SUMMARY OF 100 AM CDT
LOCATION…28.8N 88.0W
ABOUT 75 MI…120 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 115 MI…190 KM SSE OF BILOXI MISSISSIPPI
MAXIMUM SUSTAINED WINDS…90 MPH…150 KM/H
PRESENT MOVEMENT…W OR 270 DEGREES AT 3 MPH…6 KM/H
MINIMUM CENTRAL PRESSURE…986 MB…29.12 INCHES
WIND SPEED … EXTENT FROM CENTER
64 KT……. 40NE 20SE 0SW 15NW.
50 KT……. 70NE 40SE 0SW 30NW.
34 KT…….110NE 110SE 30SW 90NW.
12 FT SEAS..210NE 270SE 150SW 75NW.
FORECAST POSITIONS AND MAX WINDS
INIT 15/0300Z 28.9N 87.6W 85 KT 100 MPH
12H 15/1200Z 29.1N 88.1W 95 KT 110 MPH
24H 16/0000Z 29.6N 88.4W 90 KT 105 MPH
36H 16/1200Z 30.4N 88.3W 85 KT 100 MPH…INLAND
48H 17/0000Z 31.3N 87.4W 50 KT 60 MPH…INLAND
60H 17/1200Z 32.0N 86.3W 30 KT 35 MPH…INLAND
72H 18/0000Z 32.7N 84.9W 25 KT 30 MPH…INLAND
96H 19/0000Z 33.1N 82.3W 25 KT 30 MPH…POST-TROP/REMNT LOW
120H 20/0000Z…DISSIPATED
KEY MESSAGES
1. It is still too early to determine where Sally’s center will move onshore given the uncertainty in the timing and location of Sally’s northward turn near the central Gulf Coast. Users should not focus on the details of the official forecast track, since NHC’s average forecast error at 36 hours is around 60 miles, and dangerous storm surge, rainfall, and wind hazards will extend well away from the
center.
2. An extremely dangerous and life-threatening storm surge is expected for areas outside the southeastern Louisiana Hurricane and Storm Damage Risk Reduction System from Port Fourchon, Louisiana, to the Okaloosa/Walton County Line in the Florida Panhandle, where a Storm Surge Warning is in effect. Residents in these areas should follow any advice given by local officials.
3. Hurricane conditions are expected early Tuesday within the Hurricane Warning area in southeastern Louisiana and are expected by late Tuesday and Tuesday night within the Hurricane Warning area along the Mississippi and Alabama coastlines and the western Florida Panhandle. Tropical storm conditions are already occurring in some of these areas.
4. Life-threatening flash flooding is likely with Sally, as well as widespread minor to isolated major flooding on area rivers, along and just inland of the Central Gulf Coast. Significant flash and urban flooding, as well as widespread minor to moderate river flooding is likely across inland portions of Mississippi and Alabama and into northern Georgia, southeastern Tennessee and the western Carolinas through the week. Sally may continue to produce flash flooding across the Florida peninsula and prolong existing minor river flooding across west-central Florida through tonight.
WATCHES AND WARNINGS
A Storm Surge Warning is in effect for…
* Port Fourchon Louisiana to the Okaloosa/Walton County Line Florida
* Lake Pontchartrain, Lake Maurepas, and Lake Borgne
* Mobile Bay
A Hurricane Warning is in effect for…
* Grand Isle Louisiana to the Navarre Florida
* Lake Pontchartrain and Lake Maurepas including metropolitan New
Orleans
A Tropical Storm Warning is in effect for…
* East of of Navarre Florida to Indian Pass Florida
* West of Grand Isle to Morgan City Louisiana
DISCUSSION AND OUTLOOK
At 100 AM CDT (0600 UTC), the center of Hurricane Sally was located an Air Force Reserve reconnaissance aircraft and NOAA Doppler weather radars near latitude 28.8 North, longitude 88.0 West. Sally is moving slowly toward the west near 3 mph (6 km/h). A slow west-northwestward motion is expected to resume later this morning. A northward turn is expected this afternoon, followed by a slow north-northeastward to northeastward motion tonight and continuing through Wednesday night. On the forecast track, the center of Sally will move near the coast of southeastern Louisiana later today, and make landfall in the hurricane warning area tonight or Wednesday
morning.
Data from the reconnaissance aircraft indicate that maximum sustained winds have decreased to near 90 mph (150 km/h) with higher gusts. However, some re-strengthening is forecast early to occur later today, and Sally is expected to be a dangerous hurricane when it moves onshore along the north-central Gulf coast.
Hurricane-force winds extend outward up to 45 miles (75 km) from the center and tropical-storm-force winds extend outward up to 125 miles (205 km). A NOAA C-MAN observing station on Dauphin Island, Alabama, recently reported a wind gust of 51 mph (81 km/h), while a buoy just south of Dauphin Island recently reported a wind gust to 59 mph (94 km/h).
The estimated minimum central pressure based on data from the Air Force Hurricane Hunter aircraft is 986 mb (29.12 inches).
HAZARDS AFFECTING LAND
STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide…
Mouth of the Mississippi River to Dauphin Island including Lake Borgne…6-9 ft
Mobile Bay…6-9 ft
Lake Pontchartrain and Lake Maurepas…3-5 ft
Dauphin Island to AL/FL Border…4-7 ft
Port Fourchon to Mouth of the Mississippi River…2-4 ft
AL/FL Border to Okaloosa/Walton County Line including Pensacola Bay an Choctawhatchee Bay…2-4 ft
Okaloosa/Walton County Line to Chassahowitzka including Saint Andrew Bay…1-3 ft
Burns Point to Port Fourchon…1-2 ft
Overtopping of local levees outside of the Hurricane and Storm Damage Risk Reduction System is possible where local inundation values may be higher than those shown above.
The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and damaging waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.
WIND: Hurricane conditions are expected to begin within the hurricane warning area later today. Tropical storm conditions are occurring in portions of the warning area across Alabama, and these conditions will gradually spread westward this morning.
RAINFALL: Sally is expected to be a slow moving system as it approaches land, producing 8 to 16 inches of rainfall with isolated amounts of 24 inches over portions of the central Gulf Coast from the western Florida Panhandle to far southeastern Mississippi through the middle of the week. Life-threatening flash flooding is likely. In addition, this rainfall will likely lead to widespread minor to isolated major flooding on area rivers.
Sally is forecast to turn inland early Wednesday and track across the Southeast producing rainfall of 4 to 8 inches, with isolated maximum amounts of 12 inches, across portions of eastern Mississippi, central Alabama, northern Georgia, southeastern Tennessee, and the western Carolinas. Significant flash and urban flooding is likely, as well as widespread minor to moderate flooding on some rivers.
Outer bands of Sally could produce additional rainfall of 1 to 3 inches across the Florida peninsula through tonight. This rainfall may produce flash and urban flooding and prolong high flows and ongoing minor flooding on rivers across central Florida.
TORNADOES: A tornado or two will be possible this morning in coastal areas of the Florida Panhandle and Alabama. The threat for tornadoes should increase and slowly spread inland during the day today.
SURF: Swells from Sally will continue to affect the coast from the Florida Big Bend westward to southeastern Louisiana during the next couple of days. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.
TECHNICAL DISCUSSION
After rapidly strengthening earlier today, Sally’s intensity has plateaued for now. Both the NOAA and Air Force Hurricane Hunters have been investigating Sally this evening and they have found that the minimum pressure and winds have leveled off, and support perhaps a generous initial intensity of 85 kt. Doppler radar images and reports from both aircraft indicate the inner core of the hurricane is quite small and that the eyewall is open on the south side, likely due to some dry air that has wrapped into that portion of the circulation.
Aircraft and Doppler radar fixes indicate that Sally is moving very slowly to the west-northwest, with the latest initial motion estimated to be 300/3 kt. Weak high pressure ridging to the north and east of Sally is expected to cause the hurricane to continue to move slowly west-northwestward to northwestward for another 12 hours, bringing the center of the storm very near the northern Gulf coast. By Tuesday afternoon, when the hurricane will likely be just offshore, the models show the steering currents collapsing and Sally is likely to drift northward before finally turning northeastward ahead of a developing mid-level trough over the central U.S. by late Wednesday. There continues to be a significant amount of uncertainty on exactly where and when Sally turns northward and makes landfall, with model solutions ranging from a landfall on the Florida panhandle to a landfall in extreme southeastern Louisiana. It should be emphasized that it is always challenging to forecast the track of hurricanes in weak steering currents, and in Sally’s case the weak steering is occurring very near land. The new NHC track forecast is a little to the east of the previous one, trending toward the latest consensus aids.
Sally is still in generally favorable environmental conditions consisting of very warm SSTs and low wind shear. Since the hurricane will likely remain in those conditions through Tuesday morning, some strengthening seems likely in the short term. In 12 to 24 hours, when Sally is forecast to be very near the coast, a combination of an increase in westerly shear and cooler upwelled shelf waters should limit additional intensification. After the hurricane makes landfall, rapid weakening is forecast and Sally should become post-tropical in 3 to 4 days over the southeast U.S. The NHC intensity forecast lies at the high end of the model
guidance and is quite similar to the previous one.
Users are reminded to not focus on the exact forecast track or the specific timing and location of landfall. Hurricane-force winds, dangerous storm surge, and flooding rainfall will affect a large portion of the north-central Gulf Coast during the next few days.
