| typhoon_tip |
| (Meteorologist) |
| Fri Sep 30 2005 03:45 PM |
Re: 90/99
|
Quote:
i didn't think anything was going to form that far out this year. it waited until the last day of september, but that looks legit. it has a 1.5 on it, but all the forecast models take it more north than anything else.
99L has a 1.5 on it also... TWO says pressures are falling and you can see the turning in the low-level wind field (because there isn't much convection/dry air intrustion on the west side). when they recon it later it's just as likely to be 'too broad' like it was earlier, but slowly and inevitably this thing is developing.
HF 1433z30september
Ahhhh... Anytime a forecast is blown, or something surprises everyone and I hear that dreaded "...Climatology" word I always grin. Climatology can be beguiling often misleading tool there is available.
The following image illustrates a pervasive SST warm anomaly that encompasses virtually the entire Atlantic Basin S of (appr) 35N latitude, from the Bahamas to the Cape Verde Islands:
http://www.osdpd.noaa.gov/PSB/EPS/SST/data/anomnight.9.27.2005.gif
When knowing and understanding such that we do, that climatology is a time dependent long term statistical mean, it seems entirely reasonable to assume climate will not account for extremes that take place outside the mode on our graphs. Especially when considering that the Cape Verde season was not very prodigious during 2004 and particularly this year to date, therefore, cross-seasonal less than normal SST processing in those districts of the Atlantic Basin in question. I cannot atest for the actual depth of the thermocline...subsequently the actual upper oceanic heat content as an integrated value...but sufficed to say at least on the surface there appears to be higher SST than climatology.
In terms of pure observation I have noticed that last year and this year both have had a very peculiar middle and upper level tropospheric behavior from the Puerto Rico Archipelago east to the WNW of the Cape Verde Islands. In this region, despite having near neutral ENSO signals and/or slightly LaNina like conditions in the east Pacific there has still been heightened occurrences of unfavorable westerlies dipping fairly deeply into the tropical Atlantic. (For those of us who are unfamiliar with this, La"Nino" tends to excite stronger U/A west components in the means, effectively shearing the tops off any would be developments downwind in the Atlantic Basin...)
Much of the reason what the Cape Verde season tends to shut down in latter September so earnestly isn't just for SST, either. The activation of the westerlies in concert with season change definitely plays a pivotal role, because La Nino or not, you invariably will end up with trough incursions out there by the middle of October. This is just to point out that so long as we are running some pretty impressive cross-seasonal SST warm anomalies in the Atlantic Basin, approximately half of the "normal" reason why Cape Verde systems tend not to develop at this time of year is being compensated for by this unusual SST scenario.