Ana, Bill,--and Claudette?
After one of the slowest starts to hurricane season in the past twenty years, the hurricane season of 2009 has exploded with activity over the past 48 hours. This morning, Tropical Depression Four joined Ana and Bill in the Atlantic, and appears poised to become Tropical Storm Claudette later today. Indeed, this may already be Claudette, as morning's QuickSCAT pass showed top winds of 45 mph. NEXRAD radar animations out of Tallahassee, FL, show a small but well-organized tropical cyclone with plenty of heavy thunderstorm activity, and improving low-level spiral banding. Satellite loops show an area of intense thunderstorms with cold cloud tops expanding near the storm's center.
Figure 1. Current long-range radar out of Tallahassee, FL.
It's pretty amazing (and a little unnerving) how quickly this storm sprang up. TD 4 developed literally overnight, and has the potential to be a strong tropical storm by the time it makes landfall tonight along the Florida Peninsula. TD 4 reminds me of 2007's Hurricane Humberto, which became a hurricane just 24 hours after first appearing as a tropical depression. I don't think TD 4 has time to reach hurricane strength, since wind shear as diagnosed by the SHIPS model was moderate, 10 - 15 knots, but it does have time to strengthen into a 50 - 60 mph tropical storm before landfall. Given that the storm is so small, storm surge flooding should not exceed 3 -5 feet, and will not be the major hazard from TD 4; inland flooding from heavy rain of 3 - 6 inches is likely to be the main threat from the storm.
Tropical Storm Ana continues to struggle
Tropical Storm Ana continues to struggle. Dry air continues to plague the storm, thanks to the large area of Saharan air the storm is embedded in. Ana's heavy thunderstorms are limited to just one small spot near the center. Wind shear appears to have lessened some, though, since yesterday. Thunderstorms were not able to form at all near the center yesterday, since strong wind shear tends to blow a storm's heavy thunderstorms to one side of the storm, exposing the low-level center to view. With heavy thunderstorms building near the center this morning, shear appears to be less of a problem for the storm. Top winds seen by this morning's QuikSCAT pass were about 35 mph. The outer rain showers from Ana should appear on radar out of Martinique today.
Shear is low (5 - 10 knots), and is forecast to remain low for the next two days. SSTs are warm, 28°C, and will warm further over the next two days. However, there is so much dry air around Ana that significant strengthening appears unlikely. Nearly all of the models predict Ana will dissipate sometime in the next three days, though the HWRF and GFDL predict that this will happen because Ana will move over the rugged terrain of Hispaniola. Ana is likely not strong enough to survive an encounter with the big island that the Dominican Republic and Haiti share. At this time, it does not appear that Ana will be moist enough to cause a major flooding disaster on Hispaniola.
Figure 2. Water vapor image from this morning showing the large area of dry, Saharan air surrounding Ana, and lying to the northwest of Tropical Storm Bill. Image credit: NOAA/SSD
Tropical Storm Bill gathers strength
Tropical Storm Bill is gathering strength in the middle Atlantic Ocean, and appears poised to become a powerful Cape Verdes-type hurricane later this week. QuikSCAT data from this morning shows a large circulation with top winds of 35 - 40 mph. Water vapor imagery (Figure 2) shows that there is some dry air to the northwest of Bill, and this dry air is being drawn into Bill's center, slowing intensification. It will likely take another day before Bill can moisten the atmosphere enough to ward off the dry air, and allow more significant intensification.
Wind shear is low, 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 15 knots, for the next five days. Sea Surface Temperatures are about 27.5°C, and will remain in the 27.5 - 28°C range the next four days, then warm substantially as the storm nears the Lesser Antilles Islands. The combination of low wind shear and sufficiently warm SSTs should allow Bill to intensify steadily to hurricane strength by Wednesday.
The big news is that our most reliable computer model from last year--the ECMWF model--appears to have made the right call yesterday, forecasting that a major trough of low pressure would develop along the U.S. East Coast, turning Bill more to the north. All of the other models--with the notable exception of the UKMET model--have now jumped on the ECMWF bandwagon, forecasting that Bill will pass well north of the Lesser Antilles Islands. The UKMET has Bill hitting the islands, but is being discounted since it is an outlier. It currently appears that the trough approaching the U.S. East Coast will be strong enough to recurve Bill before it reaches the U.S., though it is too early to be confident of this. Several of the longer range models show Bill passing near Bermuda or Nova Scotia, Canada.
I'll have an update later today.
Jeff Masters
Reader Comments
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Gee...imagine that. Ana south of the models.
It's not that the center is exposed, it is that it has relocated further South. Look at the latest satellite loops on the NHC website.
I would if I had one....
Can't afford it...too many other pressing bills.
I called my mom who lives here in the same town. She didn't even know about it.
Funny all those people said Key West blob would nothing yesterday. That should have been easier to predict than Ana or paths of a storm out in the Atlantic . . .
my god, I just got back from vacation and couldn't believe my eyes. The smoke from the fires in Southern California, really hit the Ventura/Ojai area bad. Ash on the cars and thick smoke through the valley.
yeah, bad is totally relative. i was like wut... but then i got it.
great for formation, bad for folks.
The GFDL is the best model to follow IMO. All I'm saying.
seems like you left too early...
The center is .1 N and .1W of the last vortex message.
I have the COC at around 15.1.
Yep, I can see that on the visible too.
stall means still as in no movement or next to none (in a cane)
I do not see a centrer in that... not even close to exposed.
I'm with you.
I live in New England, and learned about the Hurricane of 1938 as a kid.
Nobody thinks we can get hit up here, but we do.
I wouldn't say that Bill is making me nervous, but I'm definitely keeping an eye on him.
Link
Is there a hunter in ANA right now? Because based on satellite ANA is far north of 14.9
I think the NHC has picked up on this. Let's just wait and see what they say. I am not trying to wishcast or anything, it just seems very obvious on satellite loops.
Interesting, the SHIPS takes Ana to 70 mph in 120 hrs.
Hehe perhaps. I plan on being the first person to be walking around outside in a Cat 5. I'll videotape it too.
Going back later. Got tired of catching small waves on long board after 3 hours. Fun but I am getting old . . . and saving energy hopefully for some overhead stuff.
Too shallow where she is at
What satellite loops are you looking at to get this idea? The center is almost due south of Apalachicola and that is very evident on radar. The big blow up of convection to the south on IR loops is just in the moisture influx.
it would take more than claudette to cool those waters.
Agree
They did jog the center due south so must have reformed.
Claudette really strengthening:
there is yes
still waiting for the report on the LLC spot
That storm made me angry. The center was supposed to come across BR, and since it was a weaker storm, I figured it would be fun to watch. Turns out it had other plans. haha
OMG, I live in Southern California and have been so glued to the Atlantic storms that I didn't realize we had fires burning!
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