Invest 90L:East Atlantic,Discussions,Analysis and Sat Pics

[Hyperstorm]

Thread one:

viewtopic.php?f=31&t=96892&start=0

Thread two:

viewtopic.php?f=31&t=96916

It looks like the system is ready to be upgraded per latest satellite imagery.

[cycloneye]

Hyperstorm,how do you see the system in terms of the enviroment ahead as it nears the Caribbean?

[Matt-hurricanewatcher]

Lookings like a soild depression with the LLC under the eastern side of the convection. I think it should pick up to 20 knots once pass 20 west. Which could be some what unfavorable for huge development, but other wise shear and dry air appears not to be to bad for this system.

[WindRunner]

(I had this in the other thread, but thought I'd move it in here)

Ok, another night, another run through the models. This time I have pictures too . . .


First - GFS/HWRF

HWRF 00z run, 114 hours. 973mb/100kts

Probably one of the more consistent solutions so far, the GFS (and therefore the HWRF) has been pretty dead-set on taking a moderately strong system through the central Caribbean into the NW Carib and southern Gulf. Long-term landfall is still in Tampico, too. Problem is that the GFS is still out in la-la land . . . specifically with its forecast of the cyclone's upper air pattern. The initial longwave trough off the east coast somehow lifts out just as the cyclone would be getting close enough to feel it/be affected by it. As it lifts out, the cyclone slips past the trough axis and begins to strengthen . . . and the mid-latitude trough drops an upper low off to the NE of the cyclone. This upper low "chases" the cyclone all the way into the Caribbean, finally dying out ahead of the next trough to come through the east, when the storm is around Jamaica. The new trough, even though it creates a large weakness in the ridge and leaves another upper low in its wake, does nothing to significantly effect the track of the cyclone. The storm does, however, feel a little bit of a pull to the north as the trough departs, but that's only enough to make it go around the Yucatan . . . another awfully fortunate occurance in favor of strengthening the cyclone. Then, as the storm enters the Gulf, the ridge builds right back in over top of the upper low and steers it due west to Mexico . . . another unlikely story. Point here is that the GFS continues its dream about this system . . . and most all of its related guidance, especially in the long-term, should be avoided if possible.

On that note, the HWRF (GFS-based guidance) is trending weaker with this system. Maximum intensity through 126 hours is only 973mb/100kts, as shown above. However, that in itself is a problem. Since when does 973mb provide 100kts of wind? That alone is suspicous, especially since it holds that intensity for the twelve hours prior to and during its passage through the islands. On a good note, the model does weaken the system to 980mb by the end of the run. In the short term, it also takes its time developing the system (which is probably why the final result is weaker). 12z this morning was the first advent of TS-force winds in the circulation, with pressure falling to 1003mb later today . . . and holding there for at least another day after that. 50kt winds do not show themselves until late Wed/early Thurs time frame . . . which, for the short term, is probably a reasonable solution to go with.


ECMWF

00Z Euro at 168 hours.

00Z Euro at 240 hours.

Of note here would be the overall weakness of the system . . . possibly due to a weak initialization, but it's been a consistent solution for some time now. The Euro only has three or four hours at which it puts a 1012 isobar around our wave, one of which is shown above (168h) as it moves into the islands. This solution does not seem likely considering the current state of organization of the storm. For reference, though, the weak low/wave tracks into the southern Caribbean (further south than the GFS, as you would expect with a weaker system) and then it feels the weakness in the ridge. Although I did not look at the upper levels in the Euro, it is interesting that the Euro's weaker system can find the weakness easier than the stronger one the GFS portrays, making the GFS run all the more suspicious. Of course, in feeling the weakness, the low tracks NWrd over Haiti and into the SW Bahamas, where it begins to intensify and strikes Miami at 240 hours as a relatively weak TS. One other interesting thing that does happen, however, would be the development of the wave behind this one (apparent in both the 168h and 240h images) to a moderate level, much like early Euro runs did with our present system.


And just to cover them all, the CMC is below . . .

96 hours.

162 hours.

204 hours.

Nothing too surprising here . . . the CMC develops a good strength storm early on in the period, with the system slowing around 96 hours (first image). At this point, the CMC has this stronger cylone feel the weakness in the ridge left by the first trough . . . and begins to pull it northward over the next three days, to a positon illustrated in the second image above. At this point, the ridge builds back between the troughs, and the cyclone quickly resumes a nearly due west path . . . and (of course) intensifies, leaving a 982mb (grid-scale, mind you, so an actual MSLP would be somewhat lower if it verifies) storm heading WNW towards Florida.


Also of note, the NOGAPS still doesn't develop this system nor any others in the basin . . . which is still suspicous considering the state of the seas . . .



In the end, the GFS track is proven by both the Euro and CMC to be ill-fated in its tracking of the system at such low latitudes later in the period, leaving all GFS-related guidance beyond 120 hours in the garbage. For the short-term, however, the GFS does appear to handle the track well, although the strength may be somewhat on the high side. I think the HWRF presents a good overall solution through 72 hours . . . though beyond that, I see nothing that fits the job very well besides a weaker version of the GFS. It's definatley been an interesting system so far, and things should only get moreso from here on out.

[cycloneye]

FXCA62 TJSJ 130911
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
511 AM AST MON AUG 13 2007

.DISCUSSION...RELATIVELY DRY AND STABLE CONDITIONS WILL PERSIST
ACROSS PUERTO RICO AND THE SURROUNDING ISLANDS TODAY. EXPECT THE
DEVELOPMENT OF A FEW DIURNALLY INDUCED SHOWERS OVER THE INTERIOR
AND WESTERN SECTIONS OF PUERTO RICO DURING THE AFTERNOON
HOURS...BUT LIMITED SHOWER ACTIVITY AND HAZY SKIES CAN BE EXPECTED
ELSEWHERE.

THE TUTT CENTERED OVER THE VI THIS MORNING...WILL SLOWLY DRIFT WEST
OVER THE DOMINICAN REPUBLIC BY TOMORROW AFTERNOON...HELPING TO
DESTABILIZE THE LOCAL ATMOSPHERE...AND INDUCE MORE ACTIVE WEATHER
ACROSS THE LOCAL ISLANDS FOR TUESDAY. THIS TUTT WILL THEN CONTINUE
TO MOVE NORTH AND WEST AWAY FROM THE LOCAL AREA ON
WEDNESDAY...HAVING LESS OF AN EFFECT OF THE LOCAL WEATHER.

THE NEXT MAIN FEATURE WE ARE TRACKING CONTINUES TO BE THE STRONG
TROPICAL WAVE THAT CAME OFF AFRICA ON FRIDAY...AND IS NEAR 30 W
THIS MORNING. THE ASSOCIATED 1006 MB LOW WITH THIS
WAVE...CONTINUES TO SHOW GOOD CIRCULATION ON SATELLITE IMAGERY AND
HAS APPEARED TO BECOME BETTER ORGANIZED THE PAST 24 HOURS OR SO.
LATEST COMPUTER GUIDANCE FOR THIS SYSTEM HOWEVER INDICATES SOME
DISCREPANCY WITH THE TRACK AND SPEED OF THIS LOW AS IT MOVES
ACROSS THE ATLANTIC...WITH THE LATEST UKMET BEING SLOWER AND A BIT
FURTHER NORTH THAN THE LAST GFS RUN...AND THE LATEST ECMWF NOT
EVEN INDICATING A CLOSED LOW AS THIS WAVE APPROACHES THE LOCAL
ISLANDS. NO MATTER WHICH SCENARIO PANS OUT...WILL LIKELY SEE AN
INCREASE IN WINDS AND WEATHER WITH THIS WAVE AS IT CROSSES THE
LOCAL ISLANDS IN THE FRIDAY TO SATURDAY TIME PERIOD. PREVIOUS
FORECAST ALREADY INDICATED GUSTY WINDS FOR THIS TIME PERIOD...SO
ONLY CHANGE THIS MORNING WAS TO ALSO ADD THE POTENTIAL FOR SOME
HEAVY RAIN ON FRIDAY WITH THE APPROACH OF THIS SYSTEM. OTHERWISE MADE
SOME MINOR REFINEMENTS TO THE REMAINDER OF INHERITED FORECAST THIS
MORNING...BUT NO SIGNIFICANT CHANGES WERE DEEMED NECESSARY AT THIS
TIME.



San Juan NWS Area Forecast Discussion this morning.I am reposting this as some in the area of the Caribbeean may not haved seen it.

[Nimbus]

Still plenty of shear this morning the easterlies are doing their job limiting development. looks like the LLC has picked up speed since it is getting under the convection. Great wishcast for the islands would be to have Dean roll through early as just a fast moving TS.

The GFS tracks along the north shore of Jamaica. That gave me a flashback of Charley which was a late blooming storm. The eye of Charley became visible only after it moved west of Jamaica.

There is no gulf trough in the forecast yet so the Charley comparison ends with the late blooming.

[Chris_in_Tampa]

NOGAPS tries to take 90L back to Africa. 0Z late cycle run:



This, the GFDL blanking the storm, and the ATCF database replacing old data from previous months over new data has me wondering what can be trusted at this point.

[tgenius]

I just read off Jeff Master's blog (yeah not the most reliable place for info) that the Dvorak T# went up, its 1.5/1.5 now.

[Blown Away]

Where is the LLC, is it under the convection, if so it is better organized than yesterday.

[skysummit]

I believe it to be around here.

[punkyg]

Where is the LLC, is it under the convection, if so it is better organized than yesterday.

I
think they said it was on the eastern side and yes it does look better today.

[Dean4Storms]

Yes, it does appear the LLC is now getting up under the eastern side of convection. The whole system is beginning to take on a more organized appearance with more of a CDO trying to form instead of convection spread out unorganized.

I think we see a TD by days end.

Actually I think it is already a TD.

[Stormtrack03]

From 805 TWD:


1007 MB LOW...ASSOCIATED WITH A TROPICAL WAVE ALONG 28W/29W S
OF 18N...IS LOCATED SW OF THE CAPE VERDE ISLANDS NEAR 12N MOVING
W 15 KT. THE FIRST VISIBLE SATELLITE IMAGERY SHOWS A LOW LEVEL
CIRCULATION IS UNDER THE EASTERN EDGE OF THE CONVECTION. SCATTERED STRONG CONVECTION IS FROM 10N-14N BETWEEN 30W-34W.

[cycloneye]

Finally floater 1 is over it.

[Thunder44]

Floater 1 currently shows Mexico, but it is labeled "90L" on the NHC site. So I expect SSD to reposition it shortly.

[ciclonson]

already repositioned

[Chris_in_Tampa]

Talk about an extreme closeup. Put another floater on it or zoom out a bit, lol. Although at least we have a floater. NOAA has problems on their site this morning, so I guess it is good we have this.

[Aric Dunn]

some one needs to zoom that floater out.. no need to look down it throat

[MiamiensisWx]

Personally, I think 90L's organization has improved over the past several hours. I think the current data (for the first time) solidly supports a TD. The relocated LLC (near 11.9N and 30.7W) is clearly becoming better defined - look at the latest GOES visible loop. Additionally, it looks like the strong mid-level easterly flow has been subsiding - this trend could allow further organization. The NHC should call a TD very soon - I would bet on (latest estimate) 5 p.m. EDT (more likely time is 11 a.m. EDT).

[cycloneye]

Floater 1 currently shows Mexico, but it is labeled "90L" on the NHC site. So I expect SSD to reposition it shortly.

You need to refresh the image and you will see 90L.