Stan about to leave the Yucatan

Tropical Storm Stan
Tropical Storm Stan is holding together as it moves has weakened during its passage across the Yucatan Peninsula, and is probably a tropical depression. There is very little deep convection surrounding the system, although the upper level ouflow is still good on all sides except the west.

Stan will have to re-organize once it pops out into the Gulf of Mexico Monday, and will have 36 hours or so to intensify over the warm 29 - 30C waters of the Gulf as it tracks westward. Wind shear is expected to remain very low, under 5 knots, and Stan could be a Category 1 hurricane as it approaches the Mexican coast on Tuesday. The latest model runs are still split on whether of not Stan will make it ashore on Tuesday. Two reliable models--the GFDL and Canadian--take Stan across Mexico and redevelop him as a tropical storm in the Pacific. However, the other models aren't so sure, and weaken the ridge that is driving Stan westward, allowing Stan to stall, loop back, or even turn northwards and threaten the U.S. later in the week. If Stan does stall and head northwards towards the U.S., he will have to contend with a large upper-level low pressure system forecast to form in the Gulf of Mexico by Thursday that would bring significant wind shear and weaken him.

Complicating the long range forecast is the fact that most of the computer models expect a second tropical storm to form nearby late in the week. The formation location varies depending upon which model one looks at. Two models indicate a storm will form off the east coast of Florida and scrape the Carolina coast (GFS and NOGAPS). The UKMET forms a storm near New Orleans and tracks it south into the Bay of Campeche; and the GFDL sees a new storm forming in the Yucatan Channel by the western tip of Cuba. We also need to keep an eye on the large area of thunderstorms approaching the Bahamas from the east, which could develop into a tropical storm later in the week.

Suffice to say, the waters surrounding the U.S. are expected to be very unsettled over the coming week, and this is a dangerous period of hurricane season for us. Ocean temperatures are still very warm, and the forecast is for very light wind shear over much of the hurricane breeding grounds.

Tropical Storm Otis
Tropical Storm Otis has decayed to a 45-mph tropical storm, and is forecast to continue to weaken and dissipate over the next three days. If Otis comes ashore in the Baja Peninsula, flooding and wind damage will be minimal. Otis's remains will probably not affect Arizona's weather.

Taiwan and China
Typhoon Langwang (Chinese for Dragon King), made landfall on Taiwan at dawn Sunday as a Category 3 typhoon with 120 mph winds. Passage over the 10000 foot high mountains of Taiwan significantly weakened Longwang, which struck mainland China today as a Category 1 hurricane. Longwang did heavy damage on Taiwan, killing 2,and injuring 46 people. In a freakish double-whammy, a magnitude 5.4 earthquake hit the island as Longwang came ashore, but did little damage.

Jeff Masters