Tropical Storm Bertha - 10am Friday Discussion

By: National Hurricane Center
By: National Hurricane Center

TROPICAL STORM BERTHA DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014
1100 AM AST FRI AUG 01 2014

Bertha is disorganized this morning. While satellite imagery shows
a well-defined low-cloud swirl exposed just west of the main
convective mass, reports from an Air Force Reserve Hurricane Hunter
Aircraft show that the wind field more resembles that of an open
wave. The aircraft did report 56 kt winds at 1500 feet to the
east-northeast of the center, along with an area of SFMR surface
winds in excess of 40 kt. Based on this, the initial intensity is
increased to 45 kt.

The initial motion is now 295/18, and over the past few hours
Bertha may be moving even faster. The cyclone is currently being
steered by the flow around the Atlantic subtropical ridge and this
should continue for the next 48 hours or so. After that time, the
cyclone is expected to turn northward into a break in the ridge
caused by a deep-layer trough over the eastern United States. This
should be followed by recurvature into the westerlies over the
Atlantic north of Bermuda. The track guidance remains in good
agreement with this scenario, and it has changed little since the
previous advisory. The new forecast track is therefore an update of
the previous forecast.

Bertha is currently experiencing about 15-20 kt of southwesterly
vertical wind shear. and water vapor imagery shows dry
mid-/upper-level air near the storm. The forecast track calls for
Bertha to interact with one or two upper-level troughs during the
next 48-72 hours, which should cause some shear and dry air
entrainment to continue. This, combined with the current lack
of organization, suggests little change in strength should
occur during the next 48 hours or so. After that time, Bertha is
expected to move into an environment of less shear and greater
moisture. The intensity forecast calls for modest strengthening
during that time, but it is weaker than all of the guidance except
the Florida State Superensemble. An alternative scenario is that a
combination of shear, dry air entrainment, and land interaction
causes Bertha to degenerate to a tropical wave during the next 48
hours, followed by possible regeneration in the 72-120 hours when
the system reaches the more favorable environment.


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