[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 181457
TCDAT1

TROPICAL DEPRESSION JULIA DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112016
1100 AM EDT SUN SEP 18 2016

After an early morning burst of deep convection, strong northerly
shear and dry mid-level air have significantly weakened the
convection, leaving behind only shallow convection about 50-60 nmi
east through southwest of the now fully exposed low-level
circulation center. The initial intensity is being held at 25 kt,
which could be a little conservative, based on a TAFB satellite
classification of T1.5/25 kt.

Julia has been drifting westward the past several hours, but a slow
north-northwestward or northward motion is expected begin later
today. This general motion is forecast to continue into Tuesday as a
strong shortwave trough currently over the central United States
moves quickly eastward, creating increasing southerly to
southwesterly flow over the Carolinas. There are some notable
differences between the models with the ECMWF forecasting Julia to
weaken into a shallow remnant low and drift southwestward by 72
hours, whereas the remainder of the global and regional models
maintain a somewhat deeper cyclone and lift it out poleward in the
deeper steering flow ahead of the aforementioned shortwave trough.
The NHC forecast track leans toward the model consensus and keeps
Julia a little stronger and deeper, taking the cyclone northward and
near the coast of North Carolina by 48 hours. However, rapid
weakening is likely by 72 hours due to strong southwesterly shear,
leaving Julia as a remnant low near or over the coastal regions of
eastern North Carolina.

The intensity forecast is a little tricky due to the rapidly
decreasing shear conditions that the models are forecasting to occur
during the next 24 hours or so. The current 25-30 kt of northerly
vertical wind shear is expected to decrease to 10-15 kt from the
southwest by Monday morning, which would support a repeat of strong
convective development and spinup of the vortex, similar to what
occurred overnight, especially since Julia will be moving over the
warmer waters of the Gulf Stream at that time. The intensity
forecast is identical to the previous advisory and remains on the
low side of the guidance near the LGEM model. However, due to the
possibility of the cyclone being a little stronger than forecast,
the Air Force Reserve Hurricane Hunters have been tentatively tasked
to investigate Julia tomorrow afternoon.

FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 31.8N  77.1W   25 KT  30 MPH
 12H  19/0000Z 32.5N  77.3W   25 KT  30 MPH
 24H  19/1200Z 33.4N  77.2W   30 KT  35 MPH
 36H  20/0000Z 33.8N  77.2W   30 KT  35 MPH
 48H  20/1200Z 34.2N  77.2W   30 KT  35 MPH
 72H  21/1200Z 34.5N  77.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  22/1200Z...DISSIPATED

$$
Forecaster Stewart
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