ATL: BERTHA - Post-Tropical - Discussion

[TheStormExpert]

Interesting, based on that graphic the NHC seems to think that if it hasn't formed by 60W it probably won't, as the graphic only extends upto roughly its 48hrs position. It would make sense given the models advertise a pretty rough set-up past that point.

That also goes with why for the past several TWO's it's 5-day development chances have matched with the 2-day.

[TropicalAnalystwx13]

Invest 93L shouldn't amount to much more than some sporadic showers and gusty winds for the Lesser Antilles. It was pretty much over when easterly shear allowed dry air into the circulation. Because this isn't an intensifying cyclone with active convection, it won't be able to split the upper-level trough waiting for it near the islands like the GFS suggested days ago, and it will likely be sheared to death (what remains of it, anyways).

Looking ahead, I don't see any reason to suggest things are going to improve in the Atlantic. Shear may have lowered in the central and eastern Atlantic, but the dry air and SAL are overwhelming, even despite a cool Gulf of Guinea and wet Sahel (fueling stronger-than-average waves). The MJO should lose amplitude as it heads towards our basin early next month.

For the thousandth time, cold water in the IO favors WEAKER systems. Multiple mets have stated this previously here

I didn't mention anything about the Indian Ocean, I mentioned the Gulf of Guinea (south of Africa) and the Sahel region...

But since we're on the subject, no, a cold Indian Ocean does not favor weaker systems. For the thousandth time, here is a sea surface temperature composite of the top ten ACE years in the Atlantic:



Average if not slightly cooler than average.

But if you want to continue to ignore the data, read pages 9 and 10 from the CPC's climate perspective on the 2011 Atlantic hurricane season, with contributions from the hurricane specialists at the NHC.

[cycloneye]

Let's stick to the 93L topic,thanks.

[gatorcane]

Saved image from a few hours ago since the sun's angle then really shows the situation with the dry air. Notice the large area of haziness surrounding and north and northeast of 93L - bone dry air there and is a major reason why this system is struggling:

[Gustywind]

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED JUL 30 2014


...SPECIAL FEATURES...
A 1012 MB LOW CENTERED NEAR 09.5N45W IS MOVING W-NW 15 KT. THE
LOW LIES ALONG THE MONSOON TROUGH WITH VISIBLE SATELLITE IMAGERY
SHOWING SIGNS OF ORGANIZING INTO A TROPICAL CYCLONE. HOWEVER THE
SYSTEM LACKS ANY ORGANIZED SIGNIFICANT DEEP CONVECTION. ISOLATED
MODERATE CONVECTION IS LOCATED FROM 07N-10N BETWEEN 43W-48W.
PLEASE SEE THE LATEST NHC TROPICAL WEATHER OUTLOOK UNDER
AWIPS/WMO HEADERS MIATWOAT/ABNT20 KNHC FOR MORE DETAILS.

[SeGaBob]

I personally agree with the NHC's chances at 50/50... it could go either way.

[KWT]

If its going to get going it needs to do it soon, as soon as it detaches from the ITCZ its going to have to fend off the SAL and shear without that aiding it like it still currently is. Hard to see it surviving once it hits the even higher shear zone near the Caribbean.

[Hyperstorm]

It looks like the latest GFS forecast shows it not gaining any strength until at least Friday. This is in contrast to the last few days when it was showing it developing by Thursday. In other words, it keeps pushing development further. Not only that, it develops it only weakly this time.

It looks like, regardless of weak development, this will just be a good soaker for the NE Antilles and not much more.

August is almost here...

The above post is the opinion of the poster. Refer to NHC for official information.

[Gustywind]

Very interresting to note how.... Cycloneye suffers from the drought as most of the others EC islands! Looks like we may have to wait to see huge amount of water from this one?! Bertha get up!

Tropical Storm Bertha May Still Form in Atlantic This Week

Courtney Spamer

By Courtney Spamer, Meteorologist

July 30, 2014; 1:24 PM
http://www.accuweather.com/en/weather-n ... l/31213830

The disturbance west of the Cape Verde Islands has potential to be the next named tropical storm in the Atlantic Basin.

The disturbance moved off the coast of Africa this weekend and survived cool waters and dry air thus far this week.

The disturbance is leaving cooler waters, and moving into an area with water temperatures in the lower 80s and lower wind shear, which are favorable for development.

Wind shear is a zone of strong winds at middle levels of the atmosphere that typically blows from the southwest, west or northwest. These winds can cause an organized tropical system to weaken or prevent one from forming in the first place.

According to AccuWeather.com Tropical Expert Dan Kottlowski, the system has a well defined low level circulation center.

"Development is expected to continue through the middle of the week," said Kottlowski early Wednesday morning.

If this system does continue to develop, it would be the second named storm in the Atlantic this season. "We think this could become Tropical Storm Bertha."
However, dry air and Saharan dust just to the north of the system could erode the storm's moisture.

This means the system's full development could be slowed or prevented as high pressure steers the system towards the northern Leeward Islands.

The system is forecast to take a curved, elliptical path around the high pressure area over the Atlantic but that exact path will be dependent on the strength of the system.

"A weaker system will track more to the west before making the curved path, while a stronger tropical storm early on could cause the system to curve east of the Leeward Islands," Kottlowski said.

At this point, for the coming weekend, "the Leeward Islands, Puerto Rico and the U.S. Virgin Islands are the areas being monitored very closely," Kottlowski added.
There areas could receive heavy rains and gusty winds, depending on the track of the system.

Portions of the Caribbean islands are in need of rain. For example, since January 1, 2014, San Juan, Puerto Rico, with about 23 inches of rain has only received about two-thirds of its average for the year so far.

The system could track close enough to Bermuda during the middle of next week to bring some rainfall.

[Nimbus]

Naked swirl making a run for it across 10n near -47W..
Too much dry air.

[tolakram]

So now that this is nearly dead the Euro tracks something all the way past the Bahamas.

The Atlantic conditions seem to be giving everything fits!

[Gustywind]

Tropical Storm Threat: Leeward Islands Could Feel Impacts This Weekend

By Jon Erdman Published: Jul 30, 2014, 10:39 AM EDT weather.com

http://www.weather.com/news/weather-hur ... t-20140729

The disturbance, shown at the center right of the satellite image above, has a pronounced spin above the surface, but has yet to produce sufficiently persistent convection (translation: thunderstorms) and a pronounced-enough westerly surface wind to merit classification as a tropical cyclone.

Once those two events occur, the National Hurricane Center will likely begin issuing advisories on what would be Tropical Depression Three.

Forecast: Lesser Antilles This Weekend

First, the disturbance has to overcome some dry air, light wind shear and marginal sea-surface temperatures over the next day or so.

The National Hurricane Center has tentatively scheduled a Thursday afternoon flight into the disturbance, leaving from Christiansted, Henry E. Rohlsen Airport in St. Croix. A NOAA Gulfstream jet is also scheduled to sample the environment around the disturbance Thursday, in the hopes of improving model forecasts of both track and intensity.

Assuming a tropical depression does form, the system is expected to track toward the Lesser Antilles late Friday into the weekend, possibly strengthening into a tropical storm. Its name would be Bertha.
As the system nears the islands, an area of low pressure aloft (called a tropical upper tropospheric trough or TUTT) may begin to interact with potential future tropical cyclone. If Three/Bertha is stronger at that time, the TUTT would pull the system farther north. Conversely, a weaker, less vertically-developed system would not be pulled as far north by the TUTT.

Furthermore, this TUTT may produce wind shear (change in wind direction and/or speed with height) that is hostile for tropical cyclone intensification or development as the system nears the islands.

So, for now, interests in the Lesser Antilles, U.S. Virgin Islands and Puerto Rico should monitor the forecast closely for possible impacts this weekend, including at least an increase in showers and squalls.

It is still too soon to forecast any future potential impacts farther downstream, including in the Bahamas, the U.S. or Bermuda.

Incidentally, the average date by which the Atlantic hurricane season's second named storm will have occurred is Aug. 1, so this potential Bertha is right on time, climatologically.

Check back with us at The Weather Channel and weather.com for the latest on this potential tropical threat.

[cycloneye]

18z Best Track. Finnally,it reached 10N.

AL, 93, 2014073018, , BEST, 0, 100N, 464W, 30, 1011, LO

[NDG]

One thing we should learn from 93L's failed attempt is that we should be paying more attention to the Euro next time there is a disturbance in the deep tropics of the Atlantic. The myth that the Euro does not do well in the deep tropics for tropical cyclone genesis will not work this year in the Atlantic Basin this year.
3 & 0 for King Euro.

[tolakram]

One thing we should learn from 93L's failed attempt is that we should be paying more attention to the Euro next time there is a disturbance in the deep tropics of the Atlantic. The myth that the Euro does not do well in the deep tropics for tropical cyclone genesis will not work this year in the Atlantic Basin this year.
3 & 0 for King Euro.

So are you paying attention to it now?

The Euro does not do well predicting genesis in the deep tropics and it is not a myth. It missed more storms that ended up developing in the deep tropics than other models, while the GFS develops too many storms in the same area compared to actual development stats. In a slow season where conditions are marginal the euro will do better, the GFS will do better in seasons with good conditions. No real mystery as to why that happens. This applies to the deep tropics only, and only based on past performance.

[tolakram]

The Naked Swirl.

[NDG]

One thing we should learn from 93L's failed attempt is that we should be paying more attention to the Euro next time there is a disturbance in the deep tropics of the Atlantic. The myth that the Euro does not do well in the deep tropics for tropical cyclone genesis will not work this year in the Atlantic Basin this year.
3 & 0 for King Euro.

So are you paying attention to it now?

The Euro does not do well predicting genesis in the deep tropics and it is not a myth. It missed more storms that ended up developing in the deep tropics than other models, while the GFS develops too many storms in the same area compared to actual development stats. In a slow season where conditions are marginal the euro will do better, the GFS will do better in seasons with good conditions. No real mystery as to why that happens. This applies to the deep tropics only, and only based on past performance.

Yes you are talking in average over the years may not be a myth, I am talking about right now in the tropical Atlantic the Euro has a better handle on the actual conditions of the deep tropical Atlantic.
Unless the Euro shows development, the GFS solutions of development in the deep tropics in our part of the world should be thrown out, IMO.

[wxman57]

I'm measuring a movement of 281.9 deg at 19.3 kts for the naked swirl. It's best chances of development are behind it.

[TropicalAnalystwx13]

One thing we should learn from 93L's failed attempt is that we should be paying more attention to the Euro next time there is a disturbance in the deep tropics of the Atlantic. The myth that the Euro does not do well in the deep tropics for tropical cyclone genesis will not work this year in the Atlantic Basin this year.
3 & 0 for King Euro.

So are you paying attention to it now?

The Euro does not do well predicting genesis in the deep tropics and it is not a myth. It missed more storms that ended up developing in the deep tropics than other models, while the GFS develops too many storms in the same area compared to actual development stats. In a slow season where conditions are marginal the euro will do better, the GFS will do better in seasons with good conditions. No real mystery as to why that happens. This applies to the deep tropics only, and only based on past performance.

Yes you are talking in average over the years may not be a myth, I am talking about right now in the tropical Atlantic the Euro has a better handle on the actual conditions of the deep tropical Atlantic.
Unless the Euro shows development, the GFS solutions of development in the deep tropics in our part of the world should be thrown out, IMO.

The ECMWF missed almost all of last year's storms...

[SFLcane]

I'm measuring a movement of 281.9 deg at 19.3 kts for the naked swirl. It's best chances of development are behind it.

Still should be watched very well defined circulation still there.