psu_met's Blog

TD #4
As of 11pm, 8/13/07: Winds: 35mph G: 45mph
Movement: W 19mph
Pressure: 1005 mb (29.67in.)
Position: 740 WSW of southern Cape Verde Islands

Forecast: The TD should continue to move in a general westward direction for the next fews days after which a curve to the north could occur. Wind Shear is about 15 knots down from 20 yesterday. This should continue to decrease to about 10 knots by Wednesday. SSTs (Sea Surface Temperatures) will gradually increase as the storms moves west. Between the lower shear and warmer water strengthening is likely, however not very rapidly. By the time the depression approaches the Lesser Antilles, there exists the chance of more rapid intensification.
Models: The models are not in very good agreement at this hour which leads to lots of uncertainty regarding both the track and intensity of TD 4. Several models develop the storm and bring it across the Antilles at different intensities. A couple others don't develop the storm at all. One of the models has it approaching the NJ coast by Aug 25th :-)
Longer Range: There are several possible outcomes for TD 4 at this time. The only one that doesn't seem likely at this time is the best possible outcome (storm curves harmlessly out to sea). It is possible that the storm will never get it's act together and never strenghtren above a minimal TS. If it does develop it will be influenced by a trough moving off the US East Coast. The strength of this trough will determine how far north the storm will travel. The stronger the trough the farther north. A stronger trough could mean a landfall along the East Coast, a weaker trough means a landfall along the Gulf Coast.
My Thoughts: The pattern across the Eastern US recently has been for weak troughs to quickly move off the coast. Due to this and the current model runs my best guess would be for TD 4 to continue to grow stronger reaching the Lesser Antilles as a minimal hurricane. The trough moving off the coast will only have a minimal impact on the storm as it pushes into the Gulf Coast, possibly as a major hurricane. It really is to early though to forecast the track that far out with any certainly and almost impossible to forecast the intensity.

Invest 91L: There is a disturbance moving into the Gulf of Mexico this afternoon that bears some watching. It should move to the west and make lanfall near the Mexico/Texas border sometime Wednesday or early Thursday. Conditions should improve and allow for some slow development before landfall. Even with the best conditions there is only time for the disturbance to reach minimal tropical storm strength.

Hurricane Flossie: Flossie (140mph) refuses to weaken despite cool waters and increasing wind shear. A Hurricane Watch has been issued for the Big Island of Hawaii. The hurricane is likely to pass 50-100 miles south of the island tomorrow afternoon with the biggest concern being flooding rains with some minimal wind damage. Storm surge shouldn't be a factor, but high waves are already beginning to occur.

5pm Update: The new advisory keeps TD 4 at 35mph moving W at 19mph. The official forecast track has been shifted slightly to the north, but remains highly uncertain after 2-3 days. Hurricane Flossie has finally started to weaken (125mph) but is still expected to pass Hawaii as a moderate hurricane to the south. A Tropical Storm Warning in addition to the Hurricane Watch is now in effect for the Big Island.

11pm Update: TD 4 has not changed much since this morning and remains a depression. The system at this hour looks elongated from the east-west most likely due to moderate shear. The forecast track essentially remains unchanged from the 5pm advisory. The disturbance in the Gulf (invest 91L) remains disorganized but could become a depression as early as tomorrow as upper air conditions become more favorable. A Air Force Reserve reconnassiance plane may investigate the storm tomorrow afternoon if needed. Hurricane Flossie continues to slowly weaken (120mph CAT 3) but still poses a threat to Hawaii. Some parts of the Big Island could see over 10in. of rain with 5-10in. common. A tropical storm warning and hurricane watch remain in effect for the Big Island.

Will try and get an update out tomorrow afternoon before I go to work.