Tropical Depression 5 forms; Typhoon Saola hits Taiwan; 115° in Oklahoma

Tropical Storm Watches are flying for much of the Lesser Antilles, as the islands await the arrival of Tropical Depression Five, which formed at 5 pm EDT today. The new depression is still fairly ragged looking, as seen on visible satellite loops. Heavy thunderstorm activity is only on the south side of the center, due to higher wind shear on the northern side of the storm. Wind shear over TD 5 is at the moderate level, 10 - 15 knots. TD 5 has one respectable low-level spiral band on its south side, but additional spiral bands are beginning to appear, and the areal coverage of the storm's heavy thunderstorms has increased markedly in the late afternoon hours. Water vapor satellite loops show that TD 5 has a reasonably moist environment. Ocean temperatures are 28°C, (82°F) which is about 0.5°C above average for this time of year. The first Air Force hurricane hunter aircraft will investigate TD 5 Thursday afternoon to give us a better idea of its strength.


Figure 1. Afternoon satellite image of TD 5.

Forecast for TD 5
TD 5's west-northwest motion should bring its outer rain bands to Barbados early Friday morning, and high winds and heavy rain will spread over the rest of the Windward Islands by Friday afternoon. Since wind shear will be higher on the storm's north side, I expect the heaviest weather will be on the south side of TD 5, over the Windward Islands. Wind shear is expected to remain moderate, 10 - 15 knots, through Friday, ocean temperatures will remain near 28°C, and mid-level moisture will be a moderate 60 - 70%, according to the 2 pm EDT run of the SHIPS model. This should allow TD to become Tropical Storm Ernesto by Thursday. NHC is giving a 27% chance that TD 5 will become a hurricane by Friday afternoon, when it will be passing through the islands. The reliable computer models are not in good agreement on the future intensity of TD 5. A band of high wind shear of 20 - 40 knots associated with an upper level low lies to the north of TD 5, and our most reliable model, the ECMWF, predicts that this shear will extend down into the islands on Friday and Saturday, and tear TD 5 apart. However, the almost equally reliable GFS model predicts that this band of wind shear will remain north of TD 5, and the storm will have clear sailing for the next five days, with only moderate shear of 10 - 15 knots affecting it. At this point, we'll have to wait and see how future model runs handle the shear forecast.


Figure 2. Radar image of Typhoon Saola hitting Taiwan at 2:30 am local time August 2, 2012. Image credit: Central Weather Bureau, Taiwan.

Typhoon Saola hits Taiwan
In the Western Pacific, typhoon season is in full swing with two typhoons expected to make landfall in China on Thursday. Typhoon Saola hit northern Taiwan as a Category 2 storm with 105 mph winds near 3 am local time on August 2, 2012. Saola is predicted to hit mainland China 300 miles south of Shanghai on Thursday as a Category 1 typhoon. Typhoon Damrey, a Category 1 storm located just south of Korea, is expected to hit China about 150 miles north of Shanghai on Thursday as a Tropical Storm.

Extreme heat in Oklahoma
The withering heat in Oklahoma continued on Wednesday, with the prize for most ridiculous heat a 115° temperature recorded in Okmulgee, Oklahoma. This is not far from Oklahoma's state temperature record of 120°, set in in Tipton on June 27, 1994. Oklahoma City has hit 110° thus far this afternoon, which is the 3rd highest temperature measured in the city since record keeping began in 1890. The only hotter days were August 10 - 11, 1936, when the temperature hit 112° and 113°, respectively. Chandler, Enid, Guthrie, Norman, Chickasha, and Shawnee in Oklahoma have all hit 113° today.

Jeff Masters