000
WTNT43 KNHC 030245
TCDAT3

TROPICAL STORM BERTHA DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL032014
1100 PM AST SAT AUG 02 2014

While there has been some increase in the coverage of cold
convective tops associated with Bertha this evening, the cyclone
remains disorganized. Surface observations from the Dominican
Republic have not definitively shown a closed circulation, and it is
possible that what surface circulation there was has been disrupted
by land interaction. We will maintain Bertha as a tropical cyclone
for now, but advisories could be discontinued on Sunday if the
organization of the system does not improve. The initial intensity
remains 40 kt based on rain-adjusted SFMR winds reported by the Air
Force Hurricane Hunter aircraft well east of the center prior to 00
UTC.

The initial motion estimate of 310/19 is based on a blend of the
latest satellite imagery and continuity. The synoptic reasoning
for the track forecast remains unchanged. Bertha will continue
moving northwestward along the southwestern periphery of the
subtropical ridge tonight and Sunday. Then the cyclone will
turn northward on Monday between the ridge and a deep-layer trough
over the southeastern United States, followed by a northeastward
acceleration into the mid-latitude westerlies. The track model
guidance remains in good agreement on this general scenario.
However, the models have shifted to the left this cycle at 48 hours
and beyond, showing a more gradual recurvature. The NHC track
through 36 hours is largely an update of the previous one. After
that time, the official forecast has been adjusted to the left of
the previous one, but now lies along the right side of the guidance
envelope.

There continue to be three possible scenarios for the intensity of
Bertha. The official forecast assumes that Bertha will survive its
current lack of structure, land interaction, shear, and dry air
entrainment long enough to reach a more favorable environment in
24-36 hours. At that point, the environment would likely allow for
intensification until extratropical transition begins after 96
hours. The new NHC intensity forecast is similar to the previous one
and calls for Bertha to become a hurricane in 4 days, and is close
to the latest IVCN intensity consensus. An alternate scenario is
that Bertha degenerates to a tropical wave in the next 12 to 24
hours, with possible regeneration later when the system reaches the
more favorable environment. A third possibility involves a trough of
low pressure currently situated over the central and northwestern
Bahamas. The 1200 UTC runs of the UKMET and NAVGEM forecast the
low to absorb Bertha in 48 hours or so, while the latest GFS and
ECMWF runs keep this system weaker and maintain Bertha through the
forecast period. Later model runs should help refine the likelihood
of this scenario.

FORECAST POSITIONS AND MAX WINDS

INIT  03/0300Z 19.5N  69.7W   40 KT  45 MPH
 12H  03/1200Z 21.5N  71.8W   40 KT  45 MPH
 24H  04/0000Z 24.1N  73.8W   45 KT  50 MPH
 36H  04/1200Z 27.2N  74.4W   45 KT  50 MPH
 48H  05/0000Z 30.4N  73.8W   50 KT  60 MPH
 72H  06/0000Z 36.0N  69.0W   60 KT  70 MPH
 96H  07/0000Z 41.0N  60.0W   65 KT  75 MPH
120H  08/0000Z 45.0N  50.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brennan