Monthly Weather Summary, September 2022

National Meteorological Service of Belize

September is normally the peak of the hurricane season which for the most part was off to a slow start. Most of the tropical storms and hurricanes frequent the area during the month of September. The secondary rainfall starts around this time peaking in most southern locations and are attributable to tropical waves, upper-level troughs, surface troughs, cold core lows, and mid-upper level low. Normally, a total of 7 tropical waves, both active and inactive would cross Belize. During the month, a slack pressure gradient with ridging prevailed through the first two dekad and supported a light east to south-easterly flow. This supported several days of rain throughout the month over most areas while rainfall was concentrated mostly the earlier parts of the month in the north. The highest amount of rain days occurred over south-eastern Belize near the Savannah Station with 21 rain days and the highest one-day rainfall total occurring over the Toledo district with 132.0 mm on September 17 near Punta Gorda. September had above the normal amount of rain days indicating that rainfall accumulation was distributed over most of the month except for the extreme north and south of the country. Rainfall was normal to above normal over more areas.

Moist and unstable conditions prevailed to start off the month due to the presence of a tropical wave and a surface trough near the area. This resulted in high low and upper-level moisture over Belize from September 1-3 with a decrease in upper-level moisture from the 4th to the 7th of September. The overall pattern for this week was ridging due to a slight pressure gradient over the NW Caribbean supporting light east to south-easterly winds while Tropical Storm Earl was north of the area over the northern Caribbean. The approach and passage of the tropical wave on September 2 resulted in showers and thunderstorms affecting the country overnight into the daytime further enhanced by a divergent upper-level pattern. Showers and thunderstorms continued over the area through September 4 especially over southern and inland locations. Fairer conditions prevailed from September 5-7 as upper-level moisture decreased and the ridge pattern became dominate with neutral to weakly convergent upper levels supporting mainly isolated showers, except for a few more over the south.

In week two, leading up to the peak of the hurricane season, not much activity was occurring in the tropics except for what was now Hurricane Earl south of Bermuda. Thick Cirrus clouds prevailed over the area during this week with high upper-level moisture and a divergent upper-level pattern over Belize. Isolated showers affected the Toledo district on September 8, however, by September 9, showery activity increased across the country producing moderate to heavy showers and thunderstorms. A ridge pattern supported a light to moderate east to south-easterly surface flow. Showers and rain were widespread over most areas of the country on September 11 except for northern and central locations. Isolated showers prevailed to end off the week except for over the south where some showers and thunderstorms continued. The showers over the south were enhanced by a south-westerly upper-level flow from an anticyclone over the northwest Caribbean. This flow veered and became more north-easterly.

Activity in the tropics began to pick up with Hurricane Fiona developing and churning near Puerto Rico. Upper-level moisture remained high and a south-westerly flow due to an anticyclone to the east of the country prevailed. Low level moisture was relatively moist for most of the week and showers were isolated during the week which some showers and thunderstorms affecting the southern portions of the country overnight into early morning with significant rainfall activity over the south on September 17. Troughing over the area supported a light north-easterly flow and an upper level TUTT over the western Atlantic extending into the Yucatan supported a west-south-westerly upper-level flow.

Most to very moist conditions prevailed in the last week except for September 30. Tropical Depression #9 formed east-southeast of Jamaica that would later become Tropical Storm then Hurricane Ian between September 25-28. The presence of Hurricane Ian over the NW Caribbean supported a north-easterly surface flow from September 22-25 then a shift to the north and northwest prevail to the end of the month as Ian approached the Yucatan Peninsula. A TUTT low was also present over the Yucatan from September 22-25 along with an inverted trough and the upper-level flow was south-westerly supporting a neutral to weakly divergent pattern. A few showers and thunderstorms affected mostly central and southern locations. This activity increased to some as Hurricane Ian passed near the country on September 28 and continued into the 29th become beginning to decrease.

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, most of the country experienced above normal rainfall, especially along southern coastal areas while near normal conditions was observed over the Toledo district during the month. In terms of temperatures, most of the stations sampled show near normal maximum/daytime and minimum/night-time temperatures while slightly cooler than normal minimum temperatures were recorded over Toledo district.

Monthly Rainfall Summary

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Monthly Maximum Temperatures

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Monthly Minimum Temperatures

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