Hurricane Irene Intermediate Advisory From the National Hurricane Center Miami, Florida, August 26, 2011 (2 PM EDT)

Miami, Florida—(ENEWSPF)—August 26, 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 TAKING AIM AT THE EAST COAST OF THE UNITED STATES…

Data from NOAA and air force reserve hurricane hunter aircraft suggest the intensity of Irene is slightly lower. Although peak flight-level winds at 700 mb were 111 kt…SFMR and dropsonde observations indicated that a higher-than-typical reduction of the wind from flight-level to the surface applies…and the initial intensity is reduced to 90 kt. Given the current storm structure and predicted environmental factors…little change in strength is expected during the next 12 to 24 hours. After passing North Carolina…southwesterly shear is forecast to increase and sea surface temperatures will be gradually decreasing. This should result in gradual weakening of the cyclone as it moves near the Mid-Atlantic coast. However…Irene is expected to remain a large and dangerous tropical cyclone and has the potential to produce damaging winds…storm surge flooding…and extremely heavy rains almost anywhere from eastern North Carolina northward through New England.

Irene is moving northward or 360/12 kt. There has been no change to the forecast philosophy. Irene should move northward for another 12 hours or so….followed by a gradual turn to the north-northeast as it moves along the east coast of the United States. The track guidance is in good agreement on this scenario and no change was required from the previous NHC forecast through 72 hours. Only a small adjustment was made to the hurricane warning on this advisory. It is anticipated that the hurricane warning and watch areas will need to be extended northward along the U.S. east coast this afternoon.

FORECAST POSITIONS AND MAX WINDS

 INIT  26/1500Z 30.7N  77.3W   90 KT 105 MPH  12H  27/0000Z 32.2N  77.1W   90 KT 105 MPH  24H  27/1200Z 34.4N  76.6W   90 KT 105 MPH  36H  28/0000Z 36.7N  75.6W   85 KT 100 MPH  48H  28/1200Z 39.5N  74.1W   75 KT  85 MPH  72H  29/1200Z 47.5N  68.8W   55 KT  65 MPH...INLAND  96H  30/1200Z 55.5N  57.0W   40 KT  45 MPH...POST-TROP/EXTRATROP 120H  31/1200Z 59.0N  38.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

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

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Other images: 3-Day track on – 5-Day track on – 5-Day track off
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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 kt, 50 kt, and 64 kt thresholds.

Source: nhc.noaa.gov

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