Ashcroft, J, Schwendike, J, Griffiths, SD orcid.org/0000-0002-4654-2636 et al. (2 more authors) (Cover date: October 2021 Part B) The Impact of Weak Environmental Steering Flow on Tropical Cyclone Track Predictability. Quarterly Journal of the Royal Meteorological Society, 147 (741). pp. 4122-4142. ISSN 0035-9009
Abstract
Typhoon Haiyan (2013) and Typhoon Hagupit (2014) are examples of two tropical cyclones (TCs) where, despite similarities in the track and intensity, the predictability of the TCs differed greatly. Both TCs made landfall over the Philippines having followed a similar track across the Pacific and both reached intensities in excess of 60 ms-1. Operational global ensemble forecasts showed large uncertainty in the track of Hagupit, whereas the ensemble spread for Haiyan was considerably less.
Using the Met Office's Unified Model, 5-day global ensemble forecasts were produced for both storms. Consistent with the operational forecasts produced at the time of the storms, the spread of tracks is greater in the forecasts produced for Hagupit than Haiyan. Haiyan was located on the southern periphery of the subtropical high and embedded in a strong easterly flow. In contrast, the position of Hagupit between two anticyclones earlier in the forecast is key to the subsequent motion of the storm and determining if Hagupit will make landfall over the Philippines or turn to the north. Upper level winds contribute the most to the depth-averaged steering flow. Statistically significant differences in the strength of the upper level anticyclone to the east of the storm, the strength and position of the upper level ridge downstream of the storm and the location of a detached PV streamer appear between two groups of ensemble members - those which turn to the north and those which make landfall. Positional differences of the TC in different ensemble members earlier in the forecasts, particularly in the east to west direction, are correlated to larger north-east to south-west position differences later in the forecast. Ensemble sensitivity analysis suggests that this initial east-west positional variance is linked to the upper level geopotential height directly south of the storm. Accurately representing both the steering flow of Hagupit and the position of Hagupit is vital for an accurate forecast.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2021 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Mathematics (Leeds) > Applied Mathematics (Leeds) The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst for Climate & Atmos Science (ICAS) (Leeds) |
Funding Information: | Funder Grant number Met Office P107195 |
Depositing User: | Symplectic Publications |
Date Deposited: | 05 Oct 2021 11:38 |
Last Modified: | 19 Jul 2022 11:03 |
Status: | Published |
Publisher: | Wiley |
Identification Number: | 10.1002/qj.4171 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:178670 |