Tropical Wave Impacting the Bay of Campeche

A tropical wave along 98 west and south of 20 north is flaring up showers and thunderstorms across the Bay of Campeche. This feature is looking better organized, according to the latest satellite loop, with a large, somewhat concentrated, area of deep convection. However, westerly winds aloft are too strong to allow for fast development or falling pressure. The wave is tracking to the west-northwest at 10-15 knots and will bring beneficial showers and thunderstorms to South Texas over the weekend. If this feature persists for a couple of days and becomes a depression, it could cause flooding rains over eastern Mexico.

A potent tropical wave continues to affect the eastern Caribbean. It is located along 72 west and south of 20 north and is moving west-northwest at 15-20 knots. The wave is causing numerous showers and thunderstorms from Puerto Rico to the Leeward Islands, with a large area of deep convection north of Hispaniola. This convection is being aided by a broad upper-level trough, which is causing southwesterly shear over the system, actually aiding in thunderstorm development much like upper-level shear over the Plains during spring. However, this shear will not allow for tropical development, even though the upper-level trough will move back to the west over the next couple of days, as will the shear, but the wave should continue to track under the shear, slowing the development. Tropical moisture from this wave should increase the chance of showers and thunderstorms across central and South Florida later in the weekend.

Farther east, another tropical wave is located along 54 west and south of 10 north. It is moving west at 15-20 knots and shows little sign of organization. Our last tropical wave is along 38 west and south of 10 north and shows little sign of development.

Tropical Wave Lashes Lesser Antilles and the Virgin Islands

A robust tropical wave continues to produce squally conditions across the Lesser Antilles Thursday. The wave, along 63 west and south of 20 north, is tracking to the west at 15 knots and will move into the western Caribbean later this weekend. It will bring gusty winds and numerous showers and thunderstorms to Puerto Rico today and then Hispaniola on Friday. An upper-level trough is causing a southwest shear across the eastern Caribbean and over the top of this wave so any development will be slow for the time being. The upper-level trough will back to the west over the next couple of days and so will the shear, but if the wave continues to track under the shear, then development will continue to be slow. Tropical moisture from this wave should increase the chance of showers and thunderstorms across central and South Florida later in the weekend.

Another tropical wave along 96 west and south of 20 north is moving west at 10-15 knots, but convection associated with it has greatly diminished. Moisture from this wave will bring much-needed showers and thunderstorms to South Texas over the weekend.

Farther east, another tropical wave is located along 47 west and south of 10 north. It is moving west at 10-15 knots and shows little sign of organization.

Tropical Downpours Continue in East

Low pressure continues to surge northward into the Northeast Wednesday morning, producing tropical downpours from eastern New York into New England. Gales are possible just to the east of the center as well as it moves from western Connecticut toward northern New England. But, the main story will be the flooding rain that will continue over areas that have already been hard-hit over the last couple of months.

Elsewhere in the tropics, a tropical wave is moving through Central America and the Yucatan Peninsula, and is spreading thunderstorms over much of Central America, and the northern end of the wave will cross the Bay of Campeche. There are no signs of organization with the wave at this point, but it is possible that some of this wave's moisture will be pulled into South Texas by Friday, which would result in welcome rainfall in this drought-stricken region. The weather is generally quiet over the rest of the Caribbean at this time. The only other tropical wave to watch is approaching the Lesser Antilles and will cause thunderstorms there Wednesday. This feature also shows no signs of imminent organization.

An upper-level disturbance about halfway between Puerto Rico and Bermuda will continue to move toward the northwest over the next 24 hours. This may begin to affect Bermuda with showers late Wednesday, then pass closer to the island Wednesday night or Thursday.

New threat area east of the Windward Islands

A new area worth watching has cropped up near 7N 47W, about 1050 miles east-southeast of the southern Windward Islands. There is some heavy thunderstorm activity here and a 1012 mb low pressure area has developed. This low is moving west towards an area of higher wind shear, and is not expected to develop. Wind shear over most of the Atlantic is expected to remain seasonably high over the next week, making it difficult for tropical storm formation.

Preliminary model tracks for the low east of the Windward Islands.

Intense storms blamed on heat

Storms blamed on global warming

Global warming, not natural fluctuations in ocean temperature, was the main cause of the ocean heat that energized last year's killer hurricanes, scientists at a federally funded climate laboratory said Thursday.

As a result, continued increases in the Earth's temperature likely will lead to more "enhanced hurricane activity" in future years, said climate analysts Kevin Trenberth and Dennis Shea of the National Center for Atmospheric Research in Boulder, Colo.

Hurricanes draw their energy from the ocean, and scientists on both sides of the debate agree that rising Atlantic Ocean temperatures have driven the past decade's increasingly violent hurricanes.

Last year, for example, the temperature in the tropical Atlantic, where many hurricanes originate, was about 1.6 degrees Fahrenheit above the average for the first 70 years of the 20th century.

The year produced the most named storms on record (28), forcing the National Hurricane Center to go into the Greek alphabet for names. It also brought the most intense Atlantic storm on record (Wilma), the most intense storm to hit the Gulf of Mexico (Rita) and the most destructive storm on record (Katrina).

Some experts, including National Hurricane Center Director Max Mayfield and Colorado State University forecaster William Gray, have discounted the effects of global warming.

They contend that higher ocean temperatures are a result of a long-term cycle known as the Atlantic multidecadal oscillation.

A rise and fall in the ocean's temperature has been documented as far back as the late 1800s.

But in a study described in the Geophysical Research Letters, Trenberth and Shea said the current rise is only partly caused by the oscillation.

They deducted a global temperature increase that scientists have monitored since the 1970s from changes observed in the Atlantic during the same period, and concluded that very little of the increased Atlantic temperature was caused by the ocean temperature cycle.

They attributed 0.8 degrees of the extra temperature to global warming and about 0.2 degrees to the oscillation. The remainder is due to the after-effects of the 2004-05 El Niño warm-water current in the Pacific Ocean and year-to-year variability, they said.

"I don't see how the hell they can say that," said Gray, 76, professor emeritus of atmospheric sciences at Colorado State. "We're just in one of these warming trends due to the ocean circulation and there's nothing we can do about it."

But Georgia Tech scientist Peter Webster, who this year reported that rising ocean temperatures worldwide are directly linked to a 35-year trend of increased hurricane strength, said the calculations by Trenberth and Shea were "fundamentally sound."

"The Atlantic oscillation is there, but it's being out-ridden by global warming," he said.

In a separate report released Thursday, a committee of the National Academy of Sciences said that "proxy" climate records, such as the width of tree rings and the chemical makeup of ice from deep beneath the Greenland snowpack, indicate with "high confidence" that the Earth is warmer now than it has been in the past 400 years.

The academy's study was made at the request of Congress. Industry representatives and global-warming skeptics attacked a earlier proxy temperature study that concluded that the Earth's temperature varied little for 1,000 years, then in the past 25 years began to rise sharply, at an angle reminiscent of a hockey stick.

The study has played a key role in actions by the U.N. Intergovernmental Panel on Climate Change.

The academy panel's study said the proxy evidence provides "less confidence" in climate conditions between 900 and 1600 A.D.

It said "very little confidence" could be placed in average global temperature calculations before 900.