Tropical Storm Bertha showed signs of increased organization Tuesday morning, according to the latest forecast discussion issued at 10:00 AM CDT by the National Hurricane Center in Miami.
Air Force Hurricane Hunters flying through the storm reported peak flight-level winds of 62 knots at the 850-millibar level, along with wind data from dropsondes that prompted forecasters to raise the storm’s official intensity to 50 knots. The central pressure dropped slightly to 995 millibars. Bertha’s low-level center, which had been fully exposed overnight, is now at least partially sheltered beneath a cold cloud canopy as new deep convection developed Tuesday morning.
The storm has been drifting north of its previously expected path, with an initial motion of north-northwestward at about 3 knots. Forecasters adjusted the near-term track northward to reflect this shift. Over the coming days, a mid-level ridge currently positioned near the Rockies is expected to push southeastward, which should steer Bertha to turn west-northwestward and eventually westward as it moves near or along the northern Gulf Coast through midweek.
Track forecast models are generally in agreement, though differences remain regarding how much the storm will interact with land in southeastern Louisiana and whether a new circulation center could redevelop offshore. The National Hurricane Center made little change to its track forecast beyond 24 hours, and the forecast continues to assume Bertha can hold together as a cohesive circulation while passing near or over the northern Gulf Coast.
Bertha remains an asymmetric storm, meaning the heaviest rain and strongest winds are concentrated to the south and east of the center. Strong northeasterly vertical wind shear is expected to persist through Tuesday night, limiting the storm’s ability to intensify further. Forecasters project gradual weakening over the next several days, though the degree of weakening will depend on how much land interaction occurs. There is also a chance Bertha could fall apart into a trough of low pressure even sooner than currently projected due to its disrupted structure and hostile surrounding conditions.
Several watch and warning changes were announced with this advisory. The Tropical Storm Warning was extended eastward across the Florida Panhandle and westward to the Terrebonne/Lafourche Parish line in Louisiana. A previously issued Storm Surge Watch has been replaced with a Coastal Flood Warning from the local forecast office. Minor to moderate coastal flooding is expected between the Mississippi/Alabama border and the Mouth of the Mississippi River, with water levels potentially rising up to 4 feet above ground level.
Key Messages from the National Hurricane Center:
Tropical storm conditions are expected along portions of the Gulf Coast from the Florida Panhandle westward to southeastern Louisiana later Tuesday and into Wednesday, where a Tropical Storm Warning is in effect. A Tropical Storm Watch covers Metro New Orleans and the southern Gulf Coast of Louisiana, where tropical storm conditions are possible.
A Coastal Flood Warning is in effect for the Mississippi and Louisiana coastlines, where moderate coastal flooding is anticipated.
Residents in other parts of Louisiana and Texas should continue monitoring the storm’s progress, as additional watches or warnings may be issued for those areas.
Isolated flash flooding will be possible through Friday along the Gulf Coast, stretching from western Florida through southern Louisiana and into the Upper Texas coast.
The forecast calls for the storm to dissipate by Saturday, July 26. This discussion was prepared by Forecaster Reinhart.
