Hurricane Irene Advisory, August 24, 2011 (2 PM EDT)

Miami, Florida—(ENEWSPF)—August 24, 2011 – UPDATE 2 PM EDT eNews Park Forest continues to post raw data regarding hurricane Irene to keep the public informed as quickly as possible.


Irene has continued to strengthen this morning. The eye has become more distinct in satellite imagery and it is surrounded by cloud tops colder than -70 degrees celsius. Both air force and NOAA hurricane hunter aircraft have been investigating Irene this morning. The air force plane measured a peak 700 mb flight-level wind of 112 kt just before 1200 UTC…and this supported the upgrade to a 100-kt category three hurricane at that time. Since that time the noaa aircraft reported 115 kt at 750 mb. The pressure has remained around 956 mb…and the initial intensity estimate remains 100 kt.

The outflow has become well established over the hurricane and Irene will be moving over sea surface temperatures of around 29 degrees celsius during the next 24-36 hours. These environmental factors favor additional intensification and the new intensity forecast calls for Irene to reach category four strength within 24 hours. After that time…some fluctuations in wind speeds are likely due to eyewall replacements. The uw-cimss objective secondary eyewall formation technique shows a very high likelihood of that occurring during the next 48 hours. Southwesterly shear is expected to gradually increase and the hurricane will be moving over significantly colder waters by 96 hours. This should result in gradual weakening…however Irene is forecast to remain a large and powerful hurricane during the next 5 days.

Aircraft fixes during the past 12 hours indicate that Irene has made the expected turn toward the northwest…with an initial motion of 305/10. There is no change to the track forecast reasoning and the model guidance remains in excellent agreement for the first 2-3 days. After that time…there is some question as to whether or not Irene continues on a north-northeast heading or turns back toward the north ahead of a mid-latitude trough approaching the great lakes region. The GFDL and HWRF models remain along the west side of the guidance envelope and show a track over or very close to the mid-Atlantic coast. The UKMET and NOGAPS are along the eastern side and keep the core of the hurricane well offshore. Given the typical model and official track errors…both scenarios are viable options at this time…and users are once again reminded not to focus on specific forecast points three to five days downstream. The TVCA consensus and the experimental hurricane forecast improvement project consensus were relatively close to the previous NHC forecast. The updated NHC track has been nudged eastward at 96 and 120 hours and lies between those two consensus aids.



Status Update as of August 23, 2011 – 2 PM EDT

Status Update as of August 23, 2011 – 5 PM EDT

Status Update as of August 23, 2011 – 8 PM EDT-

Status Update as of August 23, 2011 – 11 PM EDT-

Status Update as of August 24, 2011 – 2 AM EDT-

Status Update as of August 24, 2011 – 5 AM EDT –

Status Update as of August 24, 2011 – 11 AM EDT –

Coastal Watches/Warnings and 3-Day Forecast Cone for Storm Center

Click image to zoom in – Download GIS data 
Other images: 3-Day track on – 5-Day track on – 5-Day track off
 [Image of 3-day forecast and coastal areas under a warning or a watch]
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About this product:

This graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line, when selected, and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. The dot indicating the forecast center location will be black if the cyclone is forecast to be tropical and will be white with a black outline if the cyclone is forecast to be extratropical. If only an L is displayed, then the system is forecast to be a remnant low. The letter inside the dot indicates the NHC’s forecast intensity for that time: 

D: Tropical Depression – wind speed less than 39 MPH
S: Tropical Storm – wind speed between 39 MPH and 73 MPH
H: Hurricane – wind speed between 74 MPH and 110 MPH
M: Major Hurricane – wind speed greater than 110 MPH

NHC tropical cyclone forecast tracks can be in error. This forecast uncertainty is conveyed by the track forecast "cone", the solid white and stippled white areas in the graphic. The solid white area depicts the track forecast uncertainty for days 1-3 of the forecast, while the stippled area depicts the uncertainty on days 4-5. Historical data indicate that the entire 5-day path of the center of the tropical cyclone will remain within the cone about 60-70% of the time. To form the cone, a set of imaginary circles are placed along the forecast track at the 12, 24, 36, 48, 72, 96, and 120 h positions, where the size of each circle is set so that it encloses 67% of the previous five years official forecast errors. The cone is then formed by smoothly connecting the area swept out by the set of circles.

There is also uncertainty in the NHC intensity forecasts. The Maximum 1-minute Wind Speed Probability Table provides intensity forecast and uncertainty information.

It is also important to realize that a tropical cyclone is not a point. Their effects can span many hundreds of miles from the center. The area experiencing hurricane force (one-minute average wind speeds of at least 74 mph) and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can extend well beyond the white areas shown enclosing the most likely track area of the center. The distribution of hurricane and tropical storm force winds in this tropical cyclone can be seen in the Wind History graphic linked above.

Considering the combined forecast uncertainties in track, intensity, and size, the chances that any particular location will experience winds of 34 kt (tropical storm force), 50 kt, or 64 kt (hurricane force) from this tropical cyclone are presented in tabular form for selected locations and forecast positions. This information is also presented in graphical form for the 34 kt50 kt, and 64 kt thresholds.