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Hurricane Otto's deluge continues; world extreme heat record of 136.4°F bogus?

By: Dr. Jeff Masters, 2:51 PM GMT on October 08, 2010

The deluge continues over Puerto Rico, the Virgin Islands, and the northern Lesser Antilles Islands from Hurricane Otto, which is bringing a fourth straight day of heavy rains. Otto is the eighth hurricane of this very active 2010 hurricane season; our tally now stands at 15 named storms, 8 hurricanes, and 5 intense hurricanes. An average season has 10 - 11 named storms, 6 hurricanes, and 2 intense hurricanes. Otto's rains have caused a fair degree of trouble in the islands. According to Wikipedia, Heavy downpours in the U.S. Virgin Islands caused flooding across several local roads. In Saint Croix, a roadway section leading into Enfield Green collapsed on the night of October 6, temporarily cutting the south-side neighborhood off to vehicle traffic until a makeshift roadway through Carlton Estate was created the next day. On the island's North Shore in La Vallee, landslides and localized flooding in low-lying areas created some issues. There were no reports of major damage, however, and the roads remained passable. Torrential floods across the British Virgin Islands toppled several cars and caused extensive damage to utility lines and drainage pipes; dozens of people (mostly in Road Town) were left without power and water. An estimated 100 homes were flooded in Saint Lucia, and a fishing village on the island's east coast was declared a disaster zone. Schools, businesses and government offices across all of the Virgin Islands and in Saint Kitts and Nevis were closed until further notice.

In Puerto Rico, heavy rainfalls fell across the municipality of Utuado on October 7. As a result, a road to a neighborhood was made inaccessible after being severely damaged by gushing waters when parts of the Arecibo River overflowed. That same day, a landslide dragged away a communication post along the road and made it impossible for larger vehicles--including ambulances--to access the site. Meanwhile, fourteen families in the municipality of Ponce were cut off from communication because of several landslides. A residence alongside a road suffered significant damage and its inhabitants were forced to evacuate. Furthermore, a district in Cayey was isolated after a bridge collapsed, while burst riverbanks caused flooding across streets, trapping dozens of families in their homes. Across the island, 40 roads were closed due to torrential rainfall, and 19 streets had at least one lane closed.

Figure 1. Morning satellite image of Otto.

Weather radar out of Puerto Rico shows that a large area of heavy rain will continue to affect the Virgin Islands and Puerto Rico today, and flash flood warnings are posted on these islands through tonight. Martinique radar shows considerably less activity over the Lesser Antilles.

Satellite imagery shows a well-organized storm with an expanding Central Dense Overcast (CDO) of high cirrus clouds covering the center. Infrared satellite imagery shows a region of intense thunderstorms with very cold cloud tops, with the suggestion of a warm spot--an eye--forming. Otto should continue to intensify until Saturday morning, when wind shear will quickly rise to a very high 30+ knots.

Figure 2. Radar-estimated rainfall from Otto over Puerto Rico and the Virgin Islands this week shows that rains in excess of eight inches (white colors) have fallen in many regions. The strange ray-like pattern to the east of the radar location (the white "+" symbol) is due to mountains blocking the radar beam.

Western Caribbean disturbance
An area of disturbed weather in the Western Caribbean, a few hundred miles east of the coast of Nicaragua, has only a small amount of intense thunderstorms, but is showing some spin. The disturbance is nearly stationary, and is under a moderate 15 - 20 knots of wind shear. Some dry air in the Western Caribbean is interfering with development. I expect the storm will begin to build some significant heavy thunderstorms over the weekend, bringing heavy rains to northeastern Honduras and Nicaragua. None of the models develop the disturbance into a tropical depression, but it does have some potential for slow development over the next few days, and NHC is giving the disturbance a 20% chance of developing into a tropical depression by Sunday. The ECMWF model has the disturbance drifting northward next week and crossing Central Cuba on Wednesday or Thursday. Most of the other models keep the storms confined to the Caribbean.

A challenge to the validity of the world extreme heat record of 136.4°F (58°C) at Al Aziza, Libya
One of the "sacred cows" of world weather extremes has been the widely reported "hottest temperature ever recorded on earth", a reading of 58°C (136.4°F) reported from Al Azizia, Libya on Sept. 13, 1922. In a remarkable piece of research, our featured Weather Extremes blogger Christopher C. Burt concludes: the temperature observations at Al Azizia prior to 1927 (when the site and instruments were changed) are obviously invalid. The shelter housing the thermometer was most likely over exposed and measuring heat radiating of off the black-tarred concrete of the terrace on which it was placed.

Has Mr. Burt slain one of meteorology's most sacred cows? You be the judge. Check out the full story at his blog.

Jeff Masters


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