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TROPICAL DEPRESSION IDA DISCUSSION NUMBER  32
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL102015
500 AM AST SAT SEP 26 2015

Despite continued westerly shear and abundant dry air in the middle
and upper levels of the atmosphere, Ida continues to produce a
persistent cluster of deep convection to the east of its center.
The intensity remains 30 kt based on ASCAT data from last evening.

Ida's future during the next several days is highly uncertain.
SHIPS environmental parameters suggest that the worst might be over.
The vertical shear that has been affecting the cyclone could
actually decrease gradually during the next couple of days, and sea
surface temperatures are forecast to remain at least 29 degrees
Celsius.  Therefore, it is not a sure bet that the system will cease
producing organized deep convection, which is a necessary condition
for the cyclone to be declared a remnant low.  A more likely
scenario would be that the circulation becomes elongated, the center
becomes ill defined, and Ida dissipates.  Therefore, the NHC
official forecast no longer shows Ida becoming a remnant low,
keeping it as a depression for the next five days.  However, Ida
could also dissipate at any time if it no longer shows signs of a
well-defined center of circulation, as is suggested by the GFS in a
couple of days.  But, it bears repeating: this is a very uncertain
forecast.

Ida is being steered northwestward, or 325/7 kt, by a low-level
ridge to its northeast.  However, the depression is approaching a
break in the ridge, and a stronger ridge is expected to slide
eastward from New England to the north Atlantic over the next few
days.  This pattern change should cause Ida to slow down during the
next 24 hours and then move westward or west-southwestward at a
faster speed during the remainder of the forecast period.  The
updated NHC track forecast is similar to the previous one, except
that it is a little faster beyond 48 hours to be close to the
various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  26/0900Z 23.4N  46.1W   30 KT  35 MPH
 12H  26/1800Z 24.0N  46.8W   25 KT  30 MPH
 24H  27/0600Z 24.4N  47.6W   25 KT  30 MPH
 36H  27/1800Z 24.2N  48.3W   25 KT  30 MPH
 48H  28/0600Z 23.6N  49.5W   30 KT  35 MPH
 72H  29/0600Z 22.6N  53.3W   30 KT  35 MPH
 96H  30/0600Z 22.5N  58.0W   25 KT  30 MPH
120H  01/0600Z 23.0N  61.0W   25 KT  30 MPH

$$
Forecaster Berg

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