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Tropical Storm Ileana Discussion Number 7

Wiki-Hurricanes Forecast Center

4:00 AM CDT Mon Aug 6 2018

Ileana is a disorganized tropical cyclones going through cycles of massive convective bursts and subsequent wanes. At this time, the low-level circulation is on the northwestern edge of a previous convective burst and is in the process of being obscured again by several pulses of thunderstorm activity in recent frames. A 0332z ASCAT pass indicated that Ileana's low-level circulation is poorly defined and elongated. Nonetheless, that same pass showed explicit surface winds of 45kt in the northeastern quadrant. Given the low bias of the instrument, the initial intensity has been increased to 50kt, well above the new satellite estimate of T2.5/35kt from SAB.

Ileana is unlikely to behave like a normal tropical cyclone over the next two days. Despite these convective bursts, it has shown no willingness to build an inner core, likely due to the effects of moderate northerly wind shear, as well as the transient nature of the convection. In addition, the low-level center is poorly defined, with Ileana largely powered by a vigorous mid-level circulation. Shear is not expected to decrease, so this situation is unlikely to change over the next 48 hours as it remains over waters warmer than 29C and in mid-level relative humidity values above 75 percent. That being said, the storm has already intensified substantially since yesterday, and model guidance indicates the potential for further strengthening. The updated forecast has been raised slightly since the previous advisory and shows a peak of 55kt, which is closest to global modelling and a little below hurricane/statistical guidance. Ileana is expected to dissipate around 48 hours from now, becoming absorbed into the larger circulation of John to its west.

Ileana is moving steadily west-northwest thanks to a mid-level ridge to its north. This trajectory should continue for the next 48 hours. Thereafter, after the storm dissipates, its remnants should become absorbed into what will likely be a large and powerful Hurricane John.

FORECAST POSITIONS AND MAX WINDS

INIT 06/0900Z 50 KT 60 MPH

12H 06/1800Z 50 KT 60 MPH

24H 07/0600Z 55 KT 65 MPH

36H 07/1800Z 50 KT 60 MPH

48H 08/0600Z...DISSIPATED

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