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000
WTNT45 KNHC 280850
TCDAT5

TROPICAL STORM ERIKA DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052015
500 AM AST FRI AUG 28 2015

Erika remains disorganized, with the deep convection decreasing in
coverage and intensity to the east of the estimated center position
during the past few hours. Despite this, the cyclone continues to
produce a large area of tropical storm force winds east of the
center, and the initial intensity of 45 kt and central pressure of
1006 mb are based on recent surface observations from Puerto Rico.

The center of Erika continues to be rather disorganized, and the
initial position and motion of 290/15 are based on a blend of
satellite imagery and continuity. While the overall track forecast
reasoning has not changed, the initial position and motion and
an overall weaker depiction of Erika in the global models have
resulted in a leftward shift in the track guidance this cycle and
an increase in the forward speed. A west-northwestward motion is
expected for the first couple of days as Erika moves around the
southern periphery of the subtropical ridge to the north. After that
time, a northwestward and northward turn and a decrease in forward
speed are forecast as Erika moves around the western edge of the
ridge. The new NHC track is to the left of and faster than the
previous advisory and is near the multi model consensus through 36
hours. After that time, the NHC track is east of almost all the
guidance out of respect to continuity. Needless to say, confidence
in the track forecast, especially after 48 hours, remains very low
given that the details of the track depend on how much the cyclone
recovers from the shear and the effects of land interaction in the
short term.

Strong shear is expected to continue or even increase during the
next day or so. The combination of the shear and interaction with
Hispaniola suggests that Erika is likely to weaken and could even
dissipate in the next 12 to 24 hours. Assuming that the cyclone
survives, there is an opportunity for some intensification on days
2 and 3 of the forecast period as the shear decreases, and that is
reflected in the NHC forecast. After that time, since the NHC track
now takes Erika inland over the Florida peninsula, weakening is
shown at days 4 and 5. Much of the guidance has trended weaker this
cycle, and the NHC intensity forecast is close to the HWRF and the
IVCN consensus. Confidence in the intensity forecast remains very
low.

The greatest short-term threat posed by Erika continues to be
very heavy rainfall over portions of the the Virgin Islands, Puerto
Rico, the Dominican Republic, and Haiti today. These rains could
produce flash floods and mud slides.

FORECAST POSITIONS AND MAX WINDS

INIT  28/0900Z 17.7N  67.7W   45 KT  50 MPH
 12H  28/1800Z 18.8N  69.8W   40 KT  45 MPH...INLAND
 24H  29/0600Z 20.5N  72.9W   40 KT  45 MPH...OVER WATER
 36H  29/1800Z 22.0N  76.0W   40 KT  45 MPH
 48H  30/0600Z 23.2N  78.1W   45 KT  50 MPH
 72H  31/0600Z 25.6N  80.7W   50 KT  60 MPH...INLAND
 96H  01/0600Z 27.7N  81.6W   45 KT  50 MPH...INLAND
120H  02/0600Z 30.0N  82.0W   40 KT  45 MPH...INLAND

$$
Forecaster Brennan




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