Professional Forecaster experience since 1977, concentrating in Aviation, Tropical and Long Range forecasting.
By: Steve Gregory , 4:45 PM GMT on September 02, 2014
MINIMAL TROPICAL STORM DOLLY 180 MILES FROM MEXICAN COAST
INVEST 99L spun up to Depression #5 yesterday afternoon (based on RECON reports and as I reported at 1:20PM CDT) but not made officially by NHC until 3 hrs. later). Then, by the 5AM Update this AM, NHC upgraded TD#5 to Tropical Storm DOLLY with MAX sustained surface winds near 40Kts. DOLLY, now located 175NM ENE of Tampico, MX, near 23.2°N/93.2°W is moving NW at 11Kt, and the last RECON reported a central pressure of 1005mb. Another RECON is now enroute to DOLLY.
Wind shear fell-off a bit as expected, but is still a moderate 14-18Kts out of the NW, causing the bulk of the deep convection to be shifted to the SE of the storm center as clearly seen on the below VIS image (Fig 1).
In addition, satellite derived high level wind flow only shows fair to good outflow in the NE-SE-SW quadrant, with virtually none to in the opposing NW sector. With no significant change to the shear or high level wind configuration anticipated during the next 18-24 hours means there should be little further intensification of the storm prior to it going inland about 150NM north of Tampico early WED. The storm will then weaken rapidly, though it MIGHT be worth watching how the moisture flow towards the NW progresses, as it might bring some enhanced potential for shower activity (or dangerous lightning) to portions of West Texas into the SW Deserts as the summer Monsoon continues in the SW U.S. I’m NOT forecasting some type of major event – but simply advising on the potential addition of some moisture to the drought stricken region.
TROPICAL WAVES OVER THE ATLANTIC BASIN INCLUDING THE LARGE WAVE SOUTHWEST OF THE CAPE VERDES
There are a couple other low latitude and likely inconsequential waves traveling across the Atlantic, and which continue to show absolutely no signs of development. They are worth monitoring as to their potential for their re-moistening potential in the CARIB during the next 5-8 days.
The large tropical wave now southwest of the Cape Verdes still has some isolated deep convection, but no longer has ANY of the high level anti-cyclonic flow that it had, especially 2 days ago as it coming off the African coast. This pretty much confirms that the upper level Anti-clone that existed there 2 says ago, was simply a high level, ‘localized’ wind feature that was not part of the wave structure itself, as the wave appears to have simply ‘outrun’ the upper level High. OTH – low level satellite wind analysis does show some rotation around the wave axis.
Wind shear is not all that bad right now – averaging around 15Kts across the entire wave – but below 10Kts near the primary area of deep convection. This system is westbound at 20Kts – and will reach the CARIB sometime late next week. The GFS has begun to show signs of developing another cyclone in the western CARIB in 10-14 days – about the same time period that the large wave will have reached that area.
There are two(2) more fairly large, and strong looking Tropical Waves over Africa that are westbound, and the GFS appears to be developing these systems into cyclones during the next 10 days, though they are ultimately shown going out to sea. None of the other global models show any kind of significant development of either of these systems at this time.
Fig 1: Morning VIS image of Tropical Storm Dolly is on the NW side of the deep convection, with RECON reports supporting sustained surface winds around 40Kts, Storm movement continues basically towards the NW (320°) at 11Kts.
Fig 2: Radar imagery loops out of Tampico, MX seem to depict a very poorly organized looking ‘eye’ type formation, with little significant rotation detected. Echoes generally show a west/northwest movement of radar echoes. (NOTE: Confidence in the radar image quality, IMHO, is fairly low – either related to the old style unit in use there – or the method used in capturing images.)
Fig 3: The morning Shear analysis depicts modest North/Northwesterly shear of around 15Kts across the storm, causing most convection to be southeast of the central of the storm. The low level cloud circulation occasionally becomes visible just before new convection forms along the SE side of the storm. No change in shear conditions is expected before the storm makes landfall early tomorrow.
Fig 4: High level (above 28,000Ft) winds depict fair-good outflow in the ‘SE semi-circle’, with little significant outflow detected in the ‘NW Semi-circle’. A ‘nice’ 200mb (40,000ft) High pressure system is located in the Northern GOM, - but is simply way too far away to be of any consequence to DOLLY. But long range forecasts tend to show this high level anti-cyclone remaining in vicinity of the Gulf for the next 2 weeks – which may prove meaningful if another disturbance should happen to make it into the GOM.
Fig 5: The above specialized hurricane model tracks are in reasonably good agreement on a track to the NW, taking DOLLY inland early tomorrow before it dissipates. HOWEVER – I’ve drawn a POTENTIAL DASHED LINE to outline where some of the higher level moisture from Dolly could eventually move during the next 7 days; enhancing the overall risk for showers in within the outlined regions (or simply Dangerous, ‘fire setting’ lightning).
Fig 6: The ‘Overview’ of the Tropical ATL Basin shows a series of Tropical Waves from the CARIB eastward to the far eastern Atlantic. The leading waves near the CARIB and central Atlantic may help ‘moisten up’ the CARIB later this week, with the much larger wave now SW of the Cape Verdes expected to reach the CARIB next week. This system MAY find more conducive conditions for development in the western CARIB in 10-14 days.
Fig 7: Wind conditions in the upper atmosphere show a large upper air LOW pressure center near the central Bahamas, with a TROF southwestward into the SW CARIB. This type of pattern is almost always a ‘cyclone killer’ – but note how it also tends to create a large scale anti-cyclonic flow well to the east of the TROF. There’s even a small, closed off upper level HIGH in the southeast CARIB – directly over a passing Tropical Wave. (However, the lack of moisture and 20Kt shears are preventing any enhancement of this particular wave.) But the point of bringing this up is that if we had a well developed cyclone approaching the eastern CARIB – the large scale anti-cyclonic flow over the eastern half of the CARIB would be an IDEAL setup for rapid intensification of the storm. This [articular ‘couplet (Low and High) is moving westward, and will likely weaken over the coming week…
Fig 8: This morning’s African Overview shows the large Tropical wave SW of the Cape Verdes – along with two(2) fairly strong ‘waves with deep convection over Africa – both westbound at 20Kts. ‘Tis the Season’ of course … though these systems have yet to find very favorable conditions for development once they move over the Atlantic. over Africa this year.
The next FULL Tropical Update will be on Thursday, SEP 4. HOWEVER – if conditions warrant, I’ll have another brief update tomorrow.
NOTE: I'll be issuing Weather Updates 3-Days per week (Sundays, Tuesdays and Thursdays) – EXCEPT when we have or expect active Tropical Cyclones in the Atlantic Basin or major winter events during the cool season – in which case Updates will be issued as needed. In addition, if a strong cyclone is expected to impact the US mainland – I will be posting my own detailed forecast charts.
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
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