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Tropical Depression Nine-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP092019
900 PM MDT Sun Aug 11 2019

The broad low pressure system that the NHC has been tracking the
past several days has finally developed a well-defined surface
circulation and enough organized deep convection to be classified as
a tropical depression. A late-arriving 1716Z ASCAT-C scatterometer
pass indicated the surface wind field was possibly closed at that
time, but since then deep convection with tops of -75C to -80C have
persisted near and to the west of the mid-level circulation center,
suggesting that a low-level center has likely closed off now. Dvorak
satellite intensity estimates are T1.5/25 kt from both TAFB and SAB,
but the initial intensity is set at 30 kt based on 30-31 kt winds
indicated in the aforementioned scatterometer data.

The initial motion is estimated to be west-northwestward or 295/12
kt, based primarily on scatterometer and passive microwave fixes.
The small cyclone is expected to move west-northwestward around the
southern periphery of a deep-layer ridge for the next 3 days until
dissipation occurs. The NHC track forecast lies near the southern
portion of the guidance envelope, between the TVCE consensus model
and the ECMWF-ensemble mean model.

The small cyclone only has about 36 hours to strengthen before the
system moves over sub-26 deg C SSTs. The shear is forecast to be low
at less than 10 kt for the next 72 hours or so, even decreasing to
near 5 kt in 24-36 h, which would normally result in significant
development. However, intermittent intrusions of dry mid-level air
are expected to disrupt the typical intensification process, thus
only modest strengthening is forecast through 36 h, after which
much cooler waters will induce a weakening trend. The official
intensity forecast closely follows a blend of the HCCA and IVCN
intensity consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0300Z 18.9N 109.8W   30 KT  35 MPH
 12H  12/1200Z 19.4N 111.2W   35 KT  40 MPH
 24H  13/0000Z 20.3N 113.1W   35 KT  40 MPH
 36H  13/1200Z 21.3N 115.3W   35 KT  40 MPH
 48H  14/0000Z 22.1N 117.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  15/0000Z 23.7N 123.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  16/0000Z...DISSIPATED

$$
Forecaster Stewart

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