scholarly journals Comparison of ARCHER MPERC to NHC Analysis

2021 ◽  
Vol 10 (3) ◽  
Author(s):  
Lorenzo Pulmano ◽  
Leya Joykutty
Keyword(s):  
Tropical Cyclones ◽  
Passive Microwave ◽  
Central Pacific ◽  
Atlantic Basin ◽  
Wind Speeds ◽  
Eyewall Replacement Cycle ◽  
Eyewall Replacement Cycles ◽  
National Hurricane Center ◽  
Joint Typhoon Warning Center ◽  
Replacement Cycle

Eyewall replacement cycles (ERCs) are events that occur in intense tropical cyclones (TCs) and are difficult to predict.  An ERC event involves a secondary outer eyewall that surrounds the inner eyewall.  The outer eyewall slowly moves towards the eye and weakens the inner eyewall, eventually replacing the inner eyewall.  During this process, wind speeds lower and the structure of a TC becomes disorganized, further weakening the storm.  TCs often restrengthen after an ERC.  Little is known about the process and as such, poses an obstacle to forecasters.  The Automated Rotational Center Hurricane Eye Retrieval (ARCHER) Microwave-based Probability of Eyewall Replacement Cycle (MPERC) is an algorithm that uses 89-95 GHz passive microwave imagery and intensity estimates from the National Hurricane Center (NHC), Central Pacific Hurricane Center (CPHC), or the Joint Typhoon Warning Center (JTWC) to predict the possibility of an ERC.  The effectiveness and ability of ARCHER MPERC was analyzed and compared to the NHC’s official reports on all Atlantic Basin tropical cyclones from 2017 to 2019.   MPERC ultimately predicted seventeen ERCs in nine tropical cyclones.  Of those, seven were valid ERCs.  The algorithm works well, predicting approximately 41% of the total number of predictions correctly.  However, MPERC did not predict five ERCs that were cited by the NHC.  It was further found that it was true that MPERC produces incorrect results in sheared and dry environments.

Are Eyewall Replacement Cycles Governed Largely by Axisymmetric Balance Dynamics?

2015 ◽  
Vol 72 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Sergio F. Abarca ◽  
Michael T. Montgomery
Keyword(s):  
Boundary Layer ◽  
Recent Work ◽  
Balance Model ◽  
Tangential Wind ◽  
Eyewall Replacement Cycle ◽  
Physics Simulation ◽  
Physics Model ◽  
Balance Dynamics ◽  
Eyewall Replacement Cycles ◽  
Replacement Cycle

Abstract The authors question the widely held view that radial contraction of a secondary eyewall during an eyewall replacement cycle is well understood and governed largely by the classical theory of axisymmetric balance dynamics. The investigation is based on a comparison of the secondary circulation and derived tangential wind tendency between a full-physics simulation and the Sawyer–Eliassen balance model. The comparison is made at a time when the full-physics model exhibits radial contraction of the secondary eyewall during a canonical eyewall replacement cycle. It is shown that the Sawyer–Eliassen model is unable to capture the phenomenology of secondary eyewall radial contraction because it predicts a net spindown of the boundary layer tangential winds and does not represent the boundary layer spinup mechanism that has been articulated in recent work.

scholarly journals Weighted Analog Technique for Intensity and Intensity Spread Predictions of Atlantic Tropical Cyclones

2015 ◽  
Vol 30 (5) ◽  
pp. 1321-1333 ◽  
Author(s):  
Hsiao-Chung Tsai ◽  
Russell L. Elsberry
Keyword(s):  
Tropical Cyclones ◽  
Bias Correction ◽  
Western North Pacific ◽  
Probability Of Detection ◽  
Track Forecast ◽  
Sample Mean ◽  
Prediction Technique ◽  
Intensity Spread ◽  
National Hurricane Center ◽  
Joint Typhoon Warning Center

Abstract A situation-dependent intensity and intensity spread prediction technique for the Atlantic called the Weighted Analog Intensity Atlantic (WAIA) is developed using the same procedures as for a similar technique for the western North Pacific that is operational at the Joint Typhoon Warning Center. These simple techniques are based on rankings of the 10 best historical track analogs to match the official track forecast and current intensity. A key step is the development of a bias correction to eliminate an overforecast bias. The second key step is a calibration of the original intensity spread among the 10 analogs to achieve a probability of detection of about 68% at all forecast intervals, which it is proposed would be an appropriate intensity spread for the National Hurricane Center (NHC) official intensity forecasts. The advantages of WAIA as an operational intensity forecast product for Atlantic tropical cyclones are described in terms of mean absolute errors, sample-mean biases, and geographic distributions of WAIA versus various guidance products available at NHC. Specific attention is given to the four guidance products that are included in the intensity consensus (ICON) technique that is the most skillful of all the products. Evidence is given that WAIA would be an independent, and more likely skillful at longer forecast intervals, technique to include in ICON. Consequently, WAIA would likely lead to improved NHC intensity forecasts at 4–5-day intervals.

Hurricane Bonnie (1998): Maintaining Intensity during High Vertical Wind Shear and an Eyewall Replacement Cycle

2018 ◽  
Vol 146 (10) ◽  
pp. 3383-3399 ◽  
Author(s):  
Erin M. Dougherty ◽  
John Molinari ◽  
Robert F. Rogers ◽  
Jun A. Zhang ◽  
James P. Kossin
Keyword(s):  
Wind Shear ◽  
Surface Wind ◽  
Vertical Wind Shear ◽  
Surface Wind Speed ◽  
Vertical Wind ◽  
Level Data ◽  
Eyewall Replacement Cycle ◽  
Hurricane Bonnie ◽  
Eyewall Replacement Cycles ◽  
Replacement Cycle

Abstract Hurricane Bonnie (1998) was an unusually resilient hurricane that maintained a steady-state intensity while experiencing strong (12–16 m s−1) vertical wind shear and an eyewall replacement cycle. This remarkable behavior was examined using observations from flight-level data, microwave imagery, radar, and dropsondes over the 2-day period encompassing these events. Similar to other observed eyewall replacement cycles, Bonnie exhibited the development, strengthening, and dominance of a secondary eyewall while a primary eyewall decayed. However, Bonnie’s structure was highly asymmetric because of the large vertical wind shear, in contrast to the more symmetric structures observed in other hurricanes undergoing eyewall replacement cycles. It is hypothesized that the unusual nature of Bonnie’s evolution arose as a result of an increase in vertical wind shear from 2 to 12 m s−1 even as the storm intensified to a major hurricane in the presence of high ambient sea surface temperatures. These circumstances allowed for the development of outer rainbands with intense convection downshear, where the formation of the outer eyewall commenced. In addition, the circulation broadened considerably during this time. The secondary eyewall developed within a well-defined beta skirt in the radial velocity profile, consistent with an earlier theory. Despite the large ambient vertical wind shear, the outer eyewall steadily extended upshear, supported by 35% larger surface wind speed upshear than downshear. The larger radius of maximum winds during and after the eyewall replacement cycle might have aided Bonnie’s resiliency directly, but also increased the likelihood that diabatic heating would fall inside the radius of maximum winds.

scholarly journals The Impact of Best Track Discrepancies on Global Tropical Cyclone Climatologies using IBTrACS

2014 ◽  
Vol 142 (10) ◽  
pp. 3881-3899 ◽  
Author(s):  
Carl J. Schreck ◽  
Kenneth R. Knapp ◽  
James P. Kossin
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Historical Analysis ◽  
The West ◽  
West Pacific ◽  
Global Context ◽  
The North ◽  
The Impact ◽  
National Hurricane Center ◽  
Joint Typhoon Warning Center

Abstract Using the International Best Track Archive for Climate Stewardship (IBTrACS), the climatology of tropical cyclones is compared between two global best track datasets: 1) the World Meteorological Organization (WMO) subset of IBTrACS (IBTrACS-WMO) and 2) a combination of data from the National Hurricane Center and the Joint Typhoon Warning Center (NHC+JTWC). Comparing the climatologies between IBTrACS-WMO and NHC+JTWC highlights some of the heterogeneities inherent in these datasets for the period of global satellite coverage 1981–2010. The results demonstrate the sensitivity of these climatologies to the choice of best track dataset. Previous studies have examined best track heterogeneities in individual regions, usually the North Atlantic and west Pacific. This study puts those regional issues into their global context. The differences between NHC+JTWC and IBTrACS-WMO are greatest in the west Pacific, where the strongest storms are substantially weaker in IBTrACS-WMO. These disparities strongly affect the global measures of tropical cyclone activity because 30% of the world’s tropical cyclones form in the west Pacific. Because JTWC employs similar procedures throughout most of the globe, the comparisons in this study highlight differences between WMO agencies. For example, NHC+JTWC has more 96-kt (~49 m s−1) storms than IBTrACS-WMO in the west Pacific but fewer in the Australian region. This discrepancy probably points to differing operational procedures between the WMO agencies in the two regions. Without better documentation of historical analysis procedures, the only way to remedy these heterogeneities will be through systematic reanalysis.

Satellite and Aircraft Observations of the Eyewall Replacement Cycle in Typhoon Sinlaku (2008)

2015 ◽  
Vol 143 (9) ◽  
pp. 3406-3420 ◽  
Author(s):  
Elizabeth R. Sanabia ◽  
Bradford S. Barrett ◽  
Nicholas P. Celone ◽  
Zachary D. Cornelius
Keyword(s):  
Inner Core ◽  
Surface Wind ◽  
Surface Winds ◽  
Wind Speeds ◽  
Radial Profiles ◽  
Aircraft Observations ◽  
Eyewall Replacement Cycle ◽  
Flight Level ◽  
Cloud Tops ◽  
Replacement Cycle

Abstract Satellite and aircraft observations of the concurrent evolution of cloud-top brightness temperatures (BTs) and the surface and flight-level wind fields were examined before and during an eyewall replacement cycle (ERC) in Typhoon Sinlaku (2008) as part of The Observing System Research and Predictability Experiment (THORPEX) Pacific Asian Regional Campaign (T-PARC) and the Tropical Cyclone Structure 2008 (TCS08) field campaign. The structural evolution of deep convection through the life cycle of the ERC was clearly evident in the radial variation of positive water vapor (WV) minus infrared (IR) brightness temperature differences over the 96-h period. Within this framework, the ERC was divided into six broadly defined stages, wherein convective processes (including eyewall development and decay) were analyzed and then validated using microwave data. Dual maxima in aircraft wind speeds and geostationary satellite BTs along flight transects through Sinlaku were used to document the temporal evolution of the ERC within the TC inner core. Negative correlations were found between IR BTs and surface wind speeds, indicating that colder cloud tops were associated with stronger surface winds. Spatial lags indicated that the strongest surface winds were located radially inward of both the flight-level winds and coldest cloud tops. Finally, timing of the ERC was observed equally in IR and WV minus IR (WVIR) BTs with one exception. Decay of the inner eyewall was detected earlier in the WVIR data. These findings highlight the potential utility of WVIR and IR BT radial profiles, particularly so for basins without active aircraft weather reconnaissance programs such as the western North Pacific.

scholarly journals Changes of Tropical Cyclone Size in three Oceanic Basins of the Northern Hemisphere since 2001

2017 ◽  
Author(s):  
banglin zhang
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
North Pacific ◽  
Japan Meteorological Agency ◽  
Data Sets ◽  
The North ◽  
Sea Surface Temperature Anomaly ◽  
Storm Duration ◽  
National Hurricane Center ◽  
Joint Typhoon Warning Center

In this study the latest changes of tropical cyclone size are analyzed based on linear and quadratic curve fittings of the National Hurricane Center (NHC)/Joint Typhoon Warning Center (JTWC) best track data for the radius of maximum wind (RMW), the average radius of 34-kt wind (AR34), and the storm duration index “storm days” (SD) in three oceanic basins of the North Atlantic (NATL), the Western North Pacific (WPAC) and the Eastern North Pacific (EPAC). The computations are done separately for two categories of tropical cyclones: tropical storms (TS), and hurricanes in NATL and EPAC or typhoons in WPAC (HT). The results show that the RMW trends for TS are positive in all basins, and the RMW trends for HT are positive in the NATL basin, but negative in the WPAC and EPAC basins. The AR34 changes are more complex due to the fact that they reflect not only the strength of tropical cyclones, but also the environmental conditions. The trends of two other data sets, with WPAC dataset from the Japan Meteorological Agency (JMA) and the extended best track dataset for NATL and EPAC from NESDIS/RAMMB, are also consistent with the trends derived from the 16-year best track data. The relationships between storm size and sea surface temperature anomaly and the departure from the zonal mean have also been investigated, and some statistically significant correlations are found.

Trends in Track Forecasting for Tropical Cyclones Threatening the United States, 1970–2001

2003 ◽  
Vol 84 (9) ◽  
pp. 1197-1204 ◽  
Author(s):  
James L. Franklin ◽  
Colin J. McAdie ◽  
Miles B. Lawrence
Keyword(s):  
United States ◽  
Tropical Cyclones ◽  
Forecast Accuracy ◽  
The United States ◽  
Small Sample ◽  
Atlantic Basin ◽  
Long Term Trends ◽  
National Hurricane Center ◽  
Landfall Location

Previous studies have identified statistically significant long-term improvements in forecasts issued by the National Hurricane Center (NHC) for Atlantic basin tropical cyclones. Recently, however, attention has been focused on the forecast accuracy of landfall location and timing, and the long-term improvement trends for this relatively small sample of forecasts were mixed. These results may lead some to conclude that the accuracy of NHC forecasts close to the United States has not improved over time. A statistically robust dataset can be obtained by considering “landfall-threatening” storms, defined as one for which tropical cyclone watches or warnings are in effect for some portion of the continental United States. In this study, long-term trends in accuracy are determined for NHC forecasts issued during these periods of threat and compared to trends for the Atlantic basin overall. A second set of trends are determined for forecasts verifying during the periods of threat. The analysis shows that NHC forecasts for land-threatening tropical cyclones are improving. These improvement trends are statistically significant, although the improvement rates for the land-threatening storms are smaller than those for the basin overall. Over the period 1970–2001, forecasts issued during the watch/warning stage improved at annual average rates of 0.7%, 1.6%, and 1.9% at 24,48, and 72 h, respectively.

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