704
WTNT42 KNHC 220845
TCDAT2

Tropical Storm Bertha Discussion Number 12
NWS National Hurricane Center Miami FL AL022026
400 AM CDT Wed Jul 22 2026

Since the previous advisory, Bertha's appearance has gone downhill,
with the deepest convective activity separating further south from
the low-level circulation which is now mostly exposed offshore of
the coast of Alabama. An Air Force Reserve reconnaissance mission in completing its last pass through Bertha found peak flight level
winds of 47 kt, and a minimum central pressure that has risen
slightly to 998 mb. While a dropsonde launched in the southeast side
of the circulation did find a 500 m layer mean wind of 54 kt, a
standard reduction from this layer still yields a slightly reduced
intensity of 45 kt for this advisory. Given Bertha's current
appearance, this could be generous.

A combination of aircraft, radar, and satellite fixes indicate that
Bertha is moving due west at 270/4 kt. The primary steering feature
resulting in Bertha's short-term motion is a mid-level ridge that
has been sliding slowly eastward from the southern Plains to become
positioned north of the tropical storm. This evolution should result
in Bertha maintaining a westward heading over the next 24-36 h,
though continued sheared bursts of deep convection forming south of
the center may still act to tug it south of this steering motion.
One thing worth keeping an eye on is the possibility a new center
may try to reform under these convective bursts in the 24-36 h
time-frame like what is depicted in some of the hurricane-regional
models, though this is not reflected in the NHC track forecast at
this time. The latest track forecast is nearly on top of the
previous, but just a little faster, roughly in between the latest
Google DeepMind (GDMI) and HFIP Corrected Consensus (HCCA)
solutions.

Bertha's appearance, the presence of 25-30 kt of northeasterly
vertical wind shear, and land interaction are likely to result in
slow weakening over the next 24 h or so. After that point, Bertha's
future likely depends on if the circulation remains along the Gulf
coast, or if it attempts to reform further south under the
convective bursts in the northwestern portion of the Gulf. In the
former scenario, Bertha's circulation could open up into a trough
like in the 00z ECMWF and HWRF solutions. In the latter case, a new
center could reform further south and attempt to reorganize like in
the HAFS and GFS solutions. For what it's worth, the Google DeepMind
ensemble seems to be roughly split between these two possibilities.
For now, the NHC intensity forecast does not stray far from the
previous one, showing slow weakening before Bertha moves fully
inland over Texas in 48 h, becoming post-tropical and dissipating
shortly thereafter. This intensity forecast is roughly in the middle
of the guidance envelope and closest to the GDMI solution.


Key Messages:

1. Tropical storm conditions are expected to continue along portions
of the northern Gulf Coast from the western Florida Panhandle to
southeastern Louisiana, including the Metro New Orleans area,
through tonight. Tropical storm conditions are possible for portions
of the southwestern coast of Louisiana tonight into Thursday.

2. A Coastal Flood Warning is in effect for the Mississippi and
Louisiana coastlines, where moderate coastal flooding is expected.

3. Interests elsewhere in extreme western Louisiana and along the
Upper Texas Coast should monitor the progress of this system, as
additional watches or warnings could be required for portions of
that area later today.

4. Isolated areas of flash flooding remain possible through early
Friday along the central to the western Gulf Coast from western
Florida to southern Texas.


FORECAST POSITIONS AND MAX WINDS

INIT 22/0900Z 29.4N 88.3W 45 KT 50 MPH
12H 22/1800Z 29.4N 89.4W 40 KT 45 MPH...ON THE COAST
24H 23/0600Z 29.3N 91.4W 35 KT 40 MPH...ON THE COAST
36H 23/1800Z 29.3N 93.9W 35 KT 40 MPH...OVER WATER
48H 24/0600Z 29.5N 96.3W 30 KT 35 MPH...POST-TROP/INLAND
60H 24/1800Z...DISSIPATED

$$
Forecaster Papin


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