has many interesting properties.

First, a photon has no mass, which means it can travel at a speed unlimited by its mass. The speed at which the light particle can travel in a vacuum defines the fastest known speed in the Universe, namely the speed of light, or 186,292 miles per second. Second, the photon can have properties of both a particle and a wave. But when dealing with the electromagnetic spectrum, the wave form of a photon is most important.

The electromagnetic spectrum deals with all possible photon waves, each of which are composed of the same particle, but have different energies. Along with energy, the three properties of a specific electromagnetic wave are amplitude, wavelength and frequency.



Electromagnetic waves are in a sinusoid form, meaning that they are shaped like the red line above. The distance, A, from the sinusoid axis to the peak of the curve is known as the amplitude of the wave, and the distance between peaks is known as the wavelength, while the distance between crossings of the sinusoid axis are half of a wavelength. The remaining element, frequency, is how many wavelengths the wave goes through over a certain period of time. The horizontal axis (x) on the graph above is the passage of time, and over this time, the wave modulates, or moves from peak to peak, in a cyclic manner.



The different electromagnetic waves are separated by varying amplitude and wavelength. The above chart shows five different wave types. The horizontal axis represents time, as before. On the top of the chart is the wave with the highest wavelength, but lowest frequency, and as one goes down the chart, the wavelength decreases and the frequency increases. The two properties are inversely proportional because an electromagnetic wave is traveling at a constant speed through a vacuum, the speed of light, and therefore the wavelength determines a length of time between wave peaks, namely frequency. Wavelength is measured in meters, while frequency is measured in a unit called a Hertz (Hz), with 1 Hz meaning one wavelength per second.



The entire electromagnetic spectrum (click to enlarge), including names given to specific areas of the spectrum, some uses of particular wavelengths, and the corresponding wavelength and frequency axes. The plot is a log scale of base 10, meaning that instead of counting up 1, 2, 3... the graph counts 10^1, 10^2, 10^3... The frequency increases from the bottom to the top, starting at 10^6, and ending at 10^19, and the wavelength counts in meters (m), using symbols like cm to represent increments of meters.

The waves are as follows, from lowest to highest frequency are: radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays. Each of these have their own individual posts. Click on one to enter and begin exploring the electromagnetic spectrum.

Radioactive Decay

Radioactive Decay is the decomposition of an unstable atom into multiple parts. Often, this involves the emission of radiation, hence the name radioactive decay. Some elements of the periodic table have no stable atoms, while some have stable and unstable isotopes, meaning that the number of protons remains the same, but stability can vary with the number of neutrons.

There are 118 known elements on the periodic table, and, among these, numbers 43, 61, and all above 82 possess only isotopes that are radioactive. The remaining 80 have at least one neutron number that results in a stable nucleus, but a vast majority of the possibilities are radioactive, and overcome the force, known as the strong nuclear force or the strong interaction, that binds the particles in a nucleus together.

For example, the element oxygen has 8 protons, and the number of neutrons can range from 4 to 16, because it is known that there are physical limits on how many neutrons can exist for a certain number of protons, called the nuclear drip line. It is simply impossible for 3 neutrons and 8 protons to exist in a nucleus, and if these particles are shoved together, a proton will simply drip out. Similarly, it is impossible for 8 protons and 17 neutrons to be together in a nucleus, because a neutron will "drip" out. Therefore, these nuclei do not qualify as parts of atoms, as they are never in a whole state. Unlike these, isotopes of oxygen between 4 and 16 neutrons can exist. However, all but three of these are unstable, and decay to other atoms within seconds. Atoms with 8 protons and 8, 9, and 10 neutrons, corresponding to Oxygen-16, Oxygen-17, and Oxygen-18 are stable, and occur in nature.

Also, there are different ways that atoms can decay into others. The three most common were the first types of radiation isolated, and there were named alpha, beta, and gamma decay.

Alpha decay involves an unstable nucleus of an atom emitting an entire Helium-4 nucleus, that is, two protons and two neutrons, at once. This nucleus is also known as an alpha particle. The resulting nucleus of the parent atom has two less protons and two less neutrons than it did before alpha decay. Some argue that the Helium nucleus takes two electrons with it when an atom experiences alpha decay, because otherwise there would be an unbalanced charge, and some believe that two electrons are simply released into the environment. An example alpha decay reaction is pictured below.



An example reaction involves Uranium-238, which, by alpha decay loses two neutrons and two protons. Because of this the resulting atom's atomic weight will drop from 238 to 234, and the atomic number will drop by two, becoming Thorium. Therefore the reaction is denoted

238,92U=234,92Th+4,2He

The notation above shows the two balanced sides of the reaction, with the Uranium-238 (first number before the atomic symbol is the entire weight, the second is the number of protons) atom on the left, and the Thorium-234 atom and the Helium nucleus (alpha particle) on the right. In this reaction the two elections are assumed to leave the atom with the Helium nucleus.

Beta decay involves a slightly more complicated chain of events, and there are two types: Beta negative and beta positive, denoted B- and B+ respectively. The B- reaction uses the weak nuclear force (one of the four fundamental forces of the Universe) to convert a neutron into a proton. However, there are some byproducts of this reaction, namely an electron and an electron antineutrino. Since a neutron is only slightly heavier than the proton, the loss of a tiny electron (and an electron antineutrino) is enough to convert it into a proton. Also, the change is mass is so minute that the atomic weight remains the same, but the atomic number goes up. This type of decay actually "increases" the complexity of the nucleus, instead of lowering it.



This image is an example beta decay reaction. The main picture shows only the B- particle (electron) being emitted, while the inset shows the entire reaction. The neutron splits into three parts, of which the proton stays in the nucleus, the B- particle may leave the atom or stay and compensate for the gaining of a positive charge via the proton, and the tiny electron antineutrino is emitted. To fully understand this process, one must break it down into even smaller stages, by use of a Feynman Diagram.



A Feynman Diagram graphically represents quantum phenomena to make them easier to understand. In this diagram, time progresses with respect to the vertical axis. The neutron, n, is shown as its three composite parts, u,d, and d, representing one up quark and two down quarks. The weak nuclear force has an effect on the final down quark only, instantly changing it to an up quark. As a result, the three new quarks are up, down, up (u,d,u) and these are the composite particles for a proton, hence the proton end product. However, to make this change happen, a W- boson, the carrier of the weak nuclear force, must be emitted from the down quark, to change it to an up quark. Since a down quark is heavier than an up one, the loss in mass again makes sense. The W- boson is very short lived, however, and nearly instantaneously splits into an electron and an electron antineutrino, denoted by the e- and ve+ respectively.

An example reaction of B- decay is the process of changing the Caesium-137 atom into the Barium-137 atom

137,55Cs = 137,56Ba + e- + ve+

Neutron-rich nuclei are more likely to undergo B- decay.

The other type of Beta decay is B+ decay. It is basically the opposite (in terms of particles) of the previous process, because a proton is converted into a neutron. Since the neutron is heavier than the proton, the reaction needs outside energy to add mass to the reaction (since energy can at any time by changed into mass and vice versa). This must be provided by the environment, and therefore this reaction cannot occur by itself in a vacuum. The byproducts of the reaction are the opposite of B- decay in charge; instead of a electron and an electron antineutrino being emitted, the positron (anti-electron) and electron neutrino are emitted. An example B+ decay reaction involving the transformation of Carbon-11 into Boron-11 is written below

11,6C = 11,5B + e+ + ve-

This reaction also involves the weak nuclear force, but with use of a W+ boson, rather than a W- one. The W+ boson is emitted when a up quark changes into a down quark. This particle then splits into the two mentioned above.

B+ decay is more likely to occur in proton-rich nuclei.

There are other rarer types of Beta decay, such as electron capture, where an electron is "captured" from the orbitals of the atom, and is pulled to the nucleus, where it combines with a proton to form a neutron and an electron antineutrino. An example reaction is

59,28Ni + e- = 59,27Co + ve+

Although the electron on the left side of this equation is presented as if it is separate from the atom, the electron actually originated from what was part of the atom, namely orbiting electrons.

There are also forms of Beta decay where the process happens twice simultaneously. These are called Double Beta Decay, and a similar double exists for electron capture.

Other simple types of radioactive decay include proton emission, if a nucleus is very rich in protons, and neutron emission, if a nucleus is very rich in protons. Note that this is different from proton and neutron "dripping" discussed earlier, because the nucleus does exist as one unit before the the proton or neutron is emitted.

Another famous type is the emission of a larger particle than an alpha particle, namely a heavier atomic nucleus. However, this type of decay, called cluster decay, only occurs among atoms that usually decay through the emission of an alpha particle. Some unstable atoms decay in different ways, with one occurring a certain percentage of the time, and another in the remaining percentage. An example is the atom Radium-223.

Usually, Radium-223 decays through alpha decay:

223,88Ra = 219,86Rn + 4,2He

but for one out of every one billion reactions, something else occurs, and the atom emits a Carbon-14 nucleus!

223,88Ra = 209,82Pb + 14,6C

The second reaction was the first of its kind known to occur and was discovered in 1984 at Oxford University. The heaviest known nucleus to be emitted in this fashion is Silicon-34, happening only once out of trillions and trillions of alpha decays from Plutonium-240, Americium-241, and Curium-242.

Finally, some atoms simply split into two atoms, through a process called spontaneous fission. This processes occurs when a neutron impacts the nucleus and splits it in two. Uranium, Plutonium, and Californium are three elements that have a chance for spontaneous fission, although they are more likely to decay through other processes. Californium-252 has a relatively high fission rate, with 3.09% of reactions result in fission. However, Uranium-235 decays through fission only seven reactions out of 100 billion! There are higher elements which predominately decay by fission, some of which are isotopes of Mendelevium and Rutherfordium. Some of these reactions emit neutrons in turn, and these can lead to chain reactions. Uranium-235 is one of these, and since each reaction gives out energy, it is one of the isotopes used in the detonation of atomic bombs.

Reactions of this type occur to all of the possible unstable isotopes. The chart that maps all the isotopes is known as the table of nuclides, linked to here.



This is another version of the table of nuclides, which shows the predominant mode of decay for every known nuclide. The center of the band of nuclides are the most stable (those in black are stable), and they tend to get less stable away from the center. Isotopes that undergo B+ decay or Proton Emission occur on the right (proton-rich) side of the stable isotopes, while ones that undergo B- decay or Neutron Emission occur the left (neutron-rich) side of the stable isotopes. Also, alpha decay, cluster decay and fission tend to occur with heavier atoms, toward the upper right of the chart.

Some isotopes do not decay directly into a stable nucleus, and go through multiple steps of decay before reaching stability.



An example is Uranium-238. Its decay chain is imaged above (click to enlarge), with each octagon containing the atomic number and mass of an isotope, while the arrows denote the decay chain, with letters representing the type of decay. The half-life, or average time to decay on each step, is also included under each octagon. Sometimes, the decay chain branches, when there are probabilities for other types of decay, but all of the branches converge on the stable isotope Lead-206.

Radioactive decay produces energy, and is therefore valuable as a potential power source, with drawbacks including lower feasibility and harmful radiation. Radiation is also used for other purposes, such as medical procedures, specifically for eliminating cancerous cells.

Sources: http://education.jlab.org/glossary/betadecay.gif, http://www.nature.com/nature/journal/v307/n5948/abs/307245a0.html, http://en.wikipedia.org/wiki/Table_of_nuclides_(complete)

2010 Season Summary

The 2010 hurricane season was well above average, with

21 cyclones attaining tropical depression status
19 achieving tropical storm status
12 hurricanes
and 5 major hurricanes

This is higher than my predictions of

18 cyclones attaining tropical depression status
17 cyclones attaining tropical storm status
7 cyclones attaining hurricane status
4 cyclones attaining major hurricane status

particularly in the hurricanes category.

This activity (19 named storms) was tied for the third most ever recorded in the Atlantic basin. The most powerful cyclone of the season was Igor, which attained a peak intensity of 155 mph winds and a minimum pressure of 925 mb. It also was the largest tropical cyclone ever to form in the Atlantic basin in terms of tropical storm wind diameter. Due to its colossal nature, Igor was also the third wettest tropical cyclone every recorded in Canada, dumping 9.37 inches of rain in one location in Newfoundland.

Also:

• 8 storms formed in September (tied for a record high)
• Four cyclones (Alex, Karl, Matthew, and Richard) made landfall in Belize, although two of them at tropical depression status (record high)
• Two Category 4 hurricanes (Igor and Julia) existed simultaneously for a brief period of time, an occurrence that has not happened since 1926

Overall, the 2010 Atlantic hurricane season was a very active one, and impacts were mostly in the Caribbean and Central America. The United States, surprisingly, was barely affected, with no hurricane landfalls.

Hurricane Tomas (2010)

Storm Active: October 29-November 7
On October 25, a tropical wave formed in the extreme southeastern Atlantic Ocean, near 5ºN. The wave produced only scattered shower and thunderstorm activity as it moved west over the next few days. It was a vigorous tropical wave, however, and it developed a low pressure center on October 27. The low adopted a general northwest motion, and deepened significantly over the next two days. By the afternoon of October 29, the system had a very organized circulation and outflow, and the confirmation of a closed low at its center merited the upgrading of the system into Tropical Storm Tomas.

Tropical Storm Tomas was already in a state of rapid intensification, and the winds increased rapidly as the cyclone approached the Caribbean Islands, moving westnorthwest between 10 and 15 mph. During the morning of October 30, Tomas passed directly over Barbados, with peak winds of 70 mph, causing fairly significant damage. Tomas developed a very wide eye feature (about 40 miles across) just before noon on October 30, and it was then organized enough to be upgraded to a Category 1 hurricane.

The system promptly made a direct landfall in St. Vincent during that afternoon, and heavy rain and tropical storm winds affected islands up to 100 miles north and south along the Windward and Leeward Islands. The wide eye clouded over with a flare of convection, and Tomas continued to strengthen, becoming a Category 2 by later that night. However, southwesterly shear and dry air began to impact the west side of the system early on October 31, weakening it to a Category 1 storm by the afternoon. The center became ragged in appearance, and lost definition as a result of harsh atmospheric conditions.

Tomas weakened further into a tropical storm during the night, and only stabilized on November 1, when the winds dropped to 45 mph. Tomas was pushed on a general westsouthwest course during the day. Tomas's intensity fluctuated with large variations in convection over the day of November 2. The cyclone's forward speed also decreased as it reached the edge of a ridge to its north and steering currents weakened. For a brief period on November 3, Tomas degenerated into a wide area of scattered convection covering the entire southwest Caribbean, and was therefore downgraded to a depression, but the conditions for development drastically improved later in the day and Tomas turned towards the north, and the storm underwent a fast strengthening process, regaining tropical storm status. Tomas reached an intensity of 50 mph winds, and maintained it for the next day as it slowly moved northward. Wide rain bands began to sweep across Jamaica, Haiti and Cuba by the afternoon of November 4. As Tomas approached land, it rapidly strengthened into a hurricane, reaching its secondary peak intensity of 85 mph winds and a pressure of 984 mb as it passed just west of Haiti on November 5.

Cuba and Haiti both experienced tropical storm conditions, as well as hurricane force in some areas of Haiti, as the day went on, and as Tomas began to accelerate northeast, it interacted with the land around it briefly, and weakened back to a minimal Category 1 hurricane later in the evening. Tomas passed over the Turks and Caicos islands overnight, but emerged over open Atlantic waters on November 6, weakening back to tropical storm. Unexpectedly, Tomas once again regained hurricane strength late on November 6, but a cold front quickly overtook the system, and Tomas rapidly transitioned into an extratropical low on November 7. 41 fatalities and $572 million in damage directly resulted from Tomas in the Caribbean Islands, but Tomas is also indirectly linked to an epidemic of cholera in Haiti.



Hurricane Tomas intensifying as it enters the Caribbean. A fair amount of wind shear is evident on the south side of the system.



Track of Tomas.

Hurricane Shary (2010)

Storm Active: October 28-30
A trough of low pressure formed in the Caribbean on October 26. The trough was associated with an area of convection, but strong upper-level winds prevented development. However, on October 28, the shear relaxed enough for a central low pressure to form. However, the convection remained disassociated with this low until late on October 28, when the system developed an eyewall. At this point, the low was upgraded to Tropical Storm Shary.

Tropical Storm Shary sped to the northwest through the night, and shear began to increase on the system once again, giving it a lopsided appearance. This shear was produced by a strong front moving east off of the U.S. and this front also began to turn Shary to the north and then northeast. Despite adverse conditions, Shary strengthened as it began the turn, intensifying to 60 mph winds and a pressure of 1000 mb during the afternoon of October 29. The cyclone then made its closest approach to Bermuda, causing only showers and gusty winds however, as it passed well to the east. Shary's circulation was largely exposed through the coming day, but it continued to strengthen, becoming a minimal hurricane early on October 30.

By this time, Shary was speeding off to the northeast, and it briefly reached its peak intensity of 75 mph winds and a pressure of 989 mb before quickly becoming extratropical and being absorbed by a front later that afternoon. No damage resulted from Shary.



Hurricane Shary at peak intensity.



Track of Shary.

Hurricane Richard (2010)

Storm Active: October 20-26
On October 16, an area of showers and thunderstorms developed in the extreme southwestern Caribbean. The area drifted to the northwest, and interaction with the Nicaragua-Honduras area inhibited development for a time on October 18 and 19. However, after emerging over open water, the circulation improved, and the system moved slowly northeast. Late on October 20, the system became organized enough to be Tropical Depression Nineteen. By this time, steering currents had weakened, and the cyclone had reverted to a slow southeast movement. Dry air existed near the circulation over the next day, but intensification occurred nonetheless, and Nineteen became Tropical Storm Richard on October 21.

The system did not intensify for almost a day, but convection increased as dry air moved away from the system and a ridge built over the Gulf of Mexico, steering Richard back to the west by October 22. The system finally began to strengthen that day, rapidly intensifying into a strong tropical storm the next morning. Due to its proximity to Honduras, tropical storm conditions began for coastal areas by late on October 22. Richard began accelerating to the westnorthwest late on October 23, and a burst of convection the following morning caused Richard to intensify rapidly, becoming a category 1 hurricane.

The cyclone continued to intensify and made landfall in Belize at its peak strength of 90 mph winds and a minimum pressure of 981 mb during the evening of October 24. It quickly weakened over the next day, becoming a tropical depression by October 25. The system reemerged over the Gulf of Mexico early on October 26, but conditions were hostile for restrengthening and Richard swiftly weakened to a remnant low. The effects of Richard were $24.7 million in damage and 2 fatalities.



Richard as a Category 1 hurricane before landfall.



Track of Richard.

Hurricane Paula (2010)

Storm Active: October 11-15
On October 7, a broad area of low pressure developed in the southwestern Caribbean. Disorganized showers and thunderstorms remained associated with the system as it drifted generally to the northwest over the coming days. A low pressure center formed on October 9, and deepened thereafter, becoming a tropical depression during the morning of October 11, although not being formally recognized as a tropical system until later that afternoon. By that time, the cyclone was already a strong tropical storm, and was named Paula.

The system was in the midst of rapid intensification, and was a hurricane by the morning of October 12. It turned more to the northnorthwest over the next day, but continued to strengthen, exploding into a Category 2 (albeit a small one) by the afternoon of that same day, as it approached the Yucatan Peninsula. It stalled just offshore to the east later on October 12, still maintaining its peak intensity of 100 mph winds and a pressure of 981 mb. Since Paula was a small storm, only minimal rain and wind affected the Yucatan itself, and a jet stream just to the north of the system started to push Paula to the east and weaken it by the afternoon of October 13. The system accelerated eastward slightly, and made landfall in western Cuba on October 14, as it weakened to a tropical storm. Paula continued to degenerate, becoming a remnant low by October 15. It dissipated the next day. Paula was a very small storm, and damage was therefore limited, with only one fatality recorded.



Paula at peak intensity. The system remains very small, with a correspondingly small eye feature.



Track of Paula.

Hurricane Otto (2010)

Storm Active: October 6-10
On September 28, a tropical wave over the Central Atlantic began to produce an area of showers and thunderstorms. The next day, another tropical wave to its east also began to be monitored for development. The two systems moved west, but the second caught up with the first and the two waves combined on September 30. The combined disturbance produced a wide area of showers and thunderstorms as it moved westnorthwest, but wind shear increased, and the system remained disorganized. A low pressure center began to form in association with the system, and the low deepened as it passed over the Leeward Islands on October 3-5. By October 6, a surface circulation had formed. However, unlike a tropical cyclone, the center of the system had an upper-level low situated above it, rather than an upper level high, and this fact, combined with the limited convection that was only prevalent on the southeast side of the center, resulted in the classification of the system as Subtropical Depression Seventeen early on October 6. Seventeen's convection wrapped around the center the next day, and the winds reached gale force that evening, meriting the naming of the system as Subtropical Storm Otto.

By late on October 6, Otto's winds had rapidly increased, and the cyclone had reached an intensity of 65 mph winds and a pressure of 990 mb. However, the convection remained very sparse throughout the night, and intensity was difficult to judge, although the ragged appearance of the circulation suggested a slight weakening during the morning of October 7. By later in the morning, the upper-level low that had been shearing the circulation weakened, the core had warmed, and a distinct central eyewall had appeared as the system turned northeast. Otto was now a tropical cyclone, and it was officially classified as such at 11:00 am EDT on October 7. Otto's cloud cover continued to increase as it accelerated eastnortheast, and the system strengthened further, becoming a hurricane by October 8. The system reached its peak intensity of 85 mph and a minimum central pressure of 972 mb, before beginning to weaken. The system picked up speed as it moved out to sea, and it became a tropical storm late on October 9. Otto lost most of its central convection and was displaced to the north over the next 12 hours. As a result, the system was extratropical by midmorning on October 10. The cyclone subsequently impacted the Azores with some rain and wind as it weakened, dissipating on October 12.

Otto caused $20 million in damage but no deaths were reported, most damage being caused by flooding in the Caribbean Islands when the cyclone loitered to the north. As much as 17 inches of rain was reported in parts of Puerto Rico over a six day period from October 3-8 (this and similar rainfall reports courtesy of the Hydrometeorological Prediction Center).



Hurricane Otto at peak intensity speeding off into the open Atlantic.



Track of Otto.