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Tropical Storm Erika

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94L becomes TS Erika, intensity 45kts:

TROPICAL STORM ERIKA ADVISORY NUMBER 1

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062009

500 PM EDT TUE SEP 01 2009

...ERIKA FORMS EAST OF THE NORTHERN LEEWARD ISLANDS...TROPICAL

STORM WATCHES ISSUED...

AT 5 PM...2100 UTC...THE GOVERNMENT OF THE NETHERLANDS ANTILLES HAS

ISSUED A TROPICAL STORM WATCH FOR THE ISLAND OF ST. MAARTEN.

AT 5 PM...THE GOVERNMENT OF ANTIGUA AND BARBUDA HAS ISSUED A

TROPICAL STORM WATCH FOR THE ISLANDS OF ANTIGUA...BARBUDA...ST.

KITTS...NEVIS...AND ANGUILLA.

AT 5 PM...THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WATCH

FOR THE ISLANDS OF ST. MARTIN AND ST. BARTHELEMY.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE

POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36 HOURS.

INTERESTS ELSEWHERE IN THE NORTHERN LEEWARD ISLANDS...U.S. AND

BRITISH VIRGIN ISLANDS...AND PUERTO RICO SHOULD MONITOR THE

PROGRESS OF ERIKA.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED

STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE

MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE

FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA

OUTSIDE OF THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED

BY YOUR NATIONAL METEOROLOGICAL SERVICE.

AT 500 PM EDT...2100 UTC...THE CENTER OF TROPICAL STORM ERIKA WAS

LOCATED NEAR LATITUDE 17.2 NORTH...LONGITUDE 57.3 WEST OR ABOUT 390

MILES...625 KM...EAST OF THE NORTHERN LEEWARD ISLANDS.

ERIKA IS MOVING TOWARD THE WEST-NORTHWEST NEAR 9 MPH...15 KM/HR...

AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT COUPLE

OF DAYS. ON THIS TRACK THE CENTER OF ERIKA IS EXPECTED TO REMAIN

TO THE NORTHEAST OF THE LEEWARD ISLANDS.

MAXIMUM SUSTAINED WINDS ARE NEAR 50 MPH...85 KM/HR...WITH HIGHER

GUSTS. SOME SLOW STRENGTHENING IS FORECAST DURING THE NEXT COUPLE

OF DAYS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 105 MILES...165 KM

FROM THE CENTER.

THE LATEST MINIMUM CENTRAL PRESSURE REPORTED BY AN AIR FORCE RESERVE

RECONNAISSANCE AIRCRAFT IS 1007 MB...29.74 INCHES.

...SUMMARY OF 500 PM EDT INFORMATION...

LOCATION...17.2N 57.3W

MAXIMUM SUSTAINED WINDS...50 MPH

PRESENT MOVEMENT...WEST-NORTHWEST OR 300 DEGREES AT 9 MPH

MINIMUM CENTRAL PRESSURE...1007 MB

AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE

CENTER AT 800 PM EDT FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 1100

PM EDT.

$$

FORECASTER BLAKE/FRANKLIN

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according to this it might affect Bahamas Sunday

204712W5_NL_sm.gif

20090901.2015.goes12.x.ir1km.06LERIKA.45kts-1007mb-170N-570W.100pc.jpg

at200906.gif

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Whilst short term intensification is forecast, strong shear is currently expected to weaken Erika by the time she gets in the vicinity of the Bahamas if all goes to plan.

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latest indications are for a speeding up of movement, having virtually stalled for a while.

...ERIKA BARELY MOVING...
AT 800 PM EDT...0000 UTC...THE CENTER OF TROPICAL STORM ERIKA WAS

LOCATED NEAR LATITUDE 17.2 NORTH...LONGITUDE 57.3 WEST OR ABOUT 390

MILES...625 KM...EAST OF THE NORTHERN LEEWARD ISLANDS.

ERIKA HAS BEEN MEANDERING FOR THE PAST 3 HOURS...BUT IS EXPECTED TO

BEGIN MOVING TOWARD THE WEST-NORTHWEST NEAR 9 MPH...15 KM/HR...

TONIGHT. THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT

COUPLE OF DAYS. ON THIS TRACK...THE CENTER OF ERIKA IS EXPECTED TO

REMAIN TO THE NORTHEAST OF THE LEEWARD ISLANDS.

MAXIMUM SUSTAINED WINDS ARE NEAR 50 MPH...85 KM/HR...WITH HIGHER

GUSTS. SOME SLOW STRENGTHENING IS FORECAST DURING THE NEXT COUPLE

OF DAYS.

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...ERIKA LESS ORGANIZED BUT CENTER APPEARS TO BE CLOSER TO THE

LEEWARD ISLANDS...

...SUMMARY OF 200 AM AST INFORMATION...

LOCATION...17.0N 58.7W

MAXIMUM SUSTAINED WINDS...60 MPH

PRESENT MOVEMENT...WEST OR 270 DEGREES AT 10 MPH

MINIMUM CENTRAL PRESSURE...1008 MB

Latest from NHC above.

I still think the track is very uncertain, mainly because the centre is so erratic, ECM follows the global models on the NW track, GFS has Erika going much further west over the Caribbean.

The recon currently is not finding much at all where it thought it would.

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Below is the Vortex message dropped at the centre of Erika

This puts the centre half a degree further south than the NHC expected and a bit further west. The tropical models initiated most recently BAMx etc, have placed the path for Erika much closer to PR, Cuba, Jamaica etc.

Product: Air Force Vortex Message (URNT12 KNHC)

Transmitted: 2nd day of the month at 08:19Z

Corrected: This observation corrected a previous observation.

Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 305)

Storm Number & Year: 06L in 2009

Storm Name: Erika (flight in the North Atlantic basin)

Mission Number: 2

Observation Number: 07

A. Time of Center Fix: 2nd day of the month at 7:42:20Z

B. Center Fix Coordinates: 16°25'N 59°11'W (16.4167N 59.1833W) (View map)

B. Center Fix Location: 166 miles (267 km) to the ENE (62°) from Roseau, Dominica.

C. Minimum Height at Standard Level: 1,487m (4,879ft) at 850mb

D. Estimated (by SFMR or visually) Maximum Surface Wind: 26kts (~ 29.9mph)

E. Location of the Estimated Maximum Surface Wind: 76 nautical miles (87 statute miles) to the NW (325°) of center fix

F. Maximum Flight Level Wind Inbound: From 55° at 31kts (From the NE at ~ 35.7mph)

G. Location of Maximum Flight Level Wind Inbound: 81 nautical miles (93 statute miles) to the NW/NNW (326°) of center fix

H. Minimum Sea Level Pressure: 1005mb (29.68 inHg) - Extrapolated

I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 21°C (70°F) at a pressure alt. of 1,527m (5,010ft)

J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 18°C (64°F) at a pressure alt. of 1,525m (5,003ft)

K. Dewpoint Temp (collected at same location as temp inside eye): 15°C (59°F)

K. Sea Surface Temp (collected at same location as temp inside eye): Not Available

L. Eye Character: Not Available

M. Eye Shape: Not Available

N. Fix Determined By: Penetration and Wind

N. Fix Level: 850mb

O. Navigation Fix Accuracy: 0.02 nautical miles

O. Meteorological Accuracy: 10 nautical miles

Remarks Section:

Maximum Flight Level Wind: 34kts (~ 39.1mph) in the southeast quadrant at 8:12:30Z

Sea Level Pressure Extrapolation From: 850mb

Maximum Flight Level Temp: 21°C (70°F) which was observed 65 nautical miles (75 statute miles) to the NW (323°) from the flight level center

To add to that as well, This recording was taken.

Which might well indicate that Erika has multiple centres at the moment.

07:19:00Z 17.317N 59.850W 842.9 mb

(~ 24.89 inHg) 1,548 meters

(~ 5,079 feet) 1004.7 mb

(~ 29.67 inHg) - From 11° at 20 knots

(From between the N and NNE at ~ 23.0 mph) 20.9°C

(~ 69.6°F) 15.4°C

(~ 59.7°F) 20 knots

(~ 23.0 mph) 11 knots

(~ 12.6 mph) 0 mm/hr

(~ 0 in/hr) 11.0 knots (~ 12.6 mph)

I've attached the latest pic and plotted the two centres, The Vortex one seems right to me and looks under some heavy convection, the system is still badly mishappen but does look better than it did.

post-6326-12518810729249_thumb.jpg

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Latest NHC update that's just come out, I've bolded a few bits.

And the latest path, which does show the centre of Erica now passing over land and much closer to PR.

AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS BEEN SEARCHING

FOR THE CENTER OF THE TROPICAL STORM OVER THE PAST FEW HOURS. THE

CIRCULATION HAS BECOME QUITE DISORGANIZED...BUT IT APPEARS THAT THE

CENTER HAS REFORMED TO THE SOUTHWEST OF THE PREVIOUSLY ESTIMATED

TRACK. HOWEVER THE FLIGHT-LEVEL WINDS SUGGEST THAT THERE MAY BE

MULTIPLE CENTERS...SO THE ADVISORY POSITION IS HIGHLY UNCERTAIN AND

PROBABLY REPRESENTS A MEAN CENTER...OR THE LOCATION OF THE

LOW-LEVEL VORTICITY MAXIMUM. THE INITIAL MOTION...270/4...IS OF

COURSE ALSO HIGHLY UNCERTAIN. TO MAINTAIN SOME CONTINUITY FROM THE

PREVIOUS FORECAST AND FOLLOWING THE TRACK GUIDANCE...A WEST-

NORTHWESTWARD TRACK IS PREDICTED TO RESUME. ERIKA SHOULD BE

STEERED BY THE FLOW TO THE SOUTH OF A WEAK SUBTROPICAL RIDGE FOR A

COUPLE OF DAYS. LATER IN THE FORECAST PERIOD...DYNAMICAL GUIDANCE

SHOWS A MORE NORTHWESTWARD MOTION FOR A STRONGER CYCLONE...E.G. THE

GFDL AND HWRF...AND A CONTINUED WEST-NORTHWESTWARD MOTION FOR A

WEAKER SYSTEM...E.G. THE GFS. THIS IS A LOW-CONFIDENCE TRACK

FORECAST.

post-6326-12518824190102_thumb.gif

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Anyone else think it very strange that NHC got it so wrong. It appeared fairly obvious that the storm was well below what they were showing on the various charts. I bet there are plenty of annoyed people in Antigua :pardon:

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The problem is that NHC can only really go on what Recon provide for them. At the last update Recon had only found the one centre further north. They probably had a gut feeling it had multiple centres (it seemed to yesterday on visual as well), but have to report on the evidence they have.

This path map shows how badly initialised the 00Z suite was(I think even the 06Z GFDL and HWRF will be out). You can pretty much discount all of these including the GFS and ECM IMO. The further South the less shear, but it will certainty experience shear between Leeward and PR but 30 rather 50 makes a big difference.

post-6326-12518845929626_thumb.png

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Attached is the latest path update from the NHC approx 10-15 mins ago.

I've plotted it on this chart from the US Navy site which had the 06Z updates. You can see how much further south it is and guess the assocaited consequences for the West Indies.

"AT 800 AM AST...1200 UTC...THE CENTER OF TROPICAL STORM ERIKA WAS

RELOCATED TO NEAR LATITUDE 16.5 NORTH...LONGITUDE 59.5 WEST OR

ABOUT 160 MILES...255 KM...EAST-SOUTHEAST OF THE LEEWARD ISLANDS.

ERIKA HAS BEEN MOVING GENERALLY WESTWARD NEAR 7 MPH...11 KM/HR...AND

A WEST-NORTHWESTWARD MOTION AT A SLIGHTLY FASTER FORWARD SPEED IS

EXPECTED OVER THE NEXT DAY OR TWO. ON THE FORECAST TRACK THE

CENTER WILL PASS NEAR OR OVER THE LEEWARD ISLANDS DURING THE NEXT

DAY OR SO."

post-6326-12518932953561_thumb.gif

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Take this with a pinch of salt as the models have been all over the place.

Interesting GFDL takes her very close to Jamaica, PR and Cuba before ending with a CAT 4 in the Bahamas.

I do hope that these countries are not just following the NHC and are looking at the models.

Once Erika gets past Jamaica shear should ease and strengthening occur.

GFS takes it on a similar route and to Florida eventually and this really can't be discounted IMO.

Anything beyond 24 hrs is highly uncertain atm which IMO make this tropical storm fasinating. :mellow:

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Another little piccie.

On visual sat a swirling low level centre seems to have moved quickly westwards, however there looks like another LLCC under the newly fired convection near to where NHC pointed it at lunchtime.

I would really not like to put together the next NHC Full update out in about 15 mins. There is very little confidence in the path or intensity.

TS, I am not not whether she will become a hurricane or not, most of the guidance points to it, but I am not sure I believe anything really atm.

post-6326-12519025195405_thumb.png

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Well they've issued their forecast and it's now SOUTH of the West Indies and crossing the tip of Jamaica before going into the Bahamas.

They've acknowledged the appearence of multi low level cloud swirls(centre) and also lowered the intensity due to Shear effects (they nolonger make her a Hurricane). However all the models do.

A bit Dannysque in this regard.

Rainfall could be a severe problem though as it's slow moving and has a very large convective field.

VISIBLE SATELLITE IMAGES AND AIR FORCE RESERVE HURRICANE HUNTER

DATA SHOW THAT ERIKA IS A POORLY ORGANIZED SYSTEM. THERE ARE

MULTIPLE SWIRLS APPARENT ON THE SATELLITE IMAGERY ROTATING IN THE

LARGER CIRCULATION ENVELOPE WITH A MEAN CENTER TO THE WEST OF THE

DEEP CONVECTION. THE SFMR EARLIER REPORTED WINDS OF ABOUT 35

KT...WHICH IS IN GOOD AGREEMENT WITH SATELLITE INTENSITY

ESTIMATES...SO THAT VALUE WILL BE USED AS THE INITIAL INTENSITY.

THE OFFICIAL FORECAST HAS BEEN SHIFTED LEFT OF THE PREVIOUS ONE AND IS LEFT OF THE DYNAMICAL

CONSENSUS DUE TO THE ANTICIPATION OF ERIKA REMAINING WEAK. IT

SHOULD BE EMPHASIZED THAT...OVERALL...THIS IS A LOW-CONFIDENCE

TRACK FORECAST.

INITIAL 02/1500Z 16.5N 60.4W 35 KT

12HR VT 03/0000Z 16.9N 61.5W 35 KT

24HR VT 03/1200Z 17.4N 62.8W 40 KT

36HR VT 04/0000Z 18.0N 64.2W 45 KT

48HR VT 04/1200Z 18.6N 65.5W 40 KT

72HR VT 05/1200Z 20.0N 68.5W 35 KT

96HR VT 06/1200Z 21.5N 71.5W 30 KT

120HR VT 07/1200Z 23.5N 73.5W 30 KT

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Erika is going nowhere near Jamaica Iceberg, unless the track gets shifted MUCH further south, lol. I think you meant Puerto Rico.

Interesting the note of Erika's possibly dissipating, shear doesn't look favourable and the current disorganisation of Erika shows it's struggling even in moderate shear. Let's hope Erika doesn't ramp up because with the southward shifts Erika looks more and more landbound.

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They look similar :D

Thanks Somerset.

I would add somerset that I wouldn't want to try and forecast Erica, I am not sure that NHC have the centre right, but shear is a real issue, also they've struggled to forecast this shear 12 hrs ahead so 120 hrs down the line is in real nomans land.

No doubt tomorrow the forecast will be completly different again.

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Good timing Cookie I've done a piccie with the center on, but it's very clear from your picture.

There now only seems to be 1 LLCC, which has very little convection and is totally sheared.

I disagree re the Shear outlook from NHC this will continue to head west until it gets convection, by this point it should avoid the worst of the shear.

The path really is anyones guess, GFS has it entering the GOM to the west of Florida breifly, Others are all over the place with GFDL suggesting a Florida hit eventually, but the truth is no one has a clue it all depends on what she does.

Recon are in and have already found enough to keep Erica as Erica.

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000

WTNT41 KNHC 030836

TCDAT1

TROPICAL STORM ERIKA DISCUSSION NUMBER 7

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062009

500 AM AST THU SEP 03 2009

ALTHOUGH THE HURRICANE HUNTERS FIXED A FLIGHT-LEVEL CENTER...THERE

ARE A FAIR NUMBER OF SURFACE OBSERVATIONS OVER THE NORTHEASTERN

CARIBBEAN SEA REGION...AND THESE SHOW THAT THE SURFACE CIRCULATION

IS AT BEST POORLY-DEFINED. THE SYSTEM MAY BE OPENING UP INTO A

TROUGH ORIENTED FROM SOUTH-SOUTHWEST TO NORTH-NORTHEAST. THERE

WERE A FEW 34 TO 37-KT SFMR SURFACE WIND READINGS SOME 40-75 N MI

NORTH AND NORTHEAST OF THE FLIGHT-LEVEL CENTER...SO THE INTENSITY

IS MAINTAINED AT 35 KT. EVEN THOUGH THERE MAY NO LONGER BE A

DEFINITE SURFACE CENTER OF CIRCULATION...WE WILL MAINTAIN

ADVISORIES ON THE SYSTEM PENDING ADDITIONAL DATA FROM THE

RECONNAISSANCE AIRCRAFT AND VISIBLE IMAGERY. RADIOSONDE DATA FROM

THE EASTERN CARIBBEAN SEA AREA SUGGEST THAT THE STORM HAS BEEN

EXPERIENCING WESTERLY SHEAR DUE TO FLOW AT ABOUT THE 250 MB

LEVEL...WHICH IS LIKELY JUST BELOW THE TROPICAL CYCLONE OUTFLOW

LAYER. GLOBAL MODELS SHOW INCREASING WEST-SOUTHWESTERLY SHEAR OVER

ERIKA DURING THE NEXT COUPLE OF DAYS DUE TO STRENGTHENING

UPPER-TROPOSPHERIC WINDS. IN SPITE OF THE STRONG SHEAR...THE GFDL

AND HWRF MODELS CONTINUE TO FORECAST THAT ERIKA WILL INTENSIFY

SIGNIFICANTLY. THE SHIPS AND LGEM GUIDANCE ARE MUCH LESS

AGGRESSIVE...PARTICULARLY THE LATTER. THE OFFICIAL INTENSITY

FORECAST IS THE SAME AS THAT FROM THE PREVIOUS ADVISORY AND

ANTICIPATES THAT THE TROPICAL CYCLONE WILL DISSIPATE BY 72

HOURS.

BECAUSE OF THE UNCERTAINTIES IN THE LOCATION...OR EXISTENCE...OF THE

SURFACE CENTER...THE INITIAL MOTION ESTIMATE OF 295/6 IS MORE OF AN

EDUCATED GUESS. A WEAK MID-LEVEL RIDGE LIES TO THE NORTH OF ERIKA.

AS THE MODELS BUILD THIS RIDGE SOMEWHAT DURING THE NEXT COUPLE OF

DAYS...A SLIGHT INCREASE IN FORWARD SPEED IS LIKELY. LATER IN THE

PERIOD A MORE NORTHWESTWARD TRACK IS FORECAST AS THE CYCLONE NEARS

THE WESTERN PERIPHERY OF THE RIDGE. THE OFFICIAL FORECAST IS

SHIFTED A LITTLE NORTH OF THE PREVIOUS ONE PRIMARILY DUE TO A

SLIGHT NORTHWARD RELOCATION OF THE INITIAL POSITION.

EVEN IF ERIKA LOSES ITS TROPICAL CYCLONE STATUS...IT COULD MAINTAIN

VIGOROUS DEEP CONVECTION WHICH WOULD PRODUCE VERY HEAVY RAINS OVER

THE NORTHERN LESSER ANTILLES AND PUERTO RICO.

FORECAST POSITIONS AND MAX WINDS

INITIAL 03/0900Z 16.5N 62.7W 35 KT

12HR VT 03/1800Z 17.1N 64.1W 35 KT

24HR VT 04/0600Z 17.9N 65.6W 30 KT

36HR VT 04/1800Z 18.7N 67.1W 30 KT

48HR VT 05/0600Z 19.5N 68.5W 30 KT

72HR VT 06/0600Z 21.0N 70.8W 25 KT...REMNANT LOW

96HR VT 07/0600Z 22.5N 73.0W 20 KT...REMNANT LOW

120HR VT 08/0600Z...DISSIPATED

$$

FORECASTER PASCH

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Erika appears to be losing some convection, this coupled with the shear could lead to dissipation earlier than projected by the models.

vis-l.jpg

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Agreed Jack, with the forecast shear and Erika's current state I really cannot see how this system can last much longer. Winds have been reduced to 30kts so Erika is now a depression. As the system is so weak it has not responded to upper level steering and has instead continued to limp westwards in the low level flow. At this rate, Erika (or it's remnants) may even dip south of Hispaniola, a considerable difference to original track forecasts. Been a tricky storm to forecast this one!

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Yes, Erica has never really been steered by the upper level flow so it seems. At her current rate, I wouldn't be surprised if she dissipates before reaching Hispaniola.

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