Articles | Volume 6, issue 4
https://doi.org/10.5194/wcd-6-1443-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wcd-6-1443-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
18 Nov 2025
Research article |
| 18 Nov 2025
| 18 Nov 2025
Seasonal Predictability of Vapor Pressure Deficit in the western United States
Melissa L. Breeden
CORRESPONDING AUTHOR
NOAA Physical Sciences Laboratory, Boulder, 80305, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, 80309, USA
Andrew Hoell
NOAA Physical Sciences Laboratory, Boulder, 80305, USA
Rochelle P. Worsnop
NOAA Physical Sciences Laboratory, Boulder, 80305, USA
John R. Albers
NOAA Physical Sciences Laboratory, Boulder, 80305, USA
Mike Hobbins
NOAA Physical Sciences Laboratory, Boulder, 80305, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, 80309, USA
Rachel M. Robinson
NOAA Physical Sciences Laboratory, Boulder, 80305, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, 80309, USA
Daniel J. Vimont
Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, 53706, USA
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Melissa Leah Breeden, Andrew Hoell, John Robert Albers, and Kimberly Slinski
Weather Clim. Dynam., 4, 963–980, https://doi.org/10.5194/wcd-4-963-2023, https://doi.org/10.5194/wcd-4-963-2023, 2023
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We compare the month-to-month evolution of daily precipitation over central southwest Asia (CSWA), a data-sparse, food-insecure area prone to drought and flooding. The seasonality of CSWA precipitation aligns with the seasonality of warm conveyor belts (WCBs), the warm, rapidly ascending airstreams associated with extratropical storms, most common from February–April. El Niño conditions are related to more WCBs and precipitation and La Niña conditions the opposite, except in January.
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We use a statistical dynamical model to generate precipitation forecasts for lead times of 2–6 weeks over southwest Asia, which are needed to support humanitarian food distribution. The model signal-to-noise ratio is used to identify a smaller subset of forecasts with particularly high skill, so-called subseasonal forecasts of opportunity (SFOs). Precipitation SFOs are often related to slowly evolving tropical phenomena, namely the El Niño–Southern Oscillation and Madden–Julian Oscillation.
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Ozone transported from the stratosphere contributes to background ozone concentrations in the free troposphere and to surface ozone exceedance events that affect human health. The physical processes whereby the El Niño–Southern Oscillation (ENSO) modulates North American stratosphere-to-troposphere ozone transport during spring are documented, and the usefulness of ENSO for predicting ozone events that may cause exceedances in surface air quality standards are assessed.
John R. Albers, Amy H. Butler, Melissa L. Breeden, Andrew O. Langford, and George N. Kiladis
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Weather variability controls the transport of ozone from the stratosphere to the Earth’s surface and water vapor from oceanic source regions to continental land masses. Forecasting these types of transport has high societal value because of the negative impacts of ozone on human health and the role of water vapor in governing precipitation variability. We use upper-level wind forecasts to assess the potential for predicting ozone and water vapor transport 3–6 weeks ahead of time.
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Prior research has found a maximum in deep stratosphere-to-troposphere mass/ozone transport over the western United States in boreal spring, which can enhance surface ozone concentrations, reducing air quality. We find that the winter-to-summer evolution of the north Pacific jet increases the frequency of stratospheric intrusions that drive transport, helping explain the observed maximum. The El Niño–Southern Oscillation affects the timing of the spring jet transition and therefore transport.
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Providing early warning of coastal flooding is an emerging priority for the National Oceanic and Atmospheric Administration. We assess whether current operational forecast models can provide the basis for predicting the risks of higher-than-normal coastal sea level values up to 6 weeks in advance. For many United States coastal locations, models have sufficient prediction skill to be used as the basis for the development of a high tide flooding prediction system on subseasonal timescales.
Melissa Leah Breeden, Andrew Hoell, John Robert Albers, and Kimberly Slinski
Weather Clim. Dynam., 4, 963–980, https://doi.org/10.5194/wcd-4-963-2023, https://doi.org/10.5194/wcd-4-963-2023, 2023
Short summary
Short summary
We compare the month-to-month evolution of daily precipitation over central southwest Asia (CSWA), a data-sparse, food-insecure area prone to drought and flooding. The seasonality of CSWA precipitation aligns with the seasonality of warm conveyor belts (WCBs), the warm, rapidly ascending airstreams associated with extratropical storms, most common from February–April. El Niño conditions are related to more WCBs and precipitation and La Niña conditions the opposite, except in January.
Dillon Elsbury, Amy H. Butler, John R. Albers, Melissa L. Breeden, and Andrew O'Neil Langford
Atmos. Chem. Phys., 23, 5101–5117, https://doi.org/10.5194/acp-23-5101-2023, https://doi.org/10.5194/acp-23-5101-2023, 2023
Short summary
Short summary
One of the global hotspots where stratosphere-to-troposphere transport (STT) of ozone takes place is over Pacific North America (PNA). However, we do not know how or if STT over PNA will change in response to climate change. Using climate model experiments forced with
worst-casescenario Representative Concentration Pathway 8.5 climate change, we find that changes in net chemical production and transport of ozone in the lower stratosphere increase STT of ozone over PNA in the future.
Melissa L. Breeden, John R. Albers, and Andrew Hoell
Weather Clim. Dynam., 3, 1183–1197, https://doi.org/10.5194/wcd-3-1183-2022, https://doi.org/10.5194/wcd-3-1183-2022, 2022
Short summary
Short summary
We use a statistical dynamical model to generate precipitation forecasts for lead times of 2–6 weeks over southwest Asia, which are needed to support humanitarian food distribution. The model signal-to-noise ratio is used to identify a smaller subset of forecasts with particularly high skill, so-called subseasonal forecasts of opportunity (SFOs). Precipitation SFOs are often related to slowly evolving tropical phenomena, namely the El Niño–Southern Oscillation and Madden–Julian Oscillation.
John R. Albers, Amy H. Butler, Andrew O. Langford, Dillon Elsbury, and Melissa L. Breeden
Atmos. Chem. Phys., 22, 13035–13048, https://doi.org/10.5194/acp-22-13035-2022, https://doi.org/10.5194/acp-22-13035-2022, 2022
Short summary
Short summary
Ozone transported from the stratosphere contributes to background ozone concentrations in the free troposphere and to surface ozone exceedance events that affect human health. The physical processes whereby the El Niño–Southern Oscillation (ENSO) modulates North American stratosphere-to-troposphere ozone transport during spring are documented, and the usefulness of ENSO for predicting ozone events that may cause exceedances in surface air quality standards are assessed.
Amy McNally, Jossy Jacob, Kristi Arsenault, Kimberly Slinski, Daniel P. Sarmiento, Andrew Hoell, Shahriar Pervez, James Rowland, Mike Budde, Sujay Kumar, Christa Peters-Lidard, and James P. Verdin
Earth Syst. Sci. Data, 14, 3115–3135, https://doi.org/10.5194/essd-14-3115-2022, https://doi.org/10.5194/essd-14-3115-2022, 2022
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The Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS) global and Central Asia data streams described here generate routine estimates of snow, soil moisture, runoff, and other variables useful for tracking water availability. These data are hosted by NASA and USGS data portals for public use.
John R. Albers, Amy H. Butler, Melissa L. Breeden, Andrew O. Langford, and George N. Kiladis
Weather Clim. Dynam., 2, 433–452, https://doi.org/10.5194/wcd-2-433-2021, https://doi.org/10.5194/wcd-2-433-2021, 2021
Short summary
Short summary
Weather variability controls the transport of ozone from the stratosphere to the Earth’s surface and water vapor from oceanic source regions to continental land masses. Forecasting these types of transport has high societal value because of the negative impacts of ozone on human health and the role of water vapor in governing precipitation variability. We use upper-level wind forecasts to assess the potential for predicting ozone and water vapor transport 3–6 weeks ahead of time.
Melissa L. Breeden, Amy H. Butler, John R. Albers, Michael Sprenger, and Andrew O'Neil Langford
Atmos. Chem. Phys., 21, 2781–2794, https://doi.org/10.5194/acp-21-2781-2021, https://doi.org/10.5194/acp-21-2781-2021, 2021
Short summary
Short summary
Prior research has found a maximum in deep stratosphere-to-troposphere mass/ozone transport over the western United States in boreal spring, which can enhance surface ozone concentrations, reducing air quality. We find that the winter-to-summer evolution of the north Pacific jet increases the frequency of stratospheric intrusions that drive transport, helping explain the observed maximum. The El Niño–Southern Oscillation affects the timing of the spring jet transition and therefore transport.
Sarah F. Kew, Sjoukje Y. Philip, Mathias Hauser, Mike Hobbins, Niko Wanders, Geert Jan van Oldenborgh, Karin van der Wiel, Ted I. E. Veldkamp, Joyce Kimutai, Chris Funk, and Friederike E. L. Otto
Earth Syst. Dynam., 12, 17–35, https://doi.org/10.5194/esd-12-17-2021, https://doi.org/10.5194/esd-12-17-2021, 2021
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Motivated by the possible influence of rising temperatures, this study synthesises results from observations and climate models to explore trends (1900–2018) in eastern African (EA) drought measures. However, no discernible trends are found in annual soil moisture or precipitation. Positive trends in potential evaporation indicate that for irrigated regions more water is now required to counteract increased evaporation. Precipitation deficit is, however, the most useful indicator of EA drought.
Cited articles
Abatzoglou, J. T. and Williams, A. P.: Impact of anthropogenic climate change on wildfire across western US forests, P. Natl. Acad. Sci. USA, 113, 11770–11775, https://doi.org/10.1073/pnas.1607171113, 2016.
Albers, J. R. and Newman, M.: A priori identification of skillful extratropical subseasonal forecasts, Geophys. Res. Lett., 46, 12527–12536, https://doi.org/10.1029/2019GL085270, 2019.
Albers, J. R. and Newman, M.: Subseasonal predictability of the North Atlantic Oscillation, Environ. Res. Lett., 16, 044024, https://doi.org/10.1088/1748-9326/abe781, 2021.
Albers, J. R., Newman, M., Hoell, A., Breeden, M. L., Wang, Y., and Lou, J.: The February 2021 cold air outbreak in the United States: A subseasonal forecast of opportunity, B. Am. Meteorol. S., 103, E2887–E2904, https://doi.org/10.1175/BAMS-D-21-0266.1, 2022.
Alexander, M. A., Matrosova, L., Penland, C., Scott, J. D., and Chang, P.: Forecasting Pacific SSTs: Linear inverse model predictions of the PDO, J. Climate, 21, 385–402, https://doi.org/10.1175/2007JCLI1849.1, 2008.
Anderson, D. B.: Relative humidity or vapor pressure deficit, Ecology, 17, 277–282, https://doi.org/10.2307/1931468, 1936.
Barnett, T. P. and Preisendorfer, R. W.: Origins and levels of monthly and seasonal forecast skill for North American surface temperature determined by canonical correlation analysis, Mon. Weather Rev., 115, 1825–1850, https://doi.org/10.1175/1520-0493(1987)115<1825:OALOMA>2.0.CO;2, 1987.
Barnston, A. G.: Linear statistical short-term climate predictive skill in the northern hemisphere, J. Climate, 7, 1513–1564, https://doi.org/10.1175/1520-0442(1994)007<1513:LSSTCP>2.0.CO;2, 1994.
Baxter, I., Ding, Q., Schweiger, A., LHeureux, M., Baxter, S., Wang, T., Zhang, Q., Harnos, K., Markle, B., Topal, D., and Lu, J.: How tropical Pacific surface cooling contributed to accelerated sea ice melt from 2007 to 2012 as ice is thinned by anthropogenic forcing, Journal of Climate, 32, 8583–8602, https://doi.org/10.1175/JCLI-D-18-0783.1, 2019.
Becker, E. J., Kirtman, B. P., L'Heureux, M., Muñoz, Á. G., and Pegion, K.: A decade of the North American Multimodel Ensemble (NMME): Research, application, and future directions, B. Am. Meteorol. S., 103, E973–E995, https://doi.org/10.1175/BAMS-D-20-0327.1, 2022.
Beverley, J., Newman, M., and Hoell, A.: Rapid development of systematic ENSO-related seasonal forecast errors, Geophys. Res. Lett., 50, e2022GL102249, https://doi.org/10.1029/2022GL102249, 2023.
Bradshaw, L. S., Deeming, J. E., Burgan, R. E., and Cohen, J. D.: The 1978 National Fire-Danger Rating System: Technical documentation, USDA Forest Service, Tech. Rep. INT-169, 49 pp., https://www.fs.usda.gov/rm/pubs_int/int_gtr169.pdf (last access: 14 November 2025), 1983.
Breeden, M. L., Albers, J. R., Butler, A. H., and Newman, M.: The spring minimum in subseasonal 2 m temperature forecast skill over North America, Mon. Weather Rev., 150, 2617–2628, https://doi.org/10.1175/MWR-D-22-0062.1, 2022a.
Breeden, M. L., Albers, J. R., and Hoell, A.: Subseasonal precipitation forecasts of opportunity over central southwest Asia, Weather Clim. Dynam., 3, 1183–1197, https://doi.org/10.5194/wcd-3-1183-2022, 2022b.
Buch, J., Williams, A. P., Juang, C. S., Hansen, W. D., and Gentine, P.: SMLFire1.0: a stochastic machine learning (SML) model for wildfire activity in the western United States, Geosci. Model Dev., 16, 3407–3433, https://doi.org/10.5194/gmd-16-3407-2023, 2023.
Chiodi, A. M., Potter, B. E., and Larkin, N. K.: Multi-decadal change in western US nighttime vapor pressure deficit, Geophys. Res. Lett., 48, e2021GL092830, https://doi.org/10.1029/2021GL092830, 2021.
Cohen, J. and Deeming, J.: The National Fire Danger Rating System: Basic equations, USDA Forest Service, Pacific Southwest Forest and Range Experiment Station, Tech. Rep. PSW-82, 23 pp., https://doi.org/10.2737/PSW-GTR-82, 1985.
Colorado Division of Fire Prevention and Control: Community Preparedness, https://dfpc.colorado.gov/communityfireprep, last access: 22 May 2023.
Coop, J. D., Parks, S. A., Stevens-Rumann, C. S., Crausbay, S. D., Higuera, P. E., Hurteau, M. D., Tepley, M., Whitman, E., Assal, T., Collins, B. M., Davis, K. T., Dobrowski, S., Falk, D. A., Fornwalt, P. J., Fulé, P. Z., Harvey, B. J., Kane, V. R., Littlefield, C. E., Margolis, E. Q., North, M., Parisien, M.-A., Prichard, S., and Rodman, K. C.: Wildfire-driven forest conversion in western North American landscapes, BioScience, 70, 659–673, https://doi.org/10.1093/biosci/biaa061, 2020.
Ding, Q., Wallace, J. M., Battisti, D. S., Steig, E. J., Gallant, A. J., Kim, H.-J., and Geng, L.: Tropical forcing of the recent rapid Arctic warming in northeastern Canada and Greenland, Nature, 509, 209, https://doi.org/10.1038/nature13260, 2014.
Farrell, B. F.: Optimal excitation of neutral Rossby waves, J. Atmos. Sci., 45, 163–172, https://doi.org/10.1175/1520-0469(1988)045<0163:OEONRW>2.0.CO;2, 1988.
Farrell, B. F. and Ioannou, P. J.: Generalized stability theory. Part I: Autonomous operators, J. Atmos. Sci., 53, 2025–2040, https://doi.org/10.1175/1520-0469(1996)053<2025:GSTPIA>2.0.CO;2, 1996.
Hasselmann, K.: PIPs and POPs: The reduction of complex dynamical systems using principal interaction and oscillation patterns, J. Geophys. Res.-Atmos., 93, 11015–11021, https://doi.org/10.1029/JD093iD09p11015, 1988.
Henderson, S. A., Vimont, D. J., and Newman, M.: The critical role of non-normality in partitioning tropical and extratropical contributions to PNA growth, J. Climate, 33, 6273–6295, https://doi.org/10.1175/JCLI-D-19-0555.1, 2020.
Higgins, R. W., Kim, H.-K., and Unger, D.: Long-lead seasonal temperature and precipitation prediction using tropical Pacific SST consolidation forecasts, J. Climate, 17, 3398–3414, https://doi.org/10.1175/1520-0442(2004)017<3398:LSTAPP>2.0.CO;2, 2004.
Higuera, P. R. and Abatzoglou, J. T.: Record-setting climate enabled the extraordinary 2020 fire season in the western United States, Glob. Change Biol., 27, 1–2, https://doi.org/10.1111/gcb.15388, 2021.
Hoell, A., Funk, C., and Barlow, M.: The regional forcing of Northern hemisphere drought during recent warm tropical west Pacific Ocean La Niña events, Clim. Dynam., 42, 3289–3311, https://doi.org/10.1007/s00382-013-1799-4, 2014.
Hoell, A., Quan, X.-W., Hoerling, M., Fu, R., Mankin, J., Simpson, I., Seager, R., He, C., Lehner, F., Lisonbee, J., Livneh, B., and Sheffield, A.: Record low North American monsoon rainfall in 2020 reignites drought over the American Southwest, B. Am. Meteorol. S., 103, S26–S32, https://doi.org/10.1175/BAMS-D-21-0129.1, 2022.
Kobayashi, S., Ota, Y. Harada, Y., Ebita, A., Moriya, M., Onoda, H., Onogi, K., Kamahori, H., Kobayashi, C., Endo, H., Miyaoka, K., and Takahashi, K.: The JRA-55 reanalysis: General specifications and basic characteristics, J. Meteorol. Soc. Jn. Ser. II, 93, 5–48, https://doi.org/10.2151/jmsj.2015-001, 2015.
Kumar, S., Newman, M., Wang, Y., and Livneh, B.: Potential reemergence of seasonal soil moisture anomalies in North America, J. Climate, 32, 2707–2734, https://doi.org/10.1175/JCLI-D-18-0540.1, 2019.
L'Heureux, M., Levine, A. F. Z., Newman, M., Ganter, C., Luo, J.-J., Tippett, M. K., and Stockdale, T. N.: ENSO prediction, in: El Niño Southern Oscillation in a changing climate, edited by: McPhaden, M. J., Santoso, A., and Cai, W., American Geophysical Union, 227–246, https://doi.org/10.1002/9781119548164.ch10, 2020.
L'Heureux, M. L., Tippett, M. K., Takahashi, K., Barnston, A. G., Becker, E. J., Bell, G. D., Di Liberto, T. E., Gottschalck, J., Halpert, M. S., Hu, Z.-Z., Johnson, N. C., Xue, Y., and Wang, W.: Strength outlooks for the El Niño–Southern Oscillation, Weather Forecast., 34, 165–175, https://doi.org/10.1175/WAF-D-18-0126.1, 2019.
Liu, S., Hu, S., and Seager, R.: The West Pacific teleconnection drives the interannual variability of autumn wildfire weather in the western United States after 2000, Earth's Future, 12, e2024EF004922, https://doi.org/10.1029/2024EF004922, 2024.
Mankin, J. S., Simpson, I., Hoell, A., Fu, R., Lisonbee, J., Sheffield, A., and Barrie, D.: NOAA Drought Task Force report on the 2020–2021 southwestern U. S. drought, NOAA Drought Task Force, MAPP, and NIDIS, https://www.drought.gov/sites/default/files/2021-09/NOAA-Drought-Task-Force-IV-Southwest-Drought-Report-9-23-21.pdf, (last access: 13 November 2025), 2021.
Mariotti, A., Baggett, C., Barnes, E. A., Becker, E., Butler, A., Collins, D. C., Dirmeyer, P. A., Ferranti, L., Johnson, N. C., Jones, J., Kirtman, B. P., Lang, A. L., Molod, A., Newman, M., Robertson, A. W., Schubert, S., Waliser, D. E., and Albers, J.: Windows of Opportunity for Skillful Forecasts Subseasonal to Seasonal and Beyond, B. Am. Meteorol. Soc., 101, E608–E625, 2020.
McEvoy, D. J., Huntington, J. L., Mejia, J. F., and Hobbins, M. T.: Improved seasonal drought forecasts using reference evapotranspiration anomalies, Geophys. Res. Lett., 43, 377–385, https://doi.org/10.1002/2015GL067009, 2016.
National Interagency Fire Center (NIFC): https://www.nifc.gov/fire-information/statistics/suppression-costs (last access: 2 December 2023), 2022.
National Interagency Fire Center (NIFC): Geographic Area Coordination Centers National Website Portal, https://gacc.nifc.gov/ (last access: 13 November 2025), 2025.
Newman, M.: An empirical benchmark for decadal forecasts of global surface temperature anomalies, J. Climate, 26, 5260–5269, https://doi.org/10.1175/JCLI-D-12-00590.1, 2013.
Newman, M. and Sardeshmukh, P. D.: Are we near the predictability limit of tropical Indo-Pacific sea surface temperatures?, Geophys. Res. Lett., 44, 8520–8529, https://doi.org/10.1002/2017GL074088, 2017.
Newman, M., Sardeshmukh, P. D., Winkler, C. R., and Whitaker, J. S.: A study of subseasonal predictability, Mon. Weather Rev., 131, 1715–1732, https://doi.org/10.1175//2558.1, 2003.
Newman, M., Sardeshmukh, P. D., and Penland, C.: How important is air-sea coupling in ENSO and MJO evolution?, J. Climate, 22, 2958–2977, https://doi.org/10.1175/2008JCLI2659.1, 2009.
Newman, M., Alexander, M., and Scott, J. D.: An empirical model of tropical ocean dynamics, Clim. Dynam., 37, 1823–1841, https://doi.org/10.1007/s00382-011-1034-0, 2011.
NOAA National Centers for Environmental Information (NCEI): U.S. Billion-Dollar Weather and Climate Disasters, https://www.ncei.noaa.gov/access/billions/ (last access: 13 November 2025), https://doi.org/10.25921/stkw-7w73, 2022.
Ostoja, S. M., Crimmins, A. R., Byron, R. G., East, A. E., Méndez, M., O'Neill, S. M., Peterson, D. L., Pierce, J. R., Raymond, C., Tripati, A., and Vaidyanathan, A.: Focus on western wildfires, in: Fifth National Climate Assessment, edited by: Crimmins, A. R., Avery, C. W., Easterling, D. R., Kunkel, K. E., Stewart, B. C., and Maycock, T. K., U. S. Global Change Research Program, Washington, DC, USA, 11 pp., https://doi.org/10.7930/NCA5.2023.F2, 2023.
Patricola, C. M., O'Brien, J. P., Risser, M. D., Rhoades, A. M., O'Brien, T. A., Ullrich, P. A., Stone, D. A., and Collins, W. D.: Maximizing ENSO as a source of western US hydroclimate predictability, Clim. Dynam., 54, 351–372, https://doi.org/10.1007/s00382-019-05004-8, 2020.
Peng, P., Barnston, A. G., and Kumar, A.: A comparison of skill between two versions of the NCEP Climate Forecast System (CFS) and CPC's operational short-lead seasonal outlooks, Weather Forecast., 28, 445–462, https://doi.org/10.1175/WAF-D-12-00057.1, 2013.
Penland, C.: Random forcing and forecasting using principal oscillation pattern analysis, Mon. Weather Rev., 117, 2165–2185, https://doi.org/10.1175/1520-0493(1989)117<2165:RFAFUP>2.0.CO;2, 1989.
Penland, C. and Matrosova, L.: A balance condition for stochastic numerical models with application to the El Niño-Southern Oscillation, J. Climate, 7, 1352–1372, https://doi.org/10.1175/1520-0442(1994)007<1352:ABCFSN>2.0.CO;2, 1994.
Penland, C. and Matrosova, L.: Studies of El Niño and Interdecadal Variability in Tropical Sea Surface Temperatures Using a Nonnormal Filter, J. Climate, 19, 5796–5815, https://doi.org/10.1175/JCLI3951.1, 2006.
Penland, C. and Sardeshmukh, P. D.: The optimal growth of tropical sea surface temperature anomalies, J. Climate, 8, 1999–2024, https://doi.org/10.1175/1520-0442(1995)008<1999:TOGOTS>2.0.CO;2, 1995.
Prein, A. F., Towler, E., Ge, M., Llewellyn, D., Baker, S., Tighi, S., and Barrett, L.: Sub-seasonal predictability of North America monsoon precipitation, Geophys. Res. Lett., 49, e2021GL095602, https://doi.org/10.1029/2021GL095602, 2022.
Quan, X., Hoerling, M., Whitaker, J., Bates, G., and Xu, T.: Diagnosing sources of U. S. seasonal forecast skill, J. Climate, 19, 3279–3293, https://doi.org/10.1175/JCLI3789.1, 2006.
Rahman, M. M., Lu, M. J., and Kyi, K. H.: Variability of soil moisture memory for wet and dry basins, J. Hydrol., 523, 107–118, https://doi.org/10.1016/j.jhydrol.2015.01.033, 2015.
Risbey, J. S., Squire, D. T., Black, A. S., DelSole, T., Lepore, C., Matear, R. J., Monselesan, D. P., Moore, T. S., Richardson, D., Schepen, A., Tippett, M. K., and Tozer, C. R.: Standard assessments of climate forecast skill can be misleading, Nat. Commun., 12, 4346, https://doi.org/10.1038/s41467-021-23771-z, 2021.
Sardeshmukh, P. D., Compo, G. P., and Penland, C.: Changes of Probability Associated with El Niño, J. Climate, 13, 4268–4286, 2000.
Seager, R., Hooks, A., Williams, A. P., Cook, B., Nakamura, J., and Henderson, N.: Climatology, variability, and trends in the U. S. vapor pressure deficit, an important fire-related meteorological quantity, J. Appl. Meteorol. Clim., 54, 1121–1141, https://doi.org/10.1175/JAMC-D-14-0321.1, 2015.
Seager, R., Ting, M., Alexander, P., Nakamura, J., Liu, H., Li, C., and Simpson, I. R.: Mechanisms of a meteorological drought onset: Summer 2020 to spring 2021 in southwestern North America, J. Climate, 35, 7367–7385, https://doi.org/10.1175/JCLI-D-22-0314.1, 2022.
Seager, R., Ting, M., Alexander, P., Liu, H., Nakamura, J., Li, C., and Newman, M.: Ocean-forcing of cool season precipitation drives ongoing and future decadal drought in southwestern North America, npj Climate and Atmospheric Science, 6, 141, https://doi.org/10.1038/s41612-023-00461-9, 2023.
Simpson, I. R., McKinnon, K. A., Kennedy, D., Lawrence, D. M., Lehner, F., and Seager, R.: Observed humidity trends in dry regions contradict climate models, Proc. Natl. Acad. Sci. U. S. A., 121, e2302480120, https://doi.org/10.1073/pnas.2302480120, 2024.
Tian, D., Martinez, C. J., and Graham, W. D.: Seasonal prediction of regional reference evapotranspiration based on Climate Forecast System Version 2, J. Hydrometeorol., 15, 1166–1188, https://doi.org/10.1175/JHM-D-13-087.1, 2014.
Tziperman, E. and Ioannou, P.: Transient growth and optimal excitation of thermohaline variability, J. Phys. Oceanogr., 32, 3427–3435, https://doi.org/10.1175/1520-0485(2002)032<3427:TGAOEO>2.0.CO;2, 2002.
Vimont, D. J.: Analysis of the Atlantic meridional mode using linear inverse modeling: Seasonality and regional influences, J. Climate, 25, 1194–1212, https://doi.org/10.1175/JCLI-D-11-00012.1, 2012.
von Storch, H., Bruns, T., Fischer-Bruns, I., and Hasselmann, K.: Principal oscillation pattern analysis of the 30–60 d oscillation in a GCM equatorial troposphere, J. Geophys. Res.-Atmos., 93, 11022–11036, https://doi.org/10.1029/JD093iD09p11022, 1988.
Wang, H. and Kumar, A.: Assessing the impact of ENSO on drought in the U. S. Southwest with NCEP climate model simulations, J. Hydrol., 526, 30–41, https://doi.org/10.1016/j.jhydrol.2014.12.012, 2015.
Westerling, A. L., Hidalgo, H. G., Cayan, D. R., and Swetnam, T. W.: Warming and earlier spring increase western U. S. forest wildfire activity, Science, 313, 940–943, https://doi.org/10.1126/science.1128834, 2006.
Williams, A. P., Seager, R., Macalady, A. K., Berkelhammer, M., Crimmins, M. A., Swetnam, T. W., Trugman, A. T., Buenning, N., Noone, D., McDowell, N. G., Hryniw, N., Mora, C. I., and Rahn, T.: Correlations between components of the water balance and burned area reveal new insights for predicting forest fire area in the southwest United States, Int. J. Wildland Fire, 24, 14–26, https://doi.org/10.1071/WF14023, 2014.
Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., Smerdon, J. E., Varuolo-Clarke, A. M., Bjarke, N. R., Juang, C. S., and Lettenmaier, D. P.: Growing impact of wildfire on western US water supply, P. Natl. Acad. Sci. USA, 119, e2114069119, https://doi.org/10.1073/pnas.2114069119, 2022.
Yuan, W., Zheng, Y., Piao, S., Ciais, P., Lombardozzi, D., Wang, Y., Ryu, Y., Chen, G., Dong, W., Hu, Z., Jain, A. K., Jiang, C., Kato, E., Li, S., Lienert, S., Liu, S., Nabel, J. E. M. S., Qin, Z., Quine, T., Sitch, S., Smith, W. K., Wang, F., Wu, C., Xiao, Z., and Yang, S.: Increased atmospheric vapor pressure deficit reduces global vegetation growth, Science Advances, 5, eaax1396, https://doi.org/10.1126/sciadv.aax1396, 2019.
Zhang, Z., Pierce, D. W., and Cayan, D. R.: A deficit of seasonal temperature forecast skill over West Coast regions in NMME, Weather Forecast., 34, 833–848, https://doi.org/10.1175/WAF-D-18-0172.1, 2019.
Zhuang, Y., Fu, R., Santer, B. D., Dickinson, R. E., and Hall, A.: Quantifying contributions of natural variability and anthropogenic forcings on increased fire weather risk over the western United States, P. Natl. Acad. Sci. USA, 118, e2111875118, https://doi.org/10.1073/pnas.2111875118, 2021.
Zou, Y., Rasch, P. J., Wang, H., Xie, Z., and Zhang, R.: Increasing large wildfires over the western United States linked to diminishing sea ice in the Arctic, Nature Communications, 12, 6048, https://doi.org/10.1038/s41467-021-26232-9, 2021.
Short summary
We explore the predictability of saturation vapor pressure deficit (VPD), a key indicator of wildfire danger, one to 18 months in advance. Seasonal VPD forecasts are generated using a statistical dynamical model that produces high VPD skill related to a long-term warming trend and sea surface temperatures. Understanding where forecast skill comes from is important to for improving forecast models, and this study shows the role of multiple unique processes in contributing to VPD forecasts.
We explore the predictability of saturation vapor pressure deficit (VPD), a key indicator of...
