Meteorologists worldwide are watching two cyclones in the Northwest Pacific begin their “dance” around each other. Tropical storm Kulap and typhoon Noru are beginning to endure a weather phenomena known as the Fujiwhara Effect.
The Fujiwhara Effect occurs when two cyclones rotate or “dance” around each other in a counter-clockwise direction (for the Northern Hemisphere). The two cyclones are actually rotating around a single point, or center, on an axis that connects the cyclone centers. Binary interaction of the cyclones can occur only if the cyclone centers are separated by a distance of roughly 1400km, or nearly 870 miles. The National Weather Service defines Fujiwhara Effect as the tendency of two nearby tropical cyclones to rotate cyclonically about each other.
The Fujiwhara effect is named after Dr. Sakhuhei Fujiwhara, who was the Chief of the Central Meteorological Bureau in Tokyo, Japan after the First World War. In 1921, he performed and studied the interaction and movements of water vortices. Dr. Fujiwhara concluded that if two water vortices spinning counter-clockwise came close enough to each other, each vortex would rotate around the other. In the atmosphere, if one vortex (tropical cyclone) is stronger than the other, eventually the smaller vortex (tropical cyclone) could get caught in the circulation of the larger one.
When the Fujiwhara Effect occurs, the intensity and track of a tropical cyclone can be greatly altered, creating a complicated and difficult forecast. In the Northwest Pacific, tropical storm Kulap will weaken and dissipate as it is engulfed by typhoon Noru over the next 24 hours.
According to Dong (1983), archived data from the National Hurricane Center portrayed the western Pacific Ocean to have a higher frequency of binary interaction than the Atlantic Ocean. During a 36 year period, 1946-1981, two spatially proximate storms averaged 1.5 annually over the western Pacific compared to .33 annually over the Atlantic. This is likely due to the Pacific having an overall higher tropical cyclone frequency compared to the Atlantic Ocean. Furthermore, Dong studied the Intertropical Convergence Zone (ITCZ) over the Pacific Ocean versus the Atlantic Ocean. He concluded the ITCZ is better defined in the Pacific basin, leading to higher tropical cyclone activity, compared to the Atlantic basin. A good majority of tropical cyclones in the Atlantic spawn from tropical waves that emerge off the West African coast.
Another example of a classic Fujiwhara Effect occured during the last week of September 1994 with tropical cyclone Pat and tropical storm Ruth.
The Madden Julian Oscillation (MJO) is an intraseasonal fluctuation that primarily initiates over the warm waters of the Indian Ocean and western Pacific. The MJO is comprised of regions with various atmospheric features such as deep convection and atmospheric wind anomalies that propagate eastward along the ITCZ. During a convective phase of the MJO, there is an enhanced region of tropical convection and moisture resulting in above-average rainfall. The opposite is true for a suppressed convective phase. As the MJO continues propagating eastward, the monsoon trough weakens and may shift southward. East of the MJO the easterlies are strengthened, and to the west, the easterlies are weakened. Therefore the passing of positive phase MJO can affect atmospheric wind shear, which could in turn affect tropical cyclone activity.
Phillip Klotzbach studied the relationship between the MJO and the development of tropical systems in the Atlantic Basin. In his 2010 study, Klotzbach found a direct relationship between the increase in vertical wind shear and relative humidity, and enhanced tropical cyclone activity and intensification. In the convectively enhanced phase of the MJO, upper-level easterly and low-level westerly wind anomalies act together to reduce vertical wind shear. One primary ingredient for tropical cyclone development is reduced vertical wind shear. Relative humidity throughout the atmosphere is also needed for tropical development. In Camargo’s study (2009), he found that mid-level relative humidity played the most important role, compared to low-level absolute vorticity, vertical wind shear, and potential intensity in tropical cyclogenesis by the MJO. Therefore, when an eastward moving MJO and a tropical wave meet, it is possible for the tropical wave to develop into a tropical cyclone due to the enhanced atmospheric moisture and reduced vertical wind shear created by the MJO. If a tropical cyclone already exists, its interaction with a MJO may cause the cyclone to intensify. Kingtse C. Mo discusses an increase in tropical cyclone activity over the Atlantic Basin when the convective phase of the MJO is located the Indian Ocean rather than the Pacific Ocean.
The image above represents a forecast for Outgoing Longwave Radiation (OLR) anomalies, a key detector for active MJO regions, issued by NOAA’s Climate Prediction Center (CPC). The CPC monitors and predicts climate variability and teleconnections for government, public, and private meteorological industries. Negative OLR values indicate enhanced convection or an active MJO phase (more cloud cover indicating more convective activity). Positive OLR values represent suppressed convection (less cloud cover).
The latest forecast from the ensemble mean GFS predicts an increase in OLR, possible MJO wave, across the Indian Ocean for the next two weeks. As Kingste C. Mo found in his study, there is likely an increase in tropical activity over the Atlantic Ocean when an MJO is present over the Indian Ocean.
Although Wilkens Weather is forecasting a very low chance for tropical development in the next five days, this will be a parameter worth watching this tropical season.
Chances continue to increase for a tropical low to develop in the Caribbean for Father’s Day weekend. The time-frame for any tropical formation is Sunday-Tuesday.
So the big question on everyone’s minds, will we have a tropical storm in the Gulf of Mexico?
The answer is much more complicated than a simple “yes” or “no”. Storminess is beginning to increase across the northwestern Caribbean, however a disturbance has not been detected yet and Wilkens Weather is not expecting tropical development over the next 24 hours. Several factors are analyzed when forecasting tropical weather including sea surface temperatures (SST), vertical wind shear, and tropical atmospheric moisture. The sea surface temperatures in the southern Gulf are around 28°C, indicating favorable conditions for development. Atmospheric moisture, explained in a previous blog here, surges into the southern Gulf this weekend providing ideal conditions for tropical development. The third and final key ingredient meteorologists are monitoring is vertical wind shear. Light winds are vital to sustain and strengthen the structure of tropical systems.Read More »
With hurricane season officially underway today in the Atlantic basin, all eyes are on thunderstorms streaming northward across the Gulf of Mexico. This convection is associated with Tropical Storm Beatriz off the coast of Mexico in the East Pacific. Although Beatriz is not a direct threat to the Gulf, tropical moisture from this storm will continue to provide deep convection across the southern Gulf. This moisture will interact with an existing surface trough over the Bay of Campeche providing the potential for low pressure to develop over the weekend, but there are limiting factors for tropical development.
Regardless of tropical development, one key tropical ingredient is present: atmospheric moisture. The higher the moisture content in the atmosphere, the greater chance for deep, persistent convection which furthermore enhances development within tropical systems. Meteorologists analyze a parameter known as PWAT, Precipitable Water, to gauge atmospheric moisture content. NOAA defines PWAT as the “measure of the depth of liquid water at the surface that would result after precipitating all of the water vapor in a vertical column over a given location”. Imagine having a column of water vapor, from Earth’s surface to the top of the atmosphere, and squeezing that column of air until all the water fell out (very similar to wringing out a sponge). The resulting measure of water, calculated in inches, is a good indicator of how much rainfall a region could see.
Thirty five years ago a ruthless nor’easter swept across the Northern Atlantic Ocean catapulting a wave of disastrous events leading to the demise of an “unsinkable” oil rig.
Located nearly 300km off the Newfoundland coast in the Hibernia Oil Field in 1982, the Ocean Ranger was the largest semi-submersible offshore drilling rig in the world at the time. The platform sat atop eight columns fixed upon two pontoons beneath the surface of the water. Stability of the platform, and overall safety of crew and operations, was achieved by the placement of water and fuel in ballast tanks inside the pontoons. According to a NASA Study from the NASA Safety Center, only two men aboard the Ocean Ranger performed the huge task of maintaining the appropriate equilibrium of the platform. The two men operated in the Ballast Control Room, rotating on 12 hour shifts.
Located only 30 feet above the surface, the Ballast Control Room contained an electric control panel embedded with lighted push button switches configuring valves, pumps, and tanks. These valves were used to pump ballast forward, backward, onboard or overboard from the tanks to account for any “list” (tilt) from various cargo loads or changing sea states. As small as a five degree list would hamper drilling production. In order to assess current sea conditions, there were four circular glass portlights (windows) constructed in the control room. These portlights would eventually lead to the disaster of the Ocean Ranger.Read More »
Today, November 14, marks an extraordinary Supermoon. The last time the Moon was this close to Earth was January 1948. And according to a statement from NASA, the next time the Moon will be this close to Earth will be in November 2034. A Full Supermoon looks nearly 7% larger than your average Full Moon due to the proximity to Earth.Read More »
Early Friday morning, Hurricane Matthew was downgraded to a Category 3 before brushing along the coast of Cape Canaveral. As of 12pm ET, the eye is less than 30 miles east-northeast of Daytona Beach, Florida. According to the National Hurricane Center, sustained winds have been reported up to 73 mph with gusts of 91 mph in Daytona Beach. However, the storm has yet to make an official landfall but that doesn’t mean we’ve lost our chance. The eyewall of Matthew is currently brushing along the Florida coast. With one slight wobble to the west in the next hour or two, we could see a U.S. landfall.
If you have been to Galveston, Texas, you are quite familiar with the city’s seawall. Construction began in 1902 as a response to the Great Hurricane of 1900, which devastated the city exactly 116 years ago today.
On Sept. 4, 1900, Galveston was notified of a hurricane moving north of Cuba. Without the aid of modern forecasting technology, Galveston residents were unaware of the precise movement and potential track of the impending hurricane. As the hurricane progressed through the Gulf of Mexico it experienced rapid strengthening before it made landfall just a few miles southwest of Galveston. Meteorologists estimated winds of at least 130 miles per hour as the storm barreled through the city. With a storm surge of over 15 feet, Galveston was inundated with water. Residents received warnings of the hurricane the morning of Sept. 8, however many neglected the advisories. Texas’ fourth largest city had lost nearly 6,000 – 8,000 residents when the sun rose the next day. The Great Hurricane of 1900 is known as the “deadliest natural disaster in U.S. history”.Read More »
By now I’m sure you have seen the “spaghetti plot”- ensemble of forecast models-regarding Tropical Depression Nine. If you’re not a meteorologist or everyday weather guru, then you have every right to be confused by this graphic of overwhelming lines. With a little background on the models, you’ll be sure to impress your coworkers when they begin to bring up TD Nine or soon to be Tropical Storm Nine. Read More »