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Little change to Richard; Giri strongest cyclone ever to hit Myanmar; Megi nears China

By: Dr. Jeff Masters, 9:07 PM GMT on October 22, 2010

Tropical Storm Richard continues to struggle with dry air and wind shear, despite the fact that both of these influences have waned significantly today. However, the storm is poised to begin a period of steady intensification that should take it to hurricane strength by Sunday. There have not been any hurricane hunter aircraft in Richard since late this morning, and we have to wait until 8pm tonight for the next mission to arrive. The closest buoy to Richard is NOAA buoy 42057, which is about 80 miles north of the center. Winds at the buoy were 38 mph, gusting to 47 mph, at 3:43am EDT. Recent satellite imagery shows that Richard has not changed much in organization today. Water vapor satellite loops show considerable dry air to the west of Richard, and this dry air may cause some trouble for the storm over the next few days. The waters beneath Richard are very warm, 29°C.

Figure 1. Afternoon satellite image of Richard.

Intensity forecast for Richard
The latest SHIPS model forecast predicts that wind shear over the Western Caribbean will remain in the low range, 5 - 10 knots, Saturday through Monday. As the storm moves westwards on Saturday, it may draw close enough to coast of Honduras to hamper intensification. Assuming Richard avoids making landfall in Honduras, the light shear and warm waters that extend to great depth should allow Richard to intensify into a Category 1 hurricane by Sunday. The 5pm NHC wind probability forecast is giving Richard a 7% chance of becoming a major Category 3+ hurricane. I believe the odds are higher, near 20%. The main inhibiting factor for intensification will be interaction with the north coast of Honduras, and the possibility of the dry air to the west of Richard getting wrapped into the core of the storm while it is trying to organize. A band of very strong upper-level winds associated with the jet stream will be over the Gulf of Mexico early next week, so it is likely that if Richard crosses into the Gulf of Mexico, the storm will be unable to intensify once it passes north of the latitude of the Florida Keys.

Track forecast for Richard
The latest set of 8am EDT (12Z) model runs are similar to the previous set of runs. On Saturday, Richard will move west at an increasing rate of speed in response to a ridge of high pressure that is expected to build in over the Caribbean. This path will bring the center of Richard close to the northern coast of Honduras on Saturday and Sunday, resulting in very heavy rains of 3 - 7 inches along the coast. None of the models predict a more northwesterly path towards Cancun/Cozumel or the western tip of Cuba, and Florida is not at risk of Richard coming its way over the next five days. The 5pm EDT NHC wind probability forecast is giving the highest odds for tropical storm-force winds at Guanaja in Honduras, at 70%. Belize City is next highest, at 65%, and the odds are 31% for Cozumel. If Richard never reaches hurricane strength, it may dissipate over the Yucatan Peninsula, as predicted by the NOGAPS and ECMWF models. If Richard does intensify into a hurricane, as predicted by the GFDL model, the storm may survive crossing the Yucatan, and emerge into the Gulf of Mexico on Tuesday. Very high wind shear associated with the jet stream is expected to be over the Gulf of Mexico next week, so if Richard begins moving north or northeast towards the U.S. Gulf Coast, dissipation before landfall is to be expected.

Invest 90L
A tropical wave (Invest 90L) centered about 100 miles southwest of the Cape Verde Islands off the coast of Africa has a modest amount of spin and heavy thunderstorm activity. Wind shear is a moderate 10 - 20 knots, and the waters are warm enough to support tropical storm formation. NHC is giving the system a 40% chance of developing into a tropical depression by Sunday. By Sunday, 90L's northwest movement will take the storm into a region of high wind shear of 20 - 40 knots, discouraging further development. This system is not a threat to cross the Atlantic and affect the Lesser Antilles or North America.

Cyclone Giri hits Myanmar
Powerful Cyclone Giri made landfall this morning on the coast of Myanmar (Burma) as an upper-end Category 4 storm with 155 mph winds. Giri strengthened from a 60 mph tropical storm at 8am EDT yesterday to a 155 mph Category 4 storm by 8am this morning, becoming the strongest cyclone ever to hit Myanmar. Giri's winds at landfall were 20 mph stronger than those of Cyclone Nargis of 2008, which killed over 138,000 people. However, Giri hit a portion of the Myanmar coast that is not as heavily populated or as low-lying, so this will not be another Nargis catastrophe. Nevertheless, Giri's record strength and remarkably rapid intensification rate undoubtedly surprised an unprepared population, and the potential exists for a significant death toll due to Giri's surge and winds. Also of major concern is flooding from heavy rains. Giri is expected to dump 4 - 8 inches of rain along its path inland over Myanmar over the next 24 hours.

Figure 2. Visible MODIS satellite image of Tropical Cyclone Giri taken at 2:55am EDT October 22, 2010. At the time, Giri was a Category 4 storm with 145 mph winds. Image credit: NASA.

Typhoon Megi unleashes torrential rains on Taiwan and China
Torrential rains from Typhoon Megi have triggered flooding and landslides in Taiwan that have left 7 people dead and 23 missing. The typhoon is also being blamed for the deaths of 36 people and $176 million in damage earlier this week in the Philippines. Megi continues its slow march towards China at 5 mph, and is expected to make landfall Saturday afternoon on the Chinese coast opposite from Taiwan. Megi is a large and powerful Category 1 typhoon with 90 mph winds, but rising wind shear has significantly weakened the storm today. Megi will continue to weaken until landfall, but will still be capable of causing considerable wind and storm surge damage even at Category 1 strength. Heavy rain will likely cause serious flooding since Megi is moving slowly and is a huge storm. I expect Megi will be a billion-dollar disaster for China, mostly due to flooding from heavy rains. The outer rain bands of Megi will continue to affect Taiwan and the coast of China near Taiwan through Saturday, as seen on China's radar composite and Taiwan radar.

Figure 3. Radar image of Typhoon Megi at 4:30pm EDT (4:30am Taiwan time) on October 22, 2010. Image credit: Taiwan Central Weather Bureau.

Next update
I'll have an update Saturday.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.