Tropical Storm Sanvu

Tropical Storm Sanvu (TS) 03w, located approximately 70 nm south of andersen AFB, Guam, has tracked northwestward at 08 knots over the past six hours. Animated infrared (ir) satellite imagery shows a significant consolidation of convection around the low level circulation center (LLCC) just South West of Guam over the past six hours, leading to a much more symmetric satellite presentation. This trend is also obvious in the pgua radar base reflectivity, which clearly depicts the LLCC and associated banding structures. As a result, confidence in the position and intensity is increasing. The current position is based on the IR imagery and radar data. The current intensity is based on a pgtw Dvorak estimate of 35 knots and the noted improvement in IR and radar. Ts 03w is tracking along the southwestern periphery of the subtropical ridge (str) centered far to the northeast. Upper level analysis and animated water vapor imagery indicate a favorable environment for further development. The tropical upper tropospheric trough (tutt) cell located southwest of Guam continues to migrate westward and weaken, allowing the outflow to become more radial. Poleward outflow remains good, with a possible new TUTT cell forming to the northeast. Additionally, the water vapor loop suggests that the system may be interacting with a trough to the northwest, further enhancing outflow. The current vertical wind shear (vws) is light to moderate, at 10-15 knots, and the sea surface temperature is favorable at 30 degrees celsius.

An extension of the str to the north of the system is expected to weaken as an approaching mid-latitude trough, extending from a low currently developing south of Japan, interacts with the ridging. Ts 03w should continue to pass south and west of Guam during the next 12 hours and then track generally northwestwards around the eroding str periphery. By tau 48 the system should begin to round the str and begin a more poleward track, which will steer towards a re-curvature into the mid- latitudes. Intensity during this time should gradually increase as the upper-level environment remains favorable.

After tau 72, ts 03w is forecast to move north of the str axis and begin to interact with the mid-latitude baroclinic zone, which is expected to be very zonal and poleward of about 30 degrees north. Extra-tropical transition (ett) should begin during tau 96 with completion into the westerlies by tau 120. During this time intensity will begin to decrease due to an increase in vws and decrease in ocean heat content, which begins to drop off poleward of 22 degrees north. Most models are in agreement, showing the system fully incorporated in the mid- latitude westerlies by tau 120. The GFS continues to be the right most track outlier, and therefore faster re-curver, while the NOGAPS and WBAR continue to pull the model consensus (conw) to the left. The latest model runs have weakened the mid-latitude trough, leading to a slower recurvature. The official jtwc track forecast agrees with the conw during the first 36 hours but then deviates slightly inside of conw for Taus 48 and 72. During Taus 96-120, the forecast track is slightly inside and faster than the conw to account for ett.

By Alex Sosnowski, Expert Senior Meteorologist

There are meteorological differences between a tropical and subtropical storm. However, both can threaten lives and property in the same way.

The major difference between the two systems from a public standpoint is that subtropical storms typically do not become as intense as tropical storms or hurricanes.

That being said, both can bring flooding rain, damaging winds, beach erosion, rough seas, etc.

Interestingly, subtropical storms often cover a much larger area that the more compact tropical storms and hurricanes.

As a result, damaging winds and flooding from a subtropical storm can affect a larger area than that from a hurricane.

The difference between the two has to do with the environment in which the storms were born.

In the tropical storm, waters are very warm and the budding system has a good relationship with the upper atmosphere that allows it to “breathe” or be well ventilated, like a jet engine.

This well-tuned setup allows the storm to become compact and spin rapidly, like a figure skater pulling in his or her arms in closer to the body.

In the case of the subtropical storm, waters are relatively lukewarm, dry air is often drawn in and the storm does not have the upper atmosphere connection.

As a result, the subtropical storm compensates for these deficiencies by becoming rather large and asymmetrical.

However, while subtropical storms may be the “clunker” of their tropical streamlined cousins and may not catch as many looks, they can kill and bring destruction given the right conditions.

Sometimes, along the Atlantic coast of the U.S., these subtropical storms gain extra spin from a large high pressure system to the north.

The result can be a system as strong or stronger than the most powerful nor’easter of a nasty winter, bringing all the bells and whistles.

Hurricanes are some of the deadliest storms on the planet, and scientists predict they’ll pack even stronger punches as climate change advances. After forming over tropical oceans, these tempests wreak havoc once they make landfall, bringing with them winds of up to 140 miles (225 kilometers) per hour, storm surges and even tornados. As hurricanes approach the shore, satellites and weather radar can help project when and where a storm will hit. But forecasters have been stumped when it comes to predicting when they’ll hit peak strength. New research promises to solve this problem by keeping tabs on – of all things – lightning, which until recently, was believed to be rare in such storms.

Image of worldwide hurricane paths between 1985 and 2005 courtesy of Nilfanion via Wikimedia Commons

The research, published online in Nature Geoscience, analyzed the strongest 58 hurricanes from 2005 to 2007 and found that an increase of lightning reliably preceded the maximum winds by about a day (in all but two of the storms). “Changes in lightning activity can signal changes in storm dynamics, organization, development and so on,” according to the study led by Colin Price, a professor of atmospheric sciences at the Tel Aviv University in Israel.

Hurricane Dennis, for instance, which swept over Cuba, Haiti and Jamaica before slamming into Florida and Georgia in early July 2005, caused more than 85 deaths and $4 billion in damages. Dennis had a jump in lightning flashes – more than 1,500 flashes – on July 7 (up from about 800 on the 6th), and by July 8, winds reached peak speeds of nearly 150 miles (220 kilometers) an hour (up from about 70 miles – 110 kilometers – an hour the day before) as the storm was just off the coast of Cuba. The researchers saw the same pattern repeatedly, thanks to data collected by the World Wide Lightning Location Network (WWLLN), which provides real-time maps of lightning around the globe.

Learn more about the study.

By Katherine Harmon

Photo by Michael Braun of photos.com

On May 19, Tropical Storm Alberto began rocking the Atlantic shore from northeast Florida to South Carolina. It is only the third tropical storm to have formed prior to the official start of hurricane season in the past 31 years.

Although hurricane season officially runs from June 1 through Nov. 30, it is rare, but not impossible, for the season to begin sooner.

“Named storms before June 1 are unusual,” said Expert Senior Meteorologist Frank Strait. “There have been about 25 over the last 125 years.”

Tropical Storm Arthur was the second most recent, striking Belize and Mexico on May 31, 2008 with 45 mph winds.

Tropical Storm Ana was the third most recent pre-season tropical storm, and the only storm ever recorded to form in the North Atlantic basin during the month of April.

Ana hit Florida from April 20 to April 24, 2003, with 60-mph winds, killing two people.

The rarity of these storms before June 1 is due to the absence of favorable conditions in the Atlantic.

“First, the water outside the Caribbean and southeastern Gulf of Mexico is not usually warm enough until June,” Strait said.

Water stores solar heat and acts as fuel for a hurricane, which then redistributes the heat elsewhere.

“Second, the jet stream is usually far enough south that westerly winds are still aloft over the tropics, contributing to wind shear,” he said.

Wind shear is a critical factor.

“Strong wind shear, which is the change of wind speed or direction with altitude, causes building clouds to be tilted, restricting vertical development. Unless a tropical system has a vertically oriented core, its ability to develop are diminished,” explained Meghan Evans, inAccuWeather’s Hurricane Forecast.

“By early June, usually the jet stream is far enough to the north that the wind aloft over the tropics is either light or becoming easterly, in line with the prevailing surface wind, so you don’t see as much wind shear,” Strait said.

However, early storms such as these are not necessarily an indicator that the season will be particularly harsh.

In fact, the AccuWeather Long-Range Forecasting Team predicts this season will be less active than last year, with lower numbers of named storms.

“On the other hand, the most favorable area for development in the tropics may be over the western part of the Atlantic basin: the western Atlantic, western Caribbean and Gulf of Mexico. So, there may be more threats to North America and more land areas threatened, making it seem busier than last year even with fewer storms,” Strait said.

Tropical Depression TWO-E was captured on this NOAA satellite image early on Monday morning.

The tropical season is getting off to a fast start in the Eastern Pacific basin with the development of the second tropical depression late on Sunday.

The new depression, Tropical Depression TWO-E, is currently located a little over 500 miles to the south of Acapulco, Mexico, according to the AccuWeather.com Hurricane Center.

The storm is expected to slowly track towards the north-northwest, generally paralleling the Mexican coastline, before picking up forward speed on Monday night.

As the storm tracks northward, it will start to encounter light upper-level winds as well as very warm waters. Both are important ingredients for the development of tropical systems.

AccuWeather.com Meteorologists are expecting the depression to strengthen into a tropical storm later today. When this happens, the storm will acquire the name Bud.

Gradual strengthening is likely throughout the course of the day on Tuesday where it could develop into the first hurricane of the Eastern Pacific tropical season.

By Tuesday, a trough swinging into the West Coast of the United States will help steer the storm more towards the northeast.

Keeping in mind the details of the storm remain quite uncertain beyond Tuesday, a northeasterly track would take the storm into the central Mexican coastline.

If conditions continue to remain favorable for maintaining tropical characteristics, the storm could very well make landfall as a hurricane in central Mexico as early as Friday.

Keep checking back with AccuWeather and the AccuWeather.com Hurricane Center as we track and give you the latest up to date information on the storm.