Chris Castellano - Center for Western Weather and Water Extremes

CW3E Event Summary: 18-20 October 2024

25 October 2024

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Strong Atmospheric River Produced Heavy Rain in Southeast Alaska and British Columbia

An atmospheric river (AR) brought heavy precipitation to southwestern British Columbia and northwestern WA during 18–20 October.

The AR:

The AR formed within a plume of subtropical moisture over the central North Pacific Ocean and made landfall in British Columbia on Fri 18 Oct.
AR3–4 conditions (based on the Ralph et al. 2019 AR Scale) were observed in southern Vancouver Island and coastal WA.

Impacts:

At least 5-10 inches of precipitation fell over much of southwestern British Columbia, the Olympic Peninsula, and the North Cascades.
Heavy rain caused significant flooding on the Coquitlam River in Port Coquitlam, BC, with streamflow exceeding the previous record from March 2007.
Minor riverine flooding also occurred in northwestern WA.

MIMIC-TPW2 Total Precipitable Water

Valid: 1200 UTC 17 October – 1200 UTC 21 October 2024

Click images to see loops of GFS IVT/IWV analyses Valid 1200 UTC 17 October – 1200 UTC 21 October 2024

Summary provided by C. Castellano J. Kalansky; 25 Oct 2024

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The Atmospheric Rivers of Water Year 2024: End of Water Year Summary

October 22, 2024

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Analysis by Chad Hecht, Julie Kalansky, & F. Martin Ralph. This analysis is considered experimental. For questions regarding the data or methodology please contact Chad Hecht

CW3E Director and Director of Research Visit Karlsruhe Institute of Technology

October 21, 2024

On September 16-18, Dr. Marty Ralph (CW3E Director) and Dr. Luca Delle Monache (CW3E Director of Research) visited Karlsruhe Institute of Technology (KIT) in Karlsruhe, Germany. During their visit, Dr. Ralph and Dr. Delle Monache received a tour of the KITcube facilities and a demonstration of the KITsonde, a multi-sensor dropsonde system that provides detailed vertical profiles of temperature, humidity, and wind. They also gave a special seminar on atmospheric rivers at KIT’s Institute of Meteorology and Climate Research Troposphere Research (IMKTRO). On the final day of their visit, Dr. Ralph and Dr. Delle Monache met with the North Atlantic Waveguide, Dry Intrusion, and Downstream Impact Campaign (NAWDIC) coordination team to plan the NAWDIC Dry Run, which will take place during Atmospheric River Reconnaissance (AR Recon) between January 27, 2025 and February 7, 2025. You can read more about recent NAWDIC news here.

Dr. Marty Ralph speaking during a special seminar at IMKTRO

Dr. Marty Ralph and Dr. Luca Delle Monache listening to a demonstration of the KITsonde

CW3E Publication Notice: Impact of Atmospheric River Reconnaissance Dropsonde Data on the Assimilation of Satellite Radiance Data in GFS

CW3E Publication Notice

Impact of Atmospheric River Reconnaissance Dropsonde Data on the Assimilation of Satellite Radiance Data in GFS

September 26, 2024

A new article titled “Impact of Atmospheric River Reconnaissance Dropsonde Data on the Assimilation of Satellite Radiance Data in GFS,” led by CW3E scientist Minghua Zheng and co-authored by Luca Delle Monache (CW3E), Xingren Wu (NOAA/NCEP/EMC), Brian Kawzenuk (CW3E), F. Martin Ralph (CW3E), Yanqiu Zhu (NASA/GSFC), Ryan Torn (U. Albany), Vijay Tallapragada (NOAA/NCEP/EMC), Zhenhai Zhang (CW3E), Keqin Wu (CW3E), and Jia Wang (CW3E) was recently published in the American Meteorological Society’s Journal of Atmospheric and Oceanic Technology. This study assesses the critical role of Atmospheric River (AR) Reconnaissance dropsonde data in improving the assimilation of satellite radiance within the Global Forecast System (GFS) at NCEP. As part of CW3E’s 2019-2024 Strategic Plan to support Atmospheric River research and applications, CW3E seeks to enhance global AR monitoring through a transformative modernization of atmospheric measurements over the Pacific and in the western United States. In alignment with this goal, the study underscores the importance of data collected during AR Reconnaissance missions, which sample ARs over the northeastern Pacific, in improving satellite radiance assimilation for more accurate weather forecasting.

Satellites provide one of the largest datasets for monitoring and modeling the Earth system, but accurately estimating radiance biases poses significant challenges for numerical weather prediction (NWP) models. Non-radiance data, such as those collected by dropsondes, radiosondes, and radio occultation profiles from GPS satellites, serve as essential tools for anchoring radiance bias corrections. The study highlights how the integration of dropsonde data from Atmospheric River Reconnaissance missions enhances the GFS and Global Data Assimilation System (GDAS) by improving the model background and increasing the assimilation of microwave radiances by 5%–10% in the lower and mid-troposphere over the northeastern Pacific and North America (Fig. 1). Additionally, while the impact on tropospheric infrared radiance is small, it remains beneficial. However, the influence on radiance use in the stratosphere is minimal due to limited dropsonde data at higher altitudes.

These findings emphasize the importance of dropsonde observations, alongside other unbiased conventional data sources, in refining satellite radiance assimilation. This study reinforces the value of a diverse observational network in enhancing forecast accuracy and highlights the specific indirect effects of integrating dropsonde data into the data assimilation process within a cycled NWP system, in addition to their direct positive impacts on model analyses and forecast demonstrated in previous literature (e.g., Zheng et al. 2021; DeHaan et al. 2023).

Figure 1. Statistics of AMSU-A channel 1 radiance observations that successfully passed the QC over the Pacific and North America (PNA) region in GDAS for the Ctrl and Deny runs from 24 Jan to 18 Mar 2020. (a) Radiance counts in Ctrl (red dots) and Deny (blue dots); (b) percentage change of radiance count (green dots) in Ctrl w.r.t. Deny, and the 7-point running mean (dark green line); (c) STD (K) for OmB in Ctrl (red dots) and Deny (blue dots); (d) percent of STD change in Ctrl w.r.t. Deny; (e) abs. TBC (K) in Ctrl (red dots) and Deny (blue dots); (f) percentage change of abs. TBC in Ctrl w.r.t. Deny. Each dot represents data from a 6-h data assimilation window centered at 0000 or 1200 UTC. Magenta stars at the bottom of each panel denote 17 AR Recon IOPs during AR Recon 2020 field season. Ctrl assimilated dropsondes during the assimilation process while Deny removed dropsondes. This figure is modified from Figure 3 of Zheng et al. (2024).

Zheng, M., Delle Monache, L., Wu, X., Kawzenuk, B., Ralph, F. M., Zhu, Y., Torn, R., Tallapragada, V. S., Zhang, Z., Wu, K. and Wang, J., 2024. Impact of Atmospheric River Reconnaissance Dropsonde Data on the Assimilation of Satellite Radiance Data in GFS. Journal of Atmospheric and Oceanic Technology, 49(9), 819-832. https://doi.org/10.1175/JTECH-D-23-0167.1

Zheng, M., Delle Monache, L., Cornuelle, B. D., Ralph, F. M., Tallapragada, V. S., Subramanian, A., Haase, J. S., Zhang, Z., Wu, X., Murphy, M. J. and Higgins, T. B., 2021. Improved forecast skill through the assimilation of dropsonde observations from the Atmospheric River Reconnaissance program. Impact of Atmospheric River Reconnaissance Dropsonde Data on the Assimilation of Satellite Radiance Data in GFS. Journal of Geophysical Research: Atmospheres, 126(21), e2021JD034967. https://doi.org/10.1029/2021JD034967

DeHaan, L. L., Wilson, A. M., Kawzenuk, B., Zheng, M., Monache, L. D., Wu, X., Lavers, D. A., Ingleby, B., Tallapragada, V., Pappenberger, F. and Ralph, F. M., 2023. Impacts of Dropsonde Observations on Forecasts of Atmospheric Rivers and Associated Precipitation in the NCEP GFS and ECMWF IFS models. Weather and Forecasting, 38(12), 2397-2413. https://doi.org/10.1175/WAF-D-23-0025.1

CW3E Precipitation Outlook: 12 September 2024

Septebmer 12, 2024

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Remnants of Tropical System Forecast to Bring Precipitation to Interior Western US

A tropical depression (TD 9E) currently located south of the Baja Peninsula is forecast to strengthen into a tropical storm and track northward through the Gulf of California during the next several days.
Tropical moisture associated with the tropical cyclone (TC) is forecast to expand northward into the interior southwestern US this weekend, setting the stage for showers and thunderstorms that could produce flash flooding.
Meanwhile, a deepening mid-level trough near the US West Coast is forecast to move eastward and bring widespread light-to-moderate precipitation to the Great Basin and Northern Rockies.
As this trough moves onshore, it will interact with the remnant TC moisture, leading to a broad region of enhanced moisture transport over the Colorado River Basin.
The Global Ensemble Forecast System (GEFS) is showing a high likelihood (> 85% probability) of atmospheric river (AR) conditions (IVT ≥ 250 kg m⁻¹ s⁻¹) in southern AZ on 15–16 Sep.
The NWS Weather Prediction Center (WPC) is forecasting 0.5–1.5 inches of precipitation in portions of central and southeastern AZ, southwestern CO, northern NV, and northern UT during the next 5 days.
The NWS WPC has issued a marginal risk of rainfall exceeding flash flood guidance in central and southeastern AZ Saturday into Sunday morning, expanding to much of AZ and western NM Sunday into Monday morning, expanding further northward into southwestern CO Monday into Tuesday morning.