TS Emily: 215 Miles SSE Of San Juan, PR

[Srain]

It seems like a sharp recurve is a constant in many of the medium/long range forecasts...uncomfortably close to Florida in some of the more recent modeling, but seems like the rest of the east coast is not "on the hook" unless the trough evolution changes significantly

Yep. The slower development, which has been CW by the way, does 'open a door' for a SE tease. That said, the more likely solution is a PR/Hispaniola threat. Beyond that, the trough will likely sweep the 'remains' out of the Bahamas to the NE and OTS.

[phil882]

1. AN ELONGATED AREA OF LOW PRESSURE EXTENDING FROM THE LESSER ANTILLESEASTWARD SEVERAL HUNDRED MILES INTO THE TROPICAL ATLANTIC OCEAN ISPRODUCING A LARGE AREA OF CLOUDINESS...SHOWERS...AND THUNDERSTORMS. THE THUNDERSTORM ACTIVITY HAS BECOME MORE CONCENTRATED ABOUT 350MILES EAST OF MARTINIQUE...AND A TROPICAL DEPRESSION OR A TROPICALSTORM COULD FORM IN THIS AREA LATER TODAY. THIS SYSTEM HAS A HIGHCHANCE...90 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THENEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH. IFTHE SYSTEM BECOMES A TROPICAL CYCLONE TODAY...TROPICAL STORMWARNINGS WOULD BE ISSUED FOR PORTIONS OF THE NORTHERN WINDWARDISLANDS AND THE LEEWARD ISLANDS ON VERY SHORT NOTICE...ANDINTERESTS IN THESE AREAS SHOULD CLOSELY MONITOR THE PROGRESS OFTHIS SYSTEM. A HURRICANE HUNTER AIRCRAFT IS SCHEDULED TOINVESTIGATE THE AREA THIS MORNING. REGARDLESS OF TROPICAL CYCLONEFORMATION...THIS SYSTEM WILL BRING LOCALLY HEAVY RAINFALL AND GUSTYWINDS TO PORTIONS OF THE LESSER ANTILLES TODAY AND TONIGHT.

[CooL]

Looking healthy again tonight. That leadoff wave that blew up today is filtering out the dry air in front of future Emily.

in regards to the latest model runs and a potential impact on the u.s, looks like its all gonna depend on how amplified the trough is once it gets near the islands/bahamas.. as well as a couple other factors as Phil has already dicussed

[dan88]

00z hurricane models

HWRF, moving WNW for proceeding 12 hours.

GFDL, moving NE, has recurved

[dan88]

Likely to have some dry air problems again, with dry air still sneaking in from the South West in front of the wave.

[OHweather]

91L forecast/discussion:

91L appears to be firing off a more consolidated area of convection near the mid level circulation that has been associated with the wave the past few days. The NHC has indicated that any surface circulation is elongated; however low level vorticity is clearly pooling near the low level circulation, so consistent convection should result in a tropical cyclone being declared.

Upper level winds show a divergent pattern over 91L, with outflow evident, especially to the north of the system. The system is near an upper level anti-cyclone that is sliding west, which is resulting in fairly low shear over the invest itself, which should allow for continued gradual organization.

One possible fly in the ointment is a belt of westerlies lying only a few degrees north of the invest. While wind shear is gradually decreasing immediately ahead of 91L, some gain in latitude will likely result in some moderate wind shear impacting the system:

The 0z GFS shows why how much latitude the system will gain over the next few days is important (other than land interaction), with a small upper level anti-cyclone still over the system at hour 72, but with a belt of westerlies only a couple of degrees north of the system:

This belt of stronger upper level winds could very well serve as an efficient outflow channel for the system in the coming days however, assuming the system stays just south of them.

By days 4-5, the upper level pattern becomes slightly more uncertain. As can be seen above, the 0z GFS depicts a TUTT to the northwest of the system at 72 hours. The 0z GFS/12z ECM both slowly show the TUTT weakening and moving to the west-northwest, staying out of the way of 91L. Both models also appear to show a large upper level anti-cyclone building off the southeast coast by days 4-5, producing a large area of rather favorable weak upper level winds off the southeast coast and over the Bahamas:

0z GFS:

Vs. The 12z Euro:

For now will forecast genesis within the next 18 hours, as consolidated convection appears to be firing over the broad low level circulation. Vorticity is pooling near this convection which should enhance the consolidating/further development of a surface circulation as convection continues to fire.

Saharan Air Layer analysis reveals that there is still a moderate amount of mid level dry air to the north of the invest. While this may continue to cause some trouble for the invest with respect to firing consistent strong convection, the dry air is slowly mixing out as evidenced by fewer strato-cumulus clouds to the north of the system. In addition, the invest appears to have a fairly large and expanding moisture field associated with it. Assuming shear remains fairly low over the coming days, the combination of a slow mixing out of the dry air and the large size of the system and its moisture field should result in the dry air only having minor impacts on the over strengthening of this system.

Given favorable conditions (save some dry air) over the next 2-3 days, will forecast a steady ramp-up. Given low shear, warming sea surface temperatures and good outflow, especially in the northern quadrants, a fairly fast ramp up is possible before nearly inevitable interaction with some large islands in about 3 days. Will forecast a fairly steady 20kt per day increase in winds (only 5-10 knots day 1, due to the system still trying to develop a well defined surface circulation) per day for days 1-3. Given the prospects for some dry air intrusions and on the other hand, rapid intensification given the upper level environment, these increases in strength may come in bursts. This brings 91L up to hurricane status before running into land in 3 days. Will cut intensity down into the tropical storm range day 4 due to possibly significant interruption due to land. Will bring the system back up to a minimal Cat 1 by day 5 and nearing a Cat 2 by the end of the 5 day intensity forecast, as a faster ramp up may be possible if the middle of Hispaniola is missed given the upper level environment in place north of the island, and as a slower re-intensification is possible if the system is gutted by the island/takes a trip to Cuba on its way out.

91L is being steering briskly to the WNW on the southwesterly side of a large area of high pressure near the Azores. This general motion should continue in the near term. However, a large weakness in ridging is in place over the western Atlantic between a large ridge over the central US and the ridge near the Azores, meaning the invest will likely begin to gain more latitude as it moves farther west and gains strength.

Currently, the most recent runs of the ATCF and global models are in fairly good agreement in bringing 91L through the central Lesser Antilles Monday evening and likely south of Puerto Rico, although the 12z Euro was a northeasterly outlier, grazing western Puerto Rico and extreme northeastern Hispaniola. Given the system will likely become fairly deep by 48-72 hours out and will be rounding the base of an upper level trough towards a rather large and well agreed upon weakness in ridging off the US east coast, this turn right seems reasonable. My forecast will follow the model consensus through day 3, taking 91L WNW through the north-central Lesser Antilles with a gradual right turn towards Hispaniola. Will be slightly north of track guidance average due to differences in center initiation, but will follow the track guidance in principle.

By days 4-5, the track forecast becomes slightly less certain. Both the 12z ECM Ensembles and 0z GFS agree on a brief rising of heights along the east coast between shortwaves. Note how by 12z Friday, both models agree in no significant weakness in ridging north of the cyclone as one trough has moved off the east coast, and the next shortwave is back over the upper Midwest:

Vs.

Both models further raise heights off the southeast coast by 12z Saturday, indicating that the system may bend back to the left days 5-6 as well as slow down a good amount:

Vs.

Both models do re-amplify the trough along the east coast by day 7 as the shortwave has completed rounding the central US ridge and is forced back south by the higher heights over Greenland/Davis Strait AKA a negative NAO:<br style="mso-special-character:line-break">

Vs.

This should result in the system to finally begin to turn significantly right and accelerate as it gets caught up in the westerlies, however this well timed break between shortwaves along the east coast may force 91L much farther west than a normal summertime –NAO/-PNA pattern normally would.

This forecast track indicates that Florida and the eastern Carolinas are not completely out of the woods yet, but that the Mid Atlantic and New England are, as they will be protected by the westerlies.

The initial position of 14N, 55W is based on low level cloud motions that were briefly evident before convection re-fired with 91L:

Intensity forecast:

0z Tuesday: 30 knots

0z Wednesday: 50 knots

0z Thursday: 55 knots

0z Friday: 60 knots

0z Saturday: 80 knots

[28storms]

This is the tropics we're talking about. I've learned to not write anything off beyond Day 5. The ridging along the eastern seaboard is definitely stronger across the model spectrum. ECMWF just barely recurves a weak low just off the east coast. If it were stronger in the model, the 594DM ridge over the Carolinas by Day 5 could have quite possibly steered it more west.

[Floydbuster]

This is the tropics we're talking about. I've learned to not write anything off beyond Day 5. The ridging along the eastern seaboard is definitely stronger across the model spectrum. ECMWF just barely recurves a weak low just off the east coast. If it were stronger in the model, the 594DM ridge over the Carolinas by Day 5 could have quite possibly steered it more west.

It's amazing what just a couple of hours does, no doubt. I still think like I said two days ago it moves into the northern islands, perhaps Puerto Rico and/or Hispaniola...then into the Bahamas with a slight westward bend with the strengthening heights above it. Whether or not that translates into a landfall in South Florida or Central Florida or not, it will pose a threat in that scenario.

As far as intensity, if it avoids land (skirts Puerto Rico, Hispaniola rather than crossing the islands) then we're potentially talking about a very powerful hurricane. If it crosses the Greater Antilles, then a re-organizing minimal hurricane at best.

Again, this all just speculation.

[phil882]

nice microwave pass... center certainly appears to be tightening up and convection has recently fired in the general vicinity as well. I'll be stunned if this is not a TD or greater by the end of the day.

[phil882]

http://philstropical...opical-cyclone/

Here are my morning thoughts on Invest 91L... I'm pretty confident today will be the day we see it develop into a tropical cyclone given recent trends. The track beyond 72 hours looks very uncertain, and a lot will weigh on how strongly the subtropical ridge builds back in as the upper level trough lifts out. Intensity wise is a crap shoot beyond 48 hours, pending on the potential impact of Hispaniola among other factors. Its not even really worth guessing at this point, because we could be dealing anywhere from a weak tropical storm to a formidable hurricane.

[David Reimer]

[free_man]

http://philstropical...opical-cyclone/

Here are my morning thoughts on Invest 91L... I'm pretty confident today will be the day we see it develop into a tropical cyclone given recent trends. The track beyond 72 hours looks very uncertain, and a lot will weigh on how strongly the subtropical ridge builds back in as the upper level trough lifts out. Intensity wise is a crap shoot beyond 48 hours, pending on the potential impact of Hispaniola among other factors. Its not even really worth guessing at this point, because we could be dealing anywhere from a weak tropical storm to a formidable hurricane.

I would say much less chance of the latter, very good chance of former.

[phil882]

I would say much less chance of the latter, very good chance of former.

If Hispaniola gets in the way, I'd totally agree with you. However it seems that the storm is consolidating further north than most of the models initial positions for the 06z cycle. Thus, if 91L can miss Hispaniola to the north, then we might have a different story.

[CandymanColumbusGA]

If Hispaniola gets in the way, I'd totally agree with you. However it seems that the storm is consolidating further north than most of the models initial positions for the 06z. Thus, if 91L can miss Hispaniola to the north, then we might have a different story.

That's going to be the million dollar question the next couple of days. If it slams into Hispaniola and is shredded to pieces, then it doesn't have much of an impact on the US. HOWEVER, if it skirts Hispaniola and keeps most of its characteristics, it could become a formidable hurricane over the Bahamas... This is all going to come down to the exact path 91L (eventually Emily). The weaker the storm, the more west it will track. Though, with the blow up of convection overnight, it appears we'll see it track more towards Puerto Rico and into the Atlantic Basin it goes... It's going to be a fun system to watch!

I know one thing though, I'm glad the western shower activity helped moisten the atmosphere ahead of the main llc, otherwise this thing could have poofed into thin air...

[kwt]

Not so sure hispaniola will be the death of any system, it will cause strong weakening for sure and will disrupt the inner core, but its going to have a fair while over the waters off the SE coast of America in what appears to be very good atmospheric conditions...

Jeanne eventually pulled it back together, expect any system that goes over Hispaniola will eventually pull it back together to some extent, may struggle though to get beyond a 1/2 though.

[Floydbuster]

Not so sure hispaniola will be the death of any system, it will cause strong weakening for sure and will disrupt the inner core, but its going to have a fair while over the waters off the SE coast of America in what appears to be very good atmospheric conditions...

Jeanne eventually pulled it back together, expect any system that goes over Hispaniola will eventually pull it back together to some extent, may struggle though to get beyond a 1/2 though.

David went from a Category 4/5 to a Tropical Storm, but slowly moved over the entire length of Hispaniola.

If this system skirts Hispaniola as a strengthening hurricane, then we would have significant problems for the Bahamas.

[tmagan]

David went from a Category 4/5 to a Tropical Storm, but slowly moved over the entire length of Hispaniola.

If this system skirts Hispaniola as a strengthening hurricane, then we would have significant problems for the Bahamas.

Hard to go around Hispaniola as a strengthening hurricane, especially since it will be entraining dry air from the Massif du Nord.

[Floydbuster]

BTW the newest GFS run now shows it skirting Hispaniola, and landfalling in Southeast Florida.

[David Reimer]

For sh*ts and giggles.

[LakeEffectKing]

Experimental HWRF certainly is in the GGEM and 06z GFS camp of a more westward (and stronger) TC:

The evolution of the synoptic pattern is not set in stone yet....we've been burned before of course....a modest rebuilding of a ridge at the right time, or a slightly weaker (than model prog consensus) trough (or quicker) is all that it would take for a more westward solution....

[David Reimer]

Experimental HWRF certainly is in the GGEM and 06z GFS camp of a more westward (and stronger) TC:

The evolution of the synoptic pattern is not set in stone yet....we've been burned before of course....a modest rebuilding of a ridge at the right time, or a slightly weaker (than model prog consensus) trough (or quicker) is all that it would take for a more westward solution....

Obviously it's model porn at this point, but its still amusing. Recon is about 150 miles out from the estimated center of Invest 91L and closing in as of 11Z.

[kwt]

Recon looks like its saying NO defined circulation...so still jsut an invest it seems.

Close but just can't quite close that circulation.

[GCANE]

Chances are looking better that we will have a GOM TC.

[Srain]

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

800 AM EDT MON AUG 1 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE VIGOROUS LOW PRESSURE SYSTEM LOCATED ABOUT 300 MILES EAST

OF MARTINIQUE IS SHOWING SOME SIGNS OF IMPROVED ORGANIZATION...AND

A TROPICAL DEPRESSION COULD FORM LATER TODAY. THIS SYSTEM HAS A

HIGH CHANCE...90 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING

THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH.

A HURRICANE HUNTER AIRCRAFT IS CURRENTLY INVESTIGATING THE

DISTURBANCE TO DETERMINE IF IT HAS A WELL-DEFINED SURFACE

CIRCULATION CENTER. IF THE SYSTEM BECOMES A TROPICAL CYCLONE

TODAY...TROPICAL STORM WARNINGS WOULD BE ISSUED FOR PORTIONS OF

THE NORTHERN WINDWARD ISLANDS AND THE LEEWARD ISLANDS ON VERY

SHORT NOTICE. INTERESTS IN THESE AREAS SHOULD CLOSELY MONITOR

THE PROGRESS OF THIS SYSTEM. REGARDLESS OF TROPICAL CYCLONE

DEVELOPMENT OF THIS SYSTEM WILL BRING LOCALLY HEAVY RAINFALL AND

GUSTY WINDS TO PORTIONS OF THE LESSER ANTILLES TODAY AND TONIGHT.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$$

FORECASTER STEWART

[Buckethead]

Recon looks like its saying NO defined circulation...so still jsut an invest it seems.

Close but just can't quite close that circulation.

It doesn't appear that they've made a pass through yet. Google earth isn't showing it and the area of interest appear to be near 14N 56.5W, and the coordinates on the obs I'm seeing show they haven't either. Could just be a communication issue on my end though.

[David Reimer]

TROPICAL WEATHER OUTLOOK

NWS NATIONAL HURRICANE CENTER MIAMI FL

800 AM EDT MON AUG 1 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE VIGOROUS LOW PRESSURE SYSTEM LOCATED ABOUT 300 MILES EAST

OF MARTINIQUE IS SHOWING SOME SIGNS OF IMPROVED ORGANIZATION...AND

A TROPICAL DEPRESSION COULD FORM LATER TODAY. THIS SYSTEM HAS A

HIGH CHANCE...90 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING

THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH.

A HURRICANE HUNTER AIRCRAFT IS CURRENTLY INVESTIGATING THE

DISTURBANCE TO DETERMINE IF IT HAS A WELL-DEFINED SURFACE

CIRCULATION CENTER. IF THE SYSTEM BECOMES A TROPICAL CYCLONE

TODAY...TROPICAL STORM WARNINGS WOULD BE ISSUED FOR PORTIONS OF

THE NORTHERN WINDWARD ISLANDS AND THE LEEWARD ISLANDS ON VERY

SHORT NOTICE. INTERESTS IN THESE AREAS SHOULD CLOSELY MONITOR

THE PROGRESS OF THIS SYSTEM. REGARDLESS OF TROPICAL CYCLONE

DEVELOPMENT OF THIS SYSTEM WILL BRING LOCALLY HEAVY RAINFALL AND

GUSTY WINDS TO PORTIONS OF THE LESSER ANTILLES TODAY AND TONIGHT.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$

FORECASTER STEWART

I notice a bit of elevated wording from Stewart regarding the possibility of short-term lead times on this event.

[dan11295]

Are my eyes are deceiving me or is there rotation in the vicinity of 14.5N 56.8W?

As far as future intensity, until the storm actually forms the models initalize w/a real circulation and possible impacts with Hispanola are examined, intensity is a pure crap shoot.

[benfica356]

[benfica356]

[am19psu]

Are my eyes are deceiving me or is there rotation in the vicinity of 14.5N 56.8W?

As far as future intensity, until the storm actually forms the models initalize w/a real circulation and possible impacts with Hispanola are examined, intensity is a pure crap shoot.

I disagree with this. Improvements in data assimilation techniques and convective/radiation parameterizations over the past few years have greatly increased the global models' ability to develop realistic tropical cyclones with skill. I still wouldn't trust GFDL/HWRF output (not that I do when there is actually a storm, either), but the Euro/GFS/UKMet are all useful for prediction prior to actual TC genesis.