Tropical Storm Iba Discussion Number 7

Wiki-Hurricanes Forecast Center

6:00 AM Mon Mar 25 2019

Iba has become a bit better organized this morning. Just like last night, deep convection has blossomed across the eastern semicircle, with cloudtops cooler than -80C featuring frequent lightning activity. Unlike last night, however, the low-level circulation has actually become embedded within this convection. On one hand, the pair of ASCAT passes around 0z showed a confined area of 30-35kt winds, which would continue to make a 40kt initial intensity most reasonable. On the other, the most recent satellite intensity estimate from SAB has increased to T3.0/45kt. Given that the effects of shear continue to be evident, combined with the uncertainty of whether organization will continue up to the next advisory, I have decided to leave Iba's strength at a now-comfortable 40kt.

Assuming wind shear remains in the ballpark of 10-15kt, some intensification is possible over the next day, as indicated by the GFS. Even the GFS, though, has trended somewhat weaker with Iba's peak intensity, and the ECMWF continues to struggle beyond a weak tropical storm. Given satellite trends this morning and the amount of time left to organize, I have left the peak intensity at 50kt; quick weakening is expected on days three and four. By day five, there are some new indications that Iba may begin to gain strength as a post-tropical entity. There are no changes to the forecast track reasoning. A drift toward the south and then acceleration toward the southeast continues to appear likely through the forecast period.


INIT 25/0900Z 40 KT 45 MPH

12H 25/1800Z 45 KT 50 MPH

24H 26/0600Z 50 KT 60 MPH

36H 26/1800Z 45 KT 50 MPH

48H 27/0600Z 35 KT 40 MPH

72H 28/0600Z 30 KT 35 MPH

96H 29/0600Z 25 KT 30 MPH...POST-TROP/REMNT LOW

120H 30/0600Z 30 KT 35 MPH...POST-TROP/REMNT LOW

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