Subseasonal forecast

Valid from    July 29 to august 25, 2024

(4 weeks)

General comment:

The last week of July the Pacific will remain under the influence of the Canicula (decrease in rain within the rainy season) although to a lesser extent than previous weeks, because a weakening of the trade winds is expected on July 21. Again from August 5, the country will return to a windier pattern, less rainy throughout the first half of August for the Pacific and Central Valley, and rainy for the Caribbean and mountainous Northern Zone.

 
Pronóstico Estacional

Fig. 1. Weekly precipitation forecast by region for the next 4 weeks.

 

1.Forecast from  july 29 to august 4, 2024

 

During this week, a decrease in the trade winds and an increase in the possibility of rain in the afternoon and evening is expected throughout the Pacific and Central Valley. Rainfall amounts will be above normal in Guanacaste (more than 80 mm per week), normal in the Pacific and Central Valley (amounts between 50-80 mm weekly) and dry in the Caribbean (accumulated less than 60-90 mm weekly).

 

Probability of extreme: low (around 30%)
Forecast uncertainty: low


2. Forecast from  august 5-11, 2024


Little precipitation and a high possibility of the presence of dust masses from the Sahara in the Pacific and Central Valley (moderate wind and little rain, which is normal for the season), weekly accumulations of between 30-70 mm. The Caribbean and North will continue with less rain than normal (less than 100 mm per week). The mountainous parts of the Caribbean and Northern Zone (Sarapiquí, Ciudad Quesada) rainier than normal.


Probability of extreme event: low (around 30%)
Prognosis uncertainty: medium


3. Forecast from  august 12-18, 2024

Much drier conditions with little rain will continue in the Pacific, so moderate trade winds are expected in the Pacific and Central Valley (moderate wind and little rain), with weekly accumulations of between 20-60 mm. The Caribbean and Northern Zone will continue with less rain than normal on the coasts (less than 70 mm weekly) and more rain in the mountains (more than 70 mm weekly)

 

Probability of extreme event: low (around 30%)
Prognosis uncertainty: medium


4. Forecast from  august 19-25, 2024

Very weak trade winds and the presence of the Intertropical Convergence Zone over the country. The Intertropical Convergence Zone is expected to favor rainy conditions throughout the Pacific and Central Valley.

Probability of extreme event: low (around 10%)
Prognosis uncertainty: high

 

 

Forecast of extreme events from    July 29, august 11, 2024

This week the conditions of little rainfall will continue, there is a high possibility of the presence of dust masses from the Sahara, so moderate trade winds and typical July conditions are expected in the Pacific and Central Valley (moderate wind and little rain), accumulated weekly between 30-60mm. The Caribbean will continue with less rain than normal (less than 60 mm per week)

Fig. 2. Forecast of extreme events for the next 2 weeks (training areas).


 

 

Forecaster: Daniel Poleo
Maps: Nury Sanabria Valverde
Unidad de aplicaciones climáticas
Departamento de Desarrollo/IMN