Monthly Weather Summary, May 2021

National Meteorological Service of Belize

May marks the end of the 2021 dry season and early May typically the onset of the rainy season for the Toledo district which then moves progressively northward with the season starting over most areas by late May and over the entire country by early June. The 2021 rainy season was no different as it officially started around May 5th in the Toledo district and in the second dekad of month (11-20th) over the remainder of the country except for Central Farm in the west whose season started early on May 2nd.

The Atlantic high pressure system dominated our weather during the first week of May supporting a light to moderate east to south-easterly airflow near the surface which became occasionally gusty as the pressure gradient tightened around the 3rd and 4th. Low level moisture remained at a minimal May 1st through 5th before becoming relatively moist towards end the week. At the upper levels, conditions were slightly more moist and neutral to weakly convergent with ridging as the main feature and an upper level TUTT over the western Caribbean that supported a west to south-westerly flow becoming north to north-westerly. This led to hot, dry and hazy conditions over the country with only isolated afternoon showers and thunderstorms concentrated over the mountains, inland and near the western border.

An increase in low level moisture in week two as a result of the close proximity to a stationary front over Bahamas and north eastern Cuba supported a few showers and isolated thunderstorms on May 8 and 9, especially over the Toledo district. Another stationary front approached the area on May 14 resulting in a few showers and thunderstorms around the country. The remainder of the week saw mainly fair weather conditions with only brief isolated showers as the Azores high dominated the area producing relatively dry conditions and a moderate east-south-easterly airflow.

Fair and relatively dry conditions persisted into week three as the high pressure ridge continued to support a moderate, gusty and dry east to southerly surface flow. Conditions started to become moist and unstable over the area around the 18th due to a trough over Mexico and northern Central America and a low pressure area with a 40% chance of development over the western Gulf of Mexico. This led to the surface winds backing and becoming more east and north-easterly and an Omega pattern caused by high amplitude ridge extending over the northern south America to the western Caribbean, trough over the central and eastern Caribbean and a ridge over the north Atlantic resulted in a west to south-westerly upper level flow. Thus, both low and upper level moisture increased and a divergent upper level pattern developed supporting the increase in afternoon thunderstorms over southern and inland areas from the 18th to 20th with several thunderstorms, showers and rain affecting mostly central and southern areas overnight into May 21.

A trough over the Yucatan Peninsula persisted to the west of the country with ridging over the western Caribbean producing a light to moderate and moist easterly flow in the last week of May. Moisture continued to be advected over the area, supporting showers and thunderstorms across the country, especially over the central and southern portions late afternoon and evening. These showers were supported and further enhanced by a moist and divergent upper level pattern with a south-westerly component. This activity lasted until May 26 and signalled the official start of the 2021 rainy season for Belize over most areas. Drier conditions began to set in the last few days of the month in what would become the start of a dry spell as ridging prevailed in a relatively dry low level and neutral pattern over the area leading to mostly fair conditions with isolated showers and thunderstorms mostly inland and south.

The graph and maps below summarize the total rainfall and average maximum and minimum temperatures. They also give an indication of how these readings compare to the normal for the month across the stations sampled. As can be seen, despite the early start of the raining season, rainfall was near normal over most central and southern parts of the country, except for the northern districts where below normal rainfall was observed. In terms of temperatures, most of the stations sampled show near normal maximum/daytime temperatures, while minimum/night-time temperatures were above normal for all the stations except for Central Farm in the west and Punta Gorda station in the south.

Monthly Rainfall Summary

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Monthly Maximum Temperatures

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Monthly Minimum Temperatures

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Rainfall Observed: May 2021 (mm)

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Rainfall Observed: May 2021 (% Above/Below Average)

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