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South American monsoon

The maximum precipitation moves from the northern end of South America in the Southern Hemisphere’s winter to the central Amazon river basin in the Southern Hemisphere’s summer (November – March).  This is monsoon season in South America and brings rainfall to much of the Amazon rainforest.

Forecast for wind and precipitation

This animation shows the forecast of precipitation (color shading) and horizontal winds at 850 hPa, which is about 1.5 km above sea level. The precipitation is the accumulation over the previous 6-hour period, in millimeters (1 inch = 25 mm), and winds are measured in m/s (1 m/s = 2.2 miles per hour). This is from a single deterministic forecast; the ensemble, probabilistic forecast for the central Amazon (marked by the red rectangle) are shown below.

All forecast data is from the Global Ensemble Forecast System (GEFS) of the U.S. National Centers for Environmental Prediction (NCEP). All forecasts use an initial atmospheric state at the time indicated on the plot (note that 00Z is midnight Universal Coordinated Time, which is 8 pm the previous day in central Brazil (Manaus), Australia or 7 pm in New York [EDT]).

Seasonal accumulation

The below plots show the daily rainfall and the total seasonal accumulation of precipitation for central South America (70-40W, 16-2S), compared to the historical average.

Australian monsoon

The northern end of Australia receives most of its precipitation during its summer monsoon season, which typically occurs during December – March.

Forecast for wind and precipitation

This animation shows the forecast of precipitation (color shading) and horizontal winds at 850 hPa, which is about 1.5 km above sea level. The precipitation is the accumulation over the previous 6-hour period, in millimeters (1 inch = 25 mm), and winds are measured in m/s (1 m/s = 2.2 miles per hour). This is from a single deterministic forecast.

All forecast data is from the Global Ensemble Forecast System (GEFS) of the U.S. National Centers for Environmental Prediction (NCEP). All forecasts use an initial atmospheric state at the time indicated on the plot (note that 00Z is midnight Universal Coordinated Time, which is 9:30 am in Darwin, Australia or 8 pm the previous day in New York [EDT]).

Seasonal accumulation

The below plots show the daily rainfall and the total seasonal accumulation of precipitation for the “top end” of Australia (120-146E, 20-5S), compared to the historical average.

 

Northeastern U.S. (with additional details for New Haven)

The northeastern U.S. is far from any monsoon region, but forecasts for this region are shown because it is home to Yale University, which hosts this website.  We show additional details for New Haven, Connecticut.

All forecast data is from the Global Ensemble Forecast System (GEFS) of the U.S. National Centers for Environmental Prediction (NCEP).  All forecasts use an initial atmospheric state at the time indicated on the plot (note that 00Z is midnight Universal Coordinated Time, which is 8 pm the previous day in New Haven [EDT]).

Forecast for wind and precipitation

This animation shows the forecast of precipitation (color shading) and horizontal winds at 850 hPa, which is about 1.5 km above sea level.  The precipitation is the accumulation over the previous 6-hour period, in millimeters (1 inch = 25 mm), and winds are measured in m/s (1 m/s = 2.2 miles per hour).  This is from a single deterministic forecast; the ensemble, probabilistic forecast for New Haven (marked by the red dot) are shown below.

Probabilities of precipitation & temperature

A collection, or ensemble, of forecasts are made from different initial conditions several times each day, and the degree to which the ensemble members diverge from each other over time provides information on the likelihood of the future atmospheric state. For New Haven (indicated by the red dot in the above map), the below plot shows how many of the ensemble of 20 forecasts made each morning predict a given amount of precipitation accumulation and maximum surface air temperature.  In other words, each line on this plot is a histogramof the predictions made during the time periods noted in the legend.  In statistical parlance, this is similar to the probability density function (PDF) for the predictors.  For example, if 15 of the forecasts are predicting 10 mm of rainfall between 1-2 days from now, while the remaining 5 forecasts are predicting 15 mm of rainfall, the dark blue line would have a sharp peak at 10 mm/day that tapers off toward zero at 15 mm/day; this would indicate fairly high confidence in a forecast of 10-15 mm/day for that time period (assuming the weather prediction model does not have large errors/bias).

New Haven precipitation forecast PDF

Seasonal rain accumulation

Also just for the city of New Haven, the below plots show the daily rainfall and the total seasonal accumulation of precipitation, compared to the historical average.

North America

Here are forecasts for the North American monsoon, which is most intense on the west coast of Mexico but does extend into the southwestern U.S.

Forecast for wind and precipitation

This animation shows the forecast of precipitation (color shading) and horizontal winds at 850 hPa, which is about 1.5 km above sea level.  The precipitation is the accumulation over the previous 6-hour period, in millimeters (1 inch = 25 mm), and winds are measured in m/s (1 m/s = 2.2 miles per hour).  This is from a single deterministic forecast; the ensemble, probabilistic forecasts for the main monsoon region (outlined in red) are shown below.

All forecast data is from the Global Ensemble Forecast System (GEFS) of the U.S. National Centers for Environmental Prediction (NCEP).  All forecasts use an initial atmospheric state at the time indicated on the plot (note that 00Z is midnight Universal Coordinated Time, which is 7 pm the previous day in western Mexico [CDT]).

Seasonal rain accumulation

Also for the main monsoon region (outlined in red on the above map), the below plots show the daily rainfall and the total seasonal accumulation of precipitation, compared to the historical average.

West Africa

Here are forecasts for the West African monsoon, which brings rain to the vast region of the Sahel just south of the Sahara desert.

Forecast for wind and precipitation

This animation shows the forecast of precipitation (color shading) and horizontal winds at 850 hPa, which is about 1.5 km above sea level.  The precipitation is the accumulation over the previous 6-hour period, in millimeters (1 inch = 25 mm), and winds are measured in m/s (1 m/s = 2.2 miles per hour).  This is from a single deterministic forecast; the ensemble, probabilistic forecast for the Sahel (outlined in red) are shown below.

All forecast data is from the Global Ensemble Forecast System (GEFS) of the U.S. National Centers for Environmental Prediction (NCEP).  All forecasts use an initial atmospheric state at the time indicated on the plot (note that 00Z is midnight Universal Coordinated Time, which is 1 am in central Africa or 8 pm the previous day in New York [EDT]).

Seasonal rain accumulation

Also for the Sahel (red box in the above map), the below plots show the daily rainfall and the total seasonal accumulation of precipitation, compared to the historical average.

South Asia

Here are forecasts and this season’s rainfall accumulation for South Asia, which is home to the strongest monsoon on the planet.

Forecast for wind and precipitation

This animation shows the forecast of precipitation (color shading) and horizontal winds at 850 hPa, which is about 1.5 km above sea level.  The precipitation is the accumulation over the previous 6-hour period, in millimeters (1 inch = 25 mm), and winds are measured in m/s (1 m/s = 2.2 miles per hour).  This is from a single deterministic forecast; the ensemble, probabilistic forecast for rainfall averaged over the red box (the core monsoon region) is shown below.

All forecast data is from the Global Ensemble Forecast System (GEFS) of the U.S. National Centers for Environmental Prediction (NCEP).  All forecasts use an initial atmospheric state at the time indicated on the plot (note that 00Z is midnight Universal Coordinated Time, which is 5:30 am in India or 8 pm the previous day in New York [EDT]).

Seasonal accumulation

The below plots show the daily rainfall and the total seasonal accumulation of precipitation, compared to the historical average, all averaged over the red box in the map above.

 

Global forecasts

Below are forecasts for the precipitation accumulation and maximum surface air temperature achieved during each of the next 3 days.  These are deterministic forecasts, meaning a single forecast is issued based on the best guess of the current state of the atmosphere (without any consideration for our uncertainty about that state).  All forecasts are direct output from the U.S. Global Forecasting System (GFS) model, and were initialized today at the time indicated below.

Day 1 forecast

Precip global forecast day 1

Day 2 forecast

Precip forecast global day 2

Day 3 forecast

Global precipitation forecast, day 3

Forecasts

Here you’ll find several types of forecasts:

Cameroon Farm

Here are details on current weather and climate for the West African monsoon, with a focus on a point near Kumbo, Cameroon at 6.261379°N, 10.948243°E.

Seasonal rain accumulation

The below plots show the daily rainfall and the total seasonal accumulation of precipitation, compared to the historical average, for our point of interest (shown by the red star in the map below).

Forecast for wind and precipitation

This animation shows the forecast of precipitation (color shading) and horizontal winds at 850 hPa, which is about 1.5 km above sea level.  The precipitation is the accumulation over the previous 6-hour period, in millimeters (1 inch = 25 mm), and winds are measured in m/s (1 m/s = 2.2 miles per hour).  This is from a single deterministic forecast; the ensemble, probabilistic forecast for the point of interest (marked by the red star on the map) is shown below.

All forecast data is from the Global Ensemble Forecast System (GEFS) of the U.S. National Centers for Environmental Prediction (NCEP).  All forecasts use an initial atmospheric state at the time indicated on the plot (note that 00Z is midnight Universal Coordinated Time, which is 1 am in central Africa or 8 pm the previous day in New York [EDT]).

Southern African monsoon

While the African monsoon that is most widely known lies north of the equator and takes place during the northern hemisphere’s summer, a monsoonal circulation does exist over the southern part of the continent during the southern hemisphere’s summer.  The precipitation maximum during this season stretches from Angola on the west coast of southern Africa all the way to Madagascar.

Forecast for wind and precipitation

This animation shows the forecast of precipitation (color shading) and horizontal winds at 850 hPa, which is about 1.5 km above sea level. The precipitation is the accumulation over the previous 6-hour period, in millimeters (1 inch = 25 mm), and winds are measured in m/s (1 m/s = 2.2 miles per hour). This is from a single deterministic forecast; the ensemble, probabilistic forecast for the primary monsoon region (marked by the red rectangle) is shown below.

All forecast data is from the Global Ensemble Forecast System (GEFS) of the U.S. National Centers for Environmental Prediction (NCEP). All forecasts use an initial atmospheric state at the time indicated on the plot (note that 00Z is midnight Universal Coordinated Time, which is 2 am in central Africa [e.g. Johannesburg] or 7 pm in New York [EDT]).

Seasonal accumulation

The below plots show the daily rainfall and the total seasonal accumulation of precipitation for southern Africa (averaged over the red box shown above), compared to the historical average.