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2020 Hurricane Season (Atlantic & East Pacific)

Gaoth Laidir

The 2020 hurricane season officially starts on June 1st and runs until November 30th. This year NOAA is forecasting it to be an active season, with a 60% chance of above average, 30% of near average and 10% chance of below average. Their forecast confidence is 70%.

In numbers, they forecast 13-19 named storms (climate average is 12), of which 6-10 become hurricanes (climatic average 6), 3-6 of theses major (Cat 3 or higher) (climatic average 3).

Factors affective hurricane activity include nuetral ENSO or a possible La Niña, which in general reduces windshear, warm tropical Atlantic waters and an active African monsoon, which should supply plenty of easterly waves that could develop into tropical systems.

https://www.noaa.gov/media-release/busy-atlantic-hurricane-season-predicted-for-2020

We already had two weak and short-lived tropical storms in the latter part of May (Arthur and Bertha) and there is currently an area of interest in the mid-Atlantic, however this is not forecast to develop into a tropical storm.

List of 2020 Atlantic names:

Arthur | Bertha | Cristobal | Dolly | Edouard | Fay | Gonzalo | Hanna | Isaias | Josephine | Kyle | Laura | Marco | Nana | Omar | Paulette | Rene | Sally | Teddy | Vicky | Wilfred.

Latest SST anomaly

Useful links

http://www.nhc.noaa.gov/
http://hurricanes.ral.ucar.edu/realtime/current/
https://www.tropicaltidbits.com/
http://rammb.cira.colostate.edu/products/tc_realtime/index.asp
https://www.nrlmry.navy.mil/TC.html
http://tropic.ssec.wisc.edu/tropic.php
http://tropical.atmos.colostate.edu/Realtime/

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Comments

Gaoth Laidir

The arse has fallen out of Isaias a bit this evening as it's back down to Tropical Storm 60 kts. Dry air, windshear and the Bahamas islands have interfered with its circulation, which never properly formed in the first place. It is expected to strengthen slightly back to 65 knots over the next day or so as it passes close to the east Florida coast, though with any real winds well out to its east there should be no real problems for Florida. Rain bands have been coming into the Miami - Pompano Beach area this evening but they're fairly broken up and relatively light. The partial eyewall is visible on Miami radar but it's nothing more than a curved band.

Tropical Depression Ten passed just north of Cabo Verde and fizzled out having maxed out briefly at 35 knots.

Gaoth Laidir

Not surprisingly, the latest NHC discussion has found Isaias to be weaker and suffering from dry air and 25 kt of wind shear. The intensity has been lowered to 55 knots (in a small area to the east) and no further strengthening is forecast as it brushes up along the east coast of Florida and into the Carolinas.

Winds along the Florida coast are in the 15-25-kt range.

Oneiric 3

Coming up against a large bank of drier air now which won't help any potential further development:

https://www.youtube.com/watch?v=sXyCAZc2OdU

And looking at a live cam of Miami beach, nothing seems out of the ordinary wind wise. A mere flutter:

https://www.youtube.com/watch?v=QMDYosSV_pk

Oneiric 3

North Carolina live cam. Sky there currently looks similar to what we have had 95% of the time here in the west of Ireland this summer, but this is east coast America, and such a sky will always proceed something just a bit bigger than a few spits of patchy light rain and drizzle.

https://www.youtube.com/watch?v=iZh6lBhALwU

Gaoth Laidir

Isaias made it back to hurricane strength just before landfall in southern North Carolina. Some isolated hurricane-force winds were recorded along the extreme coast but the majority of stations were well below it.

Hurricane Isaias Tropical Cyclone Update
NWS National Hurricane Center Miami FL
AL092020 1115 PM EDT Mon Aug 3 2020

Doppler radar imagery and surface observations indicate that eye of Hurricane Isaias made landfall in southern North Carolina around 1110 PM EDT (0310 UTC) near Ocean Isle Beach, with maximum sustained winds of 85 mph (140 km/h).

A weather station at Oak Island, North Carolina, recently reported sustained winds of 76 mph (122 km/h) and a gust to 87 mph (140 km/h).

A data buoy near the coast of North Carolina has recently reported a minimum pressure of 988 MB (29.18 inches).

Gaoth Laidir

Some tornados have sprung up

...1200 PM EDT POSITION UPDATE...
...STRONG WINDS...HEAVY RAINFALL...AND TORNADOES OCCURRING OVER SOUTHERN NEW JERSEY AND SOUTHEASTERN PENNSYLVANIA WILL CONTINUE TO SPREAD NORTHWARD ALONG THE MID-ATLANTIC COAST THIS AFTERNOON...

A Weatherflow weather station at Long Beach Island Surf, New Jersey, recently reported a sustained wind of 46 mph (74 km/h) and a gust to 59 mph (94 km/h). Around 1053 AM EDT, this same weather observing station measured a wind gust of 109 mph (176 km/h), which was associated with a tornadic thunderstorm.

Doppler weather radar data from Ft. Dix, New Jersey, indicated Doppler velocities as high as 112 mph (180 km/h) at an altitude of 1,590 above ground level at this same location. However, this wind is not considered to be representative of Isaias' larger wind field.

Also, a Weatherflow observing site located at Rutgers/Little Egg Harbor, New Jersey, recently reported a sustained wind of 52 mph (84 km/h) and a gust to 70 mph (113 km/h).

SUMMARY OF 1200 PM EDT...1600 UTC...INFORMATION
LOCATION...39.6N 75.8W
ABOUT 10 MI...20 KM WSW OF WILMINGTON DELAWARE
ABOUT 35 MI...55 KM WSW OF PHILADELPHIA PENNSYLVANIA
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NNE OR 25 DEGREES AT 35 MPH...56 KM/H
MINIMUM CENTRAL PRESSURE...993 MB...29.32 INCHES

hatrickpatrick

Once Isaias burns out, we're likely to see a lull in activity lasting until August 10th or so, with the Atlantic floodgates potentially opening during the last fortnight of August as a large sinking cell settles over the Pacific and allows wind shear and surface pressures to drop in the tropical Atlantic.

Gaoth Laidir

Not quite hurricane-related but still along the same lines

From the BOM weekly update today

http://www.bom.gov.au/climate/mjo/#mjo7

Tropical cyclone activity over the western North Pacific Ocean
For the first time since at least 1949, no named storms (i.e. equivalent to a category 1 or stronger Australian tropical cyclone) developed in the western North Pacific basin in July 2020. In a typical year, this region sees between 3 and 4 tropical cyclones in July. This continues the well below-average tropical cyclone activity in the western North Pacific Ocean this year. Only one typhoon (equivalent to a category 3 Australian tropical cyclone) had been observed to the end of July 2020, compared to the long-term average of about 5.

In the past week, 2 named storms developed over the western North Pacific Ocean, bringing the 2020 total to 4 tropical storms, compared to an average of between 8 and 9.

Ex-tropical storm Sinlaku passed over Hainan Island and the east coast of northern Vietnam on 2 August as a weak tropical storm (equivalent to category 1 Australian tropical cyclone). Sinlaku generated strong winds and heavy rain as it made landfall. As it tracks further inland as a tropical depression, it is expected to produce heavy rains across parts of mainland China.

Typhoon Hagupit (Dindo) formed to the east of the Philippines and has recently tracked towards the north. It passed close to Taiwan in the last 24 hours and more recently made landfall on mainland China's east coast with mean winds estimated at more than 125 km/h.

The active MJO pulse over the Maritime Continent, along with another tropical atmospheric wave—an equatorial Rossy wave—contributed to the development of tropical cyclones Sinlaku and Hagupit.

star gazer

NOAA's Climate Prediction Centre has a projection for an 85% chance of an above normal hurricane season incuding 7 to 11 Hurricanes of which 3 to 6 Major Hurricanes. The hurricane season ends on the 30th November.
possible extremely active Atlantic hurricane season

“This year, we expect more, stronger, and longer-lived storms than average, and our predicted ACE range extends well above NOAA’s threshold for an extremely active season,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center.

Current oceanic and atmospheric conditions that make an “extremely active” hurricane season possible are warmer-than-average sea surface temperatures in the tropical Atlantic Ocean and Caribbean Sea, reduced vertical wind shear, weaker tropical Atlantic trade winds and an enhanced west African monsoon. These conditions are expected to continue for the next several months. A main climate factor behind these conditions is the ongoing warm phase of the Atlantic Multi-Decadal Oscillation, which reappeared in 1995 and has been favoring more active hurricane seasons since that time.

Another contributing climate factor this year is the possibility of La Nina developing in the months ahead. Indicative of cooler-than-average sea surface temperatures in the equatorial regions of the eastern Pacific Ocean, La Nina can further weaken the wind shear over the Atlantic Basin, allowing storms to develop and intensify.

ACE- Accumulated Cyclone Energy
The next three named storms: Josphine, Kyle, Laura

Gaoth Laidir

Tropical Depression 11 has formed in the MDR and will likely be named Josephine very soon. However, the max intensity forecast is 45 knots, after which conditions will become more hostile as it passes to the north of the Leeward Islands over the weekend, by which time it could well disintegrate into an open trough.

Meanwhile, Hurricane Elida in the eastern Pacific is currently 85 knots but will weaken rapidly as it passes over cold waters in the next day or so, staying well out to sea from southern Baja California.

Gaoth Laidir

TS Josephine has just been named and is the earliest 10th named Atlantic system on record. Next was Jose on August 22nd, 2005.

Currently intensity is 40 knots and slight strengthening to 50 knots is expected before it disintegrates to a tropical wave in about 3-5 days. It will stay clear of land.

littlema

Is anyone following TS Kyle which is heading NE from USA and could be wandering over the Atlantic ??

Gaoth Laidir

TS Kyle will not amount to much as it moves northeastwards in the western Atlantic. The official forecast has it peaking at 45 knots before dissipating by 5 days. Kyle is the earliest eleventh-named Atlantic system on record, with Katrina (2005) the the previous holder (22nd (August). Josephine is also on death row ąt 35 knots and aetiology to weaken and dissipate over the weekend.

Again, none or these systems has been anything of note, yielding a still low ACE total for the number of system. We're ahead of average on named storm numbers/days and hurricanes but still behind on major hurricanes.

ATLANTIC SEASON STATS SO FAR (14 AUG)

Named storms: 11 (average 2.8)
Named storm days: 25.25 (9.5)
Hurricanes: 2 (0.8)
Hurricane days: 3.0 (2.1)
Major hurricanes: 0 (0.3)
Major hurricane days: 0 (0.4)
Total ACE: 24.0 (12.0)

Scrabbel

ECM seems to show Kyle’s tail end, merged with another low, giving us a windy day on Friday.

Gaoth Laidir

Kyle has weakened and become extratropical this morning and is expected to dissipate within the next 48 hours.

Shortwave infrared satellite imagery and earlier ASCAT data indicate that Kyle's circulation has become very elongated, and the center has become ill defined. Model analyses and satellite imagery also suggest that the low is now attached to a prominent warm/stationary front to its east and a weaker trailing cold front to its southwest. Therefore, Kyle has become an extratropical low, and its maximum winds are estimated to be 35 kt based on the earlier ASCAT data. Global models indicate that Kyle's winds should continue to decrease over the next couple of days, with the system dissipating or becoming absorbed by another area of low pressure in about 48 hours.

The initial motion is eastward, or 080/17 kt. Since Kyle is embedded in zonal mid-latitude flow, this general heading and speed are expected to continue during the next day or two until the cyclone dissipates.

Likewise, Josephine has also weakened and is set to become an open wave within 36 hours. We're still waiting for something to really get going in the Atlantic this season. Two more waves are coming off Africa now but have a low chance of development in the next 5 days.

Josephine's low-level center has raced out over 100 n mi to the west of a remnant area of deep convection, which itself is shrinking and becoming more disorganized. Due to the loss of organization, it is assumed that Josephine's maximum winds have decreased, and the initial intensity is set at 35 kt, which matches the latest Current Intensity estimates. Analyses from the UW-CIMSS indicate that Josephine is now being pounded by about 35 kt of southwesterly shear, and a zone of even higher shear exists to the northwest of the cyclone. Therefore, continued weakening is expected, and Josephine could lose all of its organized deep convection and become a remnant low by 36 hours, if not sooner. The NHC forecast holds a remnant low after 36 hours until the end of the forecast period, but it is entirely possible that the hostile conditions will cause Josephine to dissipate at any time, with the circulation opening up into a trough.

hatrickpatrick

Hurricane season starting to seriously ramp up now with two separate tropical waves in the MDR being watched for potential development next week. And the lid hasn't even been lifted off the Atlantic properly yet, with favourable MJO conditions not due to arrive for another week at least :eek:

Gaoth Laidir

Tropical Depression 13 has formed in mid-Atlantic is should become Tropical Storm Laura later tonight. Its future life depends on how it interacts with the northern Leeward Islands, so NHC forecast confidence is low.

The low pressure system that NHC has been monitoring over the
central tropical Atlantic has now developed a well-defined center of
circulation and maintained enough organized deep convection to be
classified as a tropical depression, the thirteenth cyclone of the
2020 Atlantic hurricane season. The depression already has some
banding features on its north and west sides as evident in
geostationary satellite and microwave images. The initial intensity
is set at 30 kt based on ASCAT data from around 0100 UTC and a
T2.0/30 kt Dvorak classifications from TAFB.

The depression has been moving fairly quickly to the west-northwest,
with the latest initial motion estimated to be 295/17 kt. It should
be noted that the initial motion is somewhat uncertain given that
the system has only recently formed. A subtropical ridge currently
over the central Atlantic is expected to build westward during the
next several days and should be the primary steering feature for
the depression through the forecast period. This pattern should
keep the depression on a fairly quick west-northwest track during
the next several days, taking the cyclone near the northern
Leeward Islands by Friday night and near the Greater Antilles
and southeastern Bahamas this weekend. The models are in fairly
good agreement, but there is some north-south spread with the GFS
being on the southern side of the guidance envelope and the ECMWF
on the northern end. The NHC track forecast lies down the middle
of the guidance suite.

The environmental conditions appear generally favorable for the
depression to strengthen, with the wind shear expected to remain
relatively low while the system moves over warm SSTs and remains in
a moist airmass. These conditions should promote gradual
strengthening and it seems quite likely that the cyclone will be a
tropical storm when it moves near or north of the northern Leeward
Islands in a couple of days. The bigger question is how
much interaction will there be with the Greater Antilles. If the
depression moves on the south side of the guidance envelope,
further strengthening would be limited due to land interaction.
Conversely, if the system gains more latitude and moves north of
these highly topographic islands, it could have the opportunity for
more significant intensification. The NHC intensity forecast, which
is of low confidence, is roughly near the middle of the guidance
envelope.

Key Messages:

1. Tropical storm conditions are possible across portions of the
northern Leeward Islands by Friday night, and Tropical Storm Watches
have been issued for some of these islands. Heavy rainfall is
likely across this area beginning late Friday.

2. There is a risk of tropical storm conditions in the Virgin
Islands and Puerto Rico Friday night and Saturday and Tropical
Storm Watches could be required for these islands tomorrow.
Interests there should closely monitor the progress of this system.

3. The details of the long-range track and intensity forecasts are
more uncertain than usual since the system could move over portions
of the Greater Antilles this weekend. However, this system could
bring some rainfall and wind impacts to portions of Hispaniola,
Cuba, the Bahamas, and Florida this weekend and early next week.
Interests there should monitor this system's progress and updates to
the forecast over the next few days.

silverharp

2020 keeps delivering

https://twitter.com/Ella__Dorsey/status/1296651073797656582

dfx-

Levi Cowan isn't buying it, two messy systems...

https://www.youtube.com/watch?v=zhA59vi2_j0

Gaoth Laidir

I would lay off any media "Breaking" tweets, such as above, for now as there is huge uncertainty in the NHC forecasts. Stick to the NHC and Levi Cowan for accurate information. There may be some interaction between TDs 13 and 14 when they get to the gulf, so watch out for sensationalist nonsense saying superstorm on the way, etc... bla bla.

Latest NHC discussions (10 am)

TD 13

Tropical Depression Thirteen remains very disorganized this morning. The associated convection is elongated from northwest to southeast, and the low-level center is located near the northwestern end of the convective area. Additionally, satellite imagery and model analyses indicate that the mid-level center is located several hundred miles to the southeast of the low-level center. Earlier aircraft and scatterometer data suggested the possibility that the system was an open wave. However, the currently available data is ambiguous on whether the system still has a closed circulation, so it will be maintained as a tropical depression. The initial intensity remains 30 kt.

The initial motion is west-northwestward or 285/18 kt. There is little change to the track forecast philosophy through about 96 h.
A strong subtropical ridge over the western Atlantic should remain north of the depression during the next few days, steering the
cyclone at a fast pace to the west-northwest. After that, the ridge weakens some over the eastern Gulf of Mexico, and Tropical
Depression Thirteen may interact with Tropical Depression Fourteen, which is also forecast to be in the Gulf by that time, with the
result of these things being a turn toward the northwest or north-northwest. The track guidance has shifted southward since the
last advisory, with the UKMET shifting far enough to the south that it takes the system over the Caribbean south of Cuba. The new
forecast track is also shifted a bit southward from the previous track. However, it lies to the north of the GFS, the UKMET, and the
various consensus models. It also lies north of the ECMWF model from 24-72 h.

The intensity forecast remains low confidence. The separation between the low- and mid-level centers, as well as some westerly
shear and dry air entrainment, suggests that significant strengthening is unlikely during the next 24 h or so. The dynamical
models suggests the centers will become more vertically aligned around 36-48 h and that the shear should diminish. However, the
system could be close to Hispaniola during this time, and be near Cuba thereafter, especially if it moves south of the forecast track.
The upper-level winds over the Gulf of Mexico should be generally favorable for development if the cyclone doesn't get too close to
Tropical Depression Fourteen. The possibilities range from the system degenerating to an open wave as seen in the GFS and ECMWF to
a major hurricane as seen in the HWRF. Given the uncertainty, the intensity forecast is unchanged from the previous advisory, and it
lies a little below the intensity consensus.

Key Messages:

1. Tropical storm conditions are possible across portions of thenorthern Leeward Islands, the Virgin Islands, Puerto Rico, the
southeastern Bahamas, and the Turks and Caicos islands later today through Saturday night, and Tropical Storm Watches have been
issued for some of these islands. Heavy rainfall is likely across this area beginning today and could cause mudslides and flash
and urban flooding through Sunday.

2. The details of the long-range track and intensity forecasts are more uncertain than usual since the system could move over portions
of the Greater Antilles this weekend. However, this system could bring some storm surge, rainfall and wind impacts to portions of
Hispaniola, Cuba, the Bahamas, and Florida this weekend and early next week. Interests there should monitor this system's progress
and updates to the forecast over the next few days.

FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 17.8N 58.5W 30 KT 35 MPH
12H 21/1800Z 18.1N 60.7W 30 KT 35 MPH
24H 22/0600Z 18.8N 64.0W 35 KT 40 MPH
36H 22/1800Z 19.7N 67.5W 40 KT 45 MPH
48H 23/0600Z 20.6N 71.1W 45 KT 50 MPH
60H 23/1800Z 21.8N 74.9W 50 KT 60 MPH
72H 24/0600Z 23.2N 78.5W 55 KT 65 MPH
96H 25/0600Z 26.5N 84.0W 65 KT 75 MPH
120H 26/0600Z 30.0N 87.0W 65 KT 75 MPH

TD 14

Recent METOP-A/B ASCAT overpasses and earlier aircraft reconnaissance data indicate that the depression's circulation is
not well-defined. In fact, the scatterometer data revealed multiple swirls, particularly, one newly developed circulation near a recent
strong burst of deep convection near the coast of Honduras. Highest sustained winds from the scatterometer pass were 25-30 kt. For this advisory, the initial position is an uncertain centroid position of the multiple surface centers and the intensity is held at 30 kt. A
53rd Air Force Reserve reconnaissance flight is scheduled for this morning and will hopefully paint a clearer picture on the
depression's location.

Deep convection has been increasing during the past few hours, especially in the north portion of the depression, so gradual
strengthening is still expected before it makes landfall on the east side of the Yucatan Peninsula in about 48 hours. After that time,
some weakening is forecast while the cyclone traverses the peninsula. The system is expected to enter the warm waters of the
southern Gulf of Mexico around the 60 hr period and restrengthen through the remainder of the forecast. Global models, however, are
indicating increasing south-southwesterly shear as the cyclone enters the northwest portion of the gulf which could prevent it from
reaching hurricane strength prior to landfall. For now, the forecast will reflect a low-end hurricane making landfall, similar
to the HCCA intensity model. The new intensity forecast is basically an update of the previous advisory and is based on a
compromise of the various multi-model consensus aids.

The initial motion is estimated to be west-northwestward, or 290/10 kt. The depression is forecast to be steered generally
northwestward during the next few days by a western extension of the atlantic subtropical ridge that stretches westward across Florida
and into the eastern and central Gulf of Mexico. This general motion should result in landfall over the northeastern Yucatan
Peninsula on Saturday, with the system entering the northwestern Gulf by the middle of next week. I think it's worth noting that
both the UKMET and the DWD, Germany ICON global models are showing some binary interaction between the depression and Tropical
Depression Thirteen around the 96-120 hr period while both systems are situated in the Gulf of Mexico. If this scenario actually
occurs, the interaction could delay or slow tropical depression Fourteen's landfall over the northwestern Gulf coast.

The NHC forecast track is again adjusted a little to the right of the previous forecast and lies close to the TVCA and HCCA
consensus solutions.

Key Messages:

1. Tropical Depression Fourteen is expected to strengthen over the northwestern Caribbean Sea through Saturday, and is likely to
produce tropical-storm-force winds and heavy rainfall over portions of the coasts of Nicaragua and Honduras, including the Bay Islands,
through today. The system is expected be near or at hurricane strength when it reaches the Yucatan Peninsula of Mexico late
Saturday where a Hurricane Watch and a Tropical Storm Warning are in effect.

2. The system is expected to move into the south-central Gulf of Mexico as a tropical storm on Sunday. Some strengthening is
anticipated while it moves northwestward over the western Gulf of Mexico early next week, but it is too soon to know exactly how
strong it will get or the location and magnitude of impacts it will produce along the central or northwestern Gulf Coast. Interests in
that area should continue monitoring the progress of this system over the next few days.

FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 15.4N 83.1W 30 KT 35 MPH
12H 21/1800Z 16.3N 84.3W 40 KT 45 MPH
24H 22/0600Z 17.7N 85.4W 50 KT 60 MPH
36H 22/1800Z 19.2N 86.4W 60 KT 70 MPH
48H 23/0600Z 20.7N 87.5W 50 KT 60 MPH...INLAND
60H 23/1800Z 22.5N 88.8W 50 KT 60 MPH...OVER WATER
72H 24/0600Z 24.5N 90.2W 65 KT 75 MPH
96H 25/0600Z 28.1N 93.0W 65 KT 75 MPH
120H 26/0600Z 30.4N 94.6W 45 KT 50 MPH...INLAND

pad199207

Inaccuweathers take

Gaoth Laidir

Thirteen has become T.S. Laura

Tropical Storm Laura Tropical Cyclone Update
NWS National Hurricane Center Miami FL AL132020
905 AM AST Fri Aug 21 2020

...NOAA HURRICANE HUNTER AIRCRAFT FINDS THAT THE DEPRESSION HAS
STRENGTHENED TO TROPICAL STORM LAURA...

Data from a NOAA Hurricane Hunter aircraft indicate that Tropical
Depression Thirteen has strengthened and is now Tropical Storm
Laura with maximum sustained winds of around 45 mph (75 km/h). The
aircraft also found that the center of Laura is located south of the
previously estimated position. These changes will be reflected in
the track and intensity forecasts with the upcoming advisory that
will be issued at 1100 AM AST (1500 UTC).

SUMMARY OF 905 AM AST...1305 UTC...INFORMATION
LOCATION...17.0N 59.8W
ABOUT 230 MI...375 KM ESE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES

Storm 10

Any of these storms likely to head our way

Gaoth Laidir

Storm 10 wrote: »

Any of these storms likely to head our way

No, they both look to be heading into the Gulf and should dissipate on or before landfall

Storm 10

Gaoth Laidir wrote: »

No, they both look to be heading into the Gulf and should dissipate on or before landfall

Where is the low coming from for Tuesday or is it just a normal Atlantic Depression

Gaoth Laidir

Storm 10 wrote: »

Where is the low coming from for Tuesday or is it just a normal Atlantic Depression

Just normal Atlantic shíte, I'm afraid.

Storm 10

Gaoth Laidir wrote: »

Just normal Atlantic shíte, I'm afraid.

Thanks thought it might be something big brewing

Gaoth Laidir

Both Laura and TD 13 continue to struggle to this evening and the ultimate intensity forecasts have been slightly reduced. 14 is failing to intensify despite being in an area of low shear and 30-degree SST.

The recent development of systems in both the East Pacific (hurricane Genevieve) and in the Atlantic are linked to a strong pulse of the MJO in the area. It is forecast to continue moving eastwards towards the Indian Ocean over the next 1-2 weeks, so exactly how activity will progress thereafter will be interesting to see. The climatological season ramps up now to a peak in mid-September, so it would be a window for the first major hurricane to form. We are lagging behind the climate mean in that respect.

Gaoth Laidir

Lastest NHC discussion has the recently named TS Marco (was TD 14) still struggling to get going, found to be due to higher stability that thought in the western Caribbean. Most models don't show it reaching hurricane status, and the official NHC forecast goes for 60 knots briefly.

Note that they specifically say that future interaction with TS Laura seems unlikely at this stage. I'm sure this point will be ignored when the headlines are being written.

Tropical Storm Marco Discussion Number 8
NWS National Hurricane Center Miami FL AL142020
400 AM CDT Sat Aug 22 2020

SFMR data from the last leg of the 53rd Air Force Reserve reconnaissance aircraft indicated a couple of 48-50 kt winds, but were associated with a significant spike in the rainfall rate. Additionally, the flight-level winds were only 36 kt in that area and the central pressure has increased a little to 1005 mb. The cloud pattern has improved during the past several hours with deep convection developing near the center and spiral bands forming over the eastern portion of cyclone. Based on a blend the hurricane hunter data and current subjective satellite intensity estimates, the initial intensity is raised to 40 kt.

Although the UW-CIMSS shear product and global models indicate a favorable upper wind pattern, GOES-16 sounder analysis data show a higher than normal vertically stable environment in the western Caribbean. This negative contribution maybe what's hampering significant development. Consequently, as shown in the previous advisory, only modest strengthening is indicated in the NHC forecast through 48 hours. Only the Decay SHIPS and LGEM intensity models indicate that Marco will become a hurricane in a couple of days. Both the HMON and HWRF have backed off of showing a hurricane in the Gulf. Afterward, increasing west-southwesterly shear should lead to weakening as the cyclone turns toward the northwestern Gulf coast. The NHC forecast lies between the higher LGEM/Decay SHIPS solution and the lower NOAA HCCA intensity model which indicates a peak intensity of 55 kt.

The initial motion is estimated to be west-northwestward, or 335/10 kt. Marco is being steered toward the northwest by a mid- to upper-level cut-off low and associated trough extending into the southwestern Gulf from the Mississippi Valley. By Sunday, the aforementioned feature is forecast to lift northeastward allowing the subtropical ridge to build back over the central gulf. This should cause Marco to turn northwestward and west-northwestward early next week toward the the northwestern Gulf coast. Large-scale guidance generally agree that any binary direct or indirect interaction, while both systems are in the gulf and at near equal latitude, is unlikely at this point. The official track forecast has been adjusted to the right of the previous advisory and lies just to the left of the various multi-model consensus aids.

The 34 kt wind radii have been adjusted based on the aircraft reconnaissance data and a 0224 UTC scatterometer pass.

Key Messages:

1. Marco is forecast to strengthen over the northwestern Caribbean Sea through Saturday as it approaches the northeast coast of the
Yucatan Peninsula. A Hurricane Watch and a Tropical Storm Warning are in effect for portions of that region.

2. The system is expected to move into the south-central Gulf of Mexico as a tropical storm on Sunday. Although some strengthening
is anticipated on Sunday, weakening is forecast as the system approaches the northwestern Gulf coast on Tuesday. It is still too
soon to know exactly the location and magnitude of impacts the system will produce along the central or northwestern Gulf Coast,
and interests in that area should continue monitoring the progress of this system over the next few days.

FORECAST POSITIONS AND MAX WINDS

INIT 22/0900Z 19.6N 85.4W 40 KT 45 MPH
12H 22/1800Z 20.9N 86.1W 45 KT 50 MPH
24H 23/0600Z 22.5N 87.1W 50 KT 60 MPH
36H 23/1800Z 24.1N 88.3W 55 KT 65 MPH
48H 24/0600Z 25.7N 89.9W 60 KT 70 MPH
60H 24/1800Z 27.3N 91.3W 55 KT 65 MPH
72H 25/0600Z 28.3N 93.4W 50 KT 60 MPH
96H 26/0600Z 29.1N 96.2W 40 KT 45 MPH...INLAND
120H 27/0600Z 29.6N 97.8W 25 KT 30 MPH...POST-TROP/REMNT LOW

Gaoth Laidir

TS Laura is now over the Virgin Islands and is slightly better organised, however it will pass down Hispaniola and Cuba, so still some uncertainty in the forecasts. The best track has it briefly reaching Cat 1 strength in the northern Gulf before landfall somewhere in the New Orleans area. That would be 15 years more or less to the day after Katrina...

Tropical Storm Laura Discussion Number 10...Corrected
NWS National Hurricane Center Miami FL AL132020
500 AM AST Sat Aug 22 2020

Corrected status at 96 and 120 h

Surface observations and Doppler radar data from Puerto Rico indicate that the center of Laura is currently over the Virgin Islands, eastern Puerto Rico, and the adjacent Caribbean waters. Overall, the system has become a little better organized since the last advisory, with strong convection forming not far from the center to the east and southeast and a somewhat better defined circulation. However, the central area of light winds is quite large, and there is evidence of several vorticity centers rotating around the mean storm center. Earlier scatterometer data suggested that the maximum winds had decreased to 35 kt, and that is the initial intensity for this advisory.

The initial motion is a somewhat uncertain 280/18. There is no change in the track forecast philosophy, as a subtropical ridge over the central and western Atlantic is expected to expand westward, causing Laura to move quickly west-northwestward for the next 3 days or so. After that, the storm should turn northwestward toward the western edge of the ridge over the northern Gulf coast. While the dynamical models are in good agreement with the general scenario, there is an unusual amount of cross track spread. The track guidance is spread from the Florida Keys to the western end of Cuba as the storm enters the Gulf of Mexico, and the models have potential landfall locations along the Gulf coast from the Florida Panhandle to the middle Texas coast. One complicating factor is the potential for interaction with Tropical Storm Marco, although at this time the model guidance suggests the storms will stay far enough apart to prevent direct interaction. The new forecast track is similar to the previous track through 72 hr, then it is shifted a bit to the west after that time. The new track lies near the various consensus models.

Laura is moving into an environment of light shear, and combined with the somewhat improved organization it suggests the storm should strengthen. However, the forecast track takes the center over Hispaniola and then down the length of Cuba, which should at least slow any intensification. This is reflected in the new intensity forecast which shows slow strengthening. Over the Gulf of Mexico, warm water and a likely favorable shear environment should allow Laura to become a hurricane, a scenario now supported by much of the guidance.

Key Messages:

1. Tropical storm conditions are expected across portions of the northern Leeward Islands, the Virgin Islands, and Puerto Rico through today. Tropical storm conditions are also expected along the northern coasts of the Dominican Republic and Haiti, and the Turks and Caicos and southeastern Bahamas Saturday into Sunday. Heavy rainfall is likely across these areas beginning and could cause mudslides and flash and urban flooding through Sunday.

2. Tropical storm conditions are possible over portions of the central Bahamas Sunday night, as well as portions of eastern and central Cuba Sunday and Sunday night.

3. The details of the long-range track and intensity forecasts remain more uncertain than usual since Laura is forecast to move near or over portions of the Greater Antilles through Monday. However, Laura could bring storm surge, rainfall, and wind impacts to portions of Cuba, the Bahamas, and Florida early next week and the northern U.S. Gulf Coast by the middle of next week. Interests there should monitor the progress of Laura and updates to the forecast during the next few days.

FORECAST POSITIONS AND MAX WINDS

INIT 22/0900Z 17.6N 65.5W 35 KT 40 MPH
12H 22/1800Z 18.2N 67.7W 40 KT 45 MPH
24H 23/0600Z 19.1N 71.0W 40 KT 45 MPH...INLAND
36H 23/1800Z 20.3N 74.6W 45 KT 50 MPH...INLAND
48H 24/0600Z 21.6N 78.3W 45 KT 50 MPH...INLAND
60H 24/1800Z 23.1N 81.8W 45 KT 50 MPH...INLAND
72H 25/0600Z 24.6N 84.7W 55 KT 65 MPH...OVER WATER
96H 26/0600Z 27.5N 89.5W 75 KT 85 MPH
120H 27/0600Z 31.0N 92.0W 55 KT 65 MPH...INLAND