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TROPICAL DEPRESSION IDA DISCUSSION NUMBER  33
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL102015
1100 AM AST SAT SEP 26 2015

There continues to be little change in the satellite appearance of
Ida with the low-level center exposed to the west of a persistent
area of deep convection.  The circulation of the system remains
large and well defined.  Recent ASCAT data suggest that the initial
intensity is still 30 kt, which is a little higher than the Dvorak
classifications.

The strong westerly shear that has been affecting Ida during the
past several days is expected to lessen by tomorrow.  Consequently,
the SHIPS guidance shows the system gaining strength.  However,
nearly all of the dynamical models show little, if any,
strengthening of Ida.  The official forecast continues to prefer
the solution provided by the dynamical models due to the continued
influence of dry air near the system. It is also possible that the
depression could dissipate in a few days when a frontal boundary
stalls just to the north of Ida, which could cause the circulation
to become elongated or open into a trough.  Given the various
scenarios provided by the guidance, this forecast is quite
uncertain.

Ida is still moving north-northwestward at about 7 kt, but it is
expected to turn west-northwestward by tonight and southwestward by
late tomorrow as a low- to mid-level ridge builds to the north of
the system.  A general westward motion with some increase in
forward speed is expected beyond that time.  Although there is some
spread in the guidance, most of the models agree on this general
theme.  A small northward adjustment was made to the previous
forecast track beyond 48 hours, to come into better agreement with
the latest consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 24.0N  46.5W   30 KT  35 MPH
 12H  27/0000Z 24.7N  47.2W   30 KT  35 MPH
 24H  27/1200Z 24.9N  47.9W   30 KT  35 MPH
 36H  28/0000Z 24.4N  48.7W   30 KT  35 MPH
 48H  28/1200Z 23.9N  50.0W   30 KT  35 MPH
 72H  29/1200Z 23.5N  53.9W   30 KT  35 MPH
 96H  30/1200Z 23.7N  57.7W   25 KT  30 MPH
120H  01/1200Z 24.1N  60.0W   25 KT  30 MPH

$$
Forecaster Cangialosi

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