Hurricane Irene Approaches the Bahamas
As of 2AM EDT, Hurricane Irene was located at 21.3N, 72.6W, 400 miles southeast of Nassau. It was moving west-northwest at 9 mph with maximum sustained winds of 100 mph, making it a Category 2 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 966 mb. Hurricane warnings have been issued for all of the Bahamas and the Turks and Caicos Islands. Tropical storm warnings are in effect for Haiti from Le Mole St. Nicholas to the Dominican Republic border.
Satellite Views
Figure 1 shows that Irene has a large eye visible in infrared imagery, (26 miles across accoring to a report from the Hurricane Hunters at 130AM) with well-defined outflow cirrus bands. Tuesday evening, TRMM, NASA's tropical research satellite, flew directly overhead Irene, getting a radar scan of the storm using it's downward pointing radar, shown in Figure 2. It is immediately apparent that Irene has well-developed bands of rain showers, with strong storms present in the eyewall.
Figure 1 IR satellite view of Irene taken at 113AM EDT, August 23, 2011
Figure 2 TRMM radar overpass of Irene at 713PM EDT, August 22, 2011. Image courtesy of the Naval Research Laboratory
Track Forecast
Irene is forecast to move to the northwest, passing over all of the Bahamas by Thursday evening, then curving to the north. Irene then makes landfall in the US near or at the Outer Banks Saturday afternoon, then traveling along the mid-Atlantic coastline of the US. After Saturday, Irene may pose a threat to Long Island and the New England coastline. However, NHC is quick to remind us that the average forecast error for day 4 is 200 miles, so don't stop your hurricane preparations if you aren't in the immediate area of landfall. It is also important to note that the windfield of Irene is expected to be large, affecting areas distant from the immediate track of Irene's center. Tropical storm forces winds are expected to be found out to at least 150 miles away from Irene's center on Friday afternoon.
NHC is forecasting for Irene to become a major hurricane (winds faster than 110 mph), within 24 hours.
Figure 3 Official track forecast of Irene at 2AM EDT.
Forecast models and adaptive observations
The different forecast models are in fairly good agreement about Irene's track through the Bahamas and along the east coast of the US. The GFDL, a dynamical hurricane forecasting model, which had been a western outlier from the other models is now agreeing with them. When a set of weather models using slighly different initial views of the atmosphere and slightly different ways of simulating how the atmosphere works all agree on a forecast, then meteorlogists tend to believe that the forecast is more likely to occur. The 00Z GFS and ECMWF (wind swath shown in Figure 4) forecasts are nearly identical, which furthur boosts forecaster confidence.
In the 11PM forecast discussion, the NHC forecaster praises the NOAA Gulfstream IV (aka Gonzo) for providing infomation about the atmosphere around Irene that will influence it's track. Looking at the plan of the day valid for today, it will be a busy day for airborne reconnaissance. Three flights for the Air Force hurricane hunters, two flights for the Gulfstream IV, and two flights for NOAA 42, a WP-3D (aka Kermit).
Figure 4 Plot of the maximum sustained winds in mph over the next week from the 00Z ECMWF forecast.
Impacts
In the immediate future, Irene will have a significant impact on the Bahamas and surrounding islands. Hurricane force winds are ongoing over the Turks and Caicos islands and southeastern Bahamas. These locations can expect storm surges that are 5-8 feet above tide levels. The northwestern Bahamas can expect hurricane force winds Thursday, and storm surges that are 7-11 feet above tide levels. The Turks and Caicos islands and all of the Bahamas can expect 6-12 inches of rain over the next two days.
I still think people living along the east coast of the US should closely monitor Irene and review their hurricane preparations. Irene will be a large storm, impacting areas far from the storm center track.
Dr. Masters will have a new blog entry this morning, and Angela Fritz will be covering the afternoon. I'll be back on third shift tonight.
Thanks for reading,
Dr. Rob Carver
Reader Comments
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There is just one thing I see in the NHC tracking map that just the Bahamas are under a warning but why not for east FL since the storm is so large or S/NC or a TS watch at least?
Thought that looked wrong... Bob was '91
That I understand... mine all came down with Charlie and I never replaced them.I hear lots of tree cutting going on in my neighborhood today and we're in the middle of the state!!!! Guess they're still a little worried.
"Keep in mind the worst ne US storms stay offshore till New england"
wind speeds away from eye
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With that said.
Delays to the graduated turn NNW @ 2512Z would bring her closer to the coast and running towards 78W.
Transmitted: 24th day of the month at 17:28Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Storm Number & Year: 09L in 2011
Storm Name: Irene (flight in the North Atlantic basin)
Mission Number: 14
Observation Number: 21
A. Time of Center Fix: 24th day of the month at 17:03:20Z
B. Center Fix Coordinates: 22°33'N 74°09'W (22.55N 74.15W)
B. Center Fix Location: 205 miles (330 km) to the NNE (32°) from Santiago de Cuba, Cuba.
C. Minimum Height at Standard Level: 2,697m (8,848ft) at 700mb
D & E. Estimated (by SFMR or visually) Maximum Surface Wind: Not Available
F. Maximum Flight Level Wind Inbound: From 34° at 80kts (From between the NNE and NE at ~ 92.1mph)
G. Location of Maximum Flight Level Wind Inbound: 13 nautical miles (15 statute miles) to the NW (315°) of center fix
H. Minimum Sea Level Pressure: 954mb (28.17 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 10°C (50°F) at a pressure alt. of 3,050m (10,007ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 18°C (64°F) at a pressure alt. of 3,037m (9,964ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 11°C (52°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Open in the southwest
M. Eye Shape & Diameter: Circular with a diameter of 16 nautical miles (18 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Levels (sfc and flt lvl centers are within 5nm of each other): Surface and 700mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 1 nautical mile
Remarks Section:
Maximum Flight Level Wind: 116kts (~ 133.5mph) in the northeast quadrant at 14:52:30Z
Maximum Flight Level Wind Outbound: 106kts (~ 122.0mph) in the southeast quadrant at 17:12:00Z
Maximum Flight Level Temp: 20°C (68°F) which was observed 9 nautical miles to the
looking at 120-125mph at the 2 pm advisory imo.
Tropical Cyclone Outlook
2:00 PM EDT August 24 2011
=================================
Showers and thunderstorms have become more concentrated near an area of low pressure located a couple hundred miles southwest of the Cape Verde Islands. Environmental conditions appear generally favorable for the development of a tropical depression during the next day or two
Tropical Cyclone Formation Potential
====================================
There is a HIGH chance of this disturbance to form into a tropical cyclone within the next 48 hours
Actually they said this many times in 2008. They also emphasized that NO ONE would be coming to save you so don't bother calling 911.
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