Pouch P04L

[colbroe]

SYNOPSIS 2012071400

* Still working on GFS computer issues.

P04L
14N, 15W
700 hPa

After two dry pouches that seem to have been the northern portions of a wave that had broken (P01L & P02L) and what may just be an artificial spin-up in the ITCZ by UKMET (P03L), P04L is the first classic AEW coming off of Africa since pouch-tracking started on 9 July 2012.

That being said, none of the models hang onto P04L much beyond 96 hours.

ECMWF: Except for a common westward jump off of the African coast, the track is relatively consistent, and lasts to 120 hours. The OW values peak at about 2x10-9 s-2 at 72 hours, but then decrease along with decreasing moisture values.

GFS:

UKMET: Takes more of a northwestward track. Notice at the end that the wave has excited another pouch on its southern end in the ITCZ. Soon thereafter, the more northern P04L and the ITCZ pouch dissipate. Moisture in P04L is decreasing at the time.

NOGAPS: Like ECMWF, has an erratic track with a stall just off the coast. Is a little slower than ECMWF. OW peaks at 60 hours, but below 2x10-9 s-2. Positions are uncertain after 96 hours.

HWRF-GEN:


ECMWF -6.4 v700/TPW 120h
GFS ---- ---- ---h
UKMET -7.3 v700/RH 96h
NOGAPS -5.8 v700/RH 120h
HWGEN ---- ---- ---h

[colbroe]

SYNOPSIS 2012071400

* Still working on GFS computer issues.

P04L
14N, 15W
700 hPa

After two dry pouches that seem to have been the northern portions of a wave that had broken (P01L & P02L) and what may just be an artificial spin-up in the ITCZ by UKMET (P03L), P04L is the first classic AEW coming off of Africa since pouch-tracking started on 9 July 2012.

That being said, none of the models hang onto P04L much beyond 96 hours.

ECMWF: Except for a common westward jump off of the African coast, the track is relatively consistent, and lasts to 120 hours. The OW values peak at about 2x10-9 s-2 at 72 hours, but then decrease along with decreasing moisture values.

GFS:

UKMET: Takes more of a northwestward track. Notice at the end that the wave has excited another pouch on its southern end in the ITCZ. Soon thereafter, the more northern P04L and the ITCZ pouch dissipate. Moisture in P04L is decreasing at the time.

NOGAPS: Like ECMWF, has an erratic track with a stall just off the coast. Is a little slower than ECMWF. OW peaks at 60 hours, but below 2x10-9 s-2. Positions are uncertain after 96 hours.

HWRF-GEN:


ECMWF -6.4 v700/TPW 120h
GFS ---- ---- ---h
UKMET -7.3 v700/RH 96h
NOGAPS -5.8 v700/RH 120h
HWGEN ---- ---- ---h

[cycloneye]

SYNOPSIS 2012071500

* Still working on GFS computer issues.

P04L
13N, 16W
700 hPa


ECMWF: Lasts for 108 hours, but is stretched zonally toward the end, while also weakening (decreasing OW and size).

GFS:

UKMET: Larger than in ECMWF and trackable to 120 hours. However, OW peaks near the beginning and then gradually decreases for the duration. OW max tends to be centered north of the cat's eye rather than on it. Zips past to the north of P03L, perhaps aided by a semi-direct-like interaction between P03L to the south and the subtropical ridge to the north.

NOGAPS: OUTLIER!! Similar OW time series to the other two models, but a very different track. Stationary just off the African coast for a couple days before creeping westward. Here's where you really have to hope that this incredibly slow NOGAPS provides "value to a consensus" because UKMET could be too fast, and NOGAPS would serve to slow down the consensus.

http://www.met.nps.edu/~mtmontgo/storms2012/P04L.html

[colbroe]

SYNOPSIS 2012071600

* Still working on GFS computer issues.

P04L
14N, 23W
700 hPa


ECMWF: Area of high OW is aligned meridionally just off the African coast in the analysis, so the initial position is uncertain; however, a distinct pouch is depicted during 12-36 hours. Shrinks and weakens after that.

GFS:

UKMET: Uncertain in analysis, but that's probably because the phase speed of -11.6 m/s is too fast for that time. However, a distinct pouch is depicted after that once the pouch accelerates westward. OW peaks at 36 hours, gradually weakening after that. Only an OW max at 108 hours. (It is possible that a position could have been determined at 120 hours, but this fast-moving system had moved off my working map. If so, it would most likely have been very weak.)

NOGAPS: Unlike the last run (2012071500), NOGAPS is not an outlier that remains stationary near the African coast. Like the other two models, NOGAPS moves P04L westward, with a peak (but not exceptional) OW value early on (at 24 hours), followed by gradual weakening as it moves across the Atlantic.

HWRF-GEN:


ECMWF -9.9 v700/RH 72h
GFS ---- ---- ---h
UKMET -11.6 v700/RH 108h
NOGAPS -9.3 v700 108h
HWGEN ---- ---- ---h

[colbroe]

Tropical wave is added off the coast of Africa along 19n20w to
13n17w moving W at 10-15 kt. The wave lies on the E side of a
surge of deep layer moisture present in total precipitable water
imagery. There is also a clearing in the Saharan dust layer with
an area of dense dust directly behind the wave. Due to this area
of dust...no deep convection is currently near the axis.