WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

Tropical Storm Emily remains weak with roadblocks ahead

By: Dr. Jeff Masters, 6:14 PM GMT on August 02, 2011

Tropical Storm Emily took a moment to pause this morning, with no forward motion to speak of in the 11am EDT advisory from the National Hurricane Center, who say Emily might have been reorganizing. Emily eventually picked up some speed, and was moving west at 12 mph with maximum sustained winds of 45 mph in the 2pm EDT advisory. Satellite loops suggest that the storm has improved since yesterday, with strong thunderstorm activity surrounding the center of circulation accompanied by moderately strong outflow at higher levels. Recent satellite estimates of circulation show some consolidation at low levels (850mb), but weak circulation at higher levels (500mb). Despite the organized presentation on satellite, Hurricane Hunters found a generally disorganized storm this morning, with multiple potential centers. The lowest pressure that the Hunters found was 1007mb. Wind shear remains strong to the north of the storm, and this feature extends west across Puerto Rico and Hispaniola. Dry air, which has been lingering to the north of the system for the past few days, has begun to wrap around the northwest side of the storm. This, along with high wind shear along its potential track, could delay or prevent further intensification over the life of the storm. Another Hurricane Hunter mission is on its way to Emily now.

Figure 1. Visible satellite of Tropical Storm Emily at 1pm EDT.

Forecast for Tropical Storm Emily
The official forecast for Emily is a track toward the west-northwest over the next day and a half, after which it will make a turn to the northwest, and by Saturday, to the north. Although the National Hurricane Center has been shifting the forecast track to the east over the past few advisories, the U.S. coastline is still within the cone of uncertainty, and if we know something about this storm, it's that the forecast is uncertain. The CMC continues to be the western boundary of the model track forecasts, bringing Emily over Cuba and into the far eastern Gulf of Mexico. Today, on the eastern boundary of potential tracks fall the HWRF and the GFDL, which forecast Emily to cross over Hispaniola on a north-northwest trajectory, skirting the eastern edge of the Bahamas, and turning northeast before ever making connection with the U.S. coast. The Hurricane Center's official track follows the model consensus, and is the most likely track. Today, Emily is not forecast to strengthen into a hurricane within the next five days by the National Hurricane Center nor most of the models. Consensus seems to be that the storm will max out at a moderate to strong tropical cyclone, but this is assuming the storm can survive the wrath of Hispaniola.

Surviving Hispaniola

Hispaniola is somewhat notorious for being a major disruptor to tropical cyclones that dare cross over it. Since 1950, around two dozen tropical cyclones have crossed Hispaniola near where the National Hurricane Center is forecasting that Emily will pass over. A handful of these cyclones were of similar intensity with a track that was similar to Emily's forecast by various models, and although some went on to intensify (the warm Gulf of Mexico waters can be quite healing) many were fatally disrupted by the second largest island in the Caribbean.

Figure 2. Tropical cyclones that have crossed Hispaniola since 1950 (plotted using the NOAA Historical Hurricane Tracker).

Fay of 2008 developed in the Mona Passage on August 15th as a tropical storm. After a rough track westward over the length of Hispaniola, Fay emerged back into open water with little to no organized circulation, but managed to survive, and skirted the southern coast of Cuba for the next couple of days before turning north toward Florida. Many remember 2008's Fay as the storm that intensified and developed an eye-like feature over Florida after making landfall.

Cindy of 1993 was not as lucky in a battle with Hispaniola. Cindy developed as a tropical depression just east of the Lesser Antilles, and over the course of two days, tracked west-northwest through the Caribbean toward Hispaniola, strengthening into a tropical storm and reaching peak intensity just before landfall. Almost immediately upon landfall in the Dominican Republic, Tropical Storm Cindy deteriorated and the National Hurricane Center stopped issuing advisories on the system.

Emily of 1987 developed well east of the Lesser Antilles in late September and tracked northwest into the Caribbean, where it underwent a period of rapid intensification and was upgraded to a hurricane and then a major hurricane (category 3) just before landfall in the Dominican Republic. As the hurricane approached Hispaniola, it began deteriorating, and within 12 hours of landfall, Emily had weakened to a tropical storm and never regained its strength. Emily then took a turn to the northeast and tracked into the open Atlantic. Hurricane Katie of 1955 had a similar fate.



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