Status: Ongoing analysis Material Finalised Material from: Linus, David L., Esti, Hao, Kristian, Mohamed
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Discussed in the following Daily reports: |
1. Impact
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Hurricane Florence made landfall in North Carolina on 14 September as a category 1 hurricane. The cyclone brought torrential rainfall as it became quasi-stationary for a few days. At least 26 people was killed due to the cyclones. |
https://www.bbc.co.uk/news/world-us-canada-45563634
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The plot below shows the evolution of central pressure in Best Track (dots) and LWDA analysis (solid line). The analysis had difficulties to capture the intense phase on 5 September, but captured the second intensification.
Track of FLORENCE with estimated central pressure
The plots below show time-series observation statistics for temperature observations from dropsondes within 1 (left) and 5 (right) degrees of Florence. Dropsondes wind and surface pressure statistics are plotted in the lower figures.
Below is a sequence of coverage maps showing the usage of wind from dropsondes
Throughout the lifetime of FLORENCE the data assimilation seem to consistently reduce the position errors.
During the lifetime of Florence an increased number of observations of ocean floats was noted (see first plot). These additional floats were ALAMO (Air-Launched Autonomous Micro Observer) float, 10 floats deployed by WHOI in order to monitor Hurricane Florence, in the predicted path of Hurricane. These floats descend to 300m every 2 hours. The behaviour of the data assimilation was checked and most response in our ocean system is already visible in the model background, which did a very good job in representing the cooling/deepening effect during Florence event. And DA only slightly corrected the temperature fields.
3.2 HRES
Total precipitation accumulated from HRES during the whole episode of Hurricane Florence. Base time 14/09/2018 at 00 UTC.
3.3 ENS
The plots below show the tracks (ensemble -grey, best track - black), position and intensity on 14 September 00UTC (ensemble - squares, best track - hourglass) in forecasts from 13 September (first plot) to 4 September (last plot). Early forecasts had problems to capture the northward "kink" on 7 September. The forecast from 4 September also had a majority of members turning northward over the Atlantic. This changed on the 5 September, and the sensitivity analysis further down is targeting this change.
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4. Experience from general performance/other cases
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5. Good and bad aspects of the forecasts for the event
- Issues with mid-Atlantic "knee" and intensification
6. Additional material
Total precipitation observed in 7 days from the hurricane Florence.
Plot of the maximum rainfall caused by North Atlantic and Northeast tropical cyclones and their remnants per state (1950-2018).