Reported by Don Thompson at location in Belmopan 17'15" N, 88'47" W
Monday, June 25, 2012
Total rainfall so far this month 244 mm or 9.6 in The weather has now become considerably more dry. The region between here and Africa is extremely dry (see image). Not sure where the next rain will be coming from.
Some thundershowers in Belmopan last night. Measured 9 mm of rain. Total rainfall so far for June is 8.6 inches or 217 mm. Cause of the unstable weather is the proximity of the Monsoon trough of low pressure. The low pressure is actually at surface. There is currently an upper high over the area with a clockwise circulation so that the high cloud is moving in from the NE rather than from the west. Meanwhile the eastern Caribbean continues to be under the influence of dry air from Africa.
The monsoon trough is now running up the west coast of Central America. Also a trough of low pressure has formed off the east coast. Last night an area of rain moved northward along the coast of Belize. A storm cell must have formed over Belmopan and I measured 66 mm (2.6") of rain this morning which was a surprise since I did not hear any heavy rain all night. Conditions in the Caribbean have changed dramatically over the past 36 hours. The dry air is rapidly being replaced with rain clouds.
Thundershowers last night from 0200 to 0500 hr with 36 mm of rain or 1.4 inches. This weather system followed almost the same pattern as previous. That is, developed in the southwest corner of Belize and moved northeast just south of Belmopan. The storm was triggered by the passage of a Tropical wave moving in from the Caribbean across the Yucatan. This wave is now dissipating as High Pressure builds to the north in the Gulf of Mexico. On the Pacific side is TS Carlotta which is heading north but may get pushed to the west by the building High in the Gulf.
This image shows that there are no storms headed this way. The mid Atlantic is covered with dry and dusty air from Africa. The weather here should remain more dry than normal for the foreseeable future. Any showers will be isolated. Rainfall is being suppressed.
A tropical wave is approaching allowing the area of rain to expand northward. We are already beginning to experience the effect with a light shower at 4:20PM. There should be more rain tonight and tomorrow as the wave moves closer. However, Saharan dust from West Africa will be suppressing any significant development.
The Caribbean in general continues to be dry including Belize. Becomes more dry the further up towards the northern part of the Yucatan. Most of the rain is concentrated down to the southern part of Central America especially around Costa Rica. Any rain in Belize will be from isolated showers and would occur mainly around midnight.
There was a repeat of the same weather pattern of the past few weeks. A thunderstorm developed overnight in the SW of Belize (2 to 3 AM) and moved north east between Belmopan and the coast. Measured 24 mm of rain. By mid morning of June 6 the storm had disappeared. The Caribbean basin itself continues to be very dry.
The area of dry is now closer however there is still a lot of moisture surrounding Central America which could set off some afternoon thundershowers similar to yesterday. The clockwise circulation around the Caribbean High Pressure is feeding the moisture northward into the Yucatan as shown in image below.
Another T-Shower developed over Belmopan this afternoon dumping more rain, I measured 22mm. This rain still due to the same weather pattern of last month. The dry air now in the Central Caribbean has not yet arrived but is getting closer.
There is a large area of hot dry dusty air headed westward towards the Caribbean as shown in the blue in the image. This could mean that the month of June here may be more dry than May, at least for the first half of June. I am going to delay any planting of seed until this African dry air is replaced with some Tropical Waves.