ISSUED AT: 07:53 AM

Date: Tuesday 11th of August 2020

Definitions used in the forecast and bulletin:

Term		Meaning
Dekad		10 day rainfall measuring period
Rain Day		A day with 1.0 mm or more of rainfall amount
Wet Day		A day with 10.0 mm or more rainfall amount
Extremely Wet Day		A day with 25.0 mm or more of rainfall amount
Normal Rainfall		Between 75% and 125% of the average
Below Normal Rainfall		Rainfall below 75% of the average
Above Normal Rainfall		Rainfall in excess of 125% of the average
Much Below Normal Rainfall		Rainfall below 50% of the average
Much Above Normal Rainfall		Rainfall above 150% of the average
Scanty Rainfall		Less than 1 mm
Moderate Rainfall		1-10 mm
Heavy Rainfall		10-50 mm
Very Heavy Rainfall		Greater than 50 mm
Probability of 1-30 %		Low Chance
Probability of 30-70 %		Moderate Chance
Probability greater than 70 %		High Chance
Term	Amount of Rain	Type of day
Scanty Rainfall	Less than 1 mm	Relatively dry day
Moderate Rainfall	1-10 mm	Relatively wet day
Heavy Rainfall	10-50 mm	Wet day
Very Heavy Rainfall	Greater than 50 mm	Excessively wet day

Weather Assessment for the period (1^st –9^th) of August 2020.

During the period 1^st to 9^th of August, mostly wet days occurred over Trinidad and Tobago. These wet days were due to the passage of tropical waves and a visitation of the Inter Tropical Convergence Zone. There were preliminary reports of flooding in northwestern Trinidad in areas such as Diego Martin. Rainfall totals’ maps for the period 1^st to 9^th of August are located below as figure 1 and figure 2.

 

Figure 1. Rainfall map of Trinidad showing measured rainfall totals for varying districts during period 1^st to 9^th of August 2020.

 

Figure 2. Rainfall map of Tobago showing measured rainfall totals for varying districts during period 1^st to 9^th of August 2020.

 

The observed temperatures (maximum/minimum), average relative humidity (maximum/minimum) and long-term 10-day (10dys) averages for Piarco International Airport and ANR Robinson International Airport during first dekad of August 2020.

Location	Maximum Temperature 0C/ Long term 10 dys average 0C	Minimum Temperature 0C /Long term 10 dys average 0C	Average maximum Relative humidity (%)/ Long term 10 dys average (%)	Average minimum Relative humidity (%)/Long term 10 dys average (%)
Trinidad (Piarco International airport)	33.7/31.9 (1981-2010)	23.2/23.6 (1981-2010)	90/93 (1990-2010)	78/70 (1990-2010)
Tobago (ANR Robinson International airport)	32.9/30.8 (1981-2010)	24.4/24.4 (1981-2010)	89/91 (1990-2010)	71/69 (1990-2010)

 

Table 1 shows the expected weather conditions during the Second Dekad (11^th –20^th) of August 2020, for Trinidad and Tobago.

Table 1.

Days:	Expected weather:
11th	Cloudy periods with a moderate probability (70%) of light to moderate showers.
12th	Intermittent cloudy patches with a moderate probability (55%) of brief showers.
13th	Cloudy periods with a moderate probability (70%) of light to moderate showers.
14th	Cloudy periods with a moderate probability (70%) of light to moderate showers.
15th	Intermittent cloudy patches with a moderate probability (55%) of brief showers.
16th	Cloudy periods with a moderate probability (70%) of light to moderate showers.
17th	Intermittent cloudy patches with a moderate probability (55%) of brief showers.
18th	Cloudy periods with a moderate probability (70%) of light to moderate showers.
19th	Cloudy periods with a moderate probability (70%) of light to moderate showers.
20th	Intermittent cloudy patches with a moderate probability (55%) of brief showers.

 

Table 2 shows the expected temperatures, humidity and dust haze days during the second dekad of August for Piarco, Trinidad.

Table 2.

Day	Maximum Temperature 0C	Minimum Temperature 0C	Average Relative humidity (%)	Dust Haze Yes/No
11th	31.0	23.0	90	No
12th	33.0	22.0	80	Yes
13th	31.0	24.0	90	No
14th	31.0	24.0	90	No
15th	33.5	22.7	70	Yes
16th	31.0	23.5	90	No
17th	33.9	24.0	75	Yes
18th	31.0	24.0	90	No
19th	31.0	24.0	90	No
20th	33.5	23.8	75	Yes

 

Table 3 shows the expected temperatures, humidity and dust haze days during the second dekad of August for the ANR Robinson, Tobago.

Table 3

Day	Maximum Temperature 0C	Minimum Temperature 0C	Average Relative humidity (%)	Dust Haze Yes/No
11th	31.0	23.0	90	No
12th	32.0	22.0	80	Yes
13th	31.0	24.0	90	No
14th	31.0	24.0	90	No
15th	32.9	22.7	70	Yes
16th	31.0	23.5	90	No
17th	32.9	23.0	75	Yes
18th	31.0	24.0	90	No
19th	31.0	24.0	90	No
20th	32.9	23.8	75	Yes

 

Trinidad’s Mean Daily Rainfall Forecast for the second Dekad of August (11^th -20^th) 2020.

Northern & Northwestern areas:

Moderate chance (65%) of mean daily rainfall up to 8.9 mm.

North-Eastern and Eastern areas:

Moderate chance (68%) of mean daily rainfall up to 12.6 mm.

Central, West-Central and inland areas:

Moderate chance (60%) of mean daily rainfall up to 6.4 mm.

South-Eastern areas:

Moderate chance (68%) of mean daily rainfall up to 12.8 mm.

Southern areas:

Moderate chance (65%) of mean daily rainfall up to 10.9 mm.

South-Western areas:

Moderate chance (65%) of mean daily rainfall up to 9.3 mm.

 

Figure 3. Rainfall map of Trinidad showing possible rainfall totals for varying districts during the second dekad of August 2020 and percentage probability of occurrence.

 

Tobago’s Mean Daily Rainfall Forecast for the Second Dekad of August (11^th -20^th) 2020.

Northeastern areas:

Moderate chance (68%) of mean daily rainfall up to 5.0 mm.

South-Western areas:

Moderate chance (68%) of mean daily rainfall up to 5.0 mm.

Figure 4. Rainfall map of Tobago showing possible rainfall totals for varying districts during the second dekad of August 2020 and percentage probability of occurrence.

 

Impacts on Agriculture:

During the second dekad of August 2020, relatively wet days are expected on the 12^th, 15^th, 17^th and 20^th; while wet days are expected on the 11^th, 13^th, 14^th, 16^th, 18^th and 19^th. There is a high (75%) probability that the anticipated rainfall will return significant soil moisture across Trinidad and Tobago. Due to the rainfall episodes of the last two consecutive dekads, rivers are likely to significantly increase in volume, water logged soils and pooling of water in low-lying areas are highly probable. Shrubs and grass-growth will continue at a fast pace. Additionally, with warm temperatures and routinely moist vegetation, there is a moderate (70%) probability for fungi spread, root rot, insects pests and warm weather diseases to develop.

Sun and Moon positions in the sky:

The sun is presently at a latitude of approximately 15.25 degrees North, and with this position, the day-length will 12.4 hours. As Trinidad and Tobago is in the heat and rainy seasons, regular cloud cover is possible, consequently, there is a moderate probability (60%) of intense solar radiation occurring during the second dekad of August 2020, when the sky is generally cloud free. There is also low probability (29%) of heat stress on young/sick/elderly animals from direct exposure to solar radiation and warm temperatures. Additionally, the moon’s third quarter phase will be on the 11^th followed by new moon phase on the 18^th of August 2020. As a result, there will be medium to low moon illumination over crop fields and livestock at night during the dekad.