Pacific Tropical Cyclones Research Articles

A possible mechanism of the impact of atmosphere-ocean interaction on the activity of tropical cyclones affecting China

In this study, tropical cyclone data from China Meteorological Administration (CMA) and the ECMWF reanalysis data for the period 1958–2001 was used to propose a possible mechanism for the impacts of air-sea interaction on the activity of tropical cyclones (TCs) affecting China. The frequency of TCs affecting China over past 40 years has trended downward, while during the same period, the air-sea interaction in the two key areas of the Pacific region has significantly weakened. Our diagnoses and simulations suggest that air-sea interactions in the central North Pacific tropics and subtropics (Area 1) have an important role in adjusting typhoon activities in the Northwest Pacific in general, and especially in TC activity affecting China. On the contrary, impacts of the air-sea interaction in the eastern part of the South Pacific tropics (Area 2) were found to be rather limited. As both observational analysis and modeling studies show that, in the past four decades and beyond, the weakening trend of the latent heat released from Area 1 matched well with the decreasing Northwest Pacific TC frequency derived from CMA datasets. Results also showed that the weakening trend of latent heat flux in the area was most likely due to the decreasing TC frequency over the Northwest Pacific, including those affecting China. Although our preliminary analysis revealed a possible mechanism through which the air-sea interaction may adjust the genesis conditions for TCs, which eventually affect China, other relevant questions, such as how TC tracks and impacts are affected by these trends, remain unanswered. Further in-depth investigations are required.

Eastern North Pacific Hurricanes 2011: An Average Season

Eastern North Pacific Hurricanes 2011: An Average Season

An Analysis of Multiple Predecessor Rain Events ahead of Tropical Cyclones Ike and Lowell: 10–15 September 2008

An analysis of three predecessor rain events (PREs) that occurred ahead of North Atlantic tropical cyclone (TC) Ike and east Pacific TC Lowell during 10–15 September 2008 is presented. The three PREs produced all-time daily record rainfall at many locations, including Lubbock, Texas (189.5 mm); Wichita, Kansas (262 mm); and Chicago–O’Hare, Illinois (169 mm), on 11–13 September, respectively.PRE 1 organized over Texas on 10 September with moisture from a stalled frontal boundary and the Bay of Campeche, and matured with moisture from TC Lowell. PRE 2 organized over the Texas Panhandle on 11 September with moisture from the Bay of Campeche, and developed and matured over Kansas and Missouri with moisture from TC Lowell. PRE 3 developed over Texas on 11 September, merged with and absorbed PRE 2 over Kansas and Missouri, and matured as it ingested moisture from TC Ike. All three PREs matured in the equatorward entrance region of an intensifying subtropical jet stream (STJ).Heavy rainfall with the three PREs occurred along a plume of moist air characterized by high precipitable water values that extended poleward over the central United States near the juxtaposition of the nose of a low-level jet, a region of lower-tropospheric forcing for ascent along a surface baroclinic zone, and the STJ equatorward entrance region. The cumulative upscale effect of persistent deep convection from the three PREs enhanced and “locked in” a favorable upper-tropospheric flow pattern conducive to ridge development over the Ohio Valley and STJ intensification over the central U.S. and Great Lakes region.

Development of Statistical Typhoon Intensity Prediction: Application to Satellite-Observed Surface Evaporation and Rain Rate (STIPER)

Abstract A statistical–dynamical model has been used for operational guidance for tropical cyclone (TC) intensity prediction. In this study, several multiple linear regression models and neural network (NN) models are developed for the intensity prediction of western North Pacific TCs at 24-, 48-, and 72-h intervals. The multiple linear regression models include a model of climatology and persistence (CLIPER), a model based on the Statistical Typhoon Intensity Prediction System (STIPS), which serves as the base regression model (BASE), and a model of STIPS with additional satellite estimates of surface evaporation (SLHF) and inner-core rain rate (IRR, STIPER model). A revised equation for the TC maximum potential intensity is derived using Tropical Rainfall Measuring Mission Microwave Imager optimally interpolated sea surface temperature data, which have higher temporal and spatial resolutions. Analyses of the resulting models show the marginal improvement of STIPER over BASE. However, IRR and SLHF are found to be significant predictors in the predictor pool. Neural network models using the same predictors as STIPER show reductions of the mean absolute errors of 7%, 11%, and 16% relative to STIPER for 24-, 48-, and 72-h forecasts, respectively. The largest improvement is found for the intensity forecasts of the rapidly intensifying and rapidly decaying TCs.

Reliability Analysis of Climate Change of Tropical Cyclone Activity over the Western North Pacific

Abstract Data homogeneity has become a significant issue in the study of tropical cyclones (TCs) and climate change. In this study, three historical datasets for the western North Pacific TCs from the Joint Typhoon Warning Center (JTWC), Japan Meteorological Agency (JMA), and China Meteorological Administration (CMA) are compared with a focus on TC intensity. Over the past 55 years (1951–2005), significant discrepancies are found among the three datasets, especially between the CMA and JTWC datasets. The TC intensity in the CMA dataset was evidently overestimated in the 1950s and from the late 1960s to the early 1970s, while it was overestimated after 1988 in the JTWC dataset, especially during 1993–2003. Large discrepancies in TC tracks exist in two periods of 1951–early 1960s and 1988–1990s. Further analysis reveals that the discrepancies are obviously related to the TC observational techniques. Before the era of meteorological satellites (1951–the early 1960s), and after the termination of aircraft reconnaissance (since 1988), large discrepancies exist in both TC intensity and track. That the intensity discrepancy was smallest during the period (1973–87) when aircraft reconnaissance data and the Dvorak technique were both available suggests that availability of the aircraft reconnaissance and the Dvorak method helps in reducing the TC intensity discrepancy. For those TCs that were included in all the three datasets, no significant increasing or decreasing trend was found over the past 50 years. Each of the three TC datasets has individual characteristics that make it difficult to tell which one is the best. For TCs that affect China, the CMA dataset has obvious advantages such as more complete and more accurate information.

An Automated, Objective, Multiple-Satellite-Platform Tropical Cyclone Surface Wind Analysis

AbstractA method to estimate objectively the surface wind fields associated with tropical cyclones using only data from multiple satellite platforms and satellite-based wind retrieval techniques is described. The analyses are computed on a polar grid using a variational data-fitting method that allows for the application of variable data weights to input data. The combination of gross quality control and the weighted variational analysis also produces wind estimates that have generally smaller errors than do the raw input data. The resulting surface winds compare well to the NOAA Hurricane Research Division H*Wind aircraft reconnaissance–based surface wind analyses, and operationally important wind radii estimated from these wind fields are shown to be generally more accurate than those based on climatological data. Most important, the analysis system produces global tropical cyclone surface wind analyses and related products every 6 h—without aircraft reconnaissance data. Also, the analysis and products are available in time for consideration by forecasters at the Joint Typhoon Warning Center, the Central Pacific Hurricane Center, and the National Hurricane Center in preparing their forecasts and advisories. This Multiplatform Tropical Cyclone Surface Wind Analysis (MTCSWA) product is slated to become an operationally supported product at the National Environmental Satellite Data and Information Service (NESDIS). The input data, analysis method, products, and verification statistics associated with the MTCSWA are discussed within.

Revision of Convection and Vertical Diffusion Schemes in the NCEP Global Forecast System

Abstract A new physics package containing revised convection and planetary boundary layer (PBL) schemes in the National Centers for Environmental Prediction’s Global Forecast System is described. The shallow convection (SC) scheme in the revision employs a mass flux parameterization replacing the old turbulent diffusion-based approach. For deep convection, the scheme is revised to make cumulus convection stronger and deeper to deplete more instability in the atmospheric column and result in the suppression of the excessive grid-scale precipitation. The PBL model was revised to enhance turbulence diffusion in stratocumulus regions. A remarkable difference between the new and old SC schemes is seen in the heating or cooling behavior in lower-atmospheric layers above the PBL. While the old SC scheme using the diffusion approach produces a pair of layers in the lower atmosphere with cooling above and heating below, the new SC scheme using the mass-flux approach produces heating throughout the convection layers. In particular, the new SC scheme does not destroy stratocumulus clouds off the west coasts of South America and Africa as the old scheme does. On the other hand, the revised deep convection scheme, having a larger cloud-base mass flux and higher cloud tops, appears to effectively eliminate the remaining instability in the atmospheric column that is responsible for the excessive grid-scale precipitation in the old scheme. The revised PBL scheme, having an enhanced turbulence mixing in stratocumulus regions, helps prevent too much low cloud from forming. An overall improvement was found in the forecasts of the global 500-hPa height, vector wind, and continental U.S. precipitation with the revised model. Consistent with the improvement in vector wind forecast errors, hurricane track forecasts are also improved with the revised model for both Atlantic and eastern Pacific hurricanes in 2008.

AN EMPIRICAL STUDY OF TROPICAL CYCLONE ACTIVITY IN THE ATLANTIC AND PACIFIC OCEANS: 1851–2005

The trends and intrinsic frequencies in the time series of the number of Tropical Cyclones (TCs), hurricanes and typhoons, and Categories 4 and 5 hurricanes and typhoons in the Atlantic and Pacific Ocean domains, and the yearly integral of hurricane wind energy, represented by the Power Density Index (PDI), in the Atlantic and Eastern North Pacific Ocean domains are studied. The results show that the Empirical Modal Decomposition (EMD) method [Huang et al. (1998)] successfully reveals that there are intrinsic modes of variations that are controlled by climate systems such as the Quasi-Biennial Oscillation (QBO), the El Nino Southern Oscillation (ENSO), and the Atlantic and Pacific Multi-Decadal Oscillations (AMO and PDO), along with the Meridional Overturning Circulation (MOC). It also reveals some oscillation modes whose controlling factors are not yet identified. In both the Atlantic and Pacific Ocean domains, the frequencies of TCs, hurricane/typhoon-strength TCs and the strongest (Saffir-Simpson Categories 4 and 5) TCs have slowly rising trends. In the Atlantic Ocean, our study indicates that since the mid-1970s, the observed rise in the number of the strongest (Cats. 4 and 5) TCs as discussed previously by Webster et al. [2005] and the rise in the measure of destructiveness, the Power Density Index (PDI), developed by Emanuel [2005], were not the cause of rising trends, but instead, they are the result of the combination of positive phases of several intrinsic frequency modes. In the Pacific Ocean, the rising trends have larger amplitudes than those in the Atlantic Ocean, but the higher frequency modes appear to play a more important role in deciding the year-to-year Pacific TC, hurricane/typhoon and Cats. 4 and 5 TC activity levels.

The 2009 Hurricane Season in the Eastern North Pacific Basin: An Analysis of Environmental Conditions

Abstract Despite the presence of an intensifying El Niño event, the 2009 eastern North Pacific hurricane season was near normal when considering overall hurricane activity. This is in contrast to the relative lull in activity observed between 1998 and 2008. Previous research has noted that the eastern North Pacific should be subdivided into two development regions, the western development region (WDR; 10°–20°N, 116°W–180°) and the eastern development region (EDR; 10°–20°N, North American coastline to 115.9°W), when examining interannual hurricane variability. In 2009, the EDR saw below average numbers of tropical cyclones of all intensities, while the WDR saw near-normal activity. However, activity in both regions varied sharply from month to month with periods of high activity in August and October and lower activity in July and September. This monthly variability was also observed in primary environmental forcing factors such as total precipitable water, tropospheric vertical wind shear, and low-level relative vorticity, particularly for the WDR. This variability was obscured by simply examining seasonal means. It is shown that for the 2009 season, large-scale environmental factors forced by the El Niño event and two cycles of the Madden–Julian oscillation contributed strongly to the observed patterns of cyclone activity across the basin.

Eastern North Pacific Hurricane Season of 2009

Abstract The 2009 eastern North Pacific hurricane season had near normal activity, with a total of 17 named storms, of which seven became hurricanes and four became major hurricanes. One hurricane and one tropical storm made landfall in Mexico, directly causing four deaths in that country along with moderate to severe property damage. Another cyclone that remained offshore caused an additional direct death in Mexico. On average, the National Hurricane Center track forecasts in the eastern North Pacific for 2009 were quite skillful.

Eastern North Pacific Hurricanes 2010: Flooding in a Slow Season

Eastern North Pacific Hurricanes 2010: Flooding in a Slow Season

Revision of Convection and Vertical Diffusion Schemes in the NCEP Global Forecast System

A new physics package containing revised convection and planetary boundary layer (PBL) schemes in the National Centers for Environmental Prediction’s Global Forecast System is described. The shallow convection (SC) scheme in the revision employs a mass flux parameterization replacing the old turbulent diffusion-based approach. For deep convection, the scheme is revised to make cumulus convection stronger and deeper to deplete more instability in the atmospheric column and result in the suppression of the excessive grid-scale precipitation. The PBL model was revised to enhance turbulence diffusion in stratocumulus regions. A remarkable difference between the new and old SC schemes is seen in the heating or cooling behavior in lower-atmospheric layers above the PBL. While the old SC scheme using the diffusion approach produces a pair of layers in the lower atmosphere with cooling above and heating below, the new SC scheme using the mass-flux approach produces heating throughout the convection layers. In particular, the new SC scheme does not destroy stratocumulus clouds off the west coasts of South America and Africa as the old scheme does. On the other hand, the revised deep convection scheme, having a larger cloud-base mass flux and higher cloud tops, appears to effectively eliminate the remaining instability in the atmospheric column that is responsible for the excessive grid-scale precipitation in the old scheme. The revised PBL scheme, having an enhanced turbulence mixing in stratocumulus regions, helps prevent too much low cloud from forming. An overall improvement was found in the forecasts of the global 500-hPa height, vector wind, and continental U.S. precipitation with the revised model. Consistent with the improvement in vector wind forecast errors, hurricane track forecasts are also improved with the revised model for both Atlantic and eastern Pacific hurricanes in 2008.

Comparison of Three Western North Pacific Tropical Cyclone Best Track Datasets in a Seasonal Context

The quality of tropical cyclone (TC) best track data has increasingly received more attention in climate research in recent years because of the rising interest in the possible effects of global warming on TC activity. In this paper, three best track datasets for the western North Pacific TCs were compared in a seasonal context. Firstly, the statistical characteristics were examined based on their distributions. Then, the potential impact of particular features within the datasets was evaluated by using contrastive cluster analyses. The mean amplitude of the annual cycle in the Japan Meteorological Agency (JMA) data is largest among the three datasets. The smallest interannual variability helped the Shanghai Typhoon Institute of China Meteorological Administration (CMA-STI) dataset to resist the negative effect of outliers. An inhomogeneity around 2003–2004 was identified in the Joint Typhoon Warning Center (JTWC) data by the outliers and was compared with the JMA and CMA-STI data. By using contrastive cluster analyses, the differences among the datasets and some effects related to particular issues, including the representation of the annual cycle, the outliers, and wind conversion were evaluated. The JTWC dataset is affected by outliers and wind conversion among the different average times, whereas the representation of the annual cycle was important for the CMA-STI data. After excluding all the outliers, the results indicated more consistent classifications of the TC annual cycle between the JMA and JTWC data.

The 2009 Eastern North Pacific Hurricane Season: A Return to Normal Activity

The 2009 Eastern North Pacific Hurricane Season: A Return to Normal Activity

Eastern North Pacific Hurricane Season of 2008

Abstract The hurricane season of 2008 in the eastern North Pacific basin is summarized, and the individual tropical cyclones are described. Official track and intensity forecasts of these cyclones are also evaluated. The 2008 eastern North Pacific season was relatively quiet, with overall activity at about 75% of the long-term median. A total of 16 tropical storms formed, of which 7 became hurricanes and 2 became major hurricanes. One hurricane, one tropical storm, and two tropical depressions made landfall in Mexico, causing eight direct deaths in that country along with significant property damage. In addition, Tropical Storm Alma was the first tropical cyclone on record to make landfall along the Pacific coast of Nicaragua. On average, the official track forecasts in the eastern Pacific for 2008 were quite skillful and set records for accuracy from 1 to 3 days. However, no appreciable improvement in mean intensity forecast skill was noted.

Interpretation of Tropical Cyclone Forecast Sensitivity from the Singular Vector Perspective

Abstract In this study, the leading singular vectors (SVs), which are the fastest-growing perturbations (in a linear sense) to a given forecast, are used to examine and classify the dynamic relationship between tropical cyclones (TCs) and synoptic-scale environmental features that influence their evolution. Based on the 72 two-day forecasts of the 18 western North Pacific TCs in 2006, the SVs are constructed to optimize perturbation energy within a 20° × 20° latitude–longitude box centered on the 48-h forecast position of the TCs using the Navy Operational Global Atmospheric Prediction System (NOGAPS) forecast and adjoint systems. Composite techniques are employed to explore these relationships and highlight how the dominant synoptic-scale features that impact TC forecasts evolve on seasonal time scales. The NOGAPS initial SVs show several different patterns that highlight the relationship between the TC forecast sensitivity and the environment during the western North Pacific typhoon season in 2006. In addition to the relation of the SV maximum to the inward flow region of the TC, there are three patterns identified where the local SV maxima collocate with low-radial-wind-speed regions. These regions are likely caused by the confluence of the flow associated with the TC itself and the flow from other synoptic systems, such as the subtropical high and the midlatitude jet. This is the new finding beyond the previous NOGAPS SV results on TCs. The subseasonal variations of these patterns corresponding to the dynamic characteristics are discussed. The SV total energy vertical structures for the different composites are used to demonstrate the contributions from kinetic and potential energy components of different vertical levels at initial and final times.

A 22 yr hurricane cycle and its relation with geomagnetic activity

Applying spectral analysis to the Atlantic and Pacific hurricane time series, we found periodicities that coincide with the main sunspot and magnetic solar cycles. To assess the possibility that these periodicities could be associated with solar activity, we obtain correlations between hurricane occurrence and several solar activity-related phenomena, such as the total solar irradiance, the cosmic ray flux and the Dst index of geomagnetic activity. Our results indicate that the highest significant correlations are found between the Atlantic and Pacific hurricanes and the Dst index. Most importantly, both oceans present the highest hurricane–Dst correlations during the ascending part of odd solar cycles and the descending phase of even solar cycles. This shows not only the existence of a 22 yr cycle but also the nature of such periodicity. Furthermore, we found that the Atlantic hurricanes behave differently from the Pacific hurricanes in relation to the solar activity-related disturbances considered.

Eastern North Pacific Hurricane Season of 2007

Abstract The hurricane season of 2007 in the eastern North Pacific Ocean basin is summarized, individual tropical cyclones are described, and a forecast verification is presented. The 2007 eastern North Pacific season was not an active one. There were 11 tropical storms, of which only 4 became hurricanes. Only one cyclone became a major hurricane. One hurricane struck Mexico and one tropical storm made landfall near the Guatemala–Mexico border. The 2007 National Hurricane Center forecast track errors were lower than the previous 5-yr means at all forecast lead times, and especially so for the 72-, 96-, and 120-h periods when the errors were 16%, 22%, and 20% lower, respectively. The official intensity forecasts had only limited skill.

Northern Hemisphere tropical cyclone activity

Recent historical Northern Hemisphere (NH) tropical cyclone (TC) inactivity is compared with strikingly large observed variability during the past three decades. Yearly totals of the combined active‐basin NH accumulated cyclone energy (ACE) are highly correlated with boreal spring sea‐surface temperature (SST) in the North Pacific Ocean and are representative of an evolving dual‐gyre, trans‐hemispheric correlation pattern throughout the calendar year. The observed offsetting nature of Eastern Pacific and North Atlantic basin ACE during the past three decades and a strong dependence of combined Pacific TC activity upon the El Niño‐Southern Oscillation reflect the interrelated modulation of overall NH integrated TC energy by large‐scale modes of climate variability. Thus, the quiescent period of overall integrated NH TC ACE continuing throughout 2008 is not unexpected in the context of previous periods of colder Pacific SSTs.

Eastern North Pacific Hurricane Season of 2006

Abstract The hurricane season of 2006 in the eastern North Pacific basin is summarized, and the individual tropical cyclones are described. Also, the official track and intensity forecasts of these cyclones are verified and evaluated. The 2006 eastern North Pacific season was an active one, in which 18 tropical storms formed. Of these, 10 became hurricanes and 5 became major hurricanes. A total of 2 hurricanes and 1 tropical depression made landfall in Mexico, causing 13 direct deaths in that country along with significant property damage. On average, the official track forecasts in the eastern Pacific for 2006 were quite skillful. No appreciable improvement in mean intensity forecasts was noted, however.