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Tropical Storm Kirk Discussion Number   3
NWS National Hurricane Center Miami FL       AL122018
1100 PM AST Sat Sep 22 2018

The overall organization of Kirk has changed little since the
previous advisory.  The deep convection that was over the western
portion of the circulation has continued to race westward ahead of
the low-level center while a new burst of convection has developed
closer to the center this evening.  A couple of ASCAT passes from
just prior to 0000 UTC did not reveal any winds as strong as
this morning, but given the recent increase in convection near the
center the initial intensity is maintained at 35 kt, which could be
a little generous.

Recent satellite fixes show that Kirk is moving west-northwestward
or 285 degrees at 14 kt.  A narrow subtropical ridge that is
forecast to build westward to the north of Kirk should steer the
cyclone quickly westward during the next few days, with forward
speeds increasing to around 20-22 kt.  After that time, the global
models predict that a weakness will develop in the ridge between
50W and 60W which is forecast to cause Kirk to slow down and turn
west-northwestward.  The updated NHC track forecast is a little
north of the previous advisory, primarily due to a slightly more
northward initial position as noted in the ASCAT data.  Otherwise,
the track forecast is similar to the previous advisory and is along
the southern edge of the guidance, closest to a blend of the GFS
and ECMWF, and the HFIP corrected consensus.

Kirk is forecast to traverse warm waters and remain within a low
shear environment during the next couple of days.  These conditions
favor strengthening, however as mentioned in the previous
discussion, some dry air lurking just to the north of Kirk could
get entrained into the circulation and limit intensification.
There is still large spread in the intensity guidance with the
statistical guidance showing much more intensification between 24
and 72 h. After 72 hours, increasing westerly shear is expected to
cause weakening.  The NHC intensity forecast remains near the HCCA
and IVCN intensity guidance, and follows the trend of the ECMWF and
GFS models that weaken Kirk later in the forecast period. Given the
spread in the guidance, the intensity forecast is of low confidence.

FORECAST POSITIONS AND MAX WINDS

INIT  23/0300Z  9.0N  26.4W   35 KT  40 MPH
 12H  23/1200Z  9.4N  28.9W   40 KT  45 MPH
 24H  24/0000Z  9.9N  33.0W   45 KT  50 MPH
 36H  24/1200Z 10.1N  37.3W   50 KT  60 MPH
 48H  25/0000Z 10.2N  41.8W   50 KT  60 MPH
 72H  26/0000Z 10.6N  49.5W   50 KT  60 MPH
 96H  27/0000Z 11.8N  55.0W   45 KT  50 MPH
120H  28/0000Z 13.3N  60.0W   40 KT  45 MPH

$$
Forecaster Brown

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