(24.3.2017) Weather is generally fair over the North Bay and partly cloudy to cloudy over the Andaman Sea and elsewhere over the Bay of Bengal.

Glossary

Degree of Certainty

Rain will be isolated/scattered/widespread… Degree of certainty is 80-100%
Likelihood of isolated/scattered/widespread rain…. Degree of certainty is 60%
Possibility of isolated/scattered/widespread rain…. Degree of certainty is 40%

Rain categories for Areawise forecast

Isolated Rain will be at 30% of the State/ Division. Especially it can be during the period of weak monsoon. (eg. Out of 10 stations in a State/Division, 3 stations got rain amount)
Scattered Rain will be at 50% of the State/ Division. Especially it can be during the period of weak monsoon. (eg. Out of 10 stations in a State/Division, 5 stations got rain amount)
Fairly widespread Rain will be at 80% of the State/ Division. Especially it can be during the period of moderate monsoon. (eg. Out of 10 stations in a State/Division, 8 stations got rain amount)
Widespread Rain will be all the State/ Division. Especially it can be during the period of strong/vigorous monsoon. (eg. Out of 10 stations in a State/Division, all stations got rain amount)

Rain categories according to intensity

Light rain During the 24 hours, rain will be below (0.5) inch for Central area and below (1.0) inch for the remaining areas.
Moderate rain During the 24 hours, rain will be between (0.5) and (1.5) inches for Central area and between (1.0) and (3.0) inches for the remaining areas.
Torrential rain During one hour, rain will be (1.0) inch and above it.
Heavy rain During the 24 hours, rain will be (1.5) inches and above for Central area and (3.0) inches and above for the remaining areas.

Rain categories according to Duration and frequency

Intermitted rain Frequent rain and it may occur when monsoon is in strong condition/ if there is storm in the Bay of Bengal.
Temporary rain Rain will be in a few hours and it may occur when thunderstorm, cumulonimbus climbed down closely to ground and pass the area.
At times / One or two rain One or two rain has been occurred during 24 hours especially moderate and moderate to strong monsoon period.
Occasional rain One or two rain with more frequent.

Rain categories according to the combination of Area and intensity

Isolated heavy fall Rain have been heavy at 30% of the State/Division during 24 hours. The amount will be (1.5) inches and above for Central area and (3.0) inches and above for the remaining areas.
Locally heavy fall Rain have been heavy at 50% of the State/Division during 24 hours. The amount will be (1.5) inches and above for Central area and (3.0) inches and above for the remaining areas.

Portions of the Bay of Bengal

North (or) Head Bay Latitude ……18.5ºN and above
West Central Bay Latitude…….between 13.0ºN and 18.5º N
Longitude…..88.5ºE and its western portion
East Central Bay Latitude…….between 13.0ºN and 18.5º N
Longitude…..88.5ºE and its eastern portion
South West Bay Latitude…….13.0ºN and its southern portion
Longitude…..86ºE and its western portion
South East Bay Latitude…….13.0ºN and its southern portion
Longitude…..between 86ºE and 93ºE
Andaman Sea Latitude……Deltaic coast, Gulf of Mottama and its southern lower latitudes
Longitude…..between 93ºE and Taninthayi coast

Categories of storms in the Bay of Bengal according to wind speed (NMC)

(1) Low Pressure Area ≤ 32 mph
(2) Tropical Depression 33-38 mph
(3) Tropical Storm 39-55 mph
(4) Cyclonic Storm 56-72 mph
(5) Severe Cyclonic Storm ≥ 73 mph
(6) Very Severe Cyclonic Storm ≥ 100 mph
(7) Very Severe Cyclonic Storm with Hurricane wind force ≥ 120 mph

The Definition of Normal, Above Normal & Below Normal (NMC, Myanmar)

Normal : Average amount of previous 30 years (at least) meteorological data
Above Normal : > 20% of the Normal
Below Normal : < 20% of the Normal

The Definition of Normal, Above & Below Normal Temperature (NMC, Myanmar)

No.

Above / Below from Normal Temperature

Maximum /Minimum Temperature Definition

1.

+3°C to +4°C

Slightly Warm

2.

+5°C to +6°C

Markedly Warm

3.

+7°C to +8°C

Heat Wave

4.

+9°C and above

Severe Heat Wave

5.

-3°C to -4°C

Slightly Cold

6.

-5°C to -6°C

Markedly Cold

7.

-7°C to -8°C

Cold Wave

8.

-9°C and above

Severe Cold Wave

State of the Sea

Slight Sea will be slight with height of about (0.5-1.25) meters
Moderate Sea will be moderate with height of about (1.25-2.5) meters
Rough Sea will be rough with height of about (2.5-4.0) meters
Very Rough Sea will be very rough with height of about (4-6) meters

Monsoon Intensity

(∆P) stands for mean sea level pressure difference between Sittwe(STW) and Mawlamyine(MLM)

For Rakhine coast(STW-MLM)

ΔP ≤ 1.5 hPa Feeble
1.5 < ΔP ≤ 3.0 hPa Weak
3.0 < ΔP ≤ 4.0 hPa Moderate
4.0 < ΔP ≤ 5.5 hPa Strong
ΔP > 5.5 hPa Vigorous

For Taninthayi coast (MLM-KTW)

ΔP ≤ 0.5 hPa Feeble
0.5 < ΔP ≤ 1.5 hPa Weak
1.5 < ΔP ≤ 2.0 hPa Moderate
2.0 < ΔP ≤ 2.5 hPa Strong
ΔP > 2.5 hPa Vigorous

For Whole coast (STW-KTW)

ΔP ≤ 2.0 hPa Feeble
2.0 < ΔP ≤ 4.0 hPa Weak
4.0 < ΔP ≤ 6.0 hPa Moderate
6.0 < ΔP ≤ 8.0 hPa Strong
ΔP > 8.0 hPa Vigorous

Key terms used in hydrological forecast

    • Danger level
      Danger level is that gauge level, which is selected and fixed in such away that if it is exceeded by the river level, the place will experience inundation with water spilling over the banks.
        • Minimum Alert level
          Minimum alert level is that gauge level, which is selected and fixed in such a way that, if the river level is fall below that level, it will cause difficulties in navigation and river pumping etc.
            • Significant water level bulletin
              This bulletin is issued with forecasting unexpected rise of water level for the coming 3 to 7 days along middle and downstream of the river, due to the abrupt rise in up- stream of Ayeyarwady and Chindwin by 200cm ( about 7 feet) and above, especially during early monsoon period. It is aimed to warn the people, who temporarily reside near the river banks.
                • Flood Warning
                  This is the warning, issue 1 to 3 days in advance, describing the possibility of the occurrence of flood (exceed of danger level) in a certain place.
                    • Flood Bulletin
                      When flood occur in a certain place, this bulletin is issued 1 to 3 days in advance, describing the condition of flood whether it will remain above danger level or fall below danger level.
                        • Flash flood
                          The flood, which occur by the result of heavy or excessive amounts of rainfall within one day or hours of time, causing water to rise and fall quite rapidly in small rivers and streams.
                            • Widespread flood
                              The flood, which occur by the result of three days and above consecutive heavy rain in the upstream catchments of the river and caused the movement of flood wave up to downstream of the river.
                                • Storm Surge
                                  Flooding that develops very quickly along the coasts or within the esfuaries of rivers as a result of the strong onshore winds during the land crossing a storm.
                                    • Trans-boundary flood
                                      Occurrence of floods in rivers , due to water flowing through trans-boundary rivers.

                                      Earthquake Glossary

                                      Earthquake

                                      An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves.

                                      Richter Magnitude Scale

                                      The Richter magnitude scale, also known as the local magnitude (ML) scale, assigns a single number to quantify the amount of seismic energy released by an earthquake.

                                      Moment Magnitude Scale

                                      The moment magnitude scale (Mw) is used by seismologists to measure the size of earthquakes in terms of the energy released.

                                      Mercalli Intensity Scale

                                      The Mercalli intensity scale is a scale used for measuring the intensity of an earthquake. The scale quantifies the effects of an earthquake on the Earth's surface, humans, objects of nature, and man-made structures on a scale of I through XII, with I denoting not felt, and XII total destruction.

                                      Primary Wave (P-wave)

                                      P-waves are type of elastic wave, also called seismic waves, that can travel through gases, solids and liquids, including the Earth. P-waves are produced by earthquakes and recorded by seismometers.

                                      Secondary Wave (S-wave)

                                      A type of seismic wave, the S-wave, secondary wave, or shear wave (sometimes called an elastic S-wave) is one of the two main types of elastic body waves, so named because they move through the body of an object, unlike surface waves.

                                      Tsunami

                                      A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, usually an ocean, though it can occur in large lakes.