Dr.Fawzy Younis:”Retreat of Summer and Early Winter Expectations”

The second half of summer 2025 is witnessing unusual climatic developments across the Eastern Mediterranean and North Africa.

Numerical weather models—most notably the NOAA GFSv16—indicate an early retreat of the subtropical high-pressure ridge and the advance of cold air masses in the upper atmospheric layers toward Egypt.

This rare scenario in August raises questions about the extent to which traditional seasonal patterns are being affected by climate change and whether it is possible to experience cold waves or winter-like atmospheric disturbances during a period that is typically dominated by hot and dry conditions.

The attached image is a weather map from the American NOAA GFSv16 model, showing the deviation of the 500 hPa geopotential height from climatological norms on August 7, 2025.

Explanation of the Attached Map:

1. The 500 hPa Layer:

This layer is located approximately 5.5 km above sea level and is commonly used to track mid- and upper-level weather systems such as troughs and jet streams.

The values (like 582 and 588) refer to the “geopotential height,” meaning the vertical distance required to reach this pressure level.

2. Blue to Green Coloring over the Mediterranean and Northern Egypt:

Indicates a significant drop in geopotential heights (below climatic averages), signifying the presence of an upper-level cold trough or atmospheric disturbance.

These systems typically lead to:

A decline in temperatures

Possible occurrence of unusual summer rainfall

3. Red Coloring over Eastern Iraq, Iran, and Eastern Saudi Arabia:

Reflects higher-than-average values, indicating a strong upper-level high-pressure system which intensifies heat and dryness in those regions.

Does This Indicate an Early Winter?

Not necessarily the literal start of winter, but it does suggest:

A temporary interruption of summer dominance

The arrival of an unusually cool air mass for August

A rare chance of summer rain

> This is commonly referred to as an “early winter” or a transitional anomaly occurring during the summer.

Key Expected Impacts on Egypt in August 2025:

1. Temporary drop in temperatures compared to seasonal norms.

2. Northerly or northwesterly cool winds affecting the Nile Delta and northern coast.

3. Possibility of light to moderate summer rainfall, particularly in Northern Delta and Sinai.

4. Slight drop in sea surface temperatures along the northern coast, potentially affecting humidity and pressure levels.

Possible Causes of This Change:

Breakdown of the subtropical ridge

Early arrival of upper-level troughs from Europe into the Eastern Mediterranean

Atmospheric oscillations such as the NAO (North Atlantic Oscillation) or AO (Arctic Oscillation)

Indirect effects from the El Niño phenomenon.

Conclusion:

The map highlights an unusual drop in upper atmospheric pressure over the Eastern Mediterranean and Egypt in early August 2025, which may signal:

A weakening of the summer season

Possible rainfall events

Autumn-like or early-winter atmospheric conditions

This anomaly is a notable climatic event and may be part of a broader trend of shifting seasonal patterns influenced by climate change.

In light of these early indicators, Egypt and its surrounding regions may be entering a new climatic transition phase, where seasonal boundaries blur, and non-traditional weather patterns become more frequent.

The early appearance of clouds and low-pressure systems over Egypt’s northern coast, along with falling temperatures and potential rainfall in August 2025, is not just an isolated event—it could reflect a deeper shift in atmospheric dynamics.

This underscores the urgent need for continuous meteorological monitoring and updated agricultural and water adaptation strategies that align with this rapidly evolving climate reality.