Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.
By: Levi32 , 11:07 PM GMT on July 19, 2008
First of all Bertha is back at hurricane status yet again, but is finally showing signs of extratropical transition, and will continue to head out over the north Atlantic posing no threat to anybody.
Tropical Storm Cristobal is located about 100 miles off the NC coast after making a jog to the north this afternoon, bringing him much closer to land. Cristobal has winds of 45mph with a pressure of 1005mb, moving NE at 6mph. This movement is expected to continue over the next several days, and Cristobal may pose a threat to the NC outer banks. Upper-air conditions are fairly ideal for development, and Cristobal is sitting over the gulf stream, where plenty of warm water resides. It would seem that all systems are go, but Cristobal's convection remains quite modest and the system is not really strengthening at this point, with the exception of continued organization of the spiral bands. I believe this is due to dry air being pulled into Cristobal by his own circulation off of the continent. The NW quad has been void of convection from the beginning, and there is a lot of dry air over the land. At this point Cristobal isn't able to overcome this, and until he can, he will remain no stronger than a 45kt system. However, residents in North Carolina should continue to monitor this system very closely, because if Cristobal does overcome the dry air before going out to sea, he could crank up really fast before anyone realizes it. Such is the nature of home-grown developments, we saw it with Humberto last year. For now Cristobal will hopefully be beneficial if he can spread some much-needed rain over the area, which probably won't be much unless he makes landfall.
Our other system, 94L, is still fighting for life in the Caribbean. This system WAS a tropical depression 2 days ago, by definition, and it was an incredible feat that it pulled that off. Since then the circulation has become open once again, but the mid-level circulation is still kicking nicely. Convection has managed to remain healthy and is now consolidating over the mid-level center, which was placed further north of the surface center. 94L has been fighting wind shear due to an ULL to its northwest, but this ULL is now weakening and shear over 94L is under 20 knots now. Eventually this ULL will pull out, providing a much nicer environment for 94L to develop in as it moves into the western Caribbean and GOM.
At this point I don't believe 94L has time to amount to very much before hitting the Yucatan Peninsula, but that's actually a bad thing. When a strong hurricane moves over the Yucatan Peninsula and emerges again over the GOM, the core gets significantly weakened. However, the outer bands of the storm stay over water the whole time. So when the storm moves back over water, what happens is the outside of the storm is in better shape than the core, and a competition between the outer bands and the heart of the system takes place. As a result most major hurricanes never regain their former glory after crossing the Yucatan. Recently, Hurricanes Wilma and Emily of 2005 are good examples of this, as well as Isidore of 2002. But a weaker system of weak TS status or under doesn't have a well set-up core yet, and is far less affected by the journey across the Yucatan than a hurricane is. Therefore 94L may not amount to much prior to hitting the Yucatan, but once it emerges in the GOM we have to watch out, because we will probably have a Cat 1, 2, or 3 hitting the Mexican coastline in 5 days.
Yeah I said Mexico....but Texas needs to watch this very closely as well. The ridge isn't horribly strong north of 94L, and the western periphery is sitting right over the western gulf. A lot of 94L's future track will depend on where it hits the Yucatan, where it exits the Yucatan, and how fast it gets there. A long-wave trough will be digging down into the eastern United States in 3-4 days, which will further weaken the ridge. Some models have 94L making landfall on the western side of the gulf already by this time, so it might not matter, but we will have to see how fast 94L really moves over the coming days. Model consensus has 94L going into Mexico on both coastlines, with the exception of the GFDL and HWRF which continue to be the northerly outliers, taking 94L through the Yucatan Channel and into Texas. The latest GFDL run and the CMC closely agree on a hit to the Mexico/Texas border as a major hurricane, but it's too early to speculate on these solutions. Right now we have to watch and wait. Interests in Texas and Mexico should closely monitor this system.
Cristobal radar imagery:
Cristobal visible satellite imagery (click for loop):
Cristobal model tracks:
Invest 94L visible satellite imagery (click for loop):
Invest 94L model tracks:
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
Comments will take a few seconds to appear.