560 
 WTPZ41 KNHC 200240
 TCDEP1
 
 TROPICAL STORM RICK DISCUSSION NUMBER   7
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212015
 800 PM MST THU NOV 19 2015
 
 Rick's cloud pattern has eroded some during the past 6 hours with
 previously solid bands of convection in the northern semicircle
 having become more fragmented during the past few hours.
 In addition, numerous small arc cloud lines have been noted
 propagating away from the cyclone, which is indicative of dry
 mid-level air having penetrated into the inner core region. This
 supposition is further supported by a 20/0006 UTC AMSU pass
 indicating only a narrow fragmented band of convection is present
 in the northwestern quadrant of the storm. Therefore, the initial
 intensity of 35 kt remains unchanged for this advisory, which is
 lower than the available satellite intensity estimates.
 
 The initial motion estimate is 295/09 kt and is based primarily on
 passive microwave satellite data. A mid-level ridge over central
 Mexico is forecast to build westward to the north and east of Rick
 during the next 24-36 hours, while a large upper-level low located
 near 27N 138W is expected to fill and gradually open up into a broad
 trough by 48-72 hours. The combination of these two steering
 mechanisms should keep Rick moving west-northwestward for the next
 48 hours, followed by a decrease in forward speed and a gradual turn
 toward the northwest and north at 72 h and 96 h, respectively. The
 official forecast track was only nudged slightly to the left of the
 previous advisory track, and essentially lies down the middle of NHC
 track guidance envelope.
 
 Rick is forecast to move into a weak vertical wind shear regime
 during the next 24-36 hours while remaining over SSTs of 29 deg C.
 These favorable conditions would normally support intensification of
 a tropical cyclone. However, the ragged and elongated inner-core
 wind field, coupled with additional entrainment of drier mid-level
 air, is expected to inhibit any significant development and
 organization of deep convection. By 48 hours and beyond, an increase
 in southwesterly vertical wind shear to more than 25 kt is forecast
 to induce gradual weakening, with Rick becoming a remnant low by 96
 hours when the cyclone will be moving over cooler waters at that
 time. Rick is expected to dissipate day 5, if not sooner. NHC
 intensity forecast is a little lower than the previous advisory and
 remains below the multi-model consensus, IVCN.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  20/0300Z 15.2N 108.1W   35 KT  40 MPH
  12H  20/1200Z 15.9N 109.5W   40 KT  45 MPH
  24H  21/0000Z 16.5N 111.1W   40 KT  45 MPH
  36H  21/1200Z 17.2N 112.4W   40 KT  45 MPH
  48H  22/0000Z 17.8N 113.4W   35 KT  40 MPH
  72H  23/0000Z 19.5N 115.0W   25 KT  30 MPH
  96H  24/0000Z 21.6N 115.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
 120H  25/0000Z...DISSIPATED
 
 $$
 Forecaster Stewart