Because why not, right?
If there is anything the 2020 Atlantic Hurricane Season has taught me, it is that Professor Nicholson was right: “All the rules always apply… except when they don’t.”
Having back-to-back systems in the Gulf, when one of those systems was the first wave to enter the gulf, but the second wave to develop in the Gulf, while moving over the same – relative – waters as a system earlier in the season is against the rules!
Except when it is not. In 2020.
From the National Hurricane Center
SUMMARY OF 1000 PM CDT
LOCATION…26.8N 92.2W
ABOUT 235 MI…375 KM SE OF GALVESTON TEXAS
ABOUT 325 MI…525 KM E OF CORPUS CHRISTI TEXAS
MAXIMUM SUSTAINED WINDS…60 MPH…95 KM/H
PRESENT MOVEMENT…NNE OR 25 DEGREES AT 2 MPH…4 KM/H
MINIMUM CENTRAL PRESSURE…997 MB…29.44 INCHES
KEY MESSAGES
1. The expected slow motion of Beta has the potential to expand a long duration rainfall event from the Louisiana coast westward into southeast Texas on Sunday and northward into the Mid-South by mid next week. The potentially prolonged period of rainfall could cause flash, urban, and river flooding, especially where tide levels are above normal.
2. There is the danger of life-threatening storm surge near times of high tide from Sunday through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
3. Tropical storm force winds are expected to begin along portions of the northwestern Gulf Coast overnight within the tropical storm warning area in Louisiana and will spread westward to the Texas coast Sunday through Monday. Hurricane-force winds are possible along portions of the Texas coast late Monday and Monday night,
where a hurricane watch is in effect.
DISCUSSION AND OUTLOOK
At 1000 PM CDT (0300 UTC), the center of Tropical Storm Beta was located near latitude 26.8 North, longitude 92.2 West. Beta has drifted toward the north-northeast near 2 mph (4 km/h) since this morning. A slow motion toward the west-northwest is forecast to begin on Sunday, followed by a slow northwest to north motion
late Monday and Tuesday. On the forecast track, the center of Beta will move toward the coast of Texas and potentially move inland late Monday or early Tuesday.
Data from an Air Force Reserve Hurricane Hunter aircraft indicate that maximum sustained winds remain near 60 mph (95 km/h) with higher gusts. Little change in strength is forecast during the next couple of days before Beta reaches the Texas coast. Weakening is anticipated once Beta moves inland Monday night or Tuesday.
Tropical-storm-force winds extend outward up to 185 miles (295 km) mainly to the north of the center.
The estimated minimum central pressure is 997 mb (29.44 inches).
FORECAST POSITIONS AND MAX WINDS
INIT 20/0300Z 26.8N 92.2W 50 KT 60 MPH
12H 20/1200Z 27.1N 93.0W 50 KT 60 MPH
24H 21/0000Z 27.4N 94.1W 50 KT 60 MPH
36H 21/1200Z 27.9N 95.2W 50 KT 60 MPH
48H 22/0000Z 28.4N 96.0W 50 KT 60 MPH
60H 22/1200Z 28.9N 96.3W 40 KT 45 MPH…INLAND
72H 23/0000Z 29.3N 96.0W 35 KT 40 MPH…INLAND
96H 24/0000Z 30.2N 94.1W 30 KT 35 MPH…INLAND
120H 25/0000Z 31.4N 92.1W 25 KT 30 MPH…POST-TROP/INLAND
The rundown on Beta
Beta spent the last six to nine hours stationary in the Gulf. There is a fair amount of dry air around the center of the system due to the storm trying to grow within an area of SW-to-NE shear. This has created a lop-sided storm with a majority of the rain and wind on the NE side of the storm.
You can see a lot of the dry air on the lower-level water vapor imagery from the College of DuPage, above. The reddish orange areas are the area with drier air. And it nearly surrounds Beta on all side – except to the east and northeast.
That dry air persists through the mid-levels, shown below.
And it sticks around through the upper levels, too. Shown below.
The persistence of dry air through the column on the west and southwest side in particular is one reason that Tropical Storm Beta is no longer forecast to become a hurricane. While some of the model guidance continues to show the chance the shear subsides, there is no real indication – in real time – that there will be any change to the SW-to-NE shear.
The overall pattern itself is also affecting the track of Tropical Storm Beta.
The above image is a look at the mid-level water vapor imagery again, but this time with a few labels on there, too. The ridge of high pressure is highlighted by the “H” and Tropical Storm Beta is designated by the “B” on the map. The arrows indicate the (general) mid-level flow within the atmosphere.
In the mid-levels there isn’t as much pushing Beta back to the west at the moment. But the ridge of high pressure is keeping Beta from continuing to move northeast. The same ridge is bullying its way back to the west across parts of the southeast. And in response to that, Beta will also push back to the west a bit in the coming 24 to 36 hours.
The Sea-Level Pressure map from Pivotal Weather shows the ridge sagging south and then pushing east.
The two above maps are from the ECMWF model. While the model hasn’t fared very well recently – in general – it does seem to handle this situations reasonably well.
The Model Data
There seems to be a reasonable amount of consensus between the model guidance regarding Beta’s track and intensity – if you look at it ‘in general’ and not specifically.
And so long as you only look out 48 hours.
That is a look at the forecast track for Beta. During the next 48 hours it moves to the west-northwest and toward Texas. It makes landfall and bring a lot of heavy rain to the Texas Gulf Coast.
The intensity guidance suggests that eta will stay as a tropical storm. And make landfall as a tropical storm.
After it makes landfall it will weaken and fall apart bringing rain to Texas, Louisiana and eventually Arkansas and Mississippi.
The Bottom Line
For places along the northern Gulf Coast in Louisiana, Mississippi and Alabama, the main concern with this system will be heavy rain, some storm surge, and some gusty wind.
For Texas, the concern will be for very heavy rain, damaging wind, storm surge, and the potential for tornadoes and flash flooding.
I know both of those sound terribly “general” but when trying to forecast a meandering tropical storm in the Gulf, it is difficult to pin down specifics with any accuracy more than 48 hours out. Sally just did a great job proving that, I suppose.
The National Hurricane Center has laid out the threats specifically…
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…
Baffin Bay, TX to Cameron, LA including Baffin Bay, Corpus Christi Bay, Copano Bay, Aransas Bay, Matagorda Bay, Galveston Bay, Sabine Lake, Calcasieu Lake, San Antonio Bay…2-4 ft
Cameron, LA to Ocean Springs, MS including Vermilion Bay…1-3 ft
Lake Borgne, Lake Pontchartrain, and Lake Maurepas…1-3 ft
Mouth of the Rio Grande to Baffin Bay, TX…1-2 ft
The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and dangerous 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: Tropical storm conditions are expected in the tropical storm warning area by Sunday night. Hurricane conditions are possible within the hurricane watch area by late Monday or Monday night. Tropical storm conditions are possible within the tropical storm watch area along the southwestern Louisiana coast as early as
tonight, and are possible within the tropical storm watch area along the south Texas coast Sunday night or Monday.
RAINFALL: Beta has the potential to produce a long duration rainfall event along the western Gulf Coast. Today through Tuesday, Beta is expected to produce rainfall accumulations of 8 to 12 inches with isolated totals of 20 inches beginning Saturday across southern Louisiana and spreading into coastal Texas on Sunday. Flash and urban flooding is likely as well as minor river flooding. Isolated moderate flooding along the middle Texas coast is possible. Additional heavy rainfall amounts across the western Gulf Coast are possible through late week as Beta is expected to move slowly near the Texas coast.
SURF: Swells are increasing and reaching the coast of Texas and the Gulf Coast of Mexico, generated by a combination of Beta and a cold front entering the northern Gulf of Mexico. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.
