Busy Tropics

The recent MJO pulse that moved into the Atlantic has created a flurry of activity not seen since 2005. On Tuesday, we had four named systems in the Atlantic basin: Gustav, Hanna, Ike, and Josephine. Gustav's dissipated on Wednesday, but we still have three systems to deal with.

JOSEPHINE
Let's deal with Tropical Storm Josephine, the system furthest east and least threat to the U.S., first. Josephine doesn't look that impressive, but maximum sustained winds are 65 mph and a minimum pressure of 994 mb. It's somewhat surprising that Josephine has strengthened as much as it has with high wind shear (20 knots). Still, water temperatures are plenty warm (82 - 84 F) and there is very little dry air around the storm. I don't expect much strengthening with the high wind shear near the center and even stronger wind shear to its northwest. With a ridge to its north, Josephine should move WNW over the next few days. As it does so, it should move into cooler waters and this will also limit the amount of strengthening. I agree with the NHC's intensity forecast with minimal short-term strengthening followed by weakening on Friday. I believe Josephine will be a re-curving storm before it can get too close to the U.S.

HANNA
The system closest to home is Tropical Storm Hanna, which has taken a Muhammad Ali-like beating at the hands of an upper-level low. The low is slowly weakening and lifting out to the northeast of Hanna. However, wind shear is still high enough to prevent significant short-term strengthening and Hanna's inflow is probably being disrupted by Haiti. By tomorrow, Hanna should be moving away from Haiti and wind shear should relax enough to promote strengthening. The shear should still be strong enough to prevent rapid intensification, but some modest intensification is possible. I expect Hanna to become a hurricane late Thursday or possibly Friday. After that, it will be in an environment supportive of slight intensification with high oceanic heat content being the main positive factor. Some dry air and moderate wind shear will likely prevent significant strengthening. Still, I expect Hanna to be a strengthening Category 2 hurricane at landfall Saturday morning.


The track of Hanna is not terribly tricky, but there is still quite a bit of disagreement with the models. Hanna should be moving along the western periphery of a ridge and this should shoot it NW and make landfall in South Carolina or North Carolina. Due to the slightly unexpected eastward movement today, I'm leaning towards a landfall between Wilmington and Morehead City, NC.

IKE
Wow is all I can say. Within six hours, Ike has gone from a minimal Category 1 hurricane to a major Category 4 hurricane! This intensification was not forecast by anyone or any model this quickly. Yes, Ike is surrounded by moist air and very low wind shear, but the thermodynamic state of the ocean isn't typically what you would see with such a rapid intensification period. It just goes to show you that as advanced as our technology is and as smart as we think we are, God still controls the weather. Given the expected conditions over the next 24 hours, it shouldn't be a surprise if Ike continues to intensify and possibly gains Category 5 intensity. I don't think that will happen given the oceanic heat content, but I didn't think it would be a Category 4 hurricane this soon either. Still, expect Ike to remain a powerful hurricane for another day or so. After that, wind shear associated with the upper-level low near Hanna is forecast to increase and may halt any strengthening. However, the upper low should pull away from Ike by Saturday as a ridge builds in. This should decrease the shear and make conditions favorable again for strengthening.


Ike should begin to move more WNW and NW tomorrow as it begins to feel the effects of the upper-level low. After it passes on Saturday, a ridge builds in and should push Ike slightly south of due west for almost 48 hours. After this time, models diverge on keeping the ridge strong or breaking it down. This results in Ike maintaining a westerly motion or turning more NW. Regardless, a powerful hurricane will likely be approaching the western Bahamas by the end of the weekend. Everyone from Florida to North Carolina needs to watch this extremely closely. We may not get off lucky this time...