507 
 WTPZ42 KNHC 102033
 TCDEP2
 
 Tropical Storm Aletta Discussion Number  21
 NWS National Hurricane Center Miami FL       EP022018
 200 PM PDT Sun Jun 10 2018
 
 Despite southerly vertical wind shear of about 15 kt, Aletta has
 been able to maintain a small cluster of strong convection in the
 northwestern quadrant. Recent ASCAT passes missed the now partially
 exposed low-level center and much of the inner-core wind field, but
 they did manage to capture tropical-storm-force winds in the eastern
 semicircle. Also, a Mexican Navy automated weather station on
 Clarion Island reported a sustained wind of 33 kt and a gust to 47
 kt a few hours ago as an outer band passed over the island. Based on
 that observation, along with a TAFB Dvorak estimate of T3.0/45 kt,
 the intensity is being maintained at 40 kt for this advisory.
 
 Microwave satellite position fixes indicate a motion of about 280/06
 kt since the previous advisory. No significant changes to the
 previous forecast track were required. The new model guidance
 remains in fair agreement on Aletta moving slowly westward for the
 next 48-72 h along the southern periphery of a weak low- to
 mid-level ridge to the north of the cyclone.  After that time,
 steering currents are forecast to collapse, along with Aletta coming
 under the influence of rapidly strengthening Hurricane Bud currently
 located to the east-southeast, which could result in the shallow
 cyclone stalling. The official forecast track is similar to the
 previous advisory and remains in the middle of the tightly packed
 track model guidance.
 
 Although the wind shear is forecast to weaken to less than 10 kt
 during the next 24-36 hours, which would generally favor
 re-strengthening, Aletta will also be moving over sub-26C SSTs and
 into a drier and more stable airmass. The poor thermodynamics, along
 with cold-air stratocumulus clouds already being ingested into the
 western and southern quadrants of the cyclone, argues for gradual
 weakening to occur over the next day or so, with Aletta degenerating
 into a remnant low pressure system by Tuesday. A steady spin down of
 the low is expected during the 72-120 hour period, with the shallow
 cyclone possibly even dissipating on day 5. The official intensity
 forecast is similar to the previous advisory, and closely follows
 a blend of the HCCA and IVCN consensus intensity models.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  10/2100Z 16.6N 115.7W   40 KT  45 MPH
  12H  11/0600Z 16.6N 116.6W   35 KT  40 MPH
  24H  11/1800Z 16.6N 117.6W   30 KT  35 MPH
  36H  12/0600Z 16.5N 118.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
  48H  12/1800Z 16.4N 119.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
  72H  13/1800Z 16.2N 120.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
  96H  14/1800Z 16.1N 120.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 120H  15/1800Z 15.9N 121.1W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
 $$
 Forecaster Stewart