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Tropical Storm Barbara Winds: 60 kt
Pressure: 990 mbar
Advisory 7 / July 1, 2019

Tropical Storm Barbara Discussion Number 7

Wiki-Hurricanes Forecast Center

8:00 AM PDT Mon Jul 01 2019

Satellite imagery from this morning shows an extensive system of rainbands encircling Barbara's circulation, with a highly dynamic central region of convection attempting to solidify. Cirrus banding is spreading outwards to the north, fanned by the impressive convective burst overnight. A 0731z GMI microwave pass indicated a mid-level eye feature, though this was still rather misshapen and displaced east of the low-level circulation by roughly half a degree. An ASCAT-C scatterometer pass at 0533z showed a very extensive region of winds in excess of 45 kt, though it also suggested that the storm was still well-rooted to the monsoon trough to the southwest. SAB increased their subjective assessment to T3.5/55kt while objective CIMSS-ADT has risen to T4.5/77kt, though this is partially a misread due to mistakenly recognizing the microwave feature as a true center. Still, good metrics from AMSU and impressive banding support a slight increase to 60 kt.

Despite general agreement between the overall motion of Barbara over the next five days, the positioning of the storm near the sharp East Pacific thermocline towards the end of the forecast window means a few degrees of variability has an enhanced effect on the late-term forecast intensity. Broadly, as Barbara intensifies, it will gradually lift from the ITCZ before attaining a more northerly component in two to three days as it rounds the periphery of the extended Baja California subtropical ridge. There is some disagreement between the track guidance over the significance of this northward ascent, with the latest EPS ensemble mean displaced 2 degrees south of the GEFS ensemble mean. However, I do note that overall guidance has trended northward, and ECMWF-IFS height fields have tended to decrease in association with ridging over the Central Pacific while the GFS has tended to remain steadfast in its depiction. At the current juncture, a more northerly component seems more likely based on the storm's intensity and these trends.

Cloud observations and satellite analyses suggest that mid-level narrow-band shear has been decreasing, attenuated by Barbara's tenacity to develop very deep and high-topped convection. Barbara is currently moving into a region of very light upper-level winds, so given its size it should have no considerable issue developing an upper-level anticyclone. Waters are sufficiently warm and the atmosphere more than sufficiently moist to support continued intensification over at least the next two days before more a more stable environment takes root near the thermocline, with a possible uptick in shear at the very end of the forecast window from an approaching trough. SHIPS metrics remain indicative of a Category 4, though they represent the upper-end of guidance. Dynamical guidance from HWRF/HMON are supportive of a storm at or above major hurricane thresholds. Although Barbara has performed well up until now, large systems, especially those still connected with the ITCZ like Barbara, are often limited in their potential until structural changes tighten the size of the circulation. If this is possible, Barbara is in position to rapidly intensify in the 24-48 hour timeframe.


FORECAST MAX WINDS

INIT 01/1500Z 60 KT 70 MPH

12H 02/0000Z 70 KT 85 MPH

24H 02/1200Z 80 KT 90 MPH

36H 03/0000Z 95 KT 115 MPH

48H 03/1200Z 105 KT 120 MPH

72H 04/1200Z 105 KT 120 MPH

96H 05/1200Z 80 KT 90 MPH

120H 06/1200Z 60 KT 70 MPH

Forecaster TheAustinMan
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