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Posted at 01:21 PM ET, 10/24/2011

Hurricane Rina rapidly develops, may strike Yucatan


Visible image of tropical storm Rina as 9 a.m. this morning. (U.S. Naval Research Lab)

2:10 p.m. UPDATE: In less than 24 hours, Rina has rapidly intensified from a tropical depression to a tropical storm to a hurricane. Peak winds have increased to 75 mph and the National Hurricane Center now predicts Rina will be a major hurricane (category 3 or higher) by late Tuesday as it approaches the Yucatan peninsula. Rina is the sixth hurricane this season in the tropical Atlantic.

From 1:21 p.m.: The 17th named storm of the 2011 Atlantic hurricane season, tropical storm Rina shows signs of intensifying, over 100 miles off the coast of Honduras. The successor to hurricane Rita, whose name was retired in 2005, it is moving northwestward at just 6 miles per hour.

Rina’s maximum sustained winds are estimated to be near 45 mph, and strengthening is expected over the next several days. The National Hurricane Center (NHC) predicts Rina will reach Category 1 hurricane strength in about 36 hours as it approaches the Yucatan Peninsula.

Rina actually looks reasonably healthy in the satellite images for a weak tropical storm. Thunderstorm clouds appear to be symmetrically distributed across the vortex, and the cirrus-cloud outflow is nearly unrestricted in the northeast quadrant.


Regions shaded in orange have very low humidity
On the flip side, destructively dry air (shaded in orange to the right) is not far away. Much of the Gulf of Mexico and western Atlantic are occupied by air masses that would weaken Rina if the storm were to inhale these surroundings. Though NHC expects Rina to intensify, the proximity of these potentially harmful conditions could hinder its future development.

Even so, Rina has found a cozy spot in the tropics that is, in some ways, quite supportive of tropical cyclone development. The water is as warm as it is anywhere in the western hemisphere (roughly 85F), and
Current sea surface temperatures (NOAA)
the wind shear across the depth of Rina’s swirl is not especially high (though outflow speeds at the northern edge of the circulation exceed 50 knots, or almost 60 mph).

In the larger context, Rina comes from a weather pattern that, in this small part of the world, has been unsettled for about a week. AL95, the tropical disturbance that just last week merged with our East Coast rainstorm, came from the same place. And just before that, the global models were telling us this area would be the place at risk for tropical cyclone development.

As long as Rina remains in this part of Caribbean atmosphere, it will probably remain a viable concern to nearby land masses.

An approach to the Yucatan at low-end hurricane strength could bring lots of rain and gusty winds to places like Belize and Cancun. The good news is that, a substantial northward move thereafter toward the southern Gulf of Mexico appears, at this point, unlikely.


The official National Hurricane Center track for Rina over the next five days (National Hurricane Center)
The models largely agree that Rina will not make it out of the Caribbean, and instead turn around and move back to the south beyond the 5-day forecast period. In the unlikely event it were to get pulled northward, the odds are that it would be coupled with a mid-latitude weather system strong enough to seriously damage its tropical characteristics.

At Wunderground, meteorologist Jeff Masters notes Rina adds to what has been a busy Atlantic season in terms of tropical storms, but not hurricanes:

Rina’s formation brings this year’s tally of named storms to seventeen, making it the 7th busiest Atlantic hurricane season since record keeping began in 1851. Only 2005, 1933, 1995, 1887, 2010, and 1969 had more named storms. However, 2011 has had an unusually low percentage of its named storms reach hurricane strength. Only 29% of this year’s named storms have made it to hurricane strength (five), and normally 55 - 60% of all named storms intensify to hurricane strength in the Atlantic.

If Rina reaches hurricane strength (2:20 p.m. UPDATE: it has done so), that percentage of storms reaching hurricane intensity will increase to 35%, still well below average.

By  |  01:21 PM ET, 10/24/2011

Categories:  Latest, Tropical Weather

 
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