For all of the shifts of the cone back and forth, the timing for landfall for Sally is still on track. Tuesday. At some point.
This is turning into quite the difficult system to forecast due to the very subtle forces acting upon it. The timeline for slowing and turning that will occur during the day today and into tomorrow are not fully known yet. And because of that, the threats for specific places are still a bit up the in air.
But that will be discussed further in my next update. For now, here is the latest from the national Hurricane Center…
SUMMARY OF 700 AM CDT
LOCATION…28.4N 87.4W
ABOUT 115 MI…185 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 165 MI…265 KM SE OF BILOXI MISSISSIPPI
MAXIMUM SUSTAINED WINDS…65 MPH…100 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 8 MPH…13 KM/H
MINIMUM CENTRAL PRESSURE…994 MB…29.35 INCHES
WATCHES AND WARNINGS
A Storm Surge Warning is in effect for…
* Port Fourchon Louisiana to the Alabama/Florida Border
* Lake Pontchartrain, Lake Maurepas, and Lake Borgne
* Mobile Bay
A Hurricane Warning is in effect for…
* Morgan City Louisiana to the Mississippi/Alabama Border
* Lake Pontchartrain and Lake Maurepas including metropolitan New
Orleans
A Tropical Storm Warning is in effect for…
* Mississippi/Alabama Border to Indian Pass Florida
* Intracoastal City Louisiana to west of Morgan City
A Hurricane Watch is in effect for…
* Mississippi/Alabama Border to the Alabama/Florida Border
A Tropical Storm Watch is in effect for…
* Indian Pass to Ochlockonee River Florida
DISCUSSION AND OUTLOOK
At 700 AM CDT (1200 UTC), the center of Tropical Storm Sally was located near latitude 28.4 North, longitude 87.4 West. Sally is moving toward the west-northwest near 8 mph (13 km/h). This general motion is expected today, followed by a decrease in forward speed and a turn to the northwest tonight and a northward turn sometime on Tuesday. On the forecast track, the center of Sally will move over the north-central Gulf of Mexico today, approach southeastern Louisiana this afternoon, and make landfall in the hurricane warning area on Tuesday. Afterward, Sally is expected to move slowly north-northeastward near the northern Gulf Coast through Wednesday.
Maximum sustained winds have increased to near 65 mph (100 km/h) with higher gusts. Strengthening is expected over the next day or so, and Sally is forecast to become a hurricane by tonight, with additional strengthening possible before the center crosses the northern Gulf Coast.
Tropical-storm-force winds extend outward up to 125 miles (205 km) from the center. NOAA buoy 42039, located about 130 miles (215 km) south-southeast of Pensacola, Florida, recently reported peak sustained winds of 49 mph (79 km/h) and a gust to 58 mph (94 km/h).
The estimated minimum central pressure is 994 mb (29.35 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 Ocean Springs including Lake Borgne…7-11 ft
Ocean Springs to MS/AL Border…5-8 ft
MS/AL Border to AL/FL Border including Mobile Bay…4-6 ft
Lake Pontchartrain and Lake Maurepas…4-6 ft
Port Fourchon to Mouth of the Mississippi River…3-5 ft
AL/FL Border to Navarre including Pensacola Bay…2-4 ft
Navarre to Chassahowitzka including Choctawhatchee Bay and Saint
Andrew Bay…1-3 ft
Burns Point to Port Fourchon…1-3 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 within the hurricane warning area starting late today. Tropical storm conditions are possible within the watch area during the next few hours, and are expected within the warning area beginning 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 southeast Louisiana through the middle of the week. Life-threatening flash flooding is possible. In addition, this rainfall will likely lead to widespread minor to isolated major flooding on area rivers.
Sally is forecast to move farther inland early Wednesday and track into the Southeast with rainfall of 6 to 12 inches possible across portions of inland southeast Mississippi and Alabama. Significant flash and urban flooding is likely, as well as widespread minor to moderate flooding on some rivers.
Further heavy rain is then anticipated across portions of eastern Tennessee, northern Georgia and western North Carolina Thursday into Friday. Flash, urban, and minor river flooding is possible across this region.
Outer bands of Sally are expected to produce additional rainfall of 1 to 3 inches across the Florida peninsula today. 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 may occur this afternoon through Tuesday over coastal areas of the Florida Panhandle, Mississippi, Alabama, and extreme southeastern Louisiana.
SURF: Swells from Sally will continue to affect areas from the west coast of the Florida peninsula westward through the coast of 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
The organization of Sally hasn’t changed much during the past several hours. While there was a large burst of convection earlier, it did not translate into any intensification, with flight-level reconnaissance and SFMR surface winds still supporting an initial wind speed of 50 kt. The Air Force Reserve plane did find that the size of tropical-storm-force wind field has notable grown to the north and northwest of the center. The storm still has time to intensify under a seemingly conducive environment during the next 24-36 hours, before a combination of increasing westerly wind shear and land interaction will probably slow the intensification rate. Model guidance has come down slightly from 6 hours ago, but it has been inconsistent from cycle to cycle. The new intensity forecast is similar to the previous one and lies near the top end of the guidance envelope.
The reconnaissance plane showed that Sally took a westward turn during the past several hours, but the storm appears to have a resumed a more west-northwestward motion recently. Weak ridging over the southern United States is expected to cause this general motion with a decrease in forward speed today before the storm slowly turns northward sometime on Tuesday due to an approaching trough. Guidance is not in good agreement on exactly when that turn occurs, causing a good deal of spread for a relatively short-range forecast. The track forecast has been shifted to the left in the short-term primarily due to the initial position, showing a track near or over extreme southeastern Louisiana, then is the near the previous one at its final landfall. The bottom line continues to be that Sally is expected to be a dangerous slow-moving hurricane near the coast of southeastern Louisiana, Mississippi and Alabama during the next 2-3 days.
KEY MESSAGES
1. It is 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 48 hours is around 80 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 Alabama/Florida border, 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 by late today within portions of the Hurricane Warning area from Morgan City, Louisiana, to the Mississippi/Alabama border, including Metropolitan New Orleans, with tropical storm conditions likely to begin by late this morning. Preparations should be rushed to completion in those areas.
4. Sally may continue to produce flash flooding across the Florida peninsula and prolong existing minor river flooding across west-central Florida through today. Life-threatening flash flooding is possible and widespread minor to isolated major flooding on area rivers is likely 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 Mississippi and Alabama through the middle of the week. Flooding impacts are expected to spread farther across the Southeast through the week.
FORECAST POSITIONS AND MAX WINDS
INIT 14/0900Z 28.3N 87.3W 50 KT 60 MPH
12H 14/1800Z 28.6N 88.1W 60 KT 70 MPH
24H 15/0600Z 29.1N 88.9W 70 KT 80 MPH
36H 15/1800Z 29.7N 89.3W 75 KT 85 MPH
48H 16/0600Z 30.6N 89.2W 60 KT 70 MPH…INLAND
60H 16/1800Z 31.6N 88.6W 30 KT 35 MPH…INLAND
72H 17/0600Z 32.5N 87.6W 25 KT 30 MPH…INLAND
96H 18/0600Z 33.5N 85.0W 20 KT 25 MPH…POST-TROP/REMNT LOW
120H 19/0600Z…DISSIPATED
