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.
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• 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.
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(10) Rock Sound, Bahamas. The weather is very similar to Nassau (see subparagraph (7).
(11) San Juan, Puerto Rico. The warmest month is September, with an average maximum of 86 Fahrenheit degrees, and the coolest months are January, February and March, each reporting an average minimum of 70 Fahrenheit degrees. The average annual precipitation is 61 inches. The seasonal range is not as great as other Caribbean stations. Fog is not a factor at San Juan, and when it does form on very infrequent occasions, it burns off soon after sunrise.
Low ceiling and visibility conditions are very infrequent, and occur mostly in heavy shower activity of very brief duration.
(12) Santo Domingo, Dominican Republic. July, August, and September are the warmest months with daily maximums of 88 Fahrenheit degrees and January and February are the coolest, reporting daily minimums of 66 Fahrenheit degrees. The average annual rainfall is 56 inches. There is a marked rainy season (May through October) where the average monthly rainfall exceeds 6 inches, and a dry season (December through March) when the average is 2 inches. Fog is very rare, occurring on an average of only two days per year. Ceilings may be lower than 1,000 feet on average of 22 days per year and visibility to be less than 1 mile on 7 days per year.
8-12. SOUTH AMERICA WEATHER INFORMATION. You will not find a pilot experienced in South American operations who has not had an unexpected and violent encounter with thunderstorms at altitude. On a moonlit night with the stars clearly visible and the cockpit lights properly dimmed, visual contact with weather is not difficult. On a moonless night, operating in a hazy layer of cirrus, even with the radar on, it may even surprise pilots. The area of greatest risk lies between lat. 10ºN. and lat. 10ºS. This area surrounding the equator is known as the ITCZ. Even thunderstorms of modest vertical development can produce substantial turbulence when operating in the vicinity. The following are some considerations in South America flying:
• ATC weather advisories do not exist.
• Use the radar frequently when operating over the South American continent, even when not anticipating weather. In the vicinity of the ITCZ, especially when in IMC conditions, there are dry top thunderstorms. Tilt the radar 2° or 3° down on MID or MAX gain in the 40 to 80 mile range. Avoid anything that paints no matter what intensity.
• Change radar ranges and sweep tilt from low to high when operating in conditions of low visibility or near known areas of thunderstorm activity.
• Listen carefully to broadcasts made on 123.45 by aircraft preceding your flight on the airways.
• Request weather information from opposite direction flights.
• Report weather encounters via in-the-blind broadcasts on 123.45.
• Send reports of weather to dispatch via company communications.
• Look through the windshield periodically.
a. Deviation. If a significant deviation around weather becomes necessary, request a clearance as you would normally do from ATC. If ATC does not respond on a VHF frequency, try to make contact on an HF frequency such as 8855, 5526 or as noted or the en route chart for the applicable ATC facility. ATC should unconditionally approve your request. If ATC does not answer your call, use good judgment. Any lateral deviation must include a broadcast of your position and extent of the off-course deviation on 123.45. Another aircraft may be able to relay your situation to ATC. Turn on exterior lights until returning to on-course. Be very conservative regarding the use of the seat belts sign.
b. Fog. 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 with January and February the only months free of them. 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.
c. Airports.
(1) Asuncion, Paraguay. The warmest month is January with an average daily maximum of 95 Fahrenheit degrees while the coldest months are June and July with average daily minimums of 53 Fahrenheit degrees. The average annual precipitation is about 52 inches a year. This amount is distributed evenly over 8 months of the year with about 6 inches a month and a definite dry season of June through September with about 2 inches a month. Snow and freezing precipitation (except hail) does not occur. Poor operational weather at Asuncion is primarily the result of polar front activity, which causes low ceilings and visibility due to rain, fog, and thunderstorms. The most severe weather type is the slow moving cold front or pre-cold frontal squall line with associated thunderstorm activity. This weather type produces some of the worst flying weather in all of South America due to the violence and severity of the squall line thunderstorms. Thunderstorms occur about 45 days out of the year, mainly in the long summer season of October through April when air mass, as well as frontal type thunderstorms, may occur. Most fogs are associated with frontal systems. They may occur at any time of the day.
Those that form at night usually clear or lift by mid-day. The prevailing surface wind is from the northeast except in October and December when southeast winds prevail. Average speeds are about 8 knots.
(2) Brasilia, Brazil. September is the warmest month with an average daily maximum of 86°F while July is the coolest month with an average daily minimum of 50 Fahrenheit degrees. The average annual precipitation is approximately 75 inches of which about 65 inches falls during the 6 month rainy season of October through March. The dry season of June through August produces less than an inch of rain per month. Snow and freezing precipitation are unknown. Good weather characterizes the dry season. Haze can occasionally cause marginal visibilities.
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(a) During the rainy season, the three following main weather situations can cause marginal or closed conditions at the airport:
1. One is an air-mass thunderstorm (usually in late afternoon) with associated rain and low scud but these seldom last for more than 30 minutes.
2. The second is a widespread continuous deck of low and middle clouds with rain caused by warm, moist unstable air moving along the plateau. Low ceilings and visibilities may prolong this condition.
3. The third comes with nocturnal clearing and light or calm winds after a period of rain resulting in the formation of ground fog, which usually dissipates rapidly after sunrise.
(b) During April and May, cold fronts often reach Brasilia, resulting in a brief return to the rain type regime and thunderstorms can occur. The surface wind is generally SE. to ESE.
during the dry season and varies from very light during the night, reaching its greatest speed during the afternoon. During the rainy season, they are usually light and variable.
(3) Buenos Aires, Argentina. The warmest month is January with an average daily maximum of 86°F and the coldest month is July with an average daily minimum of 44 Fahrenheit degrees. The average annual precipitation is 37 inches which falls in varying amounts each month ranging from 2 inches to 5.7 inches. The rainiest months are usually October through April. There is no true dry season. Snow and freezing precipitation are rare. The most frequent weather problem is fog. Fog is most frequent in June from 0400 to 0900 local time. Fog of 18 hours duration is not uncommon, beginning a few hours after sundown and lasting until early afternoon and 75 percent of all fog ends by 1000 local time. Fog may be of the radiation type with HF from May through August or of the frontal and postfrontal type, which can occur during any month at any time. Sea fog is uncommon at the airport but is often over the Rio de la Plata. The second most frequent cause of weather problems is the rapid development of temperate latitude frontal systems. These systems often produce thunderstorms, heavy rain and low stratus in addition to fog. On a yearly average, Porto Alegre is open 90 percent of the time and Montevideo is open 74 percent of the time when Buenos Aires is below 400 feet and/or 1 mile. The surface winds are primarily easterly from September through March and northerly during April through August. The average wind speed is about 6 knots.
(4) Caracas, Venezuela. September is the warmest month with an average maximum of 90 Fahrenheit degrees, and January and February are the coolest months averaging a minimum temperature of 72 Fahrenheit degrees. Maiquetia receives an average of 24.4 inches of rainfall per year. This varies from 0.6 inches for April to a maximum of 4.3 inches for February.
In spite of this great spread, there does not seem to be a generally wet or dry season as in most other tropical stations. Fog is not a weather factor at Maiquetia. Thunderstorms are very rare, occurring only on an average of about four days per year, and confined to the months of August, September, and October. Thunderstorms do form frequently over the mountains to the south of the station but have little effect upon the local weather other than some cloudiness and brief shower activity. Ceilings below 800 feet are reported only two-tenths of 1 percent of the time, and 1/3 of these cases last for only 1 hour or less.
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(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.
(6) Montevideo, Uruguay. The warmest month is January with an average daily maximum of 83 Fahrenheit degrees and the coldest months are June, July and August with average daily minimums of 43 Fahrenheit degrees. The average annual precipitation is 37 inches which is quite evenly distributed throughout the year. The weather is the result of both continental and maritime influences. The major operational problems come from a high frequency of radiation fog, frontal and postfrontal fog and sea fog. The peak of the radiation fog season comes in June when Carrasco reports below minimums in fog over a quarter of the time during the early morning hours and 16 percent of the observations for the month on a 24-hour basis are below 600-2 elevation. Often the airport closes or is marginal due to continuous fog for periods up to 3 days. October and November are the preferred months for sea fog while the frontal type fogs may occur in any month. The passage of cold fronts is common during the entire year. While thunderstorms occasionally occur during these frontal passages, they are more likely to occur as summer air-mass thunderstorms in January and February, although overall thunderstorm frequency is not great. The prevailing surface winds are northerly during the months January through August and southeasterly during August through December. The average wind speed is about 11 knots. Sea breezes are common during summer days and override the prevailing direction.
(7) Río de Janeiro, Brazil. The warmest month is February with an average daily maximum of 85°F while July is the coolest with an average daily minimum of 63 Fahrenheit degrees. The average annual precipitation is 43 inches with the monthly amounts varying from 1 1/2 inches in the dry season month of July to 5 1/2 inches in the rainy season month of December. Rio’s rainfall pattern is tropical with heavy summertime afternoon and evening showers and thunderstorms providing most of the precipitation.
(a) Rio de Janeiro has a subtropical climate with influences of both a continental and maritime nature. Except for the mid-summer months of December through February, the airport experiences weather either influenced by the polar front or by actual polar front passages.
While occurring most frequently in the winter, frontal passages may occur at any time of the year.
(b) The weather usually remains operational except when thunderstorms are present or when post-frontal fog occurs. Thunderstorms at, or in the vicinity of, the airport occur primarily in the summer months of October through April, reaching maximum occurrence in February when nearly 10 percent of the observations at 1700 local time report thunderstorms.
This late afternoon maximum, which prevails throughout the summer, is indicative of the air mass and orographic nature of most Rio thunderstorms. However, they can occur during the other months, usually in association with polar frontal passages. These thunderstorms are usually severe and their occurrence is random with regard to time of day. Hail is not uncommon, particularly to the NW. of the airport near the mountains.
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(c) There is a fairly high incidence of fog from mid-April to mid-July. This fog is both radiation and advective in nature, forms with clear skies and light winds usually in the early morning, and dissipates about 2 hours after sunrise. This is a mid-winter phenomena reaching a maximum in July at 0800 local time when over 1/3 of the observations report fog with conditions below 300 feet and/or 1/4 of a mile. Fog often forms over the harbor and drifts over the airport with northerly winds. Whether or not the fog reaches and covers the airport, it presents a difficult problem in forecasting. Haze often lowers visibility to 2 miles or less for days at a time. This phenomenon is most pronounced during the dry season.
(d) The prevailing surface wind is southeast with average speeds of 8 knots. The most significant feature of the surface wind is its land and sea breezes. In a normal diurnal pattern, the wind is light or calm or will be from the north with low wind speeds. The sea breeze takes over about noon and continues as a southeast wind until late afternoon or early evening.
(8) Sao Paulo, Brazil. The warmest months are September and October with average daily maximums of 86 Fahrenheit degrees. The coldest months are June and July with average daily minimums of 57 Fahrenheit degrees. The average annual precipitation is 59 inches with about 8 inches falling in the peak summer months and about 1 1/2 inches during mid-winter.
Thunderstorms account for most of the summer rain and frontal passages produce lesser amounts in the winter. Snow or frozen precipitation is unknown. Poor weather at Viracopas results from several weather situations among which are thunderstorms (air mass or associated with polar frontal passages), fog and low stratus with rain. The summer (October through March) is the preferred season for thunderstorms. Thunderstorms are most frequent between the hours of 1700 and 2100 local time. Most air-mass thunderstorms form to the NW. of the airport and move across the field from NW. to SE., or pass north or south of the field. The less frequent frontal-type thunderstorms may approach the airport from the SW. quadrant.
8-13. COMMUNICATION. When compared to voice communications, particularly to HF, Future Air Navigation System (FANS) 1/A data link provides a significant communications benefit in terms of error reduction and efficiency. Although communications problems were experienced initially, the system now achieves the desired level of performance. The improvement in communications performance is primarily due to work done in the South Pacific finding and resolving problems, and in developing and adopting procedures that ensure maintenance of system performance.
8-14. NAVIGATION. The navigation element has been the least problematic of the functions.
There have been few reports of problems to date and the system consistently delivers highly-accurate navigation solutions, improving efficiency and safety.
8-15. SURVEILLANCE. The airborne Automatic Dependent Surveillance (ADS) application will provide an ATS system with information on the present position of the aircraft. ADS can also provide short and long-term intent, local meteorological data, and occurrence of certain events. ADS contract requests from the ATS provider via data link determine the ADS reporting rate, triggering events, and groups of data to report. The system has the potential to deliver additional oceanic capacity through separation reduction as well as improved safety
(e.g., weather avoidance) through near-real-time surveillance.