It has been extremely warm this winter. Today high temperatures were in the mid-80°s F (29° C). Despite the warm weather it has been incredibly dry. For most locations on the peninsula of Florida this has been the driest period on record (records going back to the 1890s). Despite the warm weather we are not accustomed to developing tropical systems in February, but we would welcome the rainfall that one might bring.
This evening the first signs of something unusual occurring with the weather surprised many native Floridians as thunderstorms developed along the boundary of the east and west coast sea breeze fronts. The fronts collided over the central peninsula creating some light showers and a few rumbles of thunder.
This weather phenomenon is expected in July and August, not February. We received our first trace of rain in many weeks tonight as the collision of the fronts caused some showers across the central peninsula. It was welcome rain, however meager.
The National Weather Service's Hurricane Center issued a Special Tropical Weather Outlook statement this evening. In it they describe the system developing in the southern Gulf of Mexico as a non-tropical low pressure system interacting with an upper-level trough. The new disturbance has been dubbed Invest 90 by the Hurricane Center.
The system is producing widespread cloudiness, showers, and scattered thunderstorms across much of western and central Cuba, the Lower Florida Keys, and adjacent waters of the northwestern Caribbean sea, southeaster Gulf of Mexico and the Florida Straits.
The low is centered just west of the western tip of Cuba and a surface circulation center is gradually becoming better defined.
If the system continues to develop a subtropical depression or a subtropical storm could form during the next day or so before the disturbance merges with an approaching cold front. The Hurricane Center is giving this storm a 30% chance of developing into a named system.
Both the GFS and ECMWF computer weather simulation models predict that there is some potential for continued development of Invest 90 as it moves northeast towards South Florida.
Hurricane Season officially begins June 1, 2012 in the Atlantic Basin but it is not confined to the months of June to November, rather it occurs when conditions are conducive.
Some of those key ingredients needed for the development of at least a subtropical depression (a system with partial tropical characteristics) are currently trying to come together. Water temperatures in the south-central Gulf of Mexico are near 80° F (27° C), the threshold for tropical development.
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| Computer model forecasts of the probable path of Invest 90 |
If a storm does develop it will acquire the name Alberto, from the 2012 list of Hurricane names. Forecasters think the storm would take a similar path to the 1952 Groundhog Day storm across South Florida.
Tropical storm formation in February is very rare in the Atlantic Basin but it has occurred at least once before in modern history with the Groundhog Day Tropcial Storm of 1952.
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| Computer model forecasts of the probable path of Invest 90 long term |
It remains highly unlikely that Invest 90 has enough time or favorable enough conditions to become a tropical or subtropical disturbance (especially considering its relatively small size).
Are Category 6 Hurricanes Coming Soon?
Tropical cyclones are predicted to be more powerful this year, thanks to natural conditions, but researchers disagree on how to rate that intensity.
Atmospheric researchers tend to agree that tropical cyclones of unusual ferocity are coming this century, but the strange fact is that there is no consensus to date on the five-point scale used to classify the power of these anticipated storms.
In what may sound like a page from the script of the rock-band spoof Spinal Tap with its reference to a beyond-loud electric guitar amplifier volume 11, there is discussion of adding a sixth level to the current Saffir-Simpson hurricane scale, on which category 5 intensity means sustained winds higher than 155 miles per hour (250 kilometers per hour) for at least one minute, with no speed cap.
The lack of an upper limit on the scale results in all of the most intense tropical cyclones getting lumped together, despite their wide range of power. Category 5 becomes less descriptive when it includes 2005's Emily, which reached peak wind speeds of 257.5 kph (160 mph) and six hours in category 5; the same year's Katrina which held peak wind velocity of 280 kph (175 mph) for 18 hours in the category; and 1980's Allen, churning with peak winds at 305 kph (190 mph) maintained for 72 hours in the highest category.
And now the ferocity forecast for the century adds to this classification problem. "The severe hurricanes might actually become worse. We may have to invent a category 6," says David Enfield, a senior scientist at the University of Miami and former physical oceanographer at the U.S. National Oceanic and Atmospheric Administration (NOAA).
This new level wouldn't be an arbitrary relabeling. Global satellite data from the past 40 years indicate that the net destructive potential of hurricanes has increased, and the strongest hurricanes are becoming more common-especially in the Atlantic.
This trend could be related to warmer seas or it could simply be history repeating itself. Data gathered earlier than the 1970s, although unreliable, show cycles of quiet decades followed by active ones. The quiet '60s, '70s and '80s ended in 1995, the year that brought Felix and Opal, among others, and resulted in $13 billion in damages and more than 100 deaths in the U.S.
The pros and cons of categories: Five or six?
The average difference between the current categories equals nearly 20 mph, so a category 6 label would likely be applied to hurricanes with sustained winds over (280 kph) 175 mph. The speed and destruction of hypothetical "category 6" storms is speculative, despite the hurricanes with winds at that level.
After all, meteorologists and climate researchers may not even choose a category 5 storm from the record books if asked to identify the most powerful tropical cyclone in history, because the Saffir-Simpson scale fixates on maximum wind speed lasting for at least one minute and disregards the many other large-scale components that factor into a storm's level of devastation. The whole index should be thrown out the hurricane-proof window, some say.
"If I could do it, I would do away with categories," says Bill Read, director of NOAA's National Hurricane Center (NHC). "The whole indexing [of hurricanes] was done back in the '60s and '70s when we had no way to convey the variables of damage that the storm did. We didn't measure it that carefully; we didn't have the tools."
Even nowadays, instruments to measure actual wind speed are often destroyed during extreme storms, so estimates have to be extrapolated from satellite images and other data. Actual observations can also be suspect. It took 14 years for the World Meteorological Organization to acknowledge that an anemometer in Australia recorded a world record wind speed of 407 kph (253 mph) during Tropical Cyclone Olivia in 1996. Wind speed science has improved over the years. Since the 1990s direct wind measurements from hurricane-hunter aircraft have replaced central pressure measurements, which were often a proxy for wind speeds.
Variables used by meteorologists and climatologists to assess damage can go beyond wind speeds to include duration over land and the extent of deadly storm surges. Read sums it up this way: "Size matters: Katrina, Rita, Ike-all of them made landfall at a 2 or 3 level, but look at the damage they caused. Obviously a category did not accurately describe the impact."
A transition to "impact forecasting" began last year when NOAA's National Hurricane Center simplified the Saffir-Simpson hurricane scale and renamed it the Saffir-Simpson hurricane wind scale. This change involved stripping away the scale's former central pressure, flooding and storm surge estimates. These factors among others are now forecast separately. In 2009 the National Weather Service began using new probability models that provide storm surge estimates ranging from 0.6 to 7.6 meters (two to 25 feet).
What the future holds
History keeps us guessing about where and when the next big tropical cyclone will hit on the U.S. Atlantic or Gulf coasts. As for the most powerful hurricane ever, experts are divided. Some say 1998's Gilbert; an official answer from a NOAA Web site lists three: 1969's Camille, 1980's Allen and 2005's Wilma (the World Meteorological Organization agrees with the latter).
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