Watching for Subtropical Development

[ColdFront77]

I understand. Thank you.

[Derek Ortt]

If we dont see more water vapor in the area, there is no chance of any tropical or subtropical development. Chances are so insignificant at this time that I am not even monitoring the area, except for the occassional glance

[chadtm80]

http://www.ssd.noaa.gov/PS/TROP/DATA/RT ... -loop.html

http://www.ssd.noaa.gov/PS/TROP/DATA/RT ... -loop.html

[chadtm80]

000
AXNT20 KNHC 151101
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE 15 APR 2003

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...AND ATLANTIC OCEAN
TO THE AFRICAN COAST FROM THE EQUATOR TO 32N INCLUDING NORTHERN
SECTIONS OF SOUTH AMERICA. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

SPECIAL FEATURES...
NONE.

TROPICAL WAVES/ITCZ...
AXIS OF ITCZ-RELATED CLOUDS/CONVECTION IS CENTERED ALONG 4N1W
1N10W 3N25W EQ35W 3N51W. NUMEROUS STRONG CONVECTION FROM EQ TO
6N E OF 5W. SCATTERED STRONG CONVECTION FROM 1.5N-3.5N BETWEEN
21W-26W. WIDELY SCATTERED MODERATE CONVECTION FROM EQ TO 2N
BETWEEN 38W-50W.

MIDDLE/UPPER LEVEL SYNOPTIC FEATURES...
A FLAT MID/UPPER LEVEL TROUGH REMAINS OVER THE W ATLC BETWEEN
THE SE UNITED STATES COAST AND BERMUDA ANCHORED BY A CYCLONIC
CIRCULATION NEAR 31N74W. THE UPPER LOW HAS WEAKENED THROUGHOUT
THE NIGHT AND THE OVERALL TROUGH HAS FLATTENED. HOWEVER...A
SHORTWAVE TROUGH DIVING SE OVER THE E GLFMEX ALONG 87W IS
EXPECTED TO RE-AMPLIFY THE TROUGH SWD INTO THE NW CARIBBEAN
TODAY. ENTRANCE REGION OF UPPER JET STREAM ON THE EASTERN SIDE
OF TROUGH E OF BERMUDA WAS PRODUCING CLOUDS/CONVECTION OVER THE
N PORTION OF THE SUBTROPICAL ATLC THROUGHOUT THE NIGHT.
HOWEVER...THE JET HAS NOW LIFTED N OF AREA WITH ONLY ISOLATED
CLUSTERS OF MODERATE CONVECTION N OF 27N BETWEEN 53W-60W.
ATTENTION NOW SHIFTS FURTHER S WHERE AN AREA OF SCATTERED
SHOWERS AND THUNDERSTORMS HAS PERSISTED OVER THE S
BAHAMAS...WESTERN HISPANIOLA...E CUBA...AND WINDWARD PASSAGE
MOST OF THE NIGHT. THIS ACTIVITY IS ASSOCIATED WITH THE GLFMEX
SHORTWAVE DISTURBANCE DROPPING SE AND SHOULD CONTINUE FOR THE
NEXT 6-12 HOURS BEFORE THE SHORTWAVE BEGINS TO LIFT NWD LATER
TODAY/TONIGHT. FURTHER W...CONFLUENT FLOW INTO BASE OF TROUGH
AND ASSOCIATED DRY MIDDLE TO UPPER LEVEL AIR DOMINATES GULF OF
MEXICO...FLORIDA...NW CARIBBEAN...AND CENTRAL AMERICA N OF
PANAMA. UPSTREAM RIDGE OVER MEXICO AND CENTRAL UNITED STATES IS
PRODUCING STRONG NW FLOW W OF 90W.

MID/UPPER LEVEL FLOW OVER THE CARIBBEAN HAS FLATTENED DURING THE
LAST 12 HOURS. HOWEVER...DIGGING SHORTWAVE OVER THE E GLFMEX
WILL CREATE A MORE AMPLIFIED TROUGH-RIDGE PATTERN OVER THE NEXT
12-24 HRS. CURRENTLY...MAIN RIDGE AXIS EXTENDS NWD FROM
ANTICYCLONIC CIRCULATION OVER VENEZUELA TO THE LEEWARD ISLANDS.
A SECONDARY RIDGE AXIS EXTENDS ALONG THE N COAST OF SOUTH
AMERICA ALONG 10N/11N TO COSTA RICA. MODERATE SUBSIDENCE AND
DRY MID/UPPER LEVEL AIR IS PRESENT OVER THE EXTREME E CARIBBEAN
AND VIRGIN ISLANDS SE OF RIDGE AXIS AS WELL AS THE NW CARIBBEAN
NW OF RIDGE AXIS. WEAKER SUBSIDENCE AND HIGHER MID/UPPER LEVEL
MOISTURE CONTENT IS APPARENT ON WATER VAPOR IMAGERY AS FLOW IS
MORE DIVERGENT IN VICINITY OF RIDGE AXIS.

A HIGH OVER LOW TYPE BLOCKING PATTERN IS PRESENT OVER THE
CENTRAL TO E ATLC WITH AFOREMENTIONED CARIBBEAN RIDGE CONTINUING
FROM THE LEEWARD ISLANDS TO BEYOND 30N35W IN THE ATLC AND A
WEAKENING MID/UPPER LEVEL LOW TRAPPED UNDERNEATH RIDGE NEAR
15N54W. A WEAK SHORTWAVE TROUGH AXIS EXTENDS SW FROM THE LOW
CENTER TOWARD THE SOUTH AMERICA COAST NEAR 6N52W...AND NE FROM
CIRCULATION TO 21N40W. THE RIDGE AXIS CONTINUES TO DELINEATE
MID/UPPER LEVEL MOISTURE WITH CONFLUENT FLOW TO THE SOUTH
PRODUCING MODERATE/STRONG SUBSIDENCE OVER MUCH OF AREA TO 10N
BETWEEN 45W-66W...AND FROM 20N-30N E OF 40W. RIDGING E OF UPPER
LOW COVERS THE TROPICAL ATLC TO W AFRICA WITH SW FLOW ADVECTING
ITCZ MOISTURE NWD OVER TROPICAL ATLC S OF 20N E OF 40W.

SURFACE SYNOPTIC FEATURES...
RIDGE EXTENDS SW FROM THE W SUBTROPICAL ATLC OVER N FLORIDA TO
THE COAST OF MEXICO NEAR TAMPICO.

CENTRAL ATLC COLD FRONT ENTERS AREA NEAR 32N47W SW TO 25N60W
WHERE IT BECOMES STATIONARY TO THE N COAST OF HISPANIOLA NEAR
20N70W. PERSISTENT AREA OF SCATTERED SHOWERS/THUNDERSTORMS AND
ISOLATED MODERATE CONVECTION IS NOTED ALONG S EXTENT OF FRONT
FROM 19N-23N BETWEEN 70W-77W INCLUDING THE SOUTHERN AND CENTRAL
BAHAMA ISLANDS...NW HISPANIOLA... AND E CUBA. ISOLATED SHOWERS
AND THUNDERSTORMS ALONG FRONT N OF 27N. REMNANT FRONTAL TROUGH
EXTENDS FROM WINDWARD PASSAGE SW TO THE BORDER OF NICARAGUA AND
HONDURAS NEAR 15N84W. ISOLATED SHOWERS WITHIN 90 NM EITHER SIDE
OF TROUGH.

STRONG HIGH PRESSURE...1023 MB HIGH CENTER NEAR 27N36W...
DOMINATES THE CENTRAL AND E ATLC. SUBTROPICAL RIDGE AXIS
STRETCHES FROM 33N20W TO 23N56W. SURFACE PRESSURES ARE FAIRLY
HIGH TO THE SOUTH OF THE RIDGE PRODUCING MODERATE TRADES OVER
THE ATLC WATERS S OF 20N E OF 55W.

SIGNIFICANT CLOUDS/CONVECTION...
GULF OF MEXICO...
NONE.

CARIBBEAN SEA...
NONE.

TROPICAL ATLANTIC...
OTHER THAN ITCZ...NONE.

SUBTROPICAL ATLANTIC...
SEE SURFACE SYNOPTIC FEATURES FOR CLOUDS/CONVECTION ASSOCIATED
WITH ATLC COLD FRONT. OTHERWISE...SCATTERED SHOWERS E OF THE
NORTHERN BAHAMAS FROM 26N-27N BETWEEN 74W-76W. ISOLATED SHOWERS
ARE OVER THE STRAITS OF FLORIDA AND WATERS NEAR GRAND BAHAMA
ISLAND.

$$
RHOME

[OtherHD]

I'm with Derek. You guys keep watching watching the tropics, I'm going back to bed!! lol

But sound an alarm for me if anything comes up.

[chadtm80]

Well we are not saying this is going to develope into anything... We just enjoy watching the tropics

[cycloneye]

Exactly chad nobody has said here that this will develop into a tropical system but it is the first time this year that at least a low pressure is out there in the atlantic basin.

http://www.tormenta.net/frame_page.asp? ... XNT20.KNHC

Read the second paragrafh from the 2:05 PM discussion where they mention the low forming near the Bahamas.

[wx247]

We are just monitoring the tropics. No one has sounded the development alert bell yet.

[Anonymous]

Originally posted by Cycloneye:
Exactly chad nobody has said here that this will develop into a tropical system but it is the first time this year that at least a low pressure is out there in the atlantic basin.

This low is not the first, but it is the most suspicious one.

In any event, I am not holding my breath. Remember the UKMET, and other models to a smaller extent, jumped on several of the lows earlier this year. The environment is not the best for a classified tropical cyclone to form; strong wind shear, dry air, and marginal SSTs.

HOWEVER, if you look at the environment subtropical-wise, its a slightly different story. Subtropical systems, remember, are more immune to shear, stable air, and cooler SSTs. This low should not ever become tropical, but I am not ruling out the possibility of it being classified as a subtropical TD/TS.

Chance of development, even subtropical, are low. But it does bear watching. Should this somehow develop, Bermuda would likely be in the bullseye of the track. I definately don't this traveling near the east coast. We would need a very strong and sturdy ridge, which does not seem to be the case at this point. True, the models have been trending towards a stronger ridge, but so far they don't show one strong enough for an east coast hit. A slow general northward movement, perhaps with westward wobbles, seems the most likely, regardless of how strong it gets.

[Rainband]

At least we have something to watch..even if it doesn't amount to much...Bring on Cane season!!!!!!

Johnathan

[ColdFront77]

That is exactly what I mentioned above. Weather enthusiasts, as we are follow every low not matter what the potential is for development. We all know it is April, when tropical development and subtropical development is generally rare.

[Derek Ortt]

Lets save the energy for the real threats this year. I have to disagree about any chance for STC development as the air is too dry and we wont even see enough WV on one quad to make this subtrop. This low is destined to be extra-trop

[ColdFront77]

I agree, Derek. I never said the possibility was there with this system.

[chadtm80]

Lets save the energy for the real threats this year

We have plenty in reserve Were just watching it derek... thats all

[cycloneye]

I have plenty of energy to discuss the tropics all year around We dont do anything wrong to watch a low pressure even if nothing happens with it.

[ColdFront77]

Good point. I understand what Derek means, too (as I mentioned).

[Kevin_Wx]

Agree with Derek. I've been looking at the WV loop as well, and I am just having a hard time seeing where this supposed subtropical system could develop...too much dry air as Derek said. Just an interesting April feature--won't do anything though.

[ColdFront77]

I have continually noticed that we all agree that this feature will not develop and that it is nonetheless an interesting system to see in the Atlantic Basin in mid-April.

[Stormsfury]

I have continually noticed that we all agree that this feature will not develop and that it is nonetheless an interesting system to see in the Atlantic Basin in mid-April.

Ditto.

[Steve H.]

Interesting to see features like this in April. Several models show troughiness/closed lows off the SE US coast at three different intervals of the GFS run. One in the near term; at 10 days where a 1004 mb low is shown off the GA coast then deepens into 1000 mb low as it heads ENE; another at the 300+ hour range shows a weak low off the Bahamas, then pops a Bermuda type high at months end. A bit unusual - interesting.