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Tropical Storm Barbara Discussion Number 5

Wiki-Hurricanes Forecast Center

8:00 PM PDT Sun Jun 30 2019

Barbara has continued to organize since the previous advisory. Satellite imagery shows that the low-level center, which was partially exposed earlier today, has become embedded within very deep convection. In addition, a large and prominent spiral band has formed to the southwest of the center. I have spoken before how this convective shape allows intermittent intrusions of dry air. However, considering Barbara is still in its infancy, this point is largely moot anyway. 0z satellite intensity estimates from SAB and TAFB were a consensus T3.0/45kt while UW-CIMSS ADT is slightly higher at T3.3/51kt. Therefore, the initial intensity is set to a comfortable 45kt.

The initial motion is west-northwest, and this motion will continue for the next 3 days as mid-level ridging over northern Mexico remains stout. On day 4, Barbara should reach the southwest periphery of this ridge and curve more toward the northwest. Thereafter, however, the ridge should shift westward and force Barbara in that direction as well.

While some wind shear continues to plague Barbara, this is expected to become a non-factor by tomorrow as upper-level high pressure builds. Ocean temperatures will remain above 26C through day 4, around the same time mid-level relative humidity values become hostile for intensification. The biggest impediment in the short term, then, is likely to be the storm's large radius of maximum winds. Only steady intensification is expected over the next 24 hours accordingly. Thereafter, buoyed by a convectively-coupled kelvin wave, the stage appears set for a period of rapid development that is likely to bring Barbara to major hurricane strength. The SHIPS and LGEM are stronger than previous runs, reaching 105kt and 108kt, respectively. This is close to the ECMWF solution and a little weaker than the GFS. The intensity forecast has therefore been increased a little more. Weakening is expected on days four and five, and this is indicated at a faster rate than the previous advisory.

FORECAST MAX WINDS

INIT 01/0300Z 45 KT 50 MPH

12H 01/1200Z 50 KT 60 MPH

24H 02/0000Z 60 KT 70 MPH

36H 02/1200Z 75 KT 85 MPH

48H 03/0000Z 95 KT 110 MPH

72H 04/0000Z 105 KT 120 MPH

96H 05/0000Z 95 KT 110 MPH

120H 06/0000Z 75 KT 85 MPH

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