Erika dumping heavy rain on the Lesser Antilles
Tropical Storm Erika is hanging together despite strong wind shear, and is bringing high winds and much-needed heavy rain to the Lesser Antilles Islands. Winds on the south shore of Dominica Island were sustained at 37 mph this morning, and 8.03" of rain have been measured at the airport over the past two days. Winds and rain at nearby islands have been less, according to our wundermap for the region. The Hurricane Hunters are in the storm now, and have generally encountered top winds of 40 - 45 mph at the surface. They did find one spot of 50 - 65 mph winds, but that was likely due to outflow from a strong thunderstorm, and is not representative of Erika's wind field.
Figure 1. Radar image of Tropical Storm Erika at 9:15am EDT 9/3/09. Image credit: Meteo France.
Erika has improved in organization a bit since last night, but remains weak and disorganized, thanks to about 20 knots of shear at the 200 mb level, as seen on last night's Guadeloupe upper air sounding. Radar animations out of Martinique show plenty of heavy rain moving through the Lesser Antilles, but little organization of the echoes. Satellite imagery shows no low-level spiral bands and little upper-level outflow. Long range radar out of Puerto Rico is beginning to show rain echoes from Erika approaching the island.
The forecast for Erika
The computer models have come into better agreement about the track of Erika, taking the storm west-northwest over Puerto Rico and the Dominican Republic. This track will take Erika into a band of significantly higher wind shear of 25 - 35 knots, Friday through Saturday. Considering that Erika is barely maintaining itself as a tropical storm with 20 knots of shear, the combined effects of the higher shear and the encounter with the high mountains of Hispaniola and Puerto Rico should be enough to cause Erika to dissipate by Sunday. Erika's remains will still be capable of dumping very heavy rains of 3 - 5 inches over the Dominican Republic and 1 - 3 inches over Haiti and the Southeast Bahamas, due to the slow motion of the storm. By Monday, when the remains of Erika should be over the Bahamas, the storm will have penetrated through the band of high wind shear over the Greater Antilles, and shear may fall low enough for redevelopment of the storm. This is a scenario offered by the NOGAPS model, which then takes Erika northward towards North Carolina. The other models predict quite a bit more shear in the region than the NOGAPS, and any redevelopment of Erika early next week remains an iffy proposition. The GFDL and HWRF models continue to insist that Erika will brush off the high shear this weekend, avoid Hispaniola, and intensify into a Category 2 hurricane five days from now. These models have not been giving enough emphasis to how the current shear is affecting Erika, and are being discounted at this time.
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Elsewhere in the Atlantic
A large, strong tropical wave with plenty of spin emerged from the coast of Africa this morning. The wave is not yet generating much in the way of heavy thunderstorms, but has the potential to gradually develop into a tropical depression by early next week. NHC is giving this wave a low (less than 30% chance) of developing into a tropical depression by Saturday. The GFS model has been consistently developing this wave in its runs over the past few days.
I'll have an update this afternoon.
Jeff Masters
Reader Comments
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Between the westerly shear at 200 forecast to build in, and the dry air. One thing is for sure, she's going be fighting an uphill battle the whole way. Forgetting the shear for a second, I just don't see a way you can moisten an environment this dry. Downdraft will continually disrupt the circulation and prevent organization.
All that said, the low/area of strong 850 vorticity will probably stick around for quite a while unless it goes directly over Puerto Rico or Hispaniola.
She's could be a thorn in our side for another week...
As a long-time resident of Florida (both SE and NE), I find that it is these "messy" storms that do the crazy things and cause the most damage. Erika looks like a storm that will wander around and then just sit over an area of land and dump a bunch of rain for days and days. Sometimes the lower level disturbances can cause worse flooding than a cat1 hurricane that blows through rather quickly. We HAVE to watch these storms whether they make it to hurricane strength or not.
I see a spin. I don't see recon flying over there though.
Ahh, now it makes sense...tabernus, tavern...
They're not the most interesting classes but teach you to "work within the system". Red Cross also offers many classes on disaster response.
Post it here please =P
Your telling me, it has been raining for 10 hrs steady which is ok but now it is pouring down, no wind though. Our valley is definitely going to flood.
Huh?
I have a question....a true tropical storm wouldn't be going through DMIN and DMAX like Erika is doing, would it? I've read on here tropical storms and hurricanes aren't influenced by DMIN and DMAX? True?
Downgrade likely but not death. Fine silverware to be replaced with plastic sporks.
Yup, all she's doing is thrashing about in the Caribbean playing hide and seek.
Still... while I don't think she'll amount to much in the next 48 hours, *if* she does manage to survive dry air, shear and mountains (as in, have some sort of remnants - it'd be a borderline miracle if she was anything more than that), then could be interesting to see if she spins up in a better environment. If one is still there by that time.
I concur. Even though, it doesn't take much forcing to steer that shallow swirl. It is probably safer to watch the typical cumulus cloud overall direction that is in the mean flow rather than take heed with model solutions.
When are the next Skew-T charts coming out for Puerto Rico?
LOL.
WHXX01 KWBC 031823
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1823 UTC THU SEP 3 2009
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
ATLANTIC OBJECTIVE AIDS FOR
TROPICAL CYCLONE ERIKA (AL062009) 20090903 1800 UTC
...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090903 1800 090904 0600 090904 1800 090905 0600
LAT LON LAT LON LAT LON LAT LON
BAMS 16.6N 64.7W 17.3N 66.7W 18.1N 68.6W 18.7N 70.5W
BAMD 16.6N 64.7W 17.2N 65.9W 17.8N 67.0W 18.3N 67.9W
BAMM 16.6N 64.7W 17.1N 66.2W 17.7N 67.7W 18.1N 68.9W
LBAR 16.6N 64.7W 17.1N 66.3W 18.0N 67.8W 18.8N 69.2W
SHIP 30KTS 30KTS 33KTS 35KTS
DSHP 30KTS 30KTS 33KTS 34KTS
...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090905 1800 090906 1800 090907 1800 090908 1800
LAT LON LAT LON LAT LON LAT LON
BAMS 19.4N 72.5W 19.9N 75.8W 19.9N 78.5W 19.7N 80.6W
BAMD 18.7N 68.7W 19.5N 70.4W 20.7N 72.3W 22.3N 74.3W
BAMM 18.6N 70.1W 19.2N 72.2W 19.5N 74.0W 20.1N 75.6W
LBAR 19.5N 70.5W 20.0N 72.8W 20.1N 75.5W 20.3N 78.3W
SHIP 38KTS 46KTS 52KTS 62KTS
DSHP 35KTS 43KTS 48KTS 58KTS
...INITIAL CONDITIONS...
LATCUR = 16.6N LONCUR = 64.7W DIRCUR = 275DEG SPDCUR = 10KT
LATM12 = 16.4N LONM12 = 62.4W DIRM12 = 291DEG SPDM12 = 6KT
LATM24 = 16.3N LONM24 = 61.2W
WNDCUR = 30KT RMAXWD = 120NM WNDM12 = 35KT
CENPRS = 1008MB OUTPRS = 1011MB OUTRAD = 125NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
$$
NNNN
TD Erika.
But im pretty sure the higher levels shouldnt be spinning after the center has moved away. Unless it left a spin in the atmosphere.
AL 06 2009090318 BEST 0 166N 647W 30 1008 TD
lol
you have a bad feeling or you don't have a good feel on the storm track?
It's because the shear isn't at the top; more like the middle, say 500mb?
Per the current readings on UW - which are always subject to changing - she'd actually run into more.
That's what GFS was showing us with the Theta-e about a week ago through yesterday. This is why GFS continued to dissipate Erika.
I see
Nope, they're all influenced by DMIN/MAX...depending on the strength of the system it may be able to maintain better...a TS gets it worse than a CAT2, say...
no
If they are from a sounding, 12 and 0 Z are we get. A lot of places in the Caribbean only give us one or the other, as well. Not sure about that from PR. Probably both 0 and 12. Not real likely to gives 6 or 18 Z.
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