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Weekly Look Ahead

September 16, 2021 (Updated Every Thursday)

5–7 Day Outlook

The remnants of Nicholas will meander over the central Gulf Coast region during the next couple of days, delivering additional rainfall (3–6+ inches) from southeastern Louisiana into western Florida. Farther east, a low-pressure system north of the Bahamas will approach the middle Atlantic Coast and may soon become a tropical cyclone. Regardless of development, most of the significant tropical impacts should remain offshore. Elsewhere, a pattern change in the Pacific Northwest will result in cooler weather and widespread showers, starting on Friday. During the weekend, cool, showery weather will spread eastward across the nation’s northern tier—reaching northern sections of the Rockies and High Plains—and southward into northern California. However, generally dry weather will persist from central and southern California to the central and southern High Plains.

6–10 Day Outlook

The National Weather Service Climate Prediction Center's 6–10 day outlook for September 21–25 calls for the likelihood of below-normal temperatures from the Great Basin to northern sections of the Rockies and High Plains, while warmer-than-normal weather will prevail along and east of a line from southeastern Arizona to Minnesota.

Meanwhile, below-normal precipitation across much of the western half of the U.S. should contrast with wetter-than-normal conditions in the Pacific Northwest and from the Mississippi Valley eastward, excluding the northern Atlantic States.

 

This weekly look ahead is modified from the U.S. Drought Monitor's National Drought Summary for September 14, 2021, written by Brad Rippey (U.S. Department of Agriculture) and Richard Tinker (NOAA's Climate Prediction Center).

Data and Maps

Predicting drought depends on the ability to forecast precipitation and temperature within the context of complex climate interactions. Many different datasets and maps are available that predict how precipitation and temperature may change in the future.

Featured Outlooks and Forecasts

Drought Outlooks & Forecasts

NOAA's Climate Prediction Center's Monthly Drought Outlook is issued at the end of each calendar month and is valid for the upcoming month. The Outlook predicts whether drought will emerge, stay the same, or get better over the next 30 days or so. Learn more.

NOAA's Climate Prediction Center's Seasonal Drought Outlook is issued monthly on the third Thursday of each month. The Outlook predicts whether drought will emerge, stay the same, or get better in the next three months. Learn more.

Taking the U.S. Drought Monitor as a starting point, the Climate Prediction Center's Objective Drought Tendency Forecast is an integrated product that combines information from the flash drought development tool and subseasonal SPI3 forecasts. The forecast synthesizes information through a decision-tree process to determine whether drought will emerge, stay the same, or get better in the next 30 days, on a rolling basis. This tool is used to inform the official forecasts. Learn more.

Drought Outlook

The color with the hex code #9b634a identifies:
Drought persists
The color with the hex code #ded2bc identifies:
Drought remains but improves
The color with the hex code #b2ad69 identifies:
Drought removal likely
The color with the hex code #ffde63 identifies:
Drought development likely

Drought Outlook

The color with the hex code #9b634a identifies:
Drought persists
The color with the hex code #ded2bc identifies:
Drought remains but improves
The color with the hex code #b2ad69 identifies:
Drought removal likely
The color with the hex code #ffde63 identifies:
Drought development likely

Drought Outlook

The color with the hex code #8c645a identifies:
Drought persists
The color with the hex code #e1beb4 identifies:
Drought remains but improves
The color with the hex code #1eb41e identifies:
Drought removal likely
The color with the hex code #ffe878 identifies:
Drought development likely
The color with the hex code #c00000 identifies:
Drought intensification likely

Evaporative Demand and Flash Drought

The Evaporative Demand Drought Index (EDDI) is an experimental drought monitoring and early warning guidance tool. It examines how anomalous the atmospheric evaporative demand (E0; also known as "the thirst of the atmosphere") is for a given location and across a time period of interest. This experimental subseasonal EDDI forecast shows projected evaporative demand for the next 28 days from the CFS-gridMET dataset at 4-km gridded resolution. Learn more.

Created by NOAA’s Climate Prediction Center (CPC), this subseasonal tool predicts the areas susceptible for flash drought development. The real-time product started running in April 2018 and has been used to support CPC’s Monthly Drought Outlook efforts. The tool, which is used to inform official forecasts, calculates the rapid change index (RCI) using 7-day mean evapotranspiration anomalies. RCI is the accumulated magnitude of moisture stress changes occurring over multiple weeks, and drought is likely to develop when RCI is negative. In the legend below, a higher number of non-exceedances indicates a greater potential for flash drought development. Learn more.

Drought Categories

The color with the hex code #ffff00 identifies:
ED0
The color with the hex code #ffd37f identifies:
ED1
The color with the hex code #ffaa00 identifies:
ED2
The color with the hex code #e60000 identifies:
ED3
The color with the hex code #730000 identifies:
ED4

Wetness Categories

The color with the hex code #8ccdef identifies:
EW0
The color with the hex code #00bfff identifies:
EW1
The color with the hex code #1d90ff identifies:
EW2
The color with the hex code #4169e1 identifies:
EW3
The color with the hex code #0000ff identifies:
EW4

Number of Non-Exceedances (Range: 0-30)

The color with the hex code #ffffff identifies:
≤ 2
The color with the hex code #ffff99 identifies:
2 - 5
The color with the hex code #ffcc33 identifies:
5 - 10
The color with the hex code #ff6633 identifies:
10 - 15
The color with the hex code #cc3300 identifies:
15 - 20
The color with the hex code #990000 identifies:
20 - 25
The color with the hex code #663333 identifies:
≥ 25
Experimental

Challenges with Predicting Drought

Pressure Systems

High pressure systems, which hinder cloud formation and lead to low relative humidity and precipitation, can cause drought. When large-scale anomalies in atmospheric circulation patterns last for months or seasons, prolonged drought occurs (NDMC).

Temperate Zone Forecast Reliability

In temperate regions (above 30 north latitude), long-range forecasts have limited reliability. Due to differences in observed conditions and statistical models, reliable forecasts for temperate regions may not be attainable for a season or more in advance (NDMC).

Interconnected Variables

Anomalies in precipitation and temperature may last from several months to several decades, and how long they last can depend on air–sea interactions, soil moisture, land surface processes, topography, and weather systems at the global scale (NDMC).

ENSO and Global Weather Patterns

Teleconnections, such as ENSO and La Niña events, are atmospheric interactions between widely separated regions. Understanding these teleconnections can help in forecasting droughts, floods, tropical storms, and hurricanes (NDMC).