The National Hurricane Center issued its latest forecast discussion for Tropical Storm Bertha at 4:00 AM CDT Tuesday, July 21, 2026, as the storm continues to churn in the Gulf of Mexico.
Before departing the storm, an Air Force Reserve reconnaissance aircraft recorded a central pressure of 998 millibars and peak flight-level winds of 46 knots. An earlier satellite-based wind measurement pass at 3:22 AM UTC also detected peak surface winds of 43 knots on the storm’s southern side — an area the aircraft had not fully covered. Based on this combined data, Bertha’s intensity was raised to 45 knots on an intermediate advisory.
However, data gathered during an earlier mission by the NOAA-P3 aircraft showed that Bertha’s circulation remains tilted southward with altitude. Satellite imagery also reveals that the storm’s low-level center has become largely exposed north of the heaviest thunderstorm activity, a result of increasing vertical wind shear. As a result, the official intensity remains at 45 knots, or 50 mph, for this advisory cycle.
Satellite tracking of Bertha’s low-level rotation indicates the storm has resumed a slow northwestward drift at about 4 knots. The broader weather pattern is gradually shifting as a mid-level ridge over the Rocky Mountains slides toward the southeast while a longwave trough remains parked over the northeastern United States. This setup is expected to steer Bertha slowly northwestward or west-northwestward before the storm turns more westward by midweek.
Forecasters noted a complicating factor: Bertha is expected to become heavily impacted by wind shear within 24 to 48 hours. Bursts of deep thunderstorm activity on the storm’s southwestern side could pull the center off its expected steering track. The latest NHC track forecast is positioned slightly north of the previous forecast for the first 24 to 36 hours, then returns close to the earlier track — roughly splitting the difference between the most recent Google DeepMind ensemble mean and TVCN model solutions. Forecasters cautioned that the track beyond 48 hours assumes Bertha holds together as a tropical cyclone, though several models suggest it could fall apart into a trough of low pressure.
Wind shear from the northeast is already measured near 25 knots, and it is expected to increase over the next 24 hours. While ocean temperatures are warm enough to support the storm, dry air being drawn into Bertha’s center by the shear could disrupt the storm’s internal structure. The NHC intensity forecast calls for only a slight additional strengthening today before the shear becomes too strong to allow further development. Most guidance indicates Bertha will begin slowly weakening after about 12 hours, and the latest NHC forecast reflects that expectation.
As Bertha approaches the Louisiana Gulf Coast, some forecast models show the storm’s circulation becoming stretched and elongated due to a combination of land interaction and intense wind shear. While the NHC’s current forecast keeps Bertha as a tropical cyclone along the Gulf Coast through 72 hours, forecasters acknowledged another possibility — that the system could fall apart into a trough before then. The NHC intensity forecast sits roughly in the middle of the range of available guidance.
Due to the strong wind shear, Bertha is expected to have a very lopsided structure, with the heaviest rainfall and strongest winds concentrated on the southern side of the storm center.
Key Messages from the National Hurricane Center:
1. Tropical storm conditions are expected to affect portions of the Gulf Coast from Alabama westward to southeastern Louisiana tonight and Wednesday. A Tropical Storm Warning is in effect for those areas. A Tropical Storm Watch is in effect for parts of the Florida Panhandle, the Metro New Orleans area, and the southern Gulf Coast of Louisiana.
2. A Storm Surge Watch is in effect for the Alabama, Mississippi, and southeastern Louisiana coasts, where a life-threatening surge of water is possible.
3. Residents in other parts of Louisiana and Texas should keep a close eye on Bertha’s progress, as additional watches or warnings may be issued for those areas later today.
4. Flash flooding will be possible through Thursday along the Gulf Coast and nearby inland areas from the Florida Big Bend region to southern Louisiana. Isolated flash flooding could also occur westward into parts of the Texas coast later in the week.
The forecast was issued by NHC Forecaster Papin.
