Amir Mohsen
متخصص بخش هواشناسی
Synoptic Discussion - January 2014
Status: Ocean temperatures and atmospheric circulation anomalies indicated that the equatorial Pacific continued in an ENSO-neutral state during January.
Status:The MJO was incoherent for most of the month. During the last half of the month, it appeared to transition to phases 6 and 7, but this was essentially a manifestation of convective activity in the western Pacific, with Kelvin waves and low frequency variability appearing to influence the tropical precipitation pattern (as indicated by the MJO discussions for January 6, 13, 20, 27, and February 3).
Status: The daily PNA index was neutral (near zero) for the first half of the month and positive for the last half, averaging positive for the month as a whole.
Status: The daily AO index was oscillated between neutral to negative values throughout January, averaging negative for the month.
Status: The daily NAO index was near zero for most of the month, but positive at the end of January, and averaged positive for the month.
Status: The monthly WP index was positive for the month, while the three-month average WP index was negative (dominated by the strongly negative December value).
Status: The TNH index was positive during January.
Status: The SST pattern over the northeastern North Pacific during January 2014 saw a continued expansion and intensification of the large pool of warmer-than-normal SSTs in the northeastern North Pacific. The monthly EP-NP index has been positive since October, pulling the 3-month running mean well into positive territory. The positive phase of the EP-NP pattern is associated with above-average surface temperatures over the northeastern Pacific (thus, the negative phase is associated with below-normal SSTs).
Examination of these circulation indices and their teleconnection patterns, and comparison to observed January 2014 temperature, precipitation, and circulation patterns, suggest that the circulation patterns are most closely associated with the EP-NP index, but hints of other patterns were evident. ENSO was neutral, and thus not a player. The MJO was incoherent or weak for most of the month and exerted little influence on January's weather. The teleconnection patterns for the WP and NAO do not match January's weather patterns. The PNA and TNH teleconnections are reflected in parts of the country, but not others. The AO temperature teleconnections are a strong match to the observed January temperature pattern and there is some agreement with the circulation and precipitation patterns, but the best match with January 2014 circulation, temperature, and precipitation patterns occurs with the EP-NP. This suggests that the EP-NP and AO modes were in phase to reinforce cold weather east of the Rockies, but that the drivers behind the EP-NP were strongest. This month illustrates how the anomaly patterns can be strongly represented by one atmospheric driver (EP-NP in this case) but also have elements of several other drivers (or modes of atmospheric variability). [h=5]
Status: Ocean temperatures and atmospheric circulation anomalies indicated that the equatorial Pacific continued in an ENSO-neutral state during January.
Status:The MJO was incoherent for most of the month. During the last half of the month, it appeared to transition to phases 6 and 7, but this was essentially a manifestation of convective activity in the western Pacific, with Kelvin waves and low frequency variability appearing to influence the tropical precipitation pattern (as indicated by the MJO discussions for January 6, 13, 20, 27, and February 3).
Status: The daily PNA index was neutral (near zero) for the first half of the month and positive for the last half, averaging positive for the month as a whole.
Status: The daily AO index was oscillated between neutral to negative values throughout January, averaging negative for the month.
Status: The daily NAO index was near zero for most of the month, but positive at the end of January, and averaged positive for the month.
Status: The monthly WP index was positive for the month, while the three-month average WP index was negative (dominated by the strongly negative December value).
Status: The TNH index was positive during January.
Status: The SST pattern over the northeastern North Pacific during January 2014 saw a continued expansion and intensification of the large pool of warmer-than-normal SSTs in the northeastern North Pacific. The monthly EP-NP index has been positive since October, pulling the 3-month running mean well into positive territory. The positive phase of the EP-NP pattern is associated with above-average surface temperatures over the northeastern Pacific (thus, the negative phase is associated with below-normal SSTs).
Examination of these circulation indices and their teleconnection patterns, and comparison to observed January 2014 temperature, precipitation, and circulation patterns, suggest that the circulation patterns are most closely associated with the EP-NP index, but hints of other patterns were evident. ENSO was neutral, and thus not a player. The MJO was incoherent or weak for most of the month and exerted little influence on January's weather. The teleconnection patterns for the WP and NAO do not match January's weather patterns. The PNA and TNH teleconnections are reflected in parts of the country, but not others. The AO temperature teleconnections are a strong match to the observed January temperature pattern and there is some agreement with the circulation and precipitation patterns, but the best match with January 2014 circulation, temperature, and precipitation patterns occurs with the EP-NP. This suggests that the EP-NP and AO modes were in phase to reinforce cold weather east of the Rockies, but that the drivers behind the EP-NP were strongest. This month illustrates how the anomaly patterns can be strongly represented by one atmospheric driver (EP-NP in this case) but also have elements of several other drivers (or modes of atmospheric variability). [h=5]
