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WxWatcher007

Major Hurricane Laura

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The clouds around Laura seem to be implying a motion more west-northwesterly today. Maybe more towards a Northern Dominican track like Isaias. 

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Post analysis will be interesting. I'm having a hard time accepting that vortex maximum was merely a mesoscale mid-level transient feature and not the dominate vertically stacked vortex based on wind reports.

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6 minutes ago, Windspeed said:

Post analysis will be interesting. I'm having a hard time accepting that vortex maximum was merely a mesoscale mid-level transient feature and not the dominate vertically stacked vortex based on wind reports.

I agree. It really tightened nicely during the day. That area has weakened but the rotation is still there. It’ll be interesting to watch how it responds to being back over water soon.

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30 minutes ago, Windspeed said:

Post analysis will be interesting. I'm having a hard time accepting that vortex maximum was merely a mesoscale mid-level transient feature and not the dominate vertically stacked vortex based on wind reports.

Looks like the LLC pretty close to coming off shore near Arecibo PR-- NW PR.

https://www.accuweather.com/en/pr/san-juan/00901/weather-radar/275478

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The low level jet and faster windspeeds are north of hs and cu but most of the moisture and the 500mb low is south of hs/Cu and the mountains do a good job blocking moisture from coming north in large quantities.  So the storm is kind of a dilema. The new vortex won't change things much unless it tracks way north.

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Laura’s propagation westward seems more driven by downstream convective cell
development from outflow rather than a coherent circulation moving along in
the mean flow!  This is all too familiar with systems this season.  Saw it
with Gonzalo and Josephine.  Dry air is probably the main culprit here.  It's
why you get such intense convective bursts.  You are introducing dry air at
mid-levels which changes the sounding profile from moist adiabatic through the
depth of the column (typical for most organized TCs), to one that is drier at
mid-levels.  This increases CAPE and mid-level lapse rates, and with the
intense low-level convergence and very moist air at low-levels, the explosive
convection is the result, but as impressive as it looks, it is transient and
not conducive for significant strengthening.  It may even weaken it if the
outflow boundaries from the collapsing convection get too strong and numerous,
disrupting the LLCC.

No real spiral banding still on Laura.  As long as that persists, you are
not going to see too much change.

 

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I’m not quite understanding how this thing maintains TS strength if it’s going to be going over both Hispaniola and Cuba. Doesn’t that typically tear apart tropical systems? I mean if the NHC track is correct it’ll literally be over land for most of the next 2 days 

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13 minutes ago, Baltimorewx said:

I’m not quite understanding how this thing maintains TS strength if it’s going to be going over both Hispaniola and Cuba. Doesn’t that typically tear apart tropical systems? I mean if the NHC track is correct it’ll literally be over land for most of the next 2 days 

That's what I've been thinking.  10,000 ft mountains are non-trivial barrier in the way, and Laura is going to cut right down the length of the island, then Cuba as well.  OTOH, the ante would be higher if Laura was an intense hurricane with a tight inner core, but its disorganized state may not lead too much weakening in the wind field, but can a coherent center survive?  I've seen min hurricanes on the N coast of Hispaniola and their LLCC end up racing out from under the deep convection, leaving the mid-level center behind, and sometimes the TC never recovers.

Another factor to consider, if Laura ends up going to where Macro was only 2 days earlier, there is going to be a cool SST wake left behind esp. near the coast.

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1 minute ago, vortex95 said:

That's what I've been thinking.  10,000 ft mountains are non-trivial barrier in the way, and Laura is going to cut right down the length of the island, then Cuba as well.  OTOH, the ante would be higher if Laura was intense hurricane with a tight inner core, but its disorganized state may not lead too much weakening in the wind field, but can a coherent center survive?  I've seen min hurricanes on the N coast of Hispaniola and their LLCC end up racing out from under the deep convection, leaving the mid-level center behind, and sometimes the TC never recovers.

Another factor to consider, if Laura ends up going to where Macro was only 2 days earlier, there is going to be a cool SSTs wake left behind esp. near the coast.

Yeah good point with the cold water upwelling too. I think the NHC is being a bit aggressive in their forecasting but we’ll see. 

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29 minutes ago, Modfan2 said:

These northern jogs a little concerning as most of FL has written this off; Ft Lauderdale south still has to to keep their guard up

That is extremely unlikely. Not even one ensemble member has it anywhere near SE Florida.

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2 hours ago, buckeyefan1 said:

I didn’t ask you. When stating a model is wrong, there needs to be an explanation why. As for you and your hype of every single system, please read more and post less 

Anticyclonic flow . How does euro weaken it?

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3 minutes ago, wizard021 said:

Anticyclonic flow . How does euro weaken it?

Sigh....if you don’t know and have no clue how to read a model well enough to see how the euro keeps it weak, read more, post less and keep your unfounded opinions in banter. 

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18z GFS with an pristine environment that would 100% favor a major hurricane if anything resembling an organized storm emerges later tomorrow. As mentioned earlier, it appears as if the Euro has 10-15kts of mid level shear, but the GFS doesn't seem to have that and the moisture profile overall is far more moist. Interesting. I'd lean towards the GFS being closer to correct at this juncture.

 

I'd worry about dry air in the wake of the eroding/departing upper low, which is something I do think the Euro is capturing better right now, however.

 

image.thumb.png.bb359b217a1c02dd38a43c12548be228.png

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The most important, the most critical, to what this storm does over the next 2-3 days is whether the low level COC passes over Hispanola and the mountains there, or if the COC stays off shore. PR radar definitely looks like the radar identified COC is going to skim the northern edge of Hispanola. The disruption from passing over PR's mountains are minor compared to what Hispanola's mountains can do to a tropical system. I've seen well intact hurricanes completely ripped apart, never recovering, from Hispanola.

Watching both radar and IR the system looks to have convection displaced mainly south of the COC. Radar showed the low level COC being disrupted somewhat by the mountains of PR, but still intact, and on track in the northern portions of the CDO near the eastern tip of Hispanola. As long as this track continues, the system, I feel, will not be significantly impacted by Hispanola, with the low level COC just barely missing the mountains.

--

Longer term (1-3 days) we need to watch for interaction between Marco and Laura. This is one of the rare cases where we may actually witness the Fujiwara effect near land, and that may throw off forecast track somewhat.

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13 minutes ago, Random Chaos said:

The most important, the most critical, to what this storm does over the next 2-3 days is whether the low level COC passes over Hispanola and the mountains there, or if the COC stays off shore. PR radar definitely looks like the radar identified COC is going to skim the northern edge of Hispanola. The disruption from passing over PR's mountains are minor compared to what Hispanola's mountains can do to a tropical system. I've seen well intact hurricanes completely ripped apart, never recovering, from Hispanola.

Watching both radar and IR the system looks to have convection displaced mainly south of the COC. Radar showed the low level COC being disrupted somewhat by the mountains of PR, but still intact, and on track in the northern portions of the CDO near the eastern tip of Hispanola. As long as this track continues, the system, I feel, will not be significantly impacted by Hispanola, with the low level COC just barely missing the mountains.

--

Longer term (1-3 days) we need to watch for interaction between Marco and Laura. This is one of the rare cases where we may actually witness the Fujiwara effect near land, and that may throw off forecast track somewhat.

However we were down this road before with Isaias.  The topography of Hispaniola in the east and northeastern part of the island is rather flat.  The tallest mountains are in the central interior, south coast, and western peninsula.  So Laura won’t be too disrupted relative to the eastern and northeast part of the island.  
 


AF1589B5-BFD2-4428-AB59-D3140F4525E1.jpeg

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20 minutes ago, WxWatcher007 said:

While high altitude recon has been flying for much of the day ahead and around Laura, the first low level recon mission of the day is heading out now. 

  Some pretty interesting sondes, and some confusing at least to me lol, from the GIV around the wave envelope.  Looks like there are still multiple small vortices through the column.  The only drops that were pretty moist all the way down were the 2 just SSW of Puerto Rico.  All of the drops N seemed to indicate some fairly dry air, which I guess would be expected as that dry air to the N as been moving in tangent with this all across the Atlantic on the southern side of the "current steering ridge".  

  Those drops SSW of Puerto Rico raised my eyebrows a bit with a much more saturated column more in line with the fairly vigorous mid level vort earlier.  I think there's still some decent possibility of a LLC forming south of the DR.  Planetary gears in action?  Guess what I'm trying to figure out is deeper moisture could invigorate convection and have a stronger sustained rising column and begin to have a lower surface pressure than the surrounding shallower moisture boundaries?  Current recon should give a better idea.  I never trust any LLC in a weak TC.

 Below is one of the drops to the N around where that meso vort should've exited PR and the second is one of the 2 that are fairly well saturated  SSW of PR.....

Surface and Standard Isobaric Surfaces
Level    Geo. Height    Air Temp.    Dew Point    Wind Direction    Wind Speed
1010mb (29.83 inHg)     Surface (Sea Level)     27.6°C (81.7°F)     24.3°C (76°F)     130° (from the SE)     39 knots (45 mph)
1000mb     86m (282 ft)     26.4°C (79.5°F)     22.7°C (73°F)     135° (from the SE)     40 knots (46 mph)
925mb     770m (2,526 ft)     21.6°C (70.9°F)     19.4°C (67°F)     145° (from the SE)     42 knots (48 mph)
850mb     1,502m (4,928 ft)     19.2°C (66.6°F)     15.3°C (60°F)     140° (from the SE)     44 knots (51 mph)
700mb     3,148m (10,328 ft)     10.0°C (50.0°F)     6.4°C (44°F)     115° (from the ESE)     47 knots (54 mph)
500mb     5,880m (19,291 ft)    -3.9°C (25.0°F)     About -12°C (10°F)     95° (from the E)     54 knots (62 mph)
400mb     7,610m (24,967 ft)    -15.3°C (4.5°F)     About -21°C (-6°F)     80° (from the E)     43 knots (49 mph)
300mb     9,730m (31,923 ft)    -28.9°C (-20.0°F)    -32.1°C (-26°F)     110° (from the ESE)     32 knots (37 mph)
250mb     11,000m (36,089 ft)    -39.3°C (-38.7°F)    -42.4°C (-44°F)     125° (from the SE)     35 knots (40 mph)
200mb     12,490m (40,978 ft)    -51.9°C (-61.4°F)     About -59°C (-74°F)     145° (from the SE)     37 knots (43 mph)
150mb     14,290m (46,883 ft)    Height extrapolated since sonde was released within 25mbs below this level.

SSW of PR

Surface and Standard Isobaric Surfaces
Level    Geo. Height    Air Temp.    Dew Point    Wind Direction    Wind Speed
1009mb (29.80 inHg)     Surface (Sea Level)     25.8°C (78.4°F)     23.6°C (74°F)     150° (from the SSE)     35 knots (40 mph)
1000mb     81m (266 ft)     25.0°C (77.0°F)     22.8°C (73°F)     150° (from the SSE)     45 knots (52 mph)
925mb     763m (2,503 ft)     20.4°C (68.7°F)     19.5°C (67°F)     145° (from the SE)     45 knots (52 mph)
850mb     1,494m (4,902 ft)     17.6°C (63.7°F)     17.6°C (64°F)     160° (from the SSE)     30 knots (35 mph)
700mb     3,137m (10,292 ft)     9.4°C (48.9°F)     9.2°C (49°F)     165° (from the SSE)     5 knots (6 mph)
500mb     5,860m (19,226 ft)    -4.5°C (23.9°F)    -5.5°C (22°F)     155° (from the SSE)     7 knots (8 mph)
400mb     7,590m (24,902 ft)    -13.7°C (7.3°F)    -16.3°C (3°F)     220° (from the SW)     5 knots (6 mph)
300mb     9,720m (31,890 ft)    -28.3°C (-18.9°F)    -31.5°C (-25°F)     135° (from the SE)     9 knots (10 mph)
250mb     11,000m (36,089 ft)    -38.3°C (-36.9°F)    -42.6°C (-45°F)     160° (from the SSE)     15 knots (17 mph)
200mb     12,490m (40,978 ft)    -51.3°C (-60.3°F)     About -57°C (-71°F)     155° (from the SSE)     18 knots (21 mph)
150mb     14,290m (46,883 ft)    Height extrapolated since sonde was released within 25mbs below this level.

 

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21 minutes ago, Kevin Reilly said:

However we were down this road before with Isaias.  The topography of Hispaniola in the east and northeastern part of the island is rather flat.  The tallest mountains are in the central interior, south coast, and western peninsula.  So Laura won’t be too disrupted relative to the eastern and northeast part of the island.  
 

 

AF1589B5-BFD2-4428-AB59-D3140F4525E1.jpeg

There are mountains on the north coast of the Dominican Republic that are actually similar in elevation to Puerto Rico’s mountains, ~4K feet. Pico Duarte the highest peak in the middle of Hispaniola is over 10k feet. We’ll see how it plays out though. 

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18z Euro weakens it in the gulf again after deepening it. There is some shear it shows, but i say it wont happen non of the other globals show that. Ukmet/ Gfs agree on a significant landfall hurricane. Ensembles favor the upper Texas coast.

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Tonight is the moment of truth. It could easily end up going across the northern coastline of Hispaniola due to land interaction. Radar center actually is quite a bit north and east of the NHC center. http://tempest.aos.wisc.edu/radar/pr3comphtml5.html And deep convective bursts are now firing over that radar center.

Basically, imagine all the easterly winds from this storm flowing across the ocean north of Hispaniola. The land friction slows those easterly winds, creating positive vorticity all along the northern coast. Makes it easy for center to go through that coastline vorticity maxima, especially since any center to the south would be destroyed. 

The very good news is that even if it does that, and ends up closer to Florida because of that, it won't be a catastrophic scenario since land interaction will keep it from intensifying too much. Only exception is if it can really 'reform' off northernmost tip of Hispaniola, then it might completely clear Cuba and have time to intensify.

By the morning it will be clear. 

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6 minutes ago, turtlehurricane said:

Tonight is the moment of truth. It could easily end up going across the northern coastline of Hispaniola due to land interaction. Radar center actually is quite a bit north and east of the NHC center. http://tempest.aos.wisc.edu/radar/pr3comphtml5.html And deep convective bursts are now firing over that radar center.

Basically, imagine all the easterly winds from this storm flowing across the ocean north of Hispaniola. The land friction slows those easterly winds, creating positive vorticity all along the northern coast. Makes it easy for center to go through that coastline vorticity maxima, especially since any center to the south would be destroyed. 

The very good news is that even if it does that, and ends up closer to Florida because of that, it won't be a catastrophic scenario since land interaction will keep it from intensifying too much. Only exception is if it can really 'reform' off northernmost tip of Hispaniola, then it might completely clear Cuba and have time to intensify.

By the morning it will be clear. 

Doubtful we have that much clarity by morning 

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44 minutes ago, Jackstraw said:

 

  Some pretty interesting sondes, and some confusing at least to me lol, from the GIV around the wave envelope.  Looks like there are still multiple small vortices through the column.  The only drops that were pretty moist all the way down were the 2 just SSW of Puerto Rico.  All of the drops N seemed to indicate some fairly dry air, which I guess would be expected as that dry air to the N as been moving in tangent with this all across the Atlantic on the southern side of the "current steering ridge".  

  Those drops SSW of Puerto Rico raised my eyebrows a bit with a much more saturated column more in line with the fairly vigorous mid level vort earlier.  I think there's still some decent possibility of a LLC forming south of the DR.  Planetary gears in action?  Guess what I'm trying to figure out is deeper moisture could invigorate convection and have a stronger sustained rising column and begin to have a lower surface pressure than the surrounding shallower moisture boundaries?  Current recon should give a better idea.  I never trust any LLC in a weak TC.

 Below is one of the drops to the N around where that meso vort should've exited PR and the second is one of the 2 that are fairly well saturated  SSW of PR.....

Surface and Standard Isobaric Surfaces
Level    Geo. Height    Air Temp.    Dew Point    Wind Direction    Wind Speed
1010mb (29.83 inHg)     Surface (Sea Level)     27.6°C (81.7°F)     24.3°C (76°F)     130° (from the SE)     39 knots (45 mph)
1000mb     86m (282 ft)     26.4°C (79.5°F)     22.7°C (73°F)     135° (from the SE)     40 knots (46 mph)
925mb     770m (2,526 ft)     21.6°C (70.9°F)     19.4°C (67°F)     145° (from the SE)     42 knots (48 mph)
850mb     1,502m (4,928 ft)     19.2°C (66.6°F)     15.3°C (60°F)     140° (from the SE)     44 knots (51 mph)
700mb     3,148m (10,328 ft)     10.0°C (50.0°F)     6.4°C (44°F)     115° (from the ESE)     47 knots (54 mph)
500mb     5,880m (19,291 ft)    -3.9°C (25.0°F)     About -12°C (10°F)     95° (from the E)     54 knots (62 mph)
400mb     7,610m (24,967 ft)    -15.3°C (4.5°F)     About -21°C (-6°F)     80° (from the E)     43 knots (49 mph)
300mb     9,730m (31,923 ft)    -28.9°C (-20.0°F)    -32.1°C (-26°F)     110° (from the ESE)     32 knots (37 mph)
250mb     11,000m (36,089 ft)    -39.3°C (-38.7°F)    -42.4°C (-44°F)     125° (from the SE)     35 knots (40 mph)
200mb     12,490m (40,978 ft)    -51.9°C (-61.4°F)     About -59°C (-74°F)     145° (from the SE)     37 knots (43 mph)
150mb     14,290m (46,883 ft)    Height extrapolated since sonde was released within 25mbs below this level.

SSW of PR

Surface and Standard Isobaric Surfaces
Level    Geo. Height    Air Temp.    Dew Point    Wind Direction    Wind Speed
1009mb (29.80 inHg)     Surface (Sea Level)     25.8°C (78.4°F)     23.6°C (74°F)     150° (from the SSE)     35 knots (40 mph)
1000mb     81m (266 ft)     25.0°C (77.0°F)     22.8°C (73°F)     150° (from the SSE)     45 knots (52 mph)
925mb     763m (2,503 ft)     20.4°C (68.7°F)     19.5°C (67°F)     145° (from the SE)     45 knots (52 mph)
850mb     1,494m (4,902 ft)     17.6°C (63.7°F)     17.6°C (64°F)     160° (from the SSE)     30 knots (35 mph)
700mb     3,137m (10,292 ft)     9.4°C (48.9°F)     9.2°C (49°F)     165° (from the SSE)     5 knots (6 mph)
500mb     5,860m (19,226 ft)    -4.5°C (23.9°F)    -5.5°C (22°F)     155° (from the SSE)     7 knots (8 mph)
400mb     7,590m (24,902 ft)    -13.7°C (7.3°F)    -16.3°C (3°F)     220° (from the SW)     5 knots (6 mph)
300mb     9,720m (31,890 ft)    -28.3°C (-18.9°F)    -31.5°C (-25°F)     135° (from the SE)     9 knots (10 mph)
250mb     11,000m (36,089 ft)    -38.3°C (-36.9°F)    -42.6°C (-45°F)     160° (from the SSE)     15 knots (17 mph)
200mb     12,490m (40,978 ft)    -51.3°C (-60.3°F)     About -57°C (-71°F)     155° (from the SSE)     18 knots (21 mph)
150mb     14,290m (46,883 ft)    Height extrapolated since sonde was released within 25mbs below this level.

 

When the LLC of a tropical storm reforms it almost always reforms closer to or further along the LLJ.   I've never seen one reform further away or upwind from so I'd be surprised if it happened.  I'm not an expert though.

NiLtlIp.png

 

 

 

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