WASM – The WASM Regional Center issues the monthly bulletin for October 2024, based on data from the WASM Regional Center's climate model, which operates on a main cycle on 25-9 and uses calibrated statistical similarity periods in a flexible manner. This model distinguished itself with superior accuracy over previous years.
General Situation|
October is expected to be slightly cooler than normal with occasional short warm periods sometimes coinciding with atmospheric disturbances. No significant or major rainfall events are expected before mid-month. Major rainfall cases are expected to increase from the 20th of the month, with a major rainfall event that could be strong expected during the end of the month and final days.
Rainfall will concentrate in the western regions of the Kingdom and, contrary to the usual pattern and as a result of different rotational atmospheric circulation compared to previous years. Temperatures are also expected to be below seasonal averages for extended periods this month, particularly during the night and early morning in an unusual manner.
An extension of the Red Sea low (which brings warmer and drier weather) is expected before mid-month in several periods and also during the end of the third week of the month. Wind speeds are expected to intensify and temperatures to drop with the disturbance of the eastern Mediterranean region and Turkey, with significant and unusual temperature drops later from the beginning of November.
Detailed Weather Conditions| (Results from WASM's climate model with more accurate results in daily bulletins) ..
From 1 to 5 of the month.. Cooler than normal conditions, with showers expected (Green Level).
From 6 to 15 of the month| Extension of the Red Sea low and rising temperatures, then temperature drop and atmospheric instability at the end of the period (Green Level).
From 16 to 19 of the month| Another dry and warm period with Red Sea low extension.
From 20 to 22 of the month| Atmospheric instability and thunderstorms in various regions (Yellow Level).
From 26 to 29 of the month| Heavy rainy and cold conditions in parts of western Kingdom (Orange Level)
Alert Levels and Their Meanings|
Green Level.. Non-impacting weather condition.
Yellow Level.. Weather condition requiring attention and affecting some aspects of public life but usually not posing a danger.
Orange Level.. Weather condition requiring caution and affecting many aspects of public life and posing danger in some areas.
Red Level.. High-risk weather condition requiring full caution and affecting most aspects of public life
Atmospheric Circulation|
Western Europe and the central Mediterranean are expected to witness continued strong rainfall storms and cooler than normal conditions for most of the coming period. As a result of Mediterranean storms approaching in some periods and due to the weak subtropical jet stream behavior, this causes remnants of these weather systems to reach Jordan, Palestine, and the eastern Mediterranean rapidly, causing temperature drops and rainfall showers.
By mid-month, weather systems over the central Mediterranean are expected to become stronger and deeper, and western European storms more consecutive, increasing the activity of the Red Sea low toward the region and creating atmospheric instability in some periods (generally weak and dry).
By the end of the month, atmospheric pressure is expected to rise over central Europe and the central Mediterranean clearly, driving very cold air masses toward southeastern Europe. These will arrive as deeper cold air masses and increase the activity of the Red Sea low, which will merge with eastern Mediterranean lows and may result in heavy and major rainfall in the region extending to northern and northwestern Saudi Arabia, with temperatures dropping significantly below seasonal averages.
The atmospheric high in central Europe is expected to gradually increase its control over western Europe during November with continued unusual weakness of the jet stream.
These results are issued from our climate model at WASM and are not final results. Daily weather forecasts will be more accurate and clearer due to the proximity of the time period.
WASM Climate Model|
The model was run on a main cycle on 25-9-2024, with new data collected, calibrated, and compared with model results from the previous period. Results from this model have remained highly accurate from 11-9 to 25-9.
This model operates using calibration of statistical similarity periods in a flexible manner, or Analogue Calibration-Dynamic Method. It is a model being developed since 2018 and produces results at 200, 500, and 700 millibar levels in atmospheric layers. It operates differently and not purely statistically, as statistical results are inaccurate and give very random results that are temporally and spatially imprecise. Through developing this model, we were able to overcome these statistical problems and manage to determine active periods with precision reaching over 90% in some periods, particularly in autumn 2022, autumn 2019, spring 2024, and summer 2023, when we were also able to use this model to precisely determine the number of tropical storms expected to form in the Arabian Sea in autumn 2019.
WASM Center does not recommend relying on global climate models, especially for our regions, as most Arab meteorological departments depend only on these models, which reflects inaccurate results due to the unavailability of climate models specific to them.
Issuing long-range forecasts is extremely complex, as atmospheric behavior must be studied with meticulous precision, and knowledge of weather conditions that may result during rainy seasons must be understood after running and calibrating the model to verify its results.
The accuracy of WASM's climate model increased from 60% to around 75% during the last season. With the addition of many developments and our ability to overcome statistical noise results responsible for errors that may occur in long-range forecasts.