g. ATC. There are significant differences in ATC facilities, procedures, and controller capability between countries. Controllers in the Caribbean and South America assume that pilots are masters of their fate and know what to do. Keep in mind that the clearance you ask for is the one you will receive. It is almost always prudent to stay on your route of flight, rather than asking for a reroute or direct. Also, never accept a clearance that you cannot complete
(e.g., “request 250 knots to the outer marker”). Let them know what you will accept, and almost always, they will grant you a clearance.
(1) Caribbean Flight Information Regions (FIR). In the Caribbean, you will cross multiple FIRs within a relatively short distance and you must use the associated FIR procedures for crossing. As a technique, locate all the communications boxes on the Jeppesen, LIDO, or Department of Transportation (DOT) charts, which give FIR guidance. They may not be anywhere near your route of flight. Jeppesen has recently begun using heavier marking around the sector frequency boxes, using a small telephone symbol as the line.
(2) Position Reports. To reduce the possibility of a communication error, remember that the controllers use a very precise order in receiving your position report. You must report your position in the proper format:
• Call sign.
• Position.
• Time.
• Altitude.
• Estimate for next fix.
• Name of succeeding fix.
(3) Controller Response. The controller’s most common response to your report is, “Aircraft 985, roger report ISANI.” Listen closely since the controllers may have you omit a report over intervening fixes. Some controllers and other foreign carriers may insert the word “position” before the name of a fix (e.g., “Aircraft 985, roger, report position ISANI” or “Aircraft 985, say estimate position TESAL.”).
(4) Phrasing Responses. Avoid taking shortcuts in communications or the inclusion of non-essential phrases or American colloquialisms (e.g., “Aircraft 984 getting moderate chop at three five oh and we’d like to go up to three nine oh”). The controller will probably respond to this request with silence or, even worse, a clearance for something totally unrelated to your request. Keep it simple: “Aircraft 984 requesting flight level three niner zero.” Expect a response such as “Aircraft 984, standby for FL 390.” Be careful not to interpret that as a clearance to climb to flight level (FL) 390. It is quite common for the controller to respond to your first request for an altitude change with “Standby FL 390.” They may have to check down line, maybe by antiquated teletype, to see if they can grant your request. Read back all clearances and report leaving any assigned altitude.
(5) Communication Difficulties. In South America, when out of reach of VHF, it may be possible to contact other aircraft on 123.45 and ask if they are talking to anyone on VHF. You can try that frequency, or ask them to relay a request or position report for you. Please volunteer to do the same for others having communication difficulty. It is also wise to get the flight Page 80 Par 8-3
numbers of the flight passing in the opposite direction to you. All flights that pass over each other between north and mid South America are great resources for weather and flight conditions along your route of flight.
(6) VHF and HF Communications. Most ATC communications is on VHF. From Los Angeles to San Salvador, expect VHF communications throughout the flight with radar coverage for most of Mexico. However, areas where VHF communication with ATC is not available require HF radios. There is a small area of central Brazil that may require the use of HF to contact Belem or Manaus centers. Do not give up on VHF too soon; the controllers may take 30 to 60 seconds to answer as they may be handling another flight on a different frequency. If the use of HF is necessary, a center that is nowhere near your location may answer. After making several calls to either Belem or Manaus, Maiquetia may take your call. They will be able to relay your position report to the proper center. Cedar Rapids Radio has very good reception throughout Central and South America.
h. ACARS. There are two VHFs in use in the Caribbean: 131.55 (ARINC/ACARS) and
131.72 (Societe International de Télécommunications Aeronautiques (SITA)/Air/ground Communications (AIRCOM)). In South America, operators use 131.55. In addition, ACARS will use SATCOM Voice if you cannot find an active VHF frequency. With these choices, ACARS can downlink messages to the company without any problem. Problems may arise, however, when dispatch tries to uplink messages to the aircraft via one of the three VHF networks.
Messages may be lost as the aircraft transitions from one VHF network to another with the message then returned to the originator as “unable to deliver.”
(1) HF LDOC Link. Until SATCOM Voice is proven reliable in South America, it is imperative to establish an HF LDOC link with the company to maintain the required operational control and ensure timely receipt of important messages. In the Caribbean, there is good ACARS coverage throughout.
(2) ACARS Gap and Approaching Top of Descent (TOD). An ACARS gap crops up occasionally about 200 to 400 miles north of Buenos Aires (EZE). Neither VHF nor SATCOM Voice will work and it is a good reason to keep confirming an LDOC link with Cedar Rapids Radio. Downlink any messages to the station prior to reaching this area. As the TOD approaches, ACARS should return. If all else fails, a call to station operations will work at TOD.
Par 8-3 Page 81
Page 82 Par 8-3 FIGURE 7. AIRCRAFT COMMUNICATIONS ADDRESSING AND REPORTING
SYSTEM GAP 16 UL304UL304
COMMUNICATIONS GAP
COMMUNICATIONS GAP
CLASS II FOR
INS AIRCRAFT
CLASS II FOR
INS AIRCRAFT 16
8-4. COLLISION AVOIDANCE. Do not assume ATC is providing aircraft separation. Listen to the ATC position reports of other aircraft. Monitor the Traffic Alert and Collision Avoidance Systems (TCAS) display on the navigation display (ND) and listen to the blind broadcast frequency. When possible, pull up the “HOWGOZIT” for other company flights and compare estimates at common fixes. Turn on a landing light when changing altitudes or when passing opposite direction traffic. Keep the lights in the cockpit at a level that does not impair distant vision. The most important glass component in any aircraft is the windshield. If an effort to avoid collision requires immediate action, respond to the TCAS RA. Consider setting one transponder TCAS to “ABV” and one to “BLW” for greatest traffic coverage. Finally, never accept a wrong way altitude. (Normal levels are 290, 330: 370, 410 southbound, 310, 350, 390, 430 northbound but some exceptions occur at eastbound/westbound magnetic course changeovers indicated with < E.)
8-5. DISPATCH. When comparing South American operations to other international remote areas, the following factors must enter into your planning:
• Weather reporting and forecasting are not as accurate as other parts of the world.
• Weather forecasts for en route airports may be 5 to 6 hours old.
• Alternate airports are unfamiliar to flightcrews as well as the language spoken.
• Weather deviations, to some extent, occur on nearly every flight.
• Cruise altitudes are limited as the result of ATC separation based on time/position reports rather than radar, and rerouting is difficult due to the limited airway structure in South America.
• If ATC assigned your planned flight altitude to a preceding flight, it may be unavailable and you may have to settle for a cruise altitude much lower than the Flight Plan Forecast.
a. Fuel Planning. The biggest factor affecting fuel planning will be the inability to secure your optimum cruise altitude, with the volume of flights conducted by all the carriers to South America. Make sure to carry enough fuel to compensate for a low cruise altitude assignment.
Consider asking for your step climb (higher filed) altitude prior to departure. Even though it might not be fuel efficient, this will ensure having a good altitude later in the flight.
b. Flight Plan. The international flight plan format is used for all flights from the continental United States to destinations in the Caribbean and South America. Like operations in the North Atlantic (NAT), maintain a master flight plan with a record of time and fuel scores regardless of whether any portion of the flight plan contains Class II navigation segments. In this area of operations, the situational awareness (SA) of position, fuel, time and developing trends has great importance. When flight planning for departure from Caribbean or South American stations, use an ICAO format flight plan. Ensure that the routing, FIR estimated time of arrivals (ETA), and altitude on this form are identical to the Flight Plan Forecast.
8-6. MAINTENANCE/DISPATCH CRITERIA.
a. Dispatch-Sensitive Systems. South American bound aircraft serviceability has proven that the following systems are dispatch-sensitive:
• Ground proximity warning system (GPWS).
• TCAS.
• Weather radar (WX).
• SATCOM Voice.
• Auxiliary power unit (APU).
• Generators.
• Engine pneumatics.
• Engine anti-ice.
• Air conditioning packs and valves.
b. Serviceable Systems. Serviceability of these minimum equipment list (MEL) deferrable systems prior to dispatch should be a line maintenance priority.
8-7. EMERGENCY PROCEDURES AND DIVERSIONS. ICAO emergency procedures apply throughout the Caribbean and South America, but crews should not rely solely on ATC for navigation or terrain avoidance. This is the case especially in South America. While no different than international operations in other parts of the world, the Federal Aviation Administration (FAA) makes the following recommendations:
Par 8-5 Page 83
• Become familiar with the location of alternate and emergency airports as depicted in brown on the SA/LA HI ENROUTE 1/2 chart or summarized in the airport location chart in a Flight Operations Manual (FOM).
• Be mindful of those circumstances which constitute an emergency or in-flight crisis:
engine failure, depressurization, cabin or cargo fire, a single electrical or hydraulic system remaining, medical problems, sabotage threats, or passenger misconduct. Each of these may require a slightly different crew response and alternate airport requirement.
• Maintain an emergency diversion plan at all times and communicate this plan to crewmembers preceding and following rest periods. Know the proximity of potential diversion airports and discuss their suitability for the previously mentioned problems.
Update weather and Notices to Airmen (NOTAM) via ACARS.
• Maintain a communication capability with company, dispatch, and ATC using SATCOM Voice as your primary choice in remote areas. When operating beyond VHF ACARS range, have a frequency for an LDOC link with San Francisco ARINC standing by in the event of an engine indicating and crew alerting system (EICAS) SATCOM Voice Lost message.
• Maintain an awareness of national boundaries not only for diversions but also for urgent weather deviations. With an emergency, an unscheduled FIR crossing may be unavoidable if it is the safest course of action. Be ready to communicate with the adjacent ATC facilities.
a. Diversion Planning. Some emergency and irregular procedures direct the captain to land at the nearest suitable airport. We consider this the diversion alternative, which, in the captain’s best judgment and considering all applicable factors, will result in the highest level of safety. Diversions differ in complexity and an unexpected diversion to an emergency airport in a foreign country resulting from an aircraft system malfunction can develop into an extended delay. This will require a high degree of coordination in order to safeguard the passengers and crew, carry the passengers to their destination and restore the aircraft to service. Operators can achieve optimized diversion planning and maximum assistance from Air Traffic Service (ATS) and airport emergency services.
b. Diversion Criteria. If a diversion becomes necessary for any reason, the best airport may be several hundred miles away. The following criteria should play a part in your decision:
• Airport that is nearest.
• Airport with the best weather.
• Airport with the best NAVAIDs or approach.
• Airport with the biggest city or best facilities.
c. Emergency Airports. Looking ahead and validating options for emergency landings will keep you prepared. Maintain a diversion plan at all times when operating in the Page 84 Par 8-7
Par 8-7 Page 85 Caribbean/South American (CAR/SAM) region. The Latin America/South America High Chart displays approved airports for most aircraft.
8-8. MEDICAL DIVERSION. When a medical emergency arises during flight in the Caribbean or South America, contact company dispatch or flight following as soon as possible.
Discussing a passenger’s illness with a physician on the ground or soliciting the aid of an onboard medical professional is essential before any diversion is undertaken. If a diversion to deal with a sick passenger is unavoidable, make a choice between the nearest airport and the airport with the best medical facilities. A diversion with a medical emergency is seldom easy and you must remember that all should not be put at risk for the sake of one. Any international flight anywhere in the world requires customs intervention when that flight does not land at its intended destination. Normally, if the ill passenger deplanes, the flight requires all remaining passengers to stay onboard. Family members accompanying the ill passenger are usually the exception. When an aircraft diverts for a medical emergency, or any other reason, with the intention of continuing flight to the original destination afterward, factor the following operational issues into the decision-making process:
• Fuel jettison, then refueling.
• Overweight landing, then overweight inspection.
• Brake cooling period.
• Quick turn-around time.
• Extended Operations (ETOPS) inspection.
• Dispatch release and new Flight Plan Forecast.
• Maintenance release.
• ATC clearance.
FIGURE 8. TERRAIN CRITICAL AREAS 21 UL304UL304TERRAIN CRITICAL AREAS
TERRAIN CRITICAL AREAS 21
8-9. DEPRESSURIZATION PROCEDURES. Some routes in South America have areas of high terrain that require specific emergency descent procedures where the minimum en route altitude (MEA) or Grid Minimum Off-Route Altitude (MORA) is above 10,000 feet. These “escape routes” should be part of the operations papers and followed in the event of a depressurization. Having all available information is imperative for proper planning and execution of the procedures. The last place that you want to look for the proper chart and altitudes is at night, in the descent, in the dark, not being able to communicate well with your fellow pilot, and looking through your mask to see the legend. Remember, some of the mountains in South America are above 23,000 feet.
NOTE: There are also differences in the charts that you use. On some South American/Latin American High En Route Charts, they give some Grid MORAs and some MEAs, but not all the jet routes have MEAs. On the Jeppesen High/Low charts, there are the MEAs, but they do not depict Grid MORAs well.
8-10. SAFETY OF FLIGHT. Those problematic external factors which we confront on every South American flight include communication, navigation facilities, terrain, weather, traffic, and the physiological impact of night operations. To handle these challenges with the utmost professionalism, a flightcrew must guard against complacency, poor SA, vigilance, and preparation when flying departure and arrival procedures.
a. Position and Minimum Altitudes. When operating along the airways in South America, there is reasonable assurance of position and minimum altitudes. The time to focus on Page 86 Par 8-8
position and terrain clearance is during radar vectoring in night visual meteorological conditions (VMC) or instrument meteorological conditions (IMC) operations apart from established airways. Use every available resource at your disposal: Low Altitude charts, 10-1 chart, approach pages, FIX pages, NAV/RAD page, hard-tuned VORs, and VOR/BRG pre-selects. Analyze NOTAMs carefully for en route airways, en route alternate and emergency airports as well as your destination airport and brief departures and arrivals thoroughly. Listen carefully to lost communication instructions. Ask for lost communication procedures if they are not provided.
Confirm voice contact with ATC if prolonged silence occurs under radar control. Ask ATC to read clearances as many times as necessary to clearly understand them. Ask for verification of your read back if you are uncomfortable. In other words, make sure you know your location and destination.
(1) Cleared Direct To. A clearance from a controller to proceed “direct” may mean proceed via the flight planned route. If the controller issued a request to report “abeam” a bypassed fix, then you can be confident that the clearance conforms to our meaning of “direct.”
In any other circumstance, request clarification and always remain cognizant of MEAs.
(2) Holding. A clearance to hold is expected to be as published. If there is no holding pattern depicted at an en route fix, then the aircraft is expected to hold on the inbound course or radial with right turns. The following is a list of international maximum holding speeds:
• 210 = up to FL 60.
• 220 = FL 60 up to and including FL 140.
• 240 = above FL 140.
(3) Fuel Report. Do not make fuel remaining reports when making ATC position reports on VHF or HF in South America. Naturally, dispatch is interested if you send down manual reports.
b. Safety Thoughts on South American Flying.
• TCAS and GPWS must be operative.
• Ensure terrain clearance by adhering to established routes.
• Only accept altitudes proper for the direction of flight.
• Monitor the position of other aircraft on your route by their reports and ND traffic displays.
• Brief all altitudes for arrival and departure,
• Do not change altitude when crossing an FIR.
• Methods or necessity for pilot-not-flying (PNF) to monitor raw data for departure, approach, and landing.
Par 8-10 Page 87
Page 88 Par 8-10
• Establish and maintain a company communications link.
• Speak slowly and use standard radio phraseology.
• Maintain cockpit lighting that permits observation of weather conditions.
8-11. CENTRAL AMERICA AND CARIBBEAN WEATHER.
a. General Area Weather/Dry Season (November-April). This season has most of the good operating weather. Apart from haze, some ground fog, and an occasional polar front with associated drizzle and low ceilings, there is little weather. The haze forms by late March and increases in area and density until the rain begins to clear the air and you may encounter dense haze and poor visibilities at lower levels.
b. Rainy Season (May-October). This season has most of the poor operating weather.
Orographic afternoon thundershowers over land and early morning thundershowers over coastal waters characterize this season. Ceilings and visibilities may be low for short periods, but generally conditions remain operational.
(1) Intertropical Convergence Zone (ITCZ). The ITCZ moves into this area during summer and early fall and has moved as far north as Guatemala City. Cumulonimbus clouds (CB) in a solid line may extend to heights above 50,000 feet. Altostratus and cirrostratus clouds spread out in sheets from the CBs, the latter accompanied by heavy rain and severe turbulence.
(2) Hurricanes. Hurricanes that develop off the west coast of this area normally move northwestward to west-northwestward into the Pacific. Hurricanes that develop in the Atlantic, Caribbean, and Gulf of Mexico can directly affect the east coast north of Panama to and including Mexico.
c. Guatemala City, Guatemala. During the dry season, early morning fog occurs frequently but usually dissipates by 9 a.m. During the rainy season, the usual weather consists of scattered stratocumulus clouds (SC) in the morning, broken to overcast cumulus clouds (CU) and scattered showers in the afternoon and CBs and heavy rains by late afternoon and evening. The prevailing surface wind is from the north at 7 knots. The average annual temperature is 68°F.
d. Managua, Nicaragua. Thunderstorms are very common and occur most frequently from May through October. They seldom close the airport for more than 20 minutes. The prevailing surface wind is from the east to southeast at 7 knots. During thunderstorms, velocities often reach 50 knots. The average annual temperature is 78 Fahrenheit degrees.
e. Merida, Mexico. Most fog occurs from September through January. It usually forms after 10 p.m. and dissipates by 9 a.m. Maximum thunderstorm activity occurs from June through August and during the afternoon. Surface winds are generally light. The average annual temperature is 79 Fahrenheit degrees.
f. Mexico City, Mexico. Most fog occurs in winter but usually clears by 9 a.m. Maximum thunderstorm activity occurs from June through August. Smoke and haze often reduce visibilities to less than 3 miles. Surface winds are generally light. The average annual temperature is
60 Fahrenheit degrees. Summertime temperatures can reach 90 Fahrenheit degrees coupled with the high density altitude.
g. Panamá City, Panamá. Thunderstorms occur frequently in the afternoon from May through November, but seldom last for more than 45 minutes. In late summer and fall, thunderstorm activity associated with easterly waves and the ITCZ may persist for 4 hours.
Surface winds are generally light. The average annual temperature is 80 Fahrenheit degrees.
h. San José, Costa Rica. Upslope fog associated with westerly wind flow forms in June, August, September, and October. The duration directly relates to the persistence of the westerly flow. Thunderstorms mostly occur during afternoon hours and from May through October. Rain falls about 5 days out of 6 during the rainy season. Surface winds are usually light. The average annual temperature is 69 Fahrenheit degrees.
i. San Salvador, El Salvador. Most fog occurs from May through October and during early morning hours. It usually dissipates by 9 a.m. Maximum thunderstorm activity is during afternoon hours from May through October. Surface winds are generally light. The average annual temperature is 77 Fahrenheit degrees. In the following weather discussion, the Caribbean area will be in two parts - the North Caribbean and the South Caribbean. The South Caribbean contains the Caribbean area airports located on the South American continent and the island of Trinidad; the North Caribbean contains the remainder of the Caribbean area airports.
j. North Caribbean. The dry season, generally November through April, is the good weather period. Cold fronts from North America penetrate the area, and on occasions, reach as far south as Panama and the north coast of South America. Pre-frontal squall lines often develop in advance of the cold front in the Florida-Bahamas area. Apart from ground fog and an occasional polar front, there is little weather from November through April.
(1) Rainy Season. The normal rainy season commences with the weakening of the Azores/ Bermuda High as the sun moves northward. Orographic and afternoon thundershowers over land areas and early morning thundershowers over water areas near the coast characterize the greater percent of the rainy season. Ceilings and visibilities may be quite low for short periods during the time of maximum occurrence, but generally conditions remain operational.
(2) Easterly Waves. The easterly wave is a disturbance in the trade wind flow with the axis of the wave generally oriented in a NNE./SSW. direction, moving from east to west. They are encountered during the late spring, summer, and early fall. Quite often intense, easterly waves develop into hurricanes. The peak of the hurricane season is during the months of August and September.
k. South Caribbean. This area is under the influence of the ITCZ of the northeast and southeast trade wind systems. The ITCZ can be described as a belt of interaction between the converging wind systems producing layers of cirrostratus, altostratus, and cumulonimbus clouds.
Regions of potentially unstable air lie on either side of the belt. The width of the unstable air on either side of the ITCZ varies seasonally and on a day versus night basis.
(1) November through March. During this period from November through March, the ITCZ migrates slowly southward, with the southern boundary normally reaching to about 10°S Par 8-11 Page 89
in the central interior of Brazil and approximately 04°S. along the coast of South America in March. During the period from April through September/October, the ITCZ migrates northward, and the northern boundary is north of Trinidad and the northern coast of South America near the end of this period.
(2) ITCZ. When the ITCZ is moving north or south and winds are converging significantly, weather conditions can become very intense. CBs in a solid line may extend from 1,000 feet above the surface to heights above 50,000 feet, accompanied by heavy rain and severe turbulence.
l. Airport Weather.
(1) Barranquilla, Columbia. The warmest months are August and September with 1300 local average of 87 Fahrenheit degrees. February is the coolest at 82 Fahrenheit degrees.
The average annual precipitation is 15.5 inches as over half of it falls in September and October.
Less than 1/3 of an inch falls from December through March. Thunderstorms are observed on an average of 10 days per month during September and October as they are normally of short duration. Fog is uncommon but can occur. Stratus is common throughout the year, causing ceilings below 1,000 feet on an average of 10 days per month during the dry season and up to 20 days per month for the remainder of the year. It burns off rapidly during daylight hours.
(2) Freeport, Bahamas. The weather is very similar to Nassau weather (see subparagraph (7)).
(3) Georgetown, Guyana. The warmest months are September and October with average daily maximums of 91 Fahrenheit degrees. While there are no particularly cool months, the minimums vary from 73 to 75 Fahrenheit degrees. Guyana receives 91 inches of rain on a yearly average, nearly all of which falls during a long rainy season lasting from December through July. Amounts vary from 12 inches a month during the peak months of May and June to 6 1/2 inches in February. During the dry (or less rainy) months of September and October, the precipitation amounts to about 3 inches per month. Warm, moist unstable air perpetually blankets Guyana and, as the result of being close to the equator, it receives a maximum of solar radiation. The effects combine to produce numerous air mass type thunderstorms, which occur most frequently during mid and late afternoon hours. In addition, the ITCZ seasonally migrates across the area, producing two peak periods in the long, rainy season. This ITCZ activity may occasionally produce below minimum conditions lasting 3 to 4 hours. Early morning fog of a radiation nature has occurred during most months, lasting from 1-2 hours and occasionally 3-4 hours, but usually clears by 1 to 2 hours after sunrise.
(4) Kingston, Jamaica. The monthly variation of the average temperature is but a few degrees with the extremes on record of 95 Fahrenheit degrees in July, and 67 Fahrenheit degrees in the 3 mid-winter months. The annual average rainfall is 34 inches, most of which falls in showers during the summer rainy season. August, September, and October account for over half of the 34 inches, while January, February, and March are nearly rain free. Visibility is generally very good. Sea fog is unknown and there is no radiation fog at the airport. Visibility is rarely reported below 1 1/4 miles. Ceilings are seldom below 1,000 feet only in the summer and fall for Page 90 Par 8-11
a very low percentage of the time. Most restrictions to both ceiling and visibility occur during heavy showers. These usually result in cloud bases about 1,000 feet and visibilities 1/2 to 1 mile.
(5) Maracaibo, Venezuela. The months of July, August, and September are the warmest with maximum temperatures averaging 94 Fahrenheit degrees, while January and February are the coolest with average minimums of 73 Fahrenheit degrees. Maracaibo receives
22.7 inches of rainfall per year. The wetter season, May through November, accounts for 21 inches of the total with the balance spread over the remaining months. Fog is not a weather problem here. Thunderstorms are reported on an average of 76 days per year, primarily in the months June through October. January and February are the only months free of thunderstorms.
Most of the precipitation is a result of this thunderstorm activity. During a 5-year period of record, visibilities 1 mile or less occurred on an average of 12 days per year, and ceilings of 1,000 feet or less occurred on an average of 56 days.
(6) Montego Bay, Jamaica. The general weather conditions at Montego Bay are the same as Kingston except that, due to the fact that Montego Bay is on the windward side of the island, precipitation is somewhat higher and unfavorable weather conditions are slightly more frequent.
(7) Nassau, Bahamas. The warmest month is August, with an average maximum of 89 Fahrenheit degrees and the coolest month is February with an average minimum of 64°F.
Nassau receives an average of 50 inches of rainfall per year. On a monthly basis, rainfall ranges from a minimum of 0.9 inches in January to a maximum of 7.5 inches in September. Cold fronts provide the mechanism for rain in the dry season. Fog (visibility less than 1/4 mile) occurs on an average of 36 days per year primarily during the months October through April, with December averaging 7 days per month. The fog is very thin, forms in the early morning hours, and dissipates soon after sunrise.
(8) Port-au-Prince, Haïti. The annual precipitation at Port-au-Prince is 54 inches.
There are two periods of rainy weather: April through June and August through October.
December and January are the driest months, reporting a little more than one inch. July is the warmest month with an average maximum of 94 Fahrenheit degrees and January and February are the coolest, reporting a minimum of 68 Fahrenheit degrees. Fog does not occur in Port-au-Prince and ceilings less than 1,000 feet are reported on an average of one day per month.
Visibilities of less than one mile are also rarely reported and never more than an average of one day per month. Thunderstorms are very common, average 107 days per year, with the majority coming in the months May through October and becoming quite scarce December through March.
(9) Port of Spain, Trinidad. The warmest month is May, reporting an average maximum of 89 Fahrenheit degrees, and the coolest months are January, February, and March, each reporting an average minimum of 67 Fahrenheit degrees. Port of Spain receives an average of 73 inches of rain per year. The amounts vary from a low of 1.2 inches in March to 11.8 in June. The wet season extends from June through August and the dry season from January through April, with the other months in transition. Fog is not a factor at Piarco.
Par 8-11 Page 91