Tropical Storm Iba Discussion Number 5

Wiki-Hurricanes Forecast Center

06:00 PM AST Sun Mar 24 2019

After a convectively impressive morning from Iba, cloud tops have become slightly more diffuse throughout the day with diurnal warming. The coldest tops have decentralized and are now mostly contained within banding features in the northeastern quadrant, though the system's structure remains well-organized; there may have been some entrainment of dry air, but the areal moisture content is relatively high so moisture cycling seems likely. Some smaller pockets of convection are attempting to re-fire closer to the center per the latest imagery, and a recovery of more centralized convection is anticipated tonight. SAB has increased to T2.0/30 kt for their satellite intensity estimates on a shear pattern. However, given no significant overall change in organization since the last advisory, the intensity for Iba this advisory remains at 40 kt.

Iba continues to crawl slowly towards the south at a leisurely pace, prompted by a low-amplitude shortwave trough. This steering feature is expected to pass to the southeast without much fanfare, but should pave the way for a more amplified trough to pull Iba out of the tropics beginning Wednesday. Conditions remain favorable for development in the interim with a band of low wind shear, good outflow, and warm surface temperatures, and models have come into better agreement over the ultimate strength of Iba. However, as the system tracks further south, it will leave its initial low-shear and high-moisture anticyclone nursery and detach from the primordial trough region, entering an area with higher subtropical jet-induced shear and dry air. This environment will gradually become more hostile over time. Divergent flow outside of the anticyclone regime may aid somewhat Wednesday, but persistent marginal humidity values and increasing wind shear will whittle Iba down afterwards. Transition to a post-tropical remnant low or extratropical cyclone is likely in the late forecast.


INIT 24/2100Z 40 KT 45 MPH

12H 25/0600Z 45 KT 50 MPH

24H 25/1800Z 50 KT 60 MPH

36H 26/0600Z 50 KT 60 MPH

48H 26/1800Z 40 KT 45 MPH

72H 27/1800Z 35 KT 40 MPH

96H 28/1800Z 30 KT 35 MPH...POST-TROP/REMNT LOW

120H 29/1800Z 20 KT 25 MPH...POST-TROP/REMNT LOW

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