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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LOL...
No one is off the hook in the Lesser Antilles, Bahamas, and the East Coast till Bill moves north of your latitude.
Possibly
(From the ESE at ~ 19.5 mph)
Current Lowest pressure: 1013.2 mb
(~ 29.92 inHg)
Glad you see the same thing as I. These graphics do play tricks on one's eyes sometimes.
Thats a closed low.
Last night Dr. Lyon
You're correct
Yesterday evening, Dr. Lyon's was saying that the wave wouldn't develop.
we also officially have Caludette
WTNT64 KNHC 161614
TCUAT4
TROPICAL STORM CLAUDETTE TROPICAL CYCLONE UPDATE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042009
1100 AM EDT SUN AUG 16 2009
...DEPRESSION BECOMES TROPICAL STORM CLAUDETTE...
DATA FROM THE NOAA DOPPLER RADAR IN TALLAHASSEE FLORIDA INDICATE
THAT SURFACE WINDS ASSOCIATED WITH THE DEPRESSION HAVE INCREASED TO
40 MPH...65 KM/HR...MAKING THE DEPRESSION TROPICAL STORM CLAUDETTE.
DETAILS WILL FOLLOW IN THE 2 PM EDT INTERMEDIATE ADVISORY.
$$
FORECASTER ROBERTS/BRENNAN
Claudette!
15:58:30Z 30.317N 87.067W 575.2 mb
(~ 16.99 inHg) 4,774 meters
(~ 15,663 feet) 1013.2 mb
(~ 29.92 inHg)
From 105° at 17 knots
(From the ESE at ~ 19.5 mph)
When you see Positioning Method : FORECAST INTERPOLATION the location is from the NHC track. The imaging algoritm was not able to find a center based on satellite data, so it use the closest position along the forecast track.
Transmitted: 16th day of the month at 16:11Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 304)
Tropical Depression: Number 4 (flight originating in the North Atlantic basin)
Mission Number: 1
Observation Number: 01
Mandatory Data...
Observation Time: Sunday, 16:07Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 30.3N 86.4W
Location: 45 miles (72 km) between the W and WNW (281°) from Panama City, FL, USA.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 870 meters
Flight Level Wind: From 100° at 17 knots (From the E at ~ 19.5 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 19°C
Flight Level Dew Point: 8°C
Weather (within 30 nautical miles): Thunderstorm(s)
925 mb Surface Altitude: 851 geopotential meters
Optional Data...
Estimated Surface Wind: From 130° at 15 knots (From the SE at ~ 17.2 mph)
Remarks Section...
Surface Wind Speed (likely by SFMR): 18 knots (~ 20.7mph)
nnw
inverted V
000
WTNT64 KNHC 161616
TCUAT4
TROPICAL STORM CLAUDETTE TROPICAL CYCLONE UPDATE...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042009
1215 PM EDT SUN AUG 16 2009
CORRECTED FOR ISSUANCE TIME
...DEPRESSION BECOMES TROPICAL STORM CLAUDETTE...
DATA FROM THE NOAA DOPPLER RADAR IN TALLAHASSEE FLORIDA INDICATE
THAT SURFACE WINDS ASSOCIATED WITH THE DEPRESSION HAVE INCREASED TO
40 MPH...65 KM/HR...MAKING THE DEPRESSION TROPICAL STORM CLAUDETTE.
DETAILS WILL FOLLOW IN THE 2 PM EDT INTERMEDIATE ADVISORY.
$$
FORECASTER ROBERTS/BRENNAN
Me also.
isnt it suppose to say
11am CDT
Yay!! Now Claudette - please die before making landfall.
They corrected the time on it just now.
000
WTNT64 KNHC 161616
TCUAT4
TROPICAL STORM CLAUDETTE TROPICAL CYCLONE UPDATE...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042009
1215 PM EDT SUN AUG 16 2009
CORRECTED FOR ISSUANCE TIME
...DEPRESSION BECOMES TROPICAL STORM CLAUDETTE...
DATA FROM THE NOAA DOPPLER RADAR IN TALLAHASSEE FLORIDA INDICATE
THAT SURFACE WINDS ASSOCIATED WITH THE DEPRESSION HAVE INCREASED TO
40 MPH...65 KM/HR...MAKING THE DEPRESSION TROPICAL STORM CLAUDETTE.
DETAILS WILL FOLLOW IN THE 2 PM EDT INTERMEDIATE ADVISORY.
$$
FORECASTER ROBERTS/BRENNAN
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